H 
 
 \ 
 
 hwn 
 
 Issued February '.», mi. 
 
 PORTO RiCO AGRICULTURAL EXPERIMENT STATION, 
 
 D. W. MAY, Special Agent in Charge, 
 
 Mayaguex, P. R. 
 
 Bulletin No. 17. 
 
 FUNGUS DISEASES OF COFFEE IN 
 PORTO RICO. 
 
 G. L. PAWCETT, 
 
 Plant Pathologist. 
 
 
 UNDER THE SUPERVISION OF 
 
 OFFICE OF EXPERIMENT STAT* 
 
 U. S. DEPARTMENT OF AGRICULTURE 
 
 WASHINGTON: 
 
 GOVERNMENT PRINTING OFFICE. 
 
 1915. . 
 
Issued February 9, 1915. 
 
 PORTO RICO AGRICULTURAL EXPERIMENT STATION, 
 
 D. W. MAY, Special Agent in Charge, 
 
 Mayaguez, P. R. 
 
 Bulletin No. 17. 
 
 FUNGUS DISEASES OF COFFEE IN 
 PORTO RICO. 
 
 BY 
 
 G. L. FAWCETT, 
 
 Plant Pathologist. 
 
 UNDER THE SUPERVISION OF 
 
 OFFICE OF EXPERIMENT STATIONS, 
 
 U. S. DEPARTMENT OF AGEICULTURE. 
 
 WASHINGTON: 
 
 GOVERNMENT PRINTING OFFICE. 
 
 1915. 
 
PORTO RICO AGRICULTURAL EXPERIMENT STATION. 
 
 [Under the supervision of A. C. True, Director of the Office of Experiment Stations, 
 United States Department of Agriculture.] 
 
 Walter H. Evans, Chief of Division of Insular Sations, Office of Experiment 
 
 Stations. 
 
 STATION STAFF. 
 
 D. W. May, Special Agent in Charge. 
 P. L. Gile, Chemist. 
 G. L. Fawcett, Plant Pathologist. 
 C. F. Kinman, Horticulturist. 
 R. H. Van Zwaluwenbubg, Entomologist. 
 T. B. McClelland, Assistant Horticulturist. 
 J. O. Cabrero, Assistant Chemist. 
 W. E. Hess, Expert Gardener. 
 C. Alemar, Jr., Cleric. 
 (2) 
 
LETTER OF TRANSMITTAL. 
 
 Porto Rico Agricultural Experiment Station . 
 
 Mayaguez, P. R., October 15, 191 4- 
 Sir: I transmit herewith a manuscript on Fungus Diseases of 
 Coffee in Porto Rico. 
 
 The seriousness of these troubles from the standpoint of one of the 
 leading industries of Porto Rico justify the studies herein set forth, 
 and the methods suggested for combating the diseases, which are 
 now causing enormous losses, should be widely disseminated among 
 the planters of the island. 
 
 I respectfully recommend that this manuscript be issued as Bul- 
 letin Xo. 17 of this station and that it be published in both English 
 and Spanish. 
 
 Respectfully, D. W. May. 
 
 Special Agent in Charge. 
 Dr. A. C. True, 
 
 Director Office of Experiment Stations, 
 
 U. S. Department of Agriculture, Washington, D. C. 
 
 Recommended for publication. 
 A. C. True, Director. 
 
 Publication authorized, 
 D. F. Houston, 
 
 Secretary of Agriculture. 
 (3) 
 
CONTENTS. 
 
 Page. 
 
 Introduction 7 
 
 Leaf rot or thread blight (Pellicularia Icoleroga) 8 
 
 Leaf spot (Stilbella Jlavida) 11 
 
 Root diseases 15 
 
 Berry spot ( Cercospora coffeicola) 21 
 
 Studies of the spot fungus 26 
 
 Miscellaneous diseases 27 
 
 Summary 29 
 
 (5) 
 
ILLUSTRATIONS 
 
 Page. 
 Plate I. Coffee branch attacked by thread blight {Pellicularia koleroga), show- 
 ing characteristic suspension of leaves by threads of the fungus 8 
 
 II. Coffee leaves attacked by the leaf spot fungus (Stilbella fiavida) 8 
 
 III. Fig. 1. — Coffee tree attacked by the root disease fungus (Rosellinia sp.) 
 
 Fig. 2. — Imperfect form of root disease fungus (Dematophora sp.) on 
 Petiveria plants 16 
 
 IV. Coffee leaves attacked by the zonal leaf spot (Cephalosporium sp.), 
 
 showing upper and lower surfaces 16 
 
 V. Trunk of coffee tree with Fusarium disease produced by inoculation.. 24 
 VI. Root of coffee tree. Roughened bark due to nematodes. Roots 
 
 killed by "white " root fungus 24 
 
 VII. A. — Spot on leaf showing fruiting bodies of Stilbella fiavida. B. — En- 
 larged head of fruiting body of Stilbella fiavida. C and D . — Threads 
 
 of Pellicularia koleroga, showing branching 24 
 
 VIII. A. — Ascus and spores of Rosellinia sp. B. — Hyphae and spores of 
 
 Dematophora sp. C. — Hyphae and spores of Cephalosporium sp .. . 24 
 
 (6) 
 
FUNGUS DISEASES OF COFFEE IN PORTO RICO. 
 
 INTRODUCTION. 
 
 Fungus diseases of coffee are common in Porto Rico, and in 
 many instances destructive. The reduction in the yield and con- 
 sequent loss which result from their activity are not definitely 
 known, but they must be large. The small crop of many plan- 
 tations is no doubt due to the constant though often inconspicuous 
 defoliation and killing of the trees which they cause. It is desired 
 not only to attract attention to these diseases, but to suggest such 
 means of getting rid of them as have been shown by experience to be 
 of value. The excellent but costly methods of fighting disease, such 
 as those practiced in the case of the intensively cultivated citrus 
 fruits, are not to be recommended so unhesitatingly for coffee, the 
 profits from which are not so great as to make the cost of production 
 of small importance. Moreover, coffee is often grown in extended 
 plantings in mountainous country where it receives so little cultiva- 
 tion as to be hardly more than a wild plant. Where these conditions 
 exist it is not likely that any more attention will be given the diseases 
 than in the past. But there are other, usually smaller, plantations 
 where it would seem worth while to take advantage of any measures 
 of value in keeping up their present good condition, either by fight- 
 ing those diseases that have already become established or keeping 
 them from the healthy young plantings. 
 
 It is expected also that a publication of this nature will be of value 
 in dispelling the idea entertained by some planters that the diseases 
 of this plant have been so neglected as to be practically unknown, but 
 only await scientific study to be entirely done away with. Some of 
 the coffee diseases of Porto Rico are common to other coffee-growing 
 countries, and were first described many years ago. Suggestions as 
 to their control have been made from time to time by laboratory 
 workers, but apparently the methods have never been tried by grow- 
 ers, else such value as these suggestions possess would have been pre- 
 viously realized. The knowledge of the life history of the parasitic 
 organisms causing the diseases has led to no entirely successful 
 method for their control, if this is taken to mean some way in which 
 the diseases may be very easily eradicated without some expense and 
 careful attention in application. 
 
 (7) 
 
8 
 
 LEAF ROT OR THREAD BLIGHT i Pellicula ria koleron 
 
 This is quite common in all plantations except those at higher alti- 
 tudes. Of all the coffee diseases it is perhaps the most conspicuous, 
 its presence being usually indicated by the blackened leaves which, 
 after having been attacked by the fungus, are held suspended for 
 some time by its threads (PL I). It has been reported from various 
 places in India and the East Indies and recently from Surinam, and 
 no doubt is foimd throughout the coffee-growing regions of the "West 
 Indies. A disease similar in character has also been reported from 
 Venezuela, where it is known as " candelillo " : the real leaf rot which 
 has been reported from that country is also known by that name. 
 
 On examination, the threads of the fungus which cause the disease 
 will be found on the lower side of the twigs where at each pair of 
 leaves it branches to form a thin web covering their undersurfaees. 
 On the newly attacked leaves this web is white, but later it becomes 
 brown. The leaves on which the fungus has obtained a better foot- 
 hold and which have turned black often have a finely mottled ap- 
 pearance, due to the thickening of the web at the points where it is 
 attached to the leaf. A further stage is represented by the develop- 
 ment of the web into a parchment-like membrane completely con- 
 cealing the lower side of the leaf. This may be removed with a 
 needle or knife point " like a piece of gold beater's skin." The webs 
 correspond to the feeding form of the fungus, serving to absorb food 
 material from the leaves: the threads to the "traveling" form, by 
 the extension of which along the stems and branches in the course of 
 growth it reaches fresh material on which to feed. The threads 
 which are at first white become brown after a time, break and fall 
 away, but fragments often remain, sometimes concealed by the bark. 
 which serve as new sources of infection. When examined micro- 
 scopically the dense places are seen to be made up of flattened, much 
 branched threads, which besides acting as holdfasts may also serve 
 to draw food material from the leaf, although the threads which 
 penetrate the leaf soon after it is attacked are probably more impor- 
 tant in food absorption. Xo spores or reproductive bodies have been 
 found in the Porto Pican fungus. The vegetative hypha? of the 
 webs are much branched and interlaced, the branching being often 
 at right angles. (PL VII, C.) 
 
 The fungus avoids the sunlight, never growing on those parts of the 
 tree which are exposed to the direct rays. Possibly this habit enables 
 it to live on and injure trees from which the shade has been removed. 
 It must have a moist atmosphere for active growth. During the 
 drier months it remains quiescent, the affected leaves drop off. and the 
 plantation may appear quite free from the disease, but enough of the 
 
 1 See also U. S. Dept. Agr., Jour. Ast. Research, 2 (1914>, No. 3, p. 231. 
 
'-_.--. 
 
Bui. 17, Porto Rico Agr. Expt Station 
 
 Plate II. 
 
 Coffee Leaves Attacked by the Leaf Spot Fungus (Stilbella flavida). 
 
fungus remains to serve to reinfect the trees when the rains become 
 frequent. Apparently it is favored by high temperatures, as it is 
 less common in the cooler higher elevations where more favorable 
 conditions prevail as to moisture than in the warmer though some- 
 what drier low lands. It spreads from one part of the tree to another 
 by growth, and in the same way to other plants and coffee trees in 
 contact with the diseased coffee trees. To other trees, however, some 
 distance away it is usually communicated by the fungus-infested 
 leaves dropping or being carried by the wind and adhering to any 
 moist leaf or stem on which they happen to fall, the fungus then 
 sending out threads which securely glue the leaves to their new host. 
 Each such leaf serves as a center of infection. That the diseased 
 leaves can not adhere so well to dried surfaces is one reason for the 
 disease not spreading in dry weather. There is apparently no other 
 way in which this fungus is distributed, and for this reason it would 
 seem to be greatly handicapped in comparison with some spore-bear- 
 ing fungi. It is, however, so widely distributed and has such a way 
 of appearing suddenly in unexpected places that it would seem as 
 though it possessed some other more effective though unapparent 
 means of distribution. 
 
 Besides coffee, the author has found this fungus on sour orange, 
 the wild vines Luff a agyptica and Cucumls angurku and the culti- 
 vated ornamentals Hibiscus and Croton. It is probably able to at- 
 tack these plants only under very favorable conditions, as they usu- 
 ally remain free from the disease even when surrounded by infested 
 coffee trees. The fungus also attacks the coffee berries, about one- 
 third of which are found to have blackened grains, the large propor- 
 tion of such grains indicating that some of the injury is due to 
 Pellicularia. In any event the number of berries attacked is so small 
 that as a berry disease it is of little importance. The loss occasioned 
 by this disease is that which results from the destruction of green 
 leaf tissue, and through this the lessened yield of berries. It is prin- 
 cipally a leaf parasite, but also causes the death of young branches, 
 which often die after defoliation. When the branch is not killed it 
 can not again bear leaves until new growth has been made. The 
 tree must be weakened and the yield correspondingly reduced by 
 the loss of foliage. What the loss from this source may be it is im- 
 possible to know, but if proportionate to the percentage of leaves 
 killed it would equal more than one-fourth in some trees noticed. 
 The loss of leaves is ordinarily much less and frequently many trees 
 escape infection. The loss in yield of berries from this source in most 
 plantations is not large. It has never been observed to kill the trees. 
 Like the " mancha de hierro," it is rarely found on poor, half-starved 
 trees for the reason, no doubt, that such trees usually are in rather 
 dry situations and have less foliage. 
 
 71478°— 15 2 
 
10 
 
 Various remedies have been tried. The gathering and burning 
 of the diseased leaves sometimes recommended gave poor results. 
 Enough of the fungus remains on the stems to serve to reinfect the 
 plant so that it is soon as badly diseased as before. The lime-sulphur 
 sprays, of which both the boiled and unboiled were used, were in- 
 effective, as was also the sulphur alone applied as powder. Bordeaux 
 mixture is really effective. 1 The fungus can not grow on a leaf 
 covered with this spray, and it adheres better than the other fungi- 
 cides, especially when made up with twice the usual amount of lime. 
 Owing to the frequent and heavy rains of the wet season even this 
 spray is washed off to some extent after a few days. In attempting 
 to increase the adhesion various substances were added to the mix- 
 ture, including borax, but the ordinary mixture with merely an extra 
 amount of lime was found to be better than any of these. In the 
 use of any spray material difficulties are met with, among which is 
 that of training the peon to direct the spray so as to cover the lower 
 sides of the leaves and to be thorough in the work, leaving no un- 
 sprayed, diseased leaves to serve as centers of infection. On many 
 of the trees reinfection takes place from the pieces of fungus threads 
 which the spray has missed or which have been partly concealed 
 under the bark, making necessary repeated sprayings if the trees are 
 to be kept clean. It is possible to destroy the fungus entirely on 
 some trees by one spraying and to prevent the infection of healthy 
 trees to a large extent, but to exterminate the disease even with re- 
 peated sprayings is difficult. The work of one year seemed to indi- 
 cate that spraying furnished excellent means of checking the dis- 
 ease, but further work has shown it to be less satisfactory than it first 
 appeared. To open up the trees to the wind and air by felling the 
 shade could only have a bad effect on the coffee and is not to be 
 recommended. 
 
 As the nearest approach to a good way of controlling the disease 
 Bordeaux mixture made up with 4 pounds of copper sulphate and 
 8 pounds of unslaked lime or 16 pounds of air-slaked lime to 50 
 gallons of water applied as spray to the underside of the leaves is 
 recommended. In no event should a larger area be treated than can 
 be conveniently looked over from time to time in order to note any 
 
 1 In case Bordeaux mixture is to be used in any except very small quantities it will 
 be well to make up stock solutions of tbe required ingredients, and take from these from 
 time to time as needed. In this way it will be always possible to have a freshly made 
 up and effective solution, that having been made up for some time spoiling. The 
 ordinary mixture, 4 : 4 : 50 formula, is made by dissolving 8 pounds of the copper 
 sulphate in 25 gallons of water. The lime and water for the other stock solution is 
 made by slaking S pounds of live lime, using enough water to form a thin paste and 
 adding to 25 gallons of water. The Bordeaux mixture is made by taking one part of 
 each of the stock solutions, two parts of water, and agitating the mixture thoroughly. It 
 is often convenient to make the mixture in the spray pump. The formula used in the 
 work with coffee differs from the above in having twice the amount of lime, which has 
 the effect of making It adhere somewhat better to the foliage. 
 
11 
 
 reappearance of the disease and resprayed when found necessary. 
 Picking the leaves before the spraying will probably be of some 
 assistance if care is taken to remove as carefully as possible all the 
 threads on the twigs, using for the purpose the cheaper labor some- 
 times available for picking the berries. 
 
 LEAF SPOT (Stilbella flavida). 
 
 This disease does not seem to be known in Porto Rico by any 
 definite common name, being merely referred to as a spotting of the 
 leaves. In Venezuela and apparently elsewhere on the continent 
 and Central America it is called " mancha de hierro," but no doubt 
 this term is made to include other small spots of both fungus and 
 insect origin. It is quite generally distributed throughout the coffee- 
 growing region of America, having been reported from Mexico, the 
 Antilles, and Brazil. In Porto Rico it is found principally in the 
 higher altitudes, where it is favored by excessive rainfall. Lower 
 down it is found near streams and where it is sheltered from winds 
 and afforded a moist atmosphere during part of the year. It is more 
 dependent on moisture than other coffee fungi, being unable to infect 
 new leaves or to form new fruits except under conditions of extreme 
 humidity. 
 
 The disease is characterized by the occurrence on the leaves of 
 small spots usually circular in outline, but sometimes ovoid along 
 the- veins. (PI. II.) The newer ones are very dark, the older ones 
 light colored. The spots are usually about 6 millimeters in diame- 
 ter, although many of the older ones become 12 to 13 millimeters in 
 diameter. Sometimes they fuse or give entrance to other tissue- 
 destroying fungi which infect the intervening tissue, producing spots 
 of considerable size. The worst affected leaves have from 30 to 40 
 or even more spots, so that a large proportion of the leaf tissue is 
 destroyed. On the upper surface of many of the spots and also to 
 some extent on the lower surface may be seen hair-like projections 
 from 1 to 4 millimeters long of a yellowish color, each bearing at the 
 end a head so that they resemble minute pins. This is the reproduc- 
 tive or fruiting stage of the fungus. (PI. VII, A and B.) Each 
 spot produces a continuous crop of these hairs so long as weather 
 conditions are favorable. The total number at any time is small 
 and in an entire season but from 20 to 50 are produced in each spot- 
 judging from the number of old filament bases. The largest number 
 observed was 70 in a spot of 7 millimeters diameter. As the leaf 
 spots become older, growth having stopped for any reason, such as 
 the advent of the dry season, the diseased tissue falls away, leaving 
 numerous circular openings in the leaf. In other leaf diseases the 
 dead tissue remains. 
 
12 
 
 Sometimes the fungus attacks young stems, where it causes con- 
 spicuous scars and so weakens the points affected that they are easily 
 broken by the wind. The berries also are attacked, a slight discolo- 
 ration of the grain being frequently caused. 
 
 The microscope shows the filaments, which are solid, not hollow, as 
 sometimes stated, to be made up of the fine fungus threads which 
 are somewhat branched in the upper part to form the head. The 
 ends of the threads are swollen and have sometimes been mis- 
 taken for spores when seen in cross section (PL VII, B), and de- 
 scribed as such. No real spores have ever been found in any of the 
 numerous specimens examined. The fungus is distributed by the 
 heads at the ends of the filaments being caught by the wind or rain- 
 drops and carried to near-by leaves, a process facilitated by the heads 
 becoming loosened in the older filaments through the formation of 
 cavities or "lacunas" near the point of attachment. (PI. VII, B.) 
 The head is soon fastened to the leaf on which it happens to fall by 
 the numerous threads which it sends out at the point of contact. 
 Within less than a week a dark circular spot is formed and new fila- 
 ments appear and new loosely attached heads are formed on these by 
 means of which the spread of the disease is continued. Apparently 
 this fungus has no other way of propagating itself, and the writer 
 has not found any other stage of Stilbella flavida, all inoculations 
 into coffee with suspected forms resulting negatively. Among other 
 fungi used in such inoculations was one which answers so fully to 
 the descriptions of Sphcerostilbe flavida 1 that it may be consid- 
 ered identical with that fungus. As Sphcerostilbe flavida is some- 
 times referred to as the perfect stage of Stilbella flavida, as full use 
 as possible was made of the small amount of material available . This 
 fungus was first found here on a berry, which, with others bearing 
 Stilbella spots, had been sterilized externally and placed in a moist 
 chamber. Later the same fungus was found on a coffee berry still 
 attached to the tree, where several of the Nectria-like fruits had de- 
 veloped in a spot made by Stilbella. These were studied more fully. 
 Direct inoculations of the perithecia into coffee berries did not take. 
 In drop cultures of the ascospores a Cephalosporium developed. In 
 pure cultures from single ascospores this fungus and later a Fusa- 
 rium developed. This material was used in inoculation both into 
 the berries on the tree and into very thoroughly disinfected and 
 washed berries in flasks. A slight infection resulted on the unpicked 
 berries. On those in the flasks perithecia identical with those from 
 which the ascospores had been taken developed. But in no case did 
 Stilbella flavida result from the inoculations. Those made into 
 leaves did not take. The work failed to show any relation between 
 the fungus used in the inoculations and Stilbella flavida. Of the 
 
 iMassee, Roy. Bot. Gard. Kew, Bui. Misc. Inform., 1909, No. 8, pp. 337-341. 
 
13 
 
 large number of berries affected with Stilbella examined no others with 
 Sphaerostilbe were found, so that even if it were a stage of Stilbella 
 it could play a very small role in the distribution of the disease in 
 this island. If the fungus is a Basidiomycete, as assumed with some 
 reason by Spegazzini, 1 it was not found to possess such a stage. 
 
 It is of interest to note that, although the coffee plant is the princi- 
 pal host of this fungus, numerous other plants are also affected to 
 some extent. The writer has found it on such unrelated host plants 
 as the orange, mango, Begonia, various ferns, several of the coitres 
 (Commelina spp.), and guava (Inga vera), and bejuco de carro 
 (Velia sicyoides) , and have noticed the spots, but not fruits, on the 
 yautia, banana, and also on several wild plants. The coitres, which 
 are perhaps most affected, and the ferns and other plants of low habit 
 of growth form in many places a continuous ground covering and 
 catch the greater part of the falling propagative bodies which escape 
 the coffee leaves, and are hence peculiarly subject to the disease. 
 They are apparently able to communicate it to unaffected plants of 
 the same kind and doubtless also to healthy coffee plants. There were 
 noticed places where the coffee was not attacked until several weeks 
 after the ground plants had become infected. 
 
 When first taking up the study of coffee diseases in Porto Rico 
 the " mancha de hierro " appeared of small importance, for the reason 
 that the area affected is so restricted by climatic conditions. But the 
 regions of the island most affected produce the best coffee, and if it 
 were not for this disease they would give larger yields. The injury 
 to the trees is not so much in the actual amount of the leaf tissue 
 destroyed, although this may amount to one-fifth or even more of the 
 entire amount in the worst cases, but in the defoliations which take 
 place after a time. The diseased leaves drop sooner than those not 
 affected, and owing to the weakened condition of the tree are not soon 
 replaced. After the first severe attack the base of each tree may be 
 seen to be surrounded by a pile of green leaves several inches deep. 
 The disease never kills the trees. They live on with scanty foliage 
 and are able to put forth some new growth and bear a small amount 
 of berries each year. 
 
 The decrease in yield following an attack of the leaf spot is marked. 
 In one experimental plat, where a record of the yield had been kept 
 for some years, it was found to be 75 per cent. In this case the dif- 
 ference between the trees before and after the attack was such as 
 accompanies the loss of the greater part of the foliage. 
 
 The fungus, Stilbella, also attacks the berries. As mentioned 
 above, however, it does not do very much harm to the fruit — much 
 less, in fact than that caused by the Cercospora fruit spot — for it 
 
 iRev. Facult. Agron. y Vet., La Plata, 2 (1896), No. 22, p. 339. 
 
14 
 
 never causes the fleshy part of the berry to adhere to the parchment, 
 in this way making the pulping more difficult. Out of several lots of 
 berries examined, of which all were affected by Stilbella, a varying 
 number, from 6 to 18 per cent, were so badly affected that the dis- 
 coloration could not be removed in the process of polishing to which 
 coffee is subjected in preparation for the market. 
 
 An experiment in the control of this disease was begun at the sub- 
 station, La Carmelita, to test the efficiency of gathering and destroy- 
 ing the diseased leaves, a method recommended in some publications 
 on this subject. Ten trees in one of the worst diseased areas were 
 selected for this purpose and the leaves with Stilbella spots removed, 
 two rows of the surrounding trees being similarly treated to prevent 
 too immediate reinfection from other trees. The effect of the leaf 
 picking on the prevalence of the fungus was roughly determined by 
 finding the relative proportions of diseased and healthy berries, both 
 being counted, in the trees of the plat and in an equal number of 
 those outside. The proportion of diseased berries in the trees of the 
 plat in the crop immediately following the first picking of leaves 
 was 38 per cent; in the outside trees, 10 per cent. During the year 
 the leaves were picked at intervals of three months. At the end of 
 the year the percentage of diseased berries in the trees with picked 
 leaves had declined to 16 per cent, but in the outside trees had in- 
 creased to 32 per cent. It is probable that an equally large increase 
 of Stilbella-affected berries would have been found in the trees from 
 which the diseased leaves were picked if it had not been for this 
 treatment, the disease having made great headway in all parts of 
 the plantation. 
 
 Further work in combating the disease was made impossible by 
 a change in the management of the plantation where the work was 
 being carried on. However, such results as have been obtained 
 would indicate that the disease might be successfully combated by 
 removing the diseased leaves. No doubt the defoliation so produced 
 is as bad for the tree as that caused by the fungus, but if the work 
 were carefully done the newly formed leaves would remain free 
 from infection, except as they might be gradually reached from trees 
 outside the treated area. The fact that the disease spreads com- 
 paratively slowly and that the diseased leaves are readily recog- 
 nized make this treatment more easily carried out. It would seem 
 that this slow and apparently impracticable method might be really 
 of value in combating the disease where the cheaper labor used on 
 some of the plantations is available. 
 
 Spraying with Bordeaux mixture will exterminate the fungus 
 if weather conditions happen to be favorable, but it is almost useless 
 where the disease is most prevalent because of the frequent rains. 
 The fungus can not infect leaves that are not moist much of the 
 
15 
 
 time; and when the leaves are dry, the time that Bordeaux would 
 be most effective by adhering best, the disease is at a standstill, as 
 any of the heads which happen to fall on such leaves do not germi- 
 nate even if they adhere. The violent downpours soon wash the 
 fungicide from the smooth upper surfaces of the leaves, where it 
 must adhere to be of any effect. Moreover, the hillsides are so steep 
 in many places that only knapsack sprayers could be used, and these 
 only with difficulty. In case spraying is resorted to, it will be of 
 most value when applied to the healthy trees near the diseased 
 ones or to those less severely attacked, for the reason that the spray 
 will prevent the infection of the leaves to which it adheres, though 
 having no effect in preventing the formation of new propagative 
 bodies on the already existing spots. 
 
 The disease does not spread with great rapidity. In one case 
 observed it progressed about 200 yards in one year. Many plantings, 
 probably newer ones, are free from this pest, although climatic con- 
 ditions are such that it could do much damage if once it obtained 
 foothold. After it appears in such places it is merely a matter of 
 time until the entire field is affected, and it is under these condi- 
 tions, when only a small area is affected, that it can be combated to 
 most advantage. Unless prevented, it will extend down the mountain 
 slopes until it reaches drier conditions, the only obstacles to its prog- 
 ress in other directions being strips of forest or grass land or an 
 especially exposed or unshaded slope. The coffee of the " altura " 
 requires less shade than that of the lower lands, but even there it is 
 seldom that there is an excess of shade. If such exists, it could be 
 lessened to advantage, for anything making for drier conditions is 
 unfavorable to this fungus. To cut the shade away entirely, how- 
 ever, would be a remedy worse than the disease, and one which no 
 experienced grower would try. 
 
 ROOT DISEASES. 
 
 In many plantations there are to be found places where all the 
 coffee trees have died out, the largest of such treeless areas covering 
 an acre or more. These areas are usually well marked, being sur- 
 rounded by healthy trees. The death of the trees is due to the action 
 of certain soil fungi which attack the roots, usually the upper ones, 
 and the base of the trunk. The first indication that a tree has been 
 attacked is the drooping and yellowing of the leaves, which later fall, 
 beginning with those of the lower branches. The roots of the trees 
 will be found to be well covered by the thread-like growth of the fungi 
 and partly decayed. There are two types of the disease, which may 
 be classified for convenience according to the color of the accompany- 
 ing fungi as the black (Rosellinia sp.) 1 and white root diseases. The 
 
 1 Apparently Rosellinia ounodes. 
 
16 
 
 black type of the disease, which is perhaps the more common, is the 
 one referred to in this bulletin unless otherwise stated, as it has been 
 possible to study it more thoroughly (PI. Ill, fig. 1). 
 
 The disease having made its appearance in one or more trees ex- 
 tends to the surrounding coffee trees. Its advance, which is very 
 slow, is marked by the dying or dead coffee trees at the edge of the 
 diseased area. In one case, when it was possible to determine the rate 
 of progress fairly readily because of the disease attacking the thick 
 herbaceous undergrowth, it covered from 10 to 12 feet in one year. 
 Usually the growth is less rapid than in this instance. The only 
 things which retard or stop its progress seem to be excessively dry or 
 excessively wet soils, natural barriers, such as brooks, and the scarcity 
 of food material (decaying vegetation) in the soil. The conditions 
 favoring its growth are those provided by moist shaded soils, which 
 usually offer an abundance of food material. Unfortunately, these con- 
 ditions are also those favorable to the coffee tree, so that the disease 
 often does most harm among the best trees, the sun-exposed dry slopes 
 of poor coffee plantations remaining quite free from the trouble. In 
 more than one instance it has seemed to start with the decay of a 
 stump or tree trunk. As the fungus is known to live on dead vege- 
 table matter, it is probable that these stumps furnish such abundance 
 of food material that it becomes strong enough to attack living plants, 
 whereas ordinarily it merety makes use of the usual decaying mate- 
 rial covering the soil in well-shaded places. 
 
 In the black form of the disease that part of the trunk- just above 
 the surface of the ground becomes covered for a few inches with a 
 thin brown closely adhering coating of the fungus mycelium soon 
 after being attacked. On the roots and parts of the trunk below 
 the surface the mycelium is gathered more into strands of a brown 
 color which later becomes black. Below the thin outer bark the 
 threads form a nearly solid layer, thickly grown together. From 
 this there extends into the bark and wood root-like branches less than 
 1 millimeter thick. On cutting away the bark and wood these ap- 
 pear as small black dots and lines, according to the angle at which 
 they are cut. These form one of the most characteristic features of 
 the disease. In trees recently killed the fungus will be found to have 
 passed but little deeper than the inner bark, although in old stumps 
 it may penetrate 2 or 3 centimeters. The attack is usually near the 
 surface of the ground, involving the trunk at the surface and some- 
 times also the uppermost roots. It later advances downward for a 
 few inches, but the deeper roots usually remain uninjured. Occa- 
 sionally on that part of the fungus growth near the base of the trunk 
 there are formed numerous small hair-like projections 1 to 3 milli- 
 meters long. These are light colored at the tips, close together, and 
 have a somewhat brush-like appearance. At first they are evenly 
 
Bui. 17, Porto Rico Agr. Expt. Station. 
 
 Plate III. 
 
Bui. 17, Porto Rico Agr. Expt. Station. 
 
 Plate IV. 
 
17 
 
 distributed, but later appear in clusters beneath which are formed 
 wart-like outgrowths (sclerotia). The hair-like projections bear 
 minute spores which doubtless serve to distribute the fungus to some 
 extent. (PL VIII, B.) This stage of the fungus (Dematophora) is 
 quite common, though produced less frequently on coffee than on 
 many other plants. (PI. Ill, fig. 2.) In the sclerotia are sometimes 
 formed other kinds of reproductive bodies that are characteristic of 
 the genus Kosellinia. (PI. VIII, A.) This seems quite rare, as the 
 writer has found it but twice, once on a wild shrub (Piper sp*.) and 
 once on coffee. 
 
 Among other plants than coffee which this fungus attacks is anamu 
 (Petiveria alliacea), a weed quite common among the coffee. It was 
 observed to kill out a thickly growing area of this plant, a grass 
 (palmilla) taking its place. No other plant among the coffee has 
 been found to be injured except young guamas. Once when the fun- 
 gus escaped from pots of infected coffee plants it destroyed the 
 near-by growing ornamentals, Graptophyllum pictum, Panax plu- 
 matum, and Acalypha mosaica. It has been noticed once among the 
 trees and low growths at the edge of a clearing, attacking and killing 
 nearly all the plants with which it came in contact, among which, be- 
 sides the rose apple, were species of Miconia, Piper, and Palicourea. 
 all of shrubby habit. A Tradescantia, one of the common ground 
 plants in well-shaded coffee, covered the ground as soon as it was 
 cleared by the fungus. A fern (Adiantum sp.) seemed to be the 
 only plant able to resist its attacks except the large, thick-barked 
 guamas and mangoes. The fungus left a vegetation quite different 
 from that which it found, causing it to appear somewhat like that 
 of the clearings made for coffee. 
 
 Although acting slowly, the losses to coffee produced by root dis- 
 eases are probably not exceeded by those from any other cause. The 
 injury is greater because the better trees suffer most, especially in 
 the case of the black root disease. The fungus causing this disease 
 is distributed throughout the coffee-growing regions of the island, 
 not being limited by climatic factors as are some other diseases. The 
 places where the trees have been killed are often left for a long time 
 before replanting, and after the trees are reestablished it is several 
 years before they bear fully. Just how long before the ground be- 
 comes fit for replanting without treating the soil with some fungicide 
 has not yet been determined, but this probably depends on the amount 
 of food material available to the fungus in the soil. In one case 
 noticed the trees replanted where the vegetation had been killed two 
 years previously have not shown, during a period of eighteen months, 
 any sign of the disease. 
 
 Some experiments were made with the hope of finding an effective 
 way of controlling the disease. These have included ditching about 
 
18 
 
 the diseased areas, a method commonly recommended for this sort 
 of disease as a means of preventing the spread of the fungus to un- 
 infected areas, and the treatment of the soil with substances having 
 some degree of fungicidal action. The ditching seemed especially 
 advisable, because the fungus is superficial, never penetrating the 
 soil for more than a few inches. The substances added to the soil 
 included lime, sulphur, chloronaphtholeum, and copper sulphate. 
 These were selected as being fairly easily procured and quite cheap, 
 if not too great quantities should be necessary for their effective 
 use. Other substances used included potassium permanganate and 
 potassium bisulphite. The effect of breaking up the soil by means of 
 heavy hoes, a method quite common in cultivating coffee, was also 
 tried in some of the check plats and in all of the other plats. Pre- 
 viously to this cultivation all diseased trees and stumps and the 
 partly decayed vegetable debris common in such places were re- 
 moved. For the lime experiment the soil was first broken, after 
 which the lime was applied at the rate of 500 grams per square 
 meter, being thrown into shallow trenches and immediately covered. 
 The trenches being close together and parallel, the application was 
 thorough, no part of the surface being overlooked. The ground was 
 sprinkled with water to slake the lime and then worked with hoes 
 to mix it with the soil. Whenever a diseased tree had been re- 
 moved an extra amount of lime was added. Similar methods were 
 used in applying the sulphur, care being taken to mix it thoroughly 
 with the soil. Two areas were treated, one receiving 500 grams per 
 square meter, the other about one-fourth of this amount. The chlo- 
 ronaphtholeum, a petroleum distillate product of the same class as 
 carboiineum, was used in one of the worst diseased places. It was 
 applied at the rate of about 50 cubic centimeters per square meter, 
 being poured in 5 per cent solution into small holes which were 
 made about a foot apart. Later the ground was sprayed with this 
 solution and then worked over with hoes to secure more thorough 
 penetration. 
 
 During the three years since the experiment was begun no trees 
 have died in plats receiving lime and the heavier application of 
 sulphur. In the check plat adjacent to that receiving lime 6 per 
 cent of the trees have died, and about 3 per cent of the trees in the 
 plat with the smaller application of sulphur and in that receiving 
 the chloronaphtholeum. In a plat of anamii showing this disease 
 an application of chloronaphtholeum amounting to 100 cubic centi- 
 meters of the undiluted preparation and another with the excessive 
 amount of 450 cubic centimeters per square meter were made. The 
 heavier application stopped the disease without injuring the healthy 
 plants. The disease was unchecked by the lighter application, all 
 the plants in this plat being killed by the fungus. In any event 
 
19 
 
 treatment with preparations of this nature is not to be considered, 
 as it is ineffective if the smaller quantities are used and its cost 
 prohibits the use of large amounts. 
 
 Although the use of lime for this disease promised little, still it 
 had the advantage of being very cheap and readily procured be- 
 sides being often useful in its effects on the physical condition of 
 the soil. Moreover, if it is even of small merit in combating the 
 disease it is to be recommended, as, being already familiar to the 
 planters, they would use it in preference to other more effective but 
 less common materials. The good results obtained from its use in 
 these field experiments may be partly due to the disinfecting action 
 of the heat of slaking and possibly, also, to lessening the amount 
 of vegetable matter in the soil which could be used by the fungus 
 as food. That the heat generated by slaking may have had some 
 fungicidal effect is further indicated by the fact that when the 
 already slaked lime was used in the form of a thin paste at the 
 rate of 200 grams per square meter on a much-diseased plat of 
 Petiveria no effect in checking the progress of the fungus was to be 
 observed. The use of air-slaked lime is not to be recommended in 
 the case of the black root disease if it is wished to check the disease 
 at once by its application. Its effect will be good only as it tends 
 to improve the soil and hasten somewhat the decomposition of the 
 vegetable matter on which the fungus feeds. Such action in any 
 event will be slow. 
 
 The good results from the use of sulphur must be referred to its 
 fungicidal properties. In well-aerated soils sulphur dioxid is prob- 
 ably formed, and hydrogen sulphid in soils excessively moist. Both 
 of these substances have weak action as disinfectants. But it is not 
 unlikely that their continuous production through several months 
 would serve at least to prevent the growth of the fungus and perhaps 
 to destroy it. Additional evidence that some such action exists was 
 obtained by mixing sulphur in the soil with which a trench about 
 4 inches deep and of equal width was filled, using about 15 grams 
 of sulphur to each meter of the trench. The fungus has killed the 
 plants up to the sulphured soil, but during the entire year on which 
 it has been observed has not passed to the healthy plants on the other 
 side. In part of the ditch which received no sulphur the fungus has 
 passed over and destroyed the Petiveria plants. 
 
 In the three years since this work was begun 2 per cent, or 6 out 
 of 317, trees have died in the treated plats, all of these being in the 
 plats receiving the smaller applications of sulphur and chloronaph- 
 tholeum. None have died in those treated with the other disin- 
 fectants, but the results from the treatment with these substances 
 are of little interest because of their cost. In the check plats which 
 were merely cleaned and ditched 5 per cent, or 16 out of 334, trees 
 
20 
 
 have died. Although it is as yet impossible to arrive at definite con- 
 clusions, it would seem that treatment of the soil with some sub- 
 stance rendering conditions unfavorable for the growth of the fungus 
 was of practical value. 
 
 As to the cost of materials used, that of lime sufficient for 100 
 square meters is but 35 cents. The cost of sulphur at the rate used 
 in the experiment would be 10 times as much. However, it would 
 be worth while to use even such remedies if cheaper materials were 
 less successful. If begun while the diseased areas are not too large 
 the expense for such treatment would be small. 
 
 As copper sulphate is a substance which is injurious to plant life, 
 except in very small quantity, it was not thought desirable to apply it 
 so freely to the soil as the other substances used. Accordingly it was 
 applied only to the trees near those attacked by Rosellinia. A quan- 
 tity equivalent to 15 grams of the salt was sprayed about the base of 
 the trees. Within a few weeks the fungus had passed the sprayed 
 trees, killing all the Petiveria except near the coffee trees. The form 
 of the disease that remains in places where the fungus has passed 
 seems to be less virulent, probably because less well nourished. After 
 the copper salt has been washed out by rains the trees so treated will 
 probably be subject to attack from the fungus as soon as enough food 
 material accumulates to give it sufficient start. The spraying of the 
 entire surface with a solution of copper sulphate was tried, the spray 
 being of such concentration as to equal 25 grams of the salt per square 
 meter. This was found in an experiment on 8 square meters of land 
 badly infested with the black-root disease to be sufficient to check and 
 apparently to exterminate the fungus, which has not reappeared 
 during the year which has passed since the spraying. The cost for 
 the copper salt alone used at this rate amounts to 50 cents, at local 
 prices, for a quantity sufficient to treat 100 square meters. Where 
 the drainage is good, as on the clay hillsides, not enough of the copper 
 is retained in the soil to be harmful to vegetation. Under such con- 
 ditions and on soil suitably cleaned this is an effective remedy. Pos- 
 sibly a considerably smaller quantity of the copper salt would be 
 equally effective. However, since satisfactory results can be secured 
 by other means, the use of copper salts in controlling the disease is 
 not to be recommended. 
 
 The work carried on so far would indicate that cleaning the land, 
 ditching, and liming were of value in combating this disease. The 
 cleaning includes the taking up and removal of the diseased and dead 
 coffee trees. The usual custom of cutting off the tops of such trees 
 and leaving the stump to decay is bad. Such material, together with 
 piled-up leaves, branches, and other debris, half-decayed vegetable 
 matter which serves the fungus as food material, should be gathered 
 in the infested places and burned. Large stumps that can not be 
 
21 
 
 removed should be ditched about, if they occur in the diseased areas 
 that are to be treated, as they sometimes seem to harbor the disease. 
 The guava and guama, which are frequently killed by borers, leave 
 many such stumps, and for this reason these trees are undesirable 
 as shade trees. If the ground is to be broken up, which is an ad- 
 vantage if lime is to be added, this should be done immediately after 
 the cleaning. The ditches should be a foot wide and of somewhat 
 greater depth. Care should be taken to examine the bases of the 
 trunks of all the trees to be inclosed by ditches in order to make 
 sure that no diseased trees have been left inside from which the dis- 
 ease can be communicated to the others. Such an examination will 
 usually show some of the healthiest looking trees to be affected with 
 the disease, often being girdled just below the surface of the soil. 
 The length of time that such trees can live and bear fruit, after 
 having been girdled, is indicated by the fact that a coffee tree of 
 which the bark was removed for a space of 4 inches about the base, 
 the wound having been painted with carbolineum to kill any living 
 tissue from which growth might set up, lived for 23 months, bearing 
 one full and one partial crop. Any tree showing a diseased patch 
 near the crown should be removed. Ditching about the diseased 
 areas, together with the gathering and destruction of the diseased 
 trees and vegetable debris, constitutes the most important step in 
 controlling the disease. After the earth has been broken up unslaked 
 lime may be applied, as already described, care being taken not to 
 place it too close to the trees. If applied in the dry season it should 
 be sprinkled with water to slake it after mixing with the soil. It 
 is not likely that a quantity of unslaked lime less than that used in 
 the experiment (500 grams per square meter) would be effective. 
 
 To summarize, ditching is recommended as preventing the fungus 
 from passing from diseased to healthy trees; cleaning up vegetable 
 debris and removal of diseased or dead coffee trees and the addition 
 of lime or some other substance to the soil are measures of some value 
 in combating the fungus. The ditches should be cleaned out from 
 time to time and vegetable material prevented from accumulating 
 in the places affected with the disease. Such measures are of special 
 value where only a few diseased trees are found among otherwise 
 healthy plantings. "Where the centers of infection are too numerous 
 it may be useless to protect with ditches and even less so to use the 
 other sanitary measures mentioned above except, perhaps, the re- 
 moval and destruction of diseased trees as soon as observed. 
 
 BERRY SPOT (Cercospora coffeicola). 
 
 This spot of the berry is troublesome since it causes the fleshy 
 part of the fruit to adhere to the parchment, thus making the process 
 of preparation more difficult. It is also the cause, at least indirectly, 
 
22 
 
 of part of the injury to the grain which results in its being classed 
 as of lower grade. 
 
 The fungus causing this spot, Cercospora coffeicola* has been re- 
 ported from Central and South America. Doubtless it occurs 
 throughout the American coffee-growing regions. In Porto Rico it 
 is present to some extent in every plantation. Both leaves and berries 
 are affected by the disease. On the leaves it causes round spots, 
 varying from 6 to 10 millimeters in diameter, of a brownish color 
 somewhat lighter toward the center than at the edge. There are 
 rarely many on any one leaf, and so little harm is done by the fungus 
 as a leaf parasite as to be negligible. On the leaves, however, they 
 produce spores which serve to spread the disease and to carry the 
 fungus over from one crop to another. On the berries the largest 
 spots, those fastening the fleshy part of the fruit to the parchment, 
 almost always are found on the upper side. Any part of the fruit 
 may be attacked, the spots appearing at first as small brown dis- 
 colorations. They are especially common on the nearly ripe berries. 
 At the time of picking, the larger spots cover about half of the fruit 
 and are velvety with the spore-bearing outgrowths of the fungus. 
 
 The occurrence of the largest and worst spots on the upper or sun- 
 exposed side of the berries is to be explained by the fact that the spots 
 develop more rapidly in the somewhat riper tissue of that side, such 
 uneven ripening of the berry being caused by the direct exposure 
 each day to the sun rays. After the berries have become infected 
 this one-sided ripening takes place more rapidly, the berries being 
 black above with the Cercospora spot and still green on the underside. 
 Whether picked at once or left until thoroughly ripe the berry is 
 difficult of preparation and yields a somewhat inferior product. 
 That the riper tissue furnishes more favorable conditions for the 
 fungus is indicated by the more rapid development of the spots pro- 
 duced by inoculation into ripe berries, and the greater number of 
 spots developing on the nearly ripe tissue. 
 
 The uniformity with which the upper side of the berries is the part 
 most injured may account for the idea that such berries are injured 
 by hail. As a matter of fact hail is almost unknown at the eleva- 
 tions where the worst affected plantations are situated. Another and 
 better explanation quite commonly given is that the berries are 
 burned by sun either directly or intensified by the lens-like action of 
 drops of water, the disease itself being for this reason sometimes re- 
 ferred to as the " sancocho " of the berries. The presence of an or- 
 ganism, of proved parasitism, even in the earliest stages of the dis- 
 eased spots, makes these theories untenable. Sunlight is a factor of 
 importance, but only as it influences the development of the spots that 
 happen to occur on the upper side of the berries. These become con- 
 spicuous and are thought to be the only ones, the others remaining 
 
23 
 
 unnoticed. There is, however, a small amount of injury to fruits 
 and leaves, not due to parasites, which is to be ascribed to the heat 
 of the sun. On the leaves of unshaded coffee trees such injury is 
 represented by brown shriveled or sunken patches of cells, which in 
 their earliest stages are free from micro-organisms. Occasionally 
 such patches of injured cells form the center of yellowish areas. A 
 similar loss of chlorophyll on the upper side of the berries precedes 
 a premature ripening of the sun-exposed fruit. The berries that 
 ripen thus without being attacked by Cercospora are few in number. 
 That the injury in the case of the leaves is sun produced is indi- 
 cated by the absence of such " burned " tissue in the leaves of shaded 
 trees and the fact that those leaves with more nearly horizontal 
 or exposed positions are the ones affected. The injury by sunlight 
 is of interest in this connection as it favors infection of the fruits by 
 Cercospora. 
 
 Since the existence of a close relationship between the distribution 
 of the disease and conditions as to shade would make possible a prac- 
 tical means of control, it -was thought worth while to secure data 
 with regard to this. Accordingly samples were taken from each of 
 the gatherings made in two fields, one with fairly heavy shade, the 
 other exposed to the full sunlight. The quantity of berries examined 
 from each field varied from 132 to 199 liters per season, amounting to 
 from 15 to 20 per cent of the entire yield. The conditions as to soil 
 and slope were fairly uniform in each, so that the samples may be 
 taken as representing the quality of output fairly well. For two 
 years determinations were made of the proportion of Cercospora- 
 spotted berries, including spots of 1 millimeter in length or more. 
 It was found to vary according to the degree of maturity of the 
 samples examined, but reached for the last year 73 per cent for the 
 shaded and 70 per cent of such berries for the sun exposed. It was 
 concluded that, so far as the actual distribution of the disease goes, it 
 is not influenced largely by differences with regard to light. The 
 relative occurrence of the more troublesome or " sancocho " form of 
 the spots was quite different as, in the determinations made the fol- 
 lowing year, when there were taken only berries in which the spots 
 were sufficiently developed to be blackened and dried to the cascara, 
 it was found to be 16 per cent in the shaded and 27 in the unshaded 
 coffee. 
 
 It is well known that there is considerable variation in the quality 
 of coffee, one of the characters of an inferior grade being the larger 
 proportion of blackened and shriveled grains. As it was thought the 
 Cercospora spot of the berry might be the cause of such grains, at 
 least indirectly, the spotted berries, used in the work already men- 
 tioned, were subjected to the usual process of preparing the grain. 
 In the case of those used in the earlier work, where even slightly 
 
24 
 
 spotted berries were included, only those of which the parchment was 
 found, in the course of preparation, to be injured or seriously dis- 
 colored were selected for the final preparation, such parchment being 
 taken as corresponding to the larger, deeper Cercospora spots. 
 Those with sound parchment were not considered farther except to 
 be measured, as it was thought that sound berries or those slightly 
 spotted would give only good grains. Later it was found that some 
 of the injury to the parchment on the berries selected for final prepa- 
 ration was due to merely mechanical injury of the pulping machine. 
 Moreover, it was found that a certain proportion of the sound berries 
 contained bad grains. The results are for this reason not given in 
 full, although they give as uniform and pronounced differences in 
 favor of the product of the shaded trees as the later, more accurate 
 work. Of the grains with any sort of injury the percentage was 33 
 for the unshaded trees and 19 for the shaded the first year, and the 
 following year 29 and 20 per cent, respectively. 
 
 During the last season in which this work was carried on only the 
 more severely attacked berries or those in- which some effect on the 
 grain seemed possible were used, the slightly affected ones being 
 classed with the sound berries. The proportion of imperfect grains 
 of all sorts was determined, and of these the blackened ones were 
 separated and also determined. The results given in percentages are 
 as follows: 
 
 The effect of shade on the quality of the grain. 
 
 Shaded. 
 
 Un- 
 shaded. 
 
 All injured grains in good berries 
 
 Blackened grains in good berries 
 
 All injured grains in badly spotted berries. 
 Blackened grains in badly spotted berries . 
 
 Per cent. 
 
 4.5 
 
 2.0 
 
 27.0 
 
 9.0 
 
 Per cent. 
 19.0 
 11.0 
 45.0 
 36.0 
 
 It is evident that the berries more severely spotted by Cercospora 
 contain a greater proportion of bad grains than the unspotted, indi- 
 cating that the fungus does influence the quality of the grain unfavor- 
 ably. That the sound-appearing berries should give so much inferior 
 grain or any at all is surprising and not yet well understood. The 
 larger proportion of bad grains in the Cercospora-affected berries 
 from the unshaded field is in accordance with the greater abundance 
 of the more severely attacked berries generally apparent in such con- 
 ditions. The results show in every instance, whether from spotted 
 or sound berries, a smaller proportion of bad grains to be produced 
 from the shaded field. 
 
 It is clear that Cercospora has nothing to do with a considerable 
 proportion of the inferior grains, since they occur in sound berries. It 
 has never been found among the organisms isolated from the grains 
 
lul. 17, Porto Rico Agr. ExDt. Station. 
 
 Plate V. 
 
 Trunk of Coffee Tree with Fusarium Disease Produced by Inoculation. 
 
Bui. 17, Porto Rico Agr. Expt. Station. 
 
 Plate VI. 
 
 Root of Coffee Tree. Roughened Bark Due to Nematodes. Roots Killed by 
 "White" Root Fungus. 
 
Bui. 17, Porto Rico Agr. Expt. Station. 
 
 Plate VII. 
 
Bui. 17, Porto Rico Agr. Expt. Station. 
 
 Plate VIII. 
 
 A.— Ascus and Spores of Rosellinia sp. (X450). B.— Hyph/eand Spores of Dema 
 tophora sp. 1X450). C— Hyph/e and Spores of Cephalosporin sp. (X450). 
 
25 
 
 of these berries nor from those of the spotted berries. Such in- 
 jurious effect as it may have on the grain- must be due to the shrink- 
 age resulting from increased loss of water from the spotted fruits, as 
 well as the admittance through the weakened tissue, at the point 
 attacked, of other organisms which attack the grain directly. Of 
 these several have so far been found, the most common being a 
 Fusarium, identical, apparently, with this stage of the Sphaerostilbe, 
 already mentioned. The injury resulting from the spot seems to 
 depend on the age of the fruit attacked. When the infection takes 
 place on undeveloped fruits the resulting injury is greater, but if 
 the grain has begun to harden before the spot develops fully it may 
 escape injury. 
 
 Another source of the inferior quality of coffee from sun-exposed 
 fields is to be found in the " granos vanos," berries that seem to be 
 well filled out and good, but which are easily recognized at the time of 
 picking by their yielding readily to the pressure of the hand and also 
 by the dried, blackened pedicels. The name could be applied as well to 
 the sound-appearing berries with bad grains mentioned above, but for 
 convenience it is here used to indicate those the injury to which is due 
 to the supply of food material having been cut off. as shown by the 
 dead pedicels. Xot isolated berries alone, but often all on one branch 
 or the entire tree are affected in this way. The shriveled grain con- 
 tained in these berries remains free from fungi or bacteria for a long 
 time, the injury being clearly not due to these organisms. The black- 
 ened tissue of the branch at the base of the pedicels always contains a 
 (xlcesporium, and occasionally a Fusarium. But neither of these 
 fungi was found to be able to attack the tissue of healthy green 
 branches when tried out by inoculations with pure cultures. It would 
 seem that they are only able to attack weakened trees exposed to full 
 sunlight and subject to the unfavorable soil conditions accompanying 
 such exposure. Xot all the trees in unfavorable conditions produced 
 berries of this sort. What the proportion may be was not determined, 
 but it is only large in the first picking. This was omitted in the 
 earlier work, and in that of the last year the " granos vanos " were 
 separated out, so that the result can not be affected to any extent by 
 their presence in the samples. The hormiguilla (Myrmelachista sp.) 
 is to some extent the cause of these " empty berries," as it often injures 
 the base of the fruit-bearing branches and sometimes the pedicels, 
 thus cutting off their supply of food. 
 
 It is known that the soil in well-shaded places is more uniformly 
 moist than in more exposed situations, and no doubt the benefit of 
 shade in coffee is in part due to better soil conditions, especially with 
 regard to moisture. The soil in unshaded places becomes very dry in 
 the season of little rains and also very hard where of the clay type. 
 The unfavorable condition as to moisture is made worse by the pres- 
 
26 
 
 ence of grasses which always come in where shade is lacking. The 
 trees in these places are slender, with few branches and but little 
 foliage. The leaves of the branches on which berries set fall when 
 these are half grown and the branches begin to die back at the tips. 
 Where the blackening extends rapidly, killing the bark and pedicels, 
 the " granos vanos " result. The trees, which are dependent on new 
 branches for leaves and berries, are able to form but few of these. 
 A product of inferior quality results, owing to the action of certain 
 diseases of the fruits and grain, thus increasing the loss caused by 
 lessened yield. 
 
 STUDIES OF THE SPOT FUNGUS. 
 
 It is desired to include at this place something of the technical part 
 of the study. In attempting to determine definitely the nature of 
 the organism producing the spots, the earliest stages of the spots 
 were studied. The berries with such spots were first sterilized and 
 then introduced into the medium, or the spot itself was cut out and 
 introduced into the medium, using the usual precautions. When the 
 sterilization had consisted in washing the berries for three minutes 
 in 90 per cent alcohol, then placing them in 4 per cent formalin for 
 three minutes, and finally washing in sterilized water, the spotted 
 berries usually gave, in addition to a sterile gray fungus, a Glceo- 
 sporium, while the check unspotted berries similarly sterilized often 
 gave a Glceosporium. With less severe sterilization a Fusarium was 
 often obtained in addition to the above. Later work, with more 
 thorough sterilization, gave only the sterile fungus from the spots. 
 Both the Fusarium and the Glceosporium were tested in inoculations, 
 but without positive results. The sterile fungus was used in inocu- 
 lations, with the results that typical spots were produced on which 
 Cercospora spores later developed. In the checks small pieces of 
 sterile absorbent cotton of about the same size as the pieces of 
 mycelium were introduced into small wounds, the purpose being 
 rougbly to duplicate the conditions of the inoculation. No infection 
 resulted in the case of those checks, although the chances of such 
 infection from natural sources existed. No attempt to sterilize the 
 berries on the trees before this inoculation was made, and the results 
 showed it to be unnecessary. From the spots resulting from the 
 inoculation the usual gray sterile fungus was reisolated. 
 
 No spores of Cercospora were borne on the mycelium in artificial 
 culture. However, on some of the mycelium placed on the berries 
 but slightly introduced into the wound, abundant spores of Cerco- 
 spora were in one instance produced. The material used in the inocu- 
 lations of the following season was obtained from spores developing 
 on typical spots of the berries. The spores, because of their com- 
 paratively large size, are easily isolated from drop cultures. The 
 
27 
 
 germinating spores were transferred directly from the agar of these 
 cultures to the usual media. In every case the typical gray sterile 
 mycelium, similar in every way to that used in the inoculations of 
 the preceding year, resulted. This when inoculated into the berries 
 produced the usual spots from which it was reisolated, and there can 
 thus be no doubt as to the identity of the organism producing this 
 spot. An attempt was made to show that the spot on the berry could 
 be produced by spores from the leaf spots. When transferred di- 
 rectly from the leaves to the berries no infection resulted. Later 
 pure cultures from the spores of the Cercospora of the leaf were 
 obtained, as in the case of that of the berry. The resulting growth, 
 which was similar in every way to that in cultures of the berry 
 fungus, when inoculated into the berries, gave positive results, typi- 
 cal Cercospora spores later developing. 
 
 In conclusion it may be said that the spot of the berries produced 
 by Cercospora coffeicola, which besides interfering with the prepa- 
 ration by causing the flesh to dry and adhere to the berry also injures 
 the grain to some extent, may be largely prevented by the use of suffi- 
 cient shade, as, for example, that of sufficient density to prevent the 
 growth of grasses other than palmilla. Such shade is distinctly 
 favorable to the production of coffee free from inferior shrunken 
 grains. 
 
 MISCELLANEOUS DISEASES. 
 
 Of less importance but perhaps worth mentioning in any general 
 discussion of coffee diseases are the "zoned" leaf spot and a root 
 and trunk disease. The leaf spot is characterized by its tendency 
 to develop concentric rings, such rings being sometimes incomplete 
 at the outside of the spot, and often beginning as entirely separate 
 spots which increase until united with the central mass (PL IV). 
 On the underside of the older spots a thin white mold appears after 
 a while, which is condensed or massed in places. This bears the 
 numerous spores of the fungus (C ephalosporium sp.) (PL VIII, C.) 
 which has been shown to be the cause of the spot by isolation from 
 the beginning spots and by inoculations from pure culture. The 
 disease is common among the best coffee, seeming to prefer the young 
 and well-shaded leaves, and all the various species and varieties 
 cultivated at this station are subject to attack, though it is most 
 common on the "Ceylon Hybrid." It has been noticed on other 
 plantations but is nowhere abundant. 
 
 Another disease is easily recognized by the smaller diameter of 
 the affected part of the trunk owing to the bark drying up and 
 shrinking (PL V). After being diseased for a long time the bark 
 falls away leaving the wood exposed and the calloused outgrowths 
 at the edge of the healthy bark. If the diseased bark is cut away 
 
28 
 
 the wood will be found to be blackened as if somewhat charred. A 
 fungus, Fusarium sp., is always present in the diseased tissue, but 
 inoculations with pure cultures have failed to produce the disease. 
 It is communicated readily to healthy trunks by means of small 
 pieces of diseased material, and when thus transferred has shown 
 itself to be rapidly developing and destructive, soon killing the 
 living tissue for several inches above and below the point of inocu- 
 lation. 
 
 Infection appears to take place through wounds, as, for example, 
 the stumps left by cutting off part of the branches close to the ground. 
 It frequently accompanies the "white" root disease, attacking the 
 yet living trunk above the diseased roots. It seems probable that it 
 can attack the tree near the crown through small wounds such as 
 those made by the machete in weeding, but no clear evidence of this 
 has been found. The characteristic Fusarium was isolated from a 
 decorticating disease of coffee where all the trees were attacked at 
 some 2 or 3 feet from the ground. In this case ants and mealy bugs 
 were also present, so that the injury was probably due in the first 
 place to these insects. The decorticated branches with the enlarged 
 outgrowths of healthy tissue at the base of the branches occasionally 
 to be seen are no doubt the after effects of this form of the trunk 
 disease. 
 
 The foregoing includes all the commoner and more destructive 
 Porto Eican coffee diseases produced by fungi. One disease, that 
 caused by Hemileia vastatrix, which is said to have caused so much 
 damage to the cultivation of this plant in India and the East Indies, 
 does not occur here and has not been reported from any American 
 coffee-growing country. The threadworm Heterodera radicicola, is 
 often active in trees suffering from root disease, being found in such 
 cases at the upper edge of the diseased area at the base of the trunk 
 (PL VI). It was thought at first that it might be the real cause of 
 the white-root disease, but since specimens have been found free from 
 this worm there can be no necessary relation between the two. It 
 attacks the bases of the trunk, however, causing them to take on a 
 roughened, somewhat swollen appearance for a foot or so above the 
 soil. When cut into with a knife there may be seen, even with the 
 naked eye, the minute globular bodies of the adult females, by which 
 such diseased tissue is characterized. No real evidence that the trees 
 are really injured by this disease has been noticed. The character- 
 istic swellings caused on roots by this worm may sometimes be seen 
 on the fine roots near the surface. The heavy nature of most Porto 
 Rican coffee soils no doubt prevents it from becoming the pest which 
 it sometimes is elsewhere. 
 
29 
 
 SUMMARY. 
 
 (1) For leaf rot (Pellicularia koleroga) there has been found no 
 really satisfactory method of control. The benefit of repeated spray- 
 ings with Bordeaux mixture is lessened by the fact that the fungus 
 is not all killed even by repeated sprayings, enough remaining to 
 reinfect the trees after a time. 
 
 (2) For leaf spot (Stilbella flavida) Bordeaux mixture is really 
 effective, and it may be recommended to prevent the disease from 
 extending to healthy and productive plantings. 
 
 (3) Cercospora spot of the berries, which causes the more badly 
 affected berries to be pulped with difficulty, and also injures the 
 grain to some extent, is to be prevented in its worst form by provid- 
 ing sufficient shade, which by rendering less harmful this and other 
 sources of injury to the grain decidedly improves the quality of the 
 output. 
 
 (4) The root disease may be prevented from spreading by ditch- 
 ing, this being preceded by the removal and destruction of vegetable 
 debris, diseased trees, and stumps. It is apparent that the addition 
 of unslaked lime, sulphur, and some other substances to the soil 
 prevents the growth of the fungus causing the disease. 
 
 (5) Importance is to be placed on the use of preventive measures 
 to keep the still healthy younger plantings in good condition rather 
 than on attempts to exterminate the diseases among the older trees. 
 
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