iilii; L I B RARY OF THE U N 1VLR5ITY Of ILLINOIS NATURAL HISTORY SURVEY. CONTROL OF ELM DISEASES IN NURSERY ELM PLANTINGS J, C, Carter STATE OF ILLDIOIS Henry Horner, Governor Department of Registration and Education NATURAL HISTORY SURVEY DIVISION Theodore H, Prison, Chief Biological Notes No. 7 Urbana, May 10, 1937 Contribution from the Section of Applied Botany and Plant Pathology Leo R, Tehon, Botanist (Publication No, 305) -••.■' ■'., cooperation with nursery o;"mers« Both dormant and summer sprays and dusts have been used. For the entire period 1932-1936 one copper fxingicide (Corona Bordeavix) and four sulphur fungicides (Koloform, Kolodust, flotation sulphur dust, and dry wett- able flotation sulphur) have been used continuously on the same trees as summer sprays. In 1935 tests were begun with two nev/ copper fungicides (Instant Bordeaux and "Z-0") and one new sulphur fungicide (liquid lime sulphur). Instant Bordeaux and "Z-0" have been used both for dormant and for siammer sprays. Liquid lime sul- phur has been applied only as a dormant spray and has been follovred by summer appli- cations of Koloform and dry wettable flotation sulphur. These fungicides may be described as follovz-s: A, Copper fungicides, 1, Corona Bordeaux is a commercial, pre-mixed Bordeaux that only needs to be mixed with proper amo\«its of water to obtain required strengths. This fvmgicide, manufactured by the Corona Chemical Division of the Pittsburg Plate Glass Company, is composed of active ingredient (copper) of not less than 13 percent and inert in- gredients of not more than 87 percent, 2, Instant Bordeaiix is a recently developed Bordeaux that can be made very quickly and easily as needed by mixing blue vitriol (copper sulphate) powder and superfine hydrated lime with water in proper proportions. To prepare 100 gal- lons of 4-4-50 Instant Bordeaux, vreigh out 8 pounds of powdered copper sulphate and 8 pounds of superfine hydrated lime. Begin filling the spray tank with water, VJhen the tank is approximately one-fourth full, start the engine and keep it running until the tank is full. As soon as the engine is started, place the copper sulphate upon the intake strainer and wash it into the tank, Vrhen the tank is three-f ourtha full, place the superfine hydrated lime on the intake strainer and wash it into the tank. -2- Let the agitator run for approximately 1 minute after the tank is full. Instant Bordeaux is then ready to use. In general. Instant Bordeaux settles out more slowly than commercially prepared Bordeaux mixtures, 3, "Z-0," which is manufactured by the Nichols Copper Company, is a copper fungicide which contains copper equivalent to 26 percent in metallic form. It has been developed as a substitute for the Bordeaux mixture used on apples and has been found practical for general spraying of ornamentals. It can be used in dust form for truck crops. There is a gradual release of copper from"Z-0," which, it is claimed, makes it less harmful to treated plants than any other copper fungi- cides, B, Sulphur sprays, 1, Liquid lime sulphiir is a standard fvingicide used in orchard practice. We have used it only as a dormant spray, at the strength of 1 to 10 (1 part liquid lime sulphur to 10 parts water). The fall dormant was applied in October or Novem- ber and the spring dormant in March or early April, 2, Koloform is a sulphur dust, sold by the Niagara Spray and Chemical Company, which forms a spray when added to water. It is composed of active ingred- ient (sulphur) of not less than 54 percent and inert ingredients of not more than 46 percent, 3, Koppers Flotation Sulphur, manufacttired by the vrhite Tar Company of New Jersey, Inc, is an exceedingly fine sulphur dust which mixes readily with water and is used as a spray. It is composed of active ingredient (sulphur) of not less than 80 percent and inert ingredients of not more than 20 percent, C, Sulphur dusts, 1, Kolodust, manufactured by the Niagara Spray and Chemical Company, is -3- , j.i J J. r.i .i-...j. C Ui ^i'irl.i- very similar to Koloform but is applied as a dust. It is composed of active ingred- ient (sulphur) of not less than 87 percent and inert ingredients of not more than 13 percent. A portion of the sulphur in Kolodust and also in Koloform consists of highly colloidal sulphur produced by the adsorption of molten sulphur into Bentonite clay. 2, Koppers Flotation Sulphur Dust is similar to Koppers Flotation Sul- phur but is used as a dust. Methods The trees received three types of treatment, and ample provision was made for maintaining untreated trees as checks against the treatments. The types of treatment were as follows: 1, Pruning: Diseased parts of infected trees in test blocks were pruned out and destroyed. 2, Fungicides: Trees in test blocks were sprayed or dusted with the proper fungicides, 3, Pruning plus fungicides: Diseased parts of infected trees in test blocks were pr\med out and destroyed. After that, the trees in such blocks were sprayed or dusted with the proper fungicides. From the beginning of the work in 1932 until the fall of 1935, applica- tions of the liquid fungicides were made with the sprayers OTOied by the nurserymen at each place where a plot of trees was located. These sprayers varied from 50- gallon hand operated outfits to 100-gallon power outfits. But since the fall of 1935 all spraying has been done with a 100-gallon Bean Little Giant Duplex outfit. -4- \ :;t .-.i.t --rrt ••vr-: \-l sn^ '■■ ■''■f' •■'^•■•'" ■«';': '..r.i 'i-' x'f"5 ••■■•.■ -^^-'v-.-'^-i'* ;* •f'^v/ s; ■•f*., *-'. 1 "* I The various capacities and types of outfits used at first naturally resulted in lack of uniformity of spray application in the different plots, bvrt since 1935 this dif- ficulty has not existed. Sulphur dusts were applied with a Niagara blower dust gxm. This gun blows a c^ood cloud of dust to a height of 8 to 10 feet. Almost without exception, the dust applications were made in early morning when dew was on the foliage and before the wind became too strong to prevent uniform dusting. Summer applications of fxingicides have been started in May or early June each year, except in 1936 when the first summer spray was applied during the last week of April. In the early period of the work, applications were made at approx- imately three-week intervals. More recently, the first svunmer spray has been applied in early May and subsequent applications have been made every ten days to tiTO weeks until the beginning of the dry weather period, which is usually about the middle of July, Three-week intervals between applications have been allowed after that time. Summer applications of fungicides vrere terminated the latter part of August, Dormant applications of liquid fungicides were started in the spring of 1935 in 2 of the 3 new plots started that year. The practice of applying both spring and fall dormants has been follov/ed, the fall dormant being applied in Oct- ober or November and the spring dormant in March or early April before the buds opened. Observations were made on the effectiveness of each fungicide used and on each type of practice employed. Data were recorded at regular intervals diu-ing the growing season on the prevalence of the "elm wilt," The trees in the several plots were divided into separate blocks and each block in a given plot received a differ- ent treatment. One block of trees in each plot remained untreated, and these served as a check on the various treatments employed, -5- f Five-year Tests with Si-unmer Treatments The data presented in table 1 summarize the results of five years of experiment with pruning and with Bordeaux mixture (Corona), Koppers flotation sul- phur, Koloform, and Kolodust. Table 1. — Results in disease control in nursery elms obtained from 5 consecutive seasons of pruning, spraying, dusting, and pruning combined with spraying or dusting. Plot numbers No, of trees and originally treatments used present Plot III check 300 Prvming 300 Bordeaux spray 300 - Bordeaux + pruning 300 Plot IV Check 500 Pruning 500 Koloform spray 500 Koloform + pruning 500 Plot VII Check 711 Bordeaiix spray 474 ITo. of trees Difference in contracting favor of (+) or disease in against (-) 5 years treatment Percentage of control (+) or lack of c ontr ol ( - ) * I I Flotation sulphur spray Plot VIII Check Pruning Kolodust Kolodust + pruning Plot IX-L Check Koloform spray 474 400 400 400 400 347 347 33 7 38 29 7 6 9 13 151 113 116 64 67 46 33 113 142 + 26 + 78,8 - 5 - 15,2 + 4 + 12,1 + 1 + 14,3 — 2 - 28.6 — 6 - 85.7 - 18** - 23** - 29 - 11.9 - 15.2 - 3 - 5.0 + 18 + 28.1 + 31 + 50.0 - 25.7 * Percentage of control obtained as follows: Treatment difference (col. 4) ^ ^^^^ P Disease in check (col. 3) I ♦* Calculated on the basis of 711 trees in each treatment. -6- Pruning out diseased parts, v>rhen done without any other treatment, gave 79 percent control in plot III and 14 percent in plot IV, but failed by 5 percent in plot VIII, A greater number of cases of wilt occurred in the blocks of sprayed trees than in the checks, Bordeaux in plot III permitted the occurrence of 15 percent more, and in plot VII 12 percent more diseased trees than occurred in the corres- ponding checks. With Koloform in plot IV, the number of diseased trees was 28 per- cent greater, and in plot IX-L 26 percent greater than occurred in the check blocks. And in the flotation sulphur block in plot VII the proportion of diseased trees was greater by 15 percent than in the check. In contrast, however, sulphur dust proved somewhat effective, Kolodust permitting the occurrence in plot VIII of 28 percent fewer cases of wilt than occurred in the check. Results obtained when pruning was combined with fungicides proved erratic. In plot III, combined with Bordeaux, trees becoming infected were 12 percent fewer than in the check and about 24 percent fewer than with Bordeaux alone. But combined with Kolofonn in plot VII, pruning appears to have increased very considerably the proportion of diseased trees, in comparison with both the check and the sprayed blocks. Done in combination with dusting Kolodust in plot VIII it appears to have been moderately effective, the number of diseased trees being but 50 percent of the number occurring in the check block, 70 percent of the number in the dusted block, and 49 percent fewer than when pruning alone was done. These five years of consecutive treatment indicate, on the basis of the results just stated, that so far as "wilt" control is concerned the use of Bordeaux and sulphur sprays for summer application alone tends to increase the prevalence of "elm wilt." The practice of pruning out diseased parts generally tends to reduce -7- the amount of disease, and the general effect of combined pruning and spraying is a decrease in the effectiveness of pruning which tends to balance the ineffectiveness of sprays. Dusting with sulphur is, however, somewhat effective and, when combined with pruning, proves the most effective among the treatments tested. Tests with Sulphur Summer Spray and Dusts Data in addition to those obtained from the uniform 5-year long treat- ments just described are furnished by plots IX-S and XIV for a sulphur spray and 2 sulphur dusts. These are summarized in table 2, I Table 2. — "V/ilt" control obtained from treatment of nursery elms by pruning, by spraying and by dusting with sulphur, and by combining pruning with spraying and with dusting for various periods. I Plot numbers and treatments used No, of trees originally present Difference in Percentage of ITo. of trees favor of ( + ) or control ( + ) contracting against (-) or lack of disease treatment* control (-) Plot IX-S (sprays) Check, 5 seasons 226 Pruning, 5 seasons 250 Koloform, 5 seasons 217 Koloform, 5 seasons + pruning, 2 seasons 200 Plot XIV (dusts, 2 seasons) Check 236 Pruning - 218 Flotation sulphur 253 Flotation sulphur + pruning 222 Kolodust 235 Kolodust + pruning 201 74 62 47 44 84 46 86 28 81 53 + 20 + 28 + 27 + 24.4 + 34,1 + 32.9 + 37 + 41,1 + 4 + 4,4 + 58 + 64,4 + 3 + 3.3 + 23 + 25,6 * Calculated on the basis of 250 trees per block in plot IX-S and 253 trees per block in plot XIV, k -8- <* ■* + 32.4 + 32.4 143 - 21.7 _— - 21.7 133 -- 0.0 0.0 474 - 15,2 - 15,2 1066 - 28,2 + 34.1 - 14,8 700 - 85.7 + 32.9 - 51,8 Flotation sulphur Flotation sulphur + pruning Kolodust Kolodust + pruning 288 283 253 - 17.4 - 82.6 !.7 - 17,4 - 13.0 - 50.1 4.4 4.4 1 2 2 222 — + 64.4 + 64,4 635 + 3.3 + 28,1 + 18,9 601 + 25.6 + 50,0 + 41,8 * This average is obtained by weighting data from individual blocks in proportion to the number of trees in the blocks, has permitted the performance of certain tests in more than one locality. Since any treatment recommended as effective should prove itself to be so in any locality, the data from individual plots should be considered from that point of view. A recapitulation of the essential data furnished by the plot tests is given in table 5, Both the number of plots in which each treatment vms tried and -12- I the total number of trees upon which it v/as tested are given, as are also the least and greatest degrees of prevention obtained. In determining average effectiveness, plot data have been weighted, whenever possible, in terms of the number of trees in the tree blocks concerned. In such cases the indexes of average control given in the table are considered to be more fairly expressive of the values of the treat- ments. A casual inspection of table 5 vd.ll leave 3 outstanding impressions; namely, that more than half of the treatments appear to have no value, that not all the treatments that do have value give consistently positive results, and that the degree of effectiveness demonstrated by effective treatments often is disappoint- ingly low. However, certain treatments negative as to their averages, have positive value under some conditions, and a few of the effective treatments have positive averages sufficiently high to indicate definite, practical usefulness, A visual comparison, based on the averages given in table 5, of the effec- tiveness of tested treatments is sho\vn in figure 1, in which bars reaching to the right represent effective and bars reaching to the left ineffective treatment, the length of the bars representing the percentage of control or lack of control. By examining this diagram it may be seen that those treatments for which effectiveness has been demonstrated include (1) priming, (2) copper sprays supple- mented by pruning, (3) sulphi;ir dusts, and (4) sulphur dusts supplemented by pruning. Those demonstrated to be ineffective include (1) copper sprays, (2) sulphur sprays, and (3) sulphur sprays supplemented by pruning, A definite basis appears to have been demonstrated for judging the effec- tiveness of any treatment. It will be noted that all the treatments extending on the positive side in figure 1 involve either pruning or dusting and that, without -13- t3 ^ .H Pi i -P a a> -P o O u -p o o o >i o t:) CO -p o iH a, u (D ra i-, CB O -— . CJ + O — - .H -P [>