UNIVERSITY OF CALIFORNIA. 
 
 AGRICULTURAL EXPERIMENT STATION. 
 
 BULLETIN NO. 53' 
 
 The Woolly Aphis and Its Repression. 
 
 Among the many diseases to which the apple 
 tree is subject, none is as persistent and hard 
 to eradicate and more wide-spread than the 
 woolly aphis, Schizoneura lanigera. The home of 
 this pest seems to be obscure. In England it 
 is supposed to have come from America, and 
 there it goes under the name of American apple 
 blight. It is found in France and Germany, 
 and wherever met is regarded as one of the 
 most formidable of pests. The Chilian Consul 
 of San Francisco stated several years ago that 
 in Chili it had destroyed whole forests of the 
 wild apple. 
 
 It seems almost unnecessary to describe this 
 pest, unfortunately so common, yet a few words 
 to novices in horticulture will not be out 
 of place. In form the woolly aphis resembles 
 closely the green aphis, so common on roses and 
 other plants, but its color is reddish brown, and 
 when crushed it yields a red juice, hence the 
 German name Bluttaus, or blood louse. The 
 insects are always eurrounded by a whitish 
 woolly substance, hence the name 4< woolly " 
 aphis. Like all aphides, this species increases 
 with astonishing rapidity, and only a few need 
 be left on a tree, to soon spread all over it. 
 While the presence of the woolly aphis makes 
 itself so conspicuous above ground, on the 
 branches, covering them as if with snow, yet 
 the most serious trouble lies out of sight, at 
 the roots, which in our dry climate they in- 
 habit as freely as they do the branches, sap- 
 ping the vitality of the tree to such an extent 
 that the fruit becomes small and valueless. If 
 allowed to go on unchecked the trees gradually 
 die. To the apple tree the woolly aphis is what 
 the phylloxera is to the grape vine, sucking and 
 causing swellings and knobs all over the roots, 
 as well as at the root crown. 
 
 A pest as serious as this has naturally been 
 long fought, and many are the remedies sug- 
 gested for its extermination. When young 
 trees first become infested, and it is discovered 
 in time, a number of remedies may be effective- 
 ly used. 
 
 Kubbing or brushing kerosene on the infested 
 spots, or washing them with lye, f pound to 
 the gallon, or with strong solution of whale oil 
 soap, or sulpho-carbonate of potassium, may 
 effectually arrest the disease. When, however, 
 the roots of a large tree once become thorough- 
 ly infested (and in this State, unfortunately 
 that requires but little time), almost all the 
 remedies usually recommended prove wholly 
 insufficient and on a large scale impracticable. 
 For a number of years we have tried at the ex- 
 perimental grounds of the University, various 
 remedies, including tobacco decoction, hot 
 water, common lime, ashes, bi sulphide of car- 
 bon, and several proposed remedies of unknown 
 composition, furnished by outside parties. Of 
 the latter that of Mr. Lille, of San Francisco, 
 appears, so far, quite promising. We must, 
 however, reserve our judgment for some time 
 yet. 
 
 Gas Lime. 
 
 On a whole, we have found no remedy as in- 
 expensive and efficacious as gas lime — the refuse 
 of gas works. Outside of its penetrating odor 
 this material has but one objection; it is a 
 strong medicine that must be used with care, 
 and the dose must be regulated somewhat ac- 
 cording to the soil and subsoil, and the age of 
 the trees. There is necessarily some difference 
 in its strength, according to its freshness, as it 
 gradually loses some of its ingredients by 
 exposure to the air, and especially to rain. 
 Nevertheless, when applied to a given spot, 
 it will retain its efficacy for at least three 
 years. Our first experiments with it began 
 four years ago, and at the convention held 
 in San Francisco that year I made my first 
 statement in regard to this remedy. I stated 
 that a marked effect had been produced by 
 it, and that the aphis had been killed, but 
 that in spite of the very strong dose applied to 
 each tree (something like ten pounds), the in- 
 sects were again descending to the roots. I 
 stated also that some of the trees on shallow 
 soil had been killed by the gas lime, and that 
 on the whole, the remedy was not satisfactory. 
 During the succeeding spring and summer, 
 however, I gained fresh confidence in it, ae, 
 with the exception of very weak trees or of 
 those in shallow soil, comparatively few died, 
 
those less injured showed returning vigor. The 
 gas lime had also been very beneficial to the 
 soil, causing the heavy, stiff loam to pulverize 
 like ashes. The next season, after the first 
 rain, I noticed the peculiar, strong odor of the 
 gas lime. Examination later on, in the spring, 
 showed that the aphis was not to be found 
 about the root3, and existed right at the sur- 
 face only. It evidently bad not gained any 
 headway. Altogether, the remedy now looked 
 so promising that it was decided to give it a 
 trial on a larger scale, but in much smaller 
 doses; these, if proving sufficient, to be in- 
 creased the next year. The call to take charge 
 of the collection of plants for the New Orleans 
 Exposition prevented me from carryiug out my 
 intentions at the time, and it was not until the 
 past season (1885-6) that experiments properly 
 guarded could be made. 
 
 The bad effect of the first application was to 
 corrode the bark on the younger trees, causing 
 it to decay. Instead of removing the soil and 
 putting the gas lime in close contact with the 
 tree, as was done the first time, there was 
 spread about a shovelful and a half, i. e., about 
 two or three pounds in a dry state, within a 
 radius of four feet over the surface around the 
 tree, trusting to the rain to wash it into the 
 soil. To prevent the apnis from remaining 
 close on the root crown, fresh nshes, a few 
 shovelfuls to each tree, were piled close about 
 the trunk. The work was done early in Oc- 
 tober, and the copious rains of this season gave 
 good opportunity for action. 
 
 On the trees examined thus far, the result 
 has been very satisfactory. They show, by the 
 knots and swellings on the roots, that they 
 were once badly infested; still, there is no aphis 
 on them now, while on a few other trees left 
 without treatment the insects are crowded. 
 Two rows of trees treated several years ago 
 and now treated again, but having had no ashes 
 placed about them, show the aphis working 
 downward again. To make the work complete 
 therefore, it seems necessary to use ashes or 
 some similar material close about the root. 
 
 The dose of gas lime to be given to a tree 
 should vary according to its size and age, and 
 the nature of the soil. In a porous, deep soil 
 there is less danger of injury than in a clayey 
 one, where the water charged with the antidote 
 permeates the soil very slowly, and has time to 
 corrode the bark. In the case of some old trees 
 in the Santa Cruz mountains treated last sea- 
 son, according to our suggestion, although the 
 gas lime had been put right on the roots after 
 the soil had been taken away, the roots were 
 perfectly sound and all the aphis killed. The 
 soil was a sandy loam, underlaid by limy sand- 
 stone. Thus, the exact dose to be recom- 
 mended is a little difficult to determine. It is 
 always safe to use a small dose first — from one 
 shovelful on a small tree, to four on a very large 
 one, spread over the surface, according to the 
 spread of the root, will generally be found 
 right. 
 
 It should be stated that a thorough treatment 
 
 of the top was never made, because we wanted 
 to see how far we could depend upon the lady- 
 bug for extermination there. From observa- 
 tions during the last few years, I believe that 
 in this locality this useful little beetle can be 
 depended upon for keeping the crown of the 
 tree free from aphis. We cannot recommend 
 too highly the protection of the lady-bugs, 
 Coccinelhe. During more than one year, we 
 have seen them completely annihilate the aphis 
 above ground in a very few days. It is gener- 
 ally stated that their larva? are the most de- 
 structive to the latter. We ourselves have 
 witnessed what an enormous quantity of aphis 
 the fully developed lady-bug will consume. As 
 the Coccinellce hibernate on evergreen trees, I 
 very strongly recommend the planting of these 
 trees, (conifers, especially) around the orchard, 
 to give the necessary shelter. I have often seen 
 them congregated on the Monterey cypress in 
 such quantities that they could be taken up by 
 the handful. Should the lady-bugs not appear 
 in numbers sutflcient to exterminate the aphis, 
 it may be necessary to kill the latter by means 
 of washes. As it is impossible to accomplish 
 this with one spraying on badly infested trees, 
 I recommend two or three sprayings. This 
 should be done in the following manner : For 
 the first application use hot water of 140 J\, 
 in the tank sprayed with great force. This will 
 wash off the greater number of the insects. For 
 the second application take tobacco water and 
 whale oil soap in the following proportions : in 
 a decoction of tobacco (one gallon water to one- 
 half pound tobacco) put half a pound of whale 
 oil soap. 4-PPty tn * s mixture at about 130° F.; 
 in about a week give another similar application. 
 If early varieties of apples are in question, leave 
 out the whale oil soap, as, especially in a cool 
 climate the odor of the whale oil will not leave 
 the fruit. 
 
 Resistant Stock. 
 
 There is a vast difference in the many varie- 
 ties of apples as regards their resistance to the 
 woolly aphis. The late John Llewelling, of 
 Napa, claims to have found by experience that 
 seedlings of Golden Russet and Rawle's Janet 
 are exempt. We have no personal experience 
 in the matter, but for several years, at the 
 experimental grounds of the University, we 
 have had growing two apple trees of an un- 
 named variety, propagated and donated by 
 John Rock, of San Jose. Although purposely 
 and repeatedly infected with the woolly aphis, 
 these insects never remained either on the top 
 or on the roots. The latter are tough and wiry, 
 and perhaps for this reason resist the aphis, 
 much as the wiry grape roots resist the phyl- 
 loxera. The only manner in which this re- 
 sistant variety can now be propagated is by 
 grafting. Although healthy, these trees have 
 been of rather slow growth. Doubtless there 
 are among the many varieties of apples others 
 equally resistant, and it would be well to pay 
 close attention to this point. W. G. Klee. 
 
 Berkeley, May 6', 1SSG.