wilii mWii" - LI B R.AFLY OF THE U N 1VER5ITY or ILLI NOIS NATURAL HISTORY SURVEY. A REPORT ON TESTS OF FUl-TGICIDES FOR TIffi CONTROL OF ELM DISEASES lU ITORGERIES J. C. Carter STATE OF ILLINOIS Honorable Henry Horner, GoTernor Department of Registration and Education NATURAL HISTORY SURVEY DIVISION Theodore K. Frison, Chief Biological Notes No, 4 Urbana, March 30, 1935 Contribution from the Section of Applied Botany and riant Pathology In considering this report, it should be remembered that the use of sprays and dusts as fungicides has been developed almost entirely in connection with orchards and plants from which a fruit crop is taken, Yfith these, the problem has been chiefly the prevention of those types of infection vrhich recur, year by year, on the leaves, blossoms, and fruit and whose effect is apparent chiefly in damage to leaves or in ruination of fruit. The value of fungicides to trees which provide ornament and shade has been inadequately tested. Formerly spraying of trees was much recommended, because it ought to do them good ; but now it is the general practice of tree experts to spray only when there is definite need. The data here presented are Eonong the first to give light on the value of spraying young growing trees for disease prevention, L, R. Tehon •Tfrj- *T-, 3, — Dry "rcttr-ble Flotat ion Sulfur . This sulfur dust, mcLnufacturod ty the Koppcrs produces' compcjiy, is similrj' to (2) above, but is produced in the manufacture of illuminating gas and is made up of extremely fine sulfur particles, 4, — Kolodust, This is a sulfur dust manufactured by the Niagara sprayer and chemical "ompany. This fungicide is similar to Koloform but is applied as a dust, 5, — Flotation Sulfur Dust, This is a sulfur dust manufactured by the Koppcrs products company. It is composed of extremely fine particles and is used as a dust. Applications of Bordeaux and wcttablo sulfurs have been made with sprayers ovmod by the nurserymen on whoso grounds the trees have been located. The apparatus has varied from a 50 gallon hcjid operated outfit to a 100 gallon pov/er machine. In different plots the quf.lity of application has necessarily varied somewhat, though every effort has been made to secure the best possible spray coverage. Applications of sulfur dusts vrcrc made with a hrjid duster of stcundard make capable of throwing dust in a good cloud to a height of 10-12 feet. In dusting, choice of the time of day v/as made so as to take advantage of dew as a dust holder. First applications have boon made yearly in May or early June, cJid those have been follov/ed at approximately 5 vrcek intervals by other applications, the last being made in the last half of August, The test plots have, thorcforc, received treatment 4 to 6 times during each growing season. Emphasis has been laid on the summer treatment, since the so-called "wilt" generally begins to appear in July, Dormant applications have not been tested, since the possible effectiveness of fungicides Tra,s unknown. Results During and at the end of each season observations on the effectiveness of the various treatments have been made with care. Those observations have related primarily, of course, to the usefulness of each f\angicide in keeping dawn the general run of olm diseases included in the term "elm wilt," as used by nursoryncn. But other questions have been kept in mind also, such as whether fungicides affect the prevalence of leaf diseases and whether their use is generally beneficial or deleterious to troos. Those points are reported on below, 1, — Control of "wilt" di::er.30s. It was realized, when these tests wore begun, that curing infections already present would be impossible, vinlcss pruning should prove effective. The measure of the usefulness of each treatment would lie in its ability to prevent the occurrence of new infections, Prosurm-.bly, the relative values of the different fungicides would be determined also by their relative degrees of success, V/hcthor complete cure and prevention could be attained would be determined from combined fungicide and pruning treatments. Table 1 on the follo^ring page shows in brief summt.ry the results noviT at hand, -2- CO § •ri -P O <« o o o C • (D UJ »-, to ^ o 1 o rH o CO CJ> Q) rH X -P <» •H hO M C g •H 3 ■P (I) > CO OJ Ki 5h (D Ph ra •H fi x3 •H m -P +J i-l rt •H Xi Oh -P X 0) >-- ^ <;-i o w -p i-\ Ti Ui OJ « 1 1 en © t- m a) as f> >. -H CO to rH ^ CO CO 00 [>- lO to ^ c- t- rH LO rH O O r-{ CO CO LO OJ r-i o o O lO 00 U5 Ta « X M -P o P 3 o o ■H . S " . S-, x: 0-, o CIS o ^ M M I oJ !> I(U o u o to oi H CO M - H 4^ O -H CD i-P -P G rH Q) -H CO CO ! © © a o I © o x: -p CO ■* CO rH r-{ (M rH CO CO "d^ •"^ CM CM O !>■ LO to ':t< © 6 -P OS © en ■p o Ph u rH CO ■H c a! o -P t-, oJ -P 3 -P CO i;h O 3 rH r-l t3 3 3 © ■P CO 3 o 3 ci © © o o ■H ft 3 © X 3 a © o cq cj n u, o <1h o ,-\ o o o W o 1> r-i © O X S u o o o rH © o x: M a CD CM LO CD rH O ^ 'i3 CO •^< <* O O <» CO O CM LO LO (T> OO o o >4< CM o o to CJl 13 OS -P -P CO to 3 3 O O rH rH O O » ^J ^s-i •H >i © -P -P to CO O O r-t r~i O O to Pi •rl ft 3 © r-l 3 10 o •H -P a -p o o u o P.. © to x; -p l>i ■ ^1 o ft © to jz; c_> -P O U^ M M In gcncrr.l, the use of the sulfur dusts ha.s been a.ccompcmiod by fewer now v.-ilt infections th;in has the use of sprays. Flotation sulfur dust bus boon sonevrhrxt more effective th!-.n Kolodust, perhaps because it is composed of finer particles and gives a norc even coverage of the leaves. The data in table 1 indicate that Bordeaux is comcv/hat more effective in reducing the number of cases of r/ilt infection than are either of the tvro sulfur sprays used. Neither sulfur spray proved materially cffootivc in preventing the occurroncc of new cases of wilt infection, 2, — Control of leaf diseases . Leaf diseases, particularly those that result in spotting, occur in varying omoimts from one year to another, their abundance and severity depending largely on the prevalence of vreather favorable or unfavorable to them, ¥/hen present in severe amounts, they bring about heavy defoliation at a timo when the loaves should be building up a reserve supply of food materials and thus undoubtedly seriously influence Diagram I, The effectiveness of certain fungicides in reducing the amount of leaf-spotting on elms by parasitic fungi in 1932, a season when this type of injury v/as exceptionally prevalent. Plots II tj^4,59 F IIll^^^^"^^^^" 1 37.38 No F\i!igicide lotation Sulfur Dust ' 32.81 IJo Fungicide JJ5^ 6.65 Bordeaux Mixture IV, VI VII VII I -I 5«^5? 12,59 Bordeaux Mixture 5r2>i 7.38 Dry ^Tettable Sulfur 1 31.25 No Fungicide IX- No Fungicide 135 . 5_3_ ^^^^:^^ 21.89 Koloform ;__"] 80,32 No Fiangicide 7.25 Bordeaux Mixture 7.07 Dry Vifettable Sulfur li 8,73 No Fungicide ■J^ 3,08 Kolodust ZZIIT-J 12,95 No F\mgicide ,, 6.22 Koloform 1 106,53 No Fungicide ^>2^ 16,57 Kolodust 10 20 30 40 60 I 80~ 100 120 140 Average Number of Spots per Leaf -4- the grovrbh of trees. They are generally more prevalent and abundant under nursery conditions, because of the short intervals between trees, the shade present, and the more moist atmosphere. The effectiveness of the fungicides used in our tests on the general prevention of leaf spottings is shoTOi in the preceding diagram, which is based on data very carefully taken in 1932, u season of exceptionally severe leaf spotting, 3, — General effect on grovrbh o f trees . In order to determine whether, aside from the coritroT~of disease, the use of treatments might have an effect on the grovfth of trees, the diameter of all trees, both under treatment and in check rows, was taken near the end of the 1934 growing season, A reasonable sale price was established for the several diameters and a money value figured for all plots and treatments. The effect of the treatments can be expressed tentatively in terms of dollars, merely to show what may be realized from the use of treatments in the hands of a nurseryman able to dispose of his stock at a fair price. The estimated money value for each treatment is listed in table 2, Recommendations The results thus far obtained in our tests indicci.te that sulfur dusts can be recommended as practical for summer use, for the purpose of preventing new infections by the so-called elm "wilt" diseases. Sprays, especially the wottablc sulfurs, do not, however, appear to be as practical for the same purpose, although good control may sometimes be obtained vfith them, V/here the problem is the prevention of leaf spotting, any of the materials tested vrill give good results, but the use of dusts may offer some economies in etjiipment and time. Instructions 1. — Application of dusts ; Sulfiu" dusts may be applied v/ith a small hc^jid power duster untTl the "trees roach a height of 8-10 feet. Thereafter, a larger apparatus is necessary. Dust should bo applied \vhcn the foliage is slightly moist, as in the early morning v/hcn dev/ is present or just after a light rain. Dusting v/hcn no moisture is present gives poor adherence of the dust and may, moreover, res\jlt in burning of the leaves, 2. — Bordeaux mixture must be sprayed onto the trees. Any sprayer that develops sufficient povrcr to force the mixture in a fine mist to the tops of the trees and give good coverage of both leaves a.nd bark will bo satisfactory. Both "3-3-50" and "4-4-50" mixtures have been used vfithout injury to the leaves. -5- Tr.ble 2. — Coiiipr.rr.tivc ostimr.tc of nonoy vr.luc of trcctcd and untreated clr. stock. j 1 Estimr.to Amount Calculated Ago of trees j Origina.1 Duration 1 1 of value gained or gain or at start | nunbcr j of experi- Treatment in 1934 lost by loss per ] of trees i ncnt, years 1 treatment 1000 trees 225 Sulfur dust $185.14 s<533.03 gain i^l46.80 gein 12th 225 " and pruning 159.82 7.71 gain 34.27 gain season 225 225 3* Pruning Chock 136.17 152.11 13,94 loss 61.95 loss 10th 100 Kolodust 108.67 42.45 gain 424,50 gEin season 100 3** Chock 66.22 400 Kolodust 76.95 .20 loss ,50 loss 3rd 400 " and pruning 94.52 17.37 gain 43,42 goin season 400 400 3 Pruning Check 87.37 77.15 10.22 gain 25,55 gain 200 Kolodust 132.40 .93 gain 4,65 grin 3rd 200 " and pruning 118.47 13.00 loss 65.00 loss season 200 200 3 Pruning Check 108.82 131.47 22.65 loss 113.25 loss 1 300 Bordeaux 132.42 22,05 loss 73.50 loss 4th 300 " and pruning 118.07 36.40 loss 121.33 loss season 300 300 4 Pruning Check 129.37 154.47 25.10 loss 83.67 loss 144 Bordeaux 88.97 30.82 loss 214.03 loss 7th 146 " and pruning 88.97 30.82 loss 211.10 loss season 140 146 / *** Pruning Chock 82,82 119.79 36.97 loss 264.07 loss 237 Bordeaux 142.30 22.13 gain 97.57 gain 2nd 237 " and diseased 138.85 19.68 gain 83.03 gain season trees rcnovod 237 3 Diseased trees removed 173.40 54.23 gain 228.81 grin 237 Chock 119.17 9th 576 3 Bordeaux 577.60 66.82 gain 116.01 Efein season 576 Cliock 510,78 237 Sulfur spray 145.80 26.63 gain 112.36 gcin 2nd 237 " raid diseased 161,40 42.24 gain 178,18 gcin season 237 3 trees removed Chock 119.17 9th 576 Sulfur spray 470.90 39.88 loss 69.23 loss season 576 3 Check 510.78 3rd 1000 Koloform 427.75 46.55 gain 46.55 gain tjeason 1000 3 Check 381,20 3rd 347 Koloform 143.82 15.45 gain 44.52 gcin season 347 3 Check 128.37 •■Treated for 2 seasons, data taken at end of 3rd season. "Treated for 1 season, data taken at end of 3rd season. *** Treated for 3 seasons, data taken at end of 4th season. -6- 4 3, — Dry wcttr.blc su lfur s arc received in the form of dust. They arc readily ni::ed v.-ith v;atcr7 the proportions required being indicated either on the container in ".vhich they are received or in instructions furnished by the manufactiu'ers, 7fc have used 15 pounds of Koloform to 100 gallons of \vater OJid 7 pounds of dry vrottablc flotation sulfur to 100 gallons of water, 4, — Tines for applications . For the control of the "wilt" diseases, not less than 4 applications should bo made each simrner. Preferably, the first should be nado as soon as the first foliage is out and solidly formed. Subsequent applications nay be made at even intervals, spaced according to the number of applications planned but also with due respect to heavy rains, which tend to v^nrish off both sprays and dusts, vnien control of leaf spotting is especially desired, applications of either sprays or dusts should be made vath reference to new leaf growth, care being taken that ncvf leaves be not left unprotected very long. Applications at 3 vrcck intervals are recommended. -7- . . • ■ • ^1- > » Lie :i^ ''»irh;^'