United States Deprtm~ent of Agriculture
Agricultural Research Administratirm
Bureau of Entomnology a-no', Plant Quarantine
DDTAPLIED AGAINST CERTAII FOREST MNECT IN 1944#
PARTICUL.ARLY !.WITH AERIAIJ E( UIPMNT
By Pilip B Doiden, division of v'orest insect Investigations,
Doal _, hitam-, Dvision of Gyps-y and Brovzi-Tail Moths Conrtrol,
-31n H.K. Townesl Diviin of Insect Ident2f.o,. tion; and Neil Hotckis, Fis~li a~nd JXildife Service, U; S, Department of the
Fora nmbe ofyears the Bureau of Entomnolor-y fnnd Pl -,n' Qua~rantine has eentesing th effectiveness of certain inseCt4icides against the gypy oth(Prthet4ria dispar (L.)) Insecticides have been tpplied both frow. th gr~n Puroin- aicrnft. During 1941.4 this work was continued, mostof ~e x,-rinental plots being laid out in northeastern Pennsylvania. In pri abut150 pounds of DDT (1-.trichloro-.2, 2-bis (p".chlorophenyl)ethne)wer~mae availtule for experiments against the gypsy moth, and it
*as ecil~dto se t1- e insecticide to t reat one 20'-acre plot of woodland from
-the, oir ,.n maller plots with Tround equipment, The airplt.ne
app ication 7rn sosucesful. th t -during the colirse of the season, as more DD"via mae aF~l-,.l, siniil ,r applications were ma-de against & number of .oterfoes isets The treatments were all ma-,de on a small scale, but
thereult wre very promising. This paper sum-marizes the season's work, andbrif l, esribhes the di s~ributing apparatus used in the airplane applica0C1,'UL 'S USED IN MIXING EDT
For pplcatonby means of Eround equipment an e-ulsion was mnade up
by LX n, pond ofDD, p '.nt of, cycoexanone, and 1~ pitsofhl
hortculura: sraybas hevy~ oil, and then adding an emls~ifier, IN-25-05
IK loo sulfate product-), matter f25gallon, and
1, ~rtof lchol, per 100) gdlons of final tank mix. The emulsion oon cetrtewa Jlue4"~ t ar equal aon c of -water a:nd then poured directly int wterinthe spra-:y t ink1. This emulsion wa-s very satisfactory in that it shwed esut could be expected with an em ulsion. However, this patiulrfoul s too expenigve to be prc~paAand cheaper materials
'A uspnsi- mideupof DD. p- rts and urea resin glue I. part
(byV~j-gt)wa alo ppied. with grund eqipment The materials were mixed
y ater th =1 h.,4 eensiftedthrugha fin -,nieh wirxe scrC "en, Ty-ater was aded loly nti athi. sury vas btined. The ziurry was added Th mix ture c logged t he strie in thespry lne etwen he ankandthepum atertabovut 300 gallons had.
been ~ ~ ~ ~ ~ ~ ~ aplel4Ti ol rbbyb vie f asi~nilar suspension were
Spay to beun -)pidfo i OatAee ie codn ofrua to- p-.. nt,-bl 1. Inec ps4ieD.toa is6vd .tesovn n thei oil r~sadd s0 ueteD5 isl edlbta ie
pints of 1) pound.O of ox DDT U nusalywar rtemertue atte ii te rue t- ma be~O adviabl rotti Ue ~1 3/ or eve 2~> 4~nso yc et on
--ti-A t i~snenn ander tr fore reqt re cosat-gtaindrn thf 'i l1i. u to evapoatW
t1 ?-Ac was e w41 thycrwo on tMeie wg. Paswee ,ietee
pounr off y DDT v.A 10 rloso aL Drntewne f pX-te &,ps Y7-'ot eggt~4 cluter ortItesado tn ali
indication 'that it increased the toxicity of the spray. In all cases larval mortelity was very high immediately following application. Tests with caged larvae showed that treated foliage also retained its toxicity for a considerable period. Fifty fifth-stage larvae that had been caged with foliage treated at the rate of 4 pounds'of DDT per acre 10 days previously and after .62 inches of rain had fallen were all dead within 6 days. Since very little foli-ge was fed upon, mortality wa's no doubt caused principally by contact with the sprayed foligige.
No foliar injury was evident on the plot sprayed before the eggs hatched (just as .buds were bursting) but rather severe burning occurred on the plots sprayed later in the season at the rate of 3 pounds of DDT p r 100 gallons. All evidence indicated. that burning was caused by the amount of oil used and not by.the DDT. .Jfhere only 1, pound of DDT per 100 gallons was used, and therefore, -about one-third- as much. oil-, injury was vefy slight. Since eomplete control was effected at the low concentration, it is believed that foliar injury can easily be avoided in future 'applications...
The fourth 1-acre plot was- treated with DDT mixed as a suspension and applied justprior to hatching. Urea':resin glue (*eldwood) Wns used as a sticker. About 6 pounds of DDT perl0O gallons were)ised. The material. went on very.nicely, and tiny'particles of DOT w ere. plainly.vis.ible on the bark of the trees. In:spite of a 1.5-inch rainfall the tight following application and 0.25 inch of rain 9 days later', the insecticide Ltdhered very well. Novertheless, a considerabletnumbbrrof gypsy moth larvAe survived &nd completed' development nt. Counts in thb fall indicated the presence. of 2l ew eggoluaters per -acre. There had been 418 per acre in the spring.,
AIRLPL E APPLICATION
DDT, in oil sprays can readily be .distributed from airplanes. Two
planes have been used for this work against forest insects-, One of them, a Piper-Cub capable of carrying approxim-tely 200 pounds of pay load, was used to trat 5 sores infested by the gypsy moth in the township of Greenfield, Saratoga County, ,. Y. The liquid spray was released under pressure from a series. of six nozzles attached to a cross pipe under the fuselage. A 7,-hite standard biplane with a capacity of about 800 pounds pay load was 'used for all other applications. For this type of work it was flown at a speed of about 80 m.p.h. at a height about 50 feet above the treetops (fig. 1). The plane was equipped with -a distributing device that was developed by the Division.of Gypsy and Brown-Tail Moths Control2 at Greenfield, Mass., primarily for distributing concentrated suspensions of lead arsenate and
The, junior author Donald 7.hittam piloted the planes in all applications Made in. 1944*.
2W. H. Campbell and Donald 7hittam are responsible for perfecting this apparatus.
cryolite. The device also worked admirably for oil s'rays containing DDT. Its essential features (fig. 2) consist of tw units of four disks each, set at each side of the fuselage and just outside the slip stream, vihich are rotated by small air-driven propellers -At 80 miles an hour these disks turn at about 2700 r.p.m. The spray mixture is fed by gravity onto these disks from a tank within the plane. As the liquid is thrown off the rapidly revolving disks, it is brcken up into a finely atomized mist.
Test flights over the airport showed that under still weather
conditions the misat settled down over a swath about 150 feet wide whereas a very light breeze increased the width of the swath to about 200 feet. There was rather light coverage at the extremities of the swath, and as a certain amount of overlapping was considered advantageous, the effective width of thc swath was figured as 120 feet in calculating the desired rate of spray flow. If,a strip 120 feet wide is covered at 80 miles per hour, about 20 acres are treated per minute. The distributing device was therefore adjusted to deliver 20 gallons of spray per minute (10 gallons per unit). This was about the maximum output possible with the distributing device as operated in 19h44; so when 2, 3, or more gallons per acre were applied the areas were covered two, three, or moree times. Then less than 1 gallon per acre was used, the device was adjusted to deliver the proper amount. 'hen
1 gallon per acre was distributed during test flights over -n open, flat surface, about 90 droplets fell per square inch of sprayed area. Droplet size ranged fromni 20 to 680 microns in diameter, with an average size of 178 (2, percent of the droplets were from 20 to 100, 37 percent from 100 to 200, 27 percent from 200 to 500, and 12 percent more than 300 microns in diameter).
In the actual spraying operation the completeness of coverage obtained throughout an arca depends largely upon the experience and flying ability of the pilot, and to a lesser degree upon a good system of marking. The area to be treated is marked by windsocks or other suitable markers. During application the pilot checks the amount of insecticide to be distributed against the number of acres in the area to be flown, and governs his progress accordingly. Owing to the extreme unevenness of the terrain and the variation in density of forest foliage, the pilot varies the spacing of his spraying runs and by so doing controls the dosage to treat suitably the laf surface below him. Obviously an inexperienced pilot may cover a considerable portion of some .strips twice and miss some areas entirely, but as experience is acquired these errors will be reduced to a minimum. The pilot will always be confronted wish wind drift and convection currents in the air, as well as physical obstacles on the ground. He will have to judge to vhat extent these atmospheric and ground conditions are affecting the application of the insecticide and be guided accordingly.
In one test at Litchfield, excellent control was obtained for a width of 55 feet when one swath of insecticide was laid down, and for a width of
158 feet when two over-lapping swaths were applied. The fact that control was not obtained over a wider strip when one swath was applied may not be .particularly significant, for this was the only test of its kind that could be satisfactorily observed during 19L. Nevertheless, it may indicate that there is a comparatively light deposit of spray on the edges of a swath, and perhaps it is advisable to fly over an area twice in order to get an even, satisfactory distribution of insecticide.
During 194) actual spray deposit was estimated by placing 6-by 6-inch glass plates on the ground throughout the treated areas and examining them for deposit of DDT crystals. Very good coverage was obtained in mixedhardwood growth when 3 gallons of spray was appl.ied per acre. Good coverage was obtained in young red pine plantations when 1 gallon per acre was used. Dense coniferous growth showed poor ground coverage even where 5 gallons per a~re was distributed. Gallonage of spray per acre must obviously be varied according to the area, density, and type of foliage to be covered.
Tests for the Control of Forest Insects
Treatments made during 19 4 are summarized in table 1. Complete
control was obtained against the gypsy moth, the green-striped maple worm (Anisota rubicunda (F,)), and the red-headed pine sawfly (Neodiprion lecontei (Extch)).
The result against the gypsy moth were particularly gratifying, for they showed that control could be obtained if applications were made prior to hatching of the eggs or after the larvae were partly developed. The first treatment was made in the township of Jefferson, Lackowanna County, Ps., on May 3, when a plot of 20 acres was sprayed. This was just prior to gypsy moth hatch, and gray birch buds were just bursting. On May 6 and 7 there was a heavy rainfall of 1.5 inches, and on ?fay 15 another 0.25 inch of rain fell. Hatching of gypsy moth eggs was general on May 8, Apparently all larvae were killed upon coming in contact with DDT crystals, either on the egg clusters or on surfaces nearby, for no larvae were observed feeding o~n olinge throughout the season, In the fall an extremely careful check for new egg clusters was made throughout the 4 acres that had been most heavily infected (counts made onla sample plot had indicated a population of 1,359 eg clusters per acre in the spring), and not a single one was found. A 5acre plo-t at Greenfield, N. Y., was treated when gypsy moth larvae were in the second and third stages and the trees were well foliated. Results were
equally.as good as those obtained at Jefferson. Both these areas iere
treated at the rate of 5 pounds of DDT in 5 gallons of spray liquid'per acre.
The same dsage was applied to young larvae of the green-striped maple worm at Derby Line, Vt. The area treated was composed mostly of large, widely space maple trees, but some beech trees were present. On this plot the larval mortality was high, not only of this species but also of Anisota virginiensis (Drury) on beech and Heterocampa spp. on both maple and beech,
A ugh no final check has be en md, Eexelent central of the green-striped mane worm was indicated.
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Applications fot ottol of the d4head4 pine sawfy wr aeo
junb 30 at Brasher, N. Y..on two plots l~i4 5out in 9-y~r>oldrdpn plantations. The degree of infestation .anged fr~om light toet'el hqavy& Hatchi.ng had begun on June~ 18, and waqs estimated to about.70i pecn Cor~leted on the day of 'spraying. One plot 'uV.as treated at the doageue on the jgypsy mnoth plots. It was 'planned to spray the other plot at the at of 73- pounds of 'DDT in 3-1 gallons of spray. However, flying conitions cue cen~iderable drift of insecticide,. and ab~oUf11 acres 'were covred insea of t 'e 7 acres laid out. The second~plot was therefore treated with an
~rageof 2-1 pounds of 07)T per core, but undoubtedly the dosage was con-> siderably lighter on the borders of the area. Since cqmpletep~ontrol was obtained on both areas,, a dosage at least~ as low as 2 pounds p'er acre is sufficient for the control of this insect in young plantations.
Three plots heavily infested with the spruce budwqorn (A rchips fumnifrn
(Clem..)) were treated in Algonquin Park in Ontario, Cana6da onjineZ[ A-t this time about 90O percent of the insects were in the6 pupal tage- abu
8 'percent were moths, and about 2 perce-nt were larvae. jmmrediately afterth capplicotion lorge numbers of the m ,t obviously affected 'by th Dwr observe-_d fluttering around the bases of the tre-es, but. meny' thiatere still in fli' Lt -appeared to be unaffected. The spray was appI~ied under appaetl
j~eJcondi4tions, although there -.dvs some ground fog and the spray~ settle very slowly. G1&.s plates placed In the ground showed very poor coerg oii all plots. It see'ried that this pooru UUole ig was due to the density o the coniferous foliag,, ppricular~y ne ar 4he gr~ound., Some plates it comp -rr ti.7eli little, foliage im-mediately o- er them had a light deposit~ of DDT crvstnis. Final results of thills work cannot be 'reported until the spring of 19~,)) when -the. -young budworms will' 14ave their hibernaeu4.a,bu it~ is known that a large population -of living larvae weznt into hibrnatin
Treatmnts aginst an imnported pine sawfly, Dipro rttri.f
we~made on four plots atLthiedo Slt ~ tThTugtl threa~of these
plots were only one swath wide, the la-rval popu],a'tion wa? sufficient to
4 i.nd -ctte thq degree of contrcl tha-t coulq'be expected against this-speciies. Very good kill was obtained on a 55-foot swath where 1 pound -of DDt per acre
an aplied in 1 gallon of spray; excellent kill was obtained for a width of 158 feet where 2 pounxd;. of DDT per )cre was applied in 2 Pilons of spray by la1ying- dow:.n two overlt.apping sw!,aths. The. resi:lts obtained in the field seemed to be considerably better than those obtained in the laboratory (te-sts described in following paragraphs), where healthy larvae fed on trecate
fole. possibly this wars due to the high percentage of~ larwe actually hit -by the spray y at the time of Papplication.
Tests on Dosage and 'Pesidual Toxicity
In the fall of 1914 a~ number of airplane" applicatio's werI..a4e in order to test -the effectiveness of DDT when applied a.t different doae
under varying conditions and in different formulas. Four'dosages were applied to exc ellent stands of~ mixed hardwood at WVendell,,Mass,, on September 12 .nd 20 and to wll-stoc,-d, 40-yeaqr-old red pine plantations at ILitohfie_-d on Sejvternber 16. Four fLormulas were applied to young red pine p1 nt'tIIions nat lendlell on SEpoternbc-r 19. S nce it, wCS too late in the sea-son to etrmn the effect of these treaItmeInts under field conditions,
11fron the tre' ted 'Plots was collected and fed to croged lerva-e of the or-e nge-~st ripe(' oaar~ Aioasnturia (A. and S."))ard Dioprion frixtetc~rum wil they were avalT Te. Later -houseflies (Yusca domestica E.) weTsdto test the residual toxicity of sprayed fol-g.'Sinrce the ,plantantions~contbined considerable oak sprout growth, it was possible to test both coniferous- and decitdu'us foliage collected from them.
Houseflies used in all labora-to~ry tests were placed-i'n clenn boxes with foliage from the plots a nd held under observation for 6 days, being fed daily. As a Cceck on t11he normal mortality of flies held under' these' conditions, 4 lcts -of 10 flies each- were heldt- in boxes with untreated oak foliage and a
similr n'r-er ere held with ,untreated pine foliage. A total of 15 flies,
7 on oak and 8 on piefoige r 19 perc-ent of the 'flies under observation,
ad died -,t t-e endl of' the &day test.
Dos-ages used: on the L0re-odred pnine plantation at Litchfield were identical '.ihthose used on nixed hadoo t 7endll, except that 2
pounds of DDlT oer qacre in 2 gallons of spray were used in place of 3 pounds per acre in 3 gallons of spray,. Residual toxicity as judgedI by exposing insects to foliage collected fro rl the v-arious plots indicates rather welldeflned rcFs its. I-crtclity of Anisotai senatoria wa s 100 percent when the larvae were- fed freshly -;.rayed ok (.li-ge from the plot tre,-te6 at the rate of3 pounds of DDT per acre, but wa-s :_nly 62, 3, and 3 percent -when the larvae were fed foliEge fror'. pIots sprayed a t the rat,+es 'of 1 and .1/2 pound of DDT in 1 gallon of spray, and 1/2 pound of DDT in 1/2 gallon of spray, respects.vely. VeIry littl f1,Eg w-rs eaten in boxes where the mortality was greatestt. Tn most insta-nces dce--th was aopcrently caused by contact with DDT cryst!?ls, After 6.6 inches o f rain, ~.:ihfell during the hurricane of September l]4, AnIsota larvae were practically unaffected by foliage front any of the untrefated plots.
The nortaliitp of ho~fIaselj in boxes with foliage from the hardwood plots sprayved with pounds cf DDT per acre was 100 percent on freshly sprayed foli,,.;e, rand! from~r 62 to 78 perce,-t rncrtality on foliag-e collected over a 72...day period d (6 collections). TM~rtalIity o~f flies uxpised to freshly sprayed flgefrom, pilots tre-ited with 1 and 1/2 pound of PDT in 1 gallon of spring ,.and,' 1/2 pound cf DDT-in 1/2 g,'dlon of spray per -cre wai 100 percent but dropped to 70, 10, and 4 5 percent when .foliage wsccllccted &fter 38,
,', an 0 r C -s C C rcsp %7tev'ly.
pour lots of Diprion frutetoru,.m larvae that werc fed foliage from the red pine Tp1at,-tion plots in Liteh-ii-eld showed no striking differences in notaliv (3 to 6~5 percentt. Possibly this was due to the advanced age
of the ,!hen vj, r e 1, r o'U Cht into tyie laboratory At least many
-of them forr ied cocoaris in t e boxes. Tb-- n 6.r t. a 1 i ty of hoitseflies was 10"U Percent, When caCec iiithr fresA foliage fa, orr, all plots. Pive-collections c r e 7 e over a 64-day period, fr'm the of ol ot -orayed at
tne- r ltr-. 2 o T; P, r acre. also causb(I 100 Y
-ercpnt mortality of
11 ar t i-o n-r. :-a 6 1 7.0 d! ---Y s a f er' treaty '10"persi I aent caused.
c ?nt rortalit,, The mor-Lality of flie'"s dt geC jith' foliage:.T -om' p-lota' s prayed a .he ra-te-, o-f 1 rj- pound- of in' 1 gallon of spray arid-: T-pp- and DDT Ln I- illon 'of -,7rav p,: r ricre was con.-iderably le'ss- from the first fi.,v'e collections than from -11.he -olot -Li-)r:-:.ved with 2 pounds of I'DT per acre, but for
-the collection made, 'iu d, ys after tre-trient, mcrt-alitir --.7as 60, '58,
e,;-cen-,, respe-ctively, froman d the three plots
LET -.i.ixed in four ciffereiit fnrrr,-,las (,-ee table 1) was applied at the ratJ- )j-' 1 1,,ourd j--n 'I allon of' -Fr-"y -er a I cre to 16:he plantation plotc of
-cun:- --ine I foliage ccllect-ed frora th -se plats showed
remark-bl ,, relidbr toxicity to hou flies. Only sliEht differences in
i-iere -ho,.,vn !. oliat,- t, cateC
mo r -I I Viith 'he different formulas. The
f o i ia ; c. fron. tiv- nlot treated -,-jjt', UE T in kerosene, wit i no other solvent,
-:a : not juite so toxic a-c tii9t fron he -ther -r.' ots. hen houseflies were c a, 4.-1:h f'oliace fror some of t'le nlct,-- nor'al-ty wa. 160 percent, up to 41-- Cj a- s a J.'t e r a pI'licaton, but after G5 69-s mortblit-y was decidedly lower on I cl a_-e i'r 0,-, 1 Z,11 P-,Ct ,I.
Tr-.e v-,eRth,---r ,iid vheir-th-se oprny-- were applied; so little tno,ov.,,-ora-k.Acn oi' the diff.-rent -prays durin?, app 14 C I- t, i on. The- to h,-.,ve acil-ered to pine fulinee somewhat
1 -3 r t I -,,A n to oak foli-.ije.
P;-I 01, ED 1-17 A PE'EP70II LTITE. TO TPEAIYENT OF "IATF R CITE, Ij
Al 40-acre wa-t(-rshe(I cf d9ciducu.- sro,,Yth, curroUnding 3-acre res--rvcir in Y .'.tston, P ., tr-,,,ite at th,3 rate o"L'-' 5 jpoundc;- -f 5LT in 5
,ray Fexr acre I o ceter,:.. arroiint of' TX pieLent in the reservoir after rain., The lor -st colTer oi' tl,.- ar R 4 y F I)by second growth varying fron mc-& rarely white oal, and' red maple to'scrub oak barrens.
oak i2 -rominent on some portions of th( area. The'ca paucity of the r--.-er- cir iE ahout 3.'- --ti-J-114-on.tallonE.
-he ar -a ;as on :,uguct 14. Ouffici-irt Spray cirifted onto the
qurfac.,- of' th-, -vv.ater 1- that a close of oil dropletz.,:jas plainly
b 1 -it",in ,i fe,:: houro this oil I'ilm had bcen blown to onu end of the r i c i r v..- s a precipitation of 0.27 inch on'the evening.o August 14 iner, cn 16. On : uc, st 17, and -again on 11ovember 161,
r, p op e a ri r' c s i,,v,: r e t a k c- n the rc-c.Prvoir and from the viater tap in a rcndc -inr, 1111 G 1: 1-1 -:ia.t-r .'or itL:boJIers directly from
the S-Lmnles of surface mud li,,cre taken i'rom 'thra margins of the
reso-r-voir -r August 14 ard 10" P:11 ti-iese sam.Fle- were te-sted for I)DT in the
ins,-.,cticjdc. I;ive sti F,at ions. 7 'he -LjatE-r contai-ied less than 1 par of 7-DT pi-r 100 million i-)arts of wat-r. The, mud contained less than 1 Part r),:-,r milli--n an Probab17 111C.11 below this figure, but it was impossible, to ::Ctablish % limit loi7cr than I'l-his.
EFFECT OF DDT OTT FOREST FUIA
Because of the hig-h toxicity of PDT to insect life in ge_-neral, and its possible direct anid indirect effect on wildlife, its application to forested aroas imit be carefutilly and in-tensively studied. II. K. Townes and4 Neil ,-otchkis,. made cbse-_rv-tions on the watorsi,, at P-ittston at the time 'tt area w.as treated,(ug 15) and they visited the 20.-acre plot at Jeffe -rson, Pa.,J which hac been trcat_ d on T~ay 3. A groat deal of information was obtained, which will be:- of great help i~n planning intensive studics for the 1946 season.
At the time the 20-acre -,.lot at JeffarSon w treated, it was observe-d that mosquitos and black flier s were practically elIiminated fromr the area. fPri 44ine 7t a lar~e draronfJly and'a burblebec, bLoth obviously affect06, were ob s erve d. TJhen Doctor Townes visited the ar;ea h 2 noted the presence, of a anh xd varied fauna of all c-pecie-s of insects that one would e5x-ct in that typo, of" woods. Of course, the area treated is not extensive; so it wac im,-possible to judge wIhat part of the fauna was from survivor,- in- the spayed are-a -and what part had migrate:d from the adjacent untreated area. Various insecti7-orous birds in cos'rb~numb._rs woere also ob served.
Qtse;rvations at Pittston indicated that. theD =-had sevrely reduced tne abundance of most of the terrestri-al insects,*but 6 days ftrthe application eno~u h specimen ns o-f most of" the sci survi-ved to rc-populate Sthe area. The-re was a iiigh~ mortality of ad--ults of sev rl sncios Of' aquatic insects, which reon or nkea,-r the-_ suriac- o)f the reser-voir, and somie mortality4 of i;mmatuire T'emi4ptera that brea, the a-t the' surface of the ,water.' The insects living at tebottom of the resjr-voir weeaparently unaf fected.
Th-ee was no indication of mortality a-mong the bird life of thc. forest, but oing to the mobility of the b-ird population at the tirin of the1 spraying it cannot be concluded th-a-t th re were nr uff c t. Othe--r -vert4brate li-fes,, ad ui-naftfected or. the, cay the spray was ap-plied, buit the nex-t mnorningabout 20- dead or oying_ bullifrogs (?ana catosbiana kS.naw), 1 dea57td tadpolc.' i(_' dead or dying sunfish yietfe)lad2Tdgle shriners
(qegoiscrysoleucas (MiTtch-ell)) ,,v-Lre found -at the vwaterls edL;-o.
Nmeous dea luoard frogs (Rana pii~ens _Schrebcr) (not aquatic but in the ran %e.-etatiorl dt the wv.atorz: viere als.o found. 7 ,o cd froigrs (Rn sylvatic5. L-Conte-) and sprinC peepers (ilyla crucifer ",ied.) wi ,re
8 dcraz-7itelynurous in the damper part of the-70-ds. ii, one wecre seen. alive ~ ert rav was applied, but only 1 was found dead. DisscctionL in4j.cgted that theic irogs h, d f( hteqviy on species of aquatic ins ,.cts that ha.d be't k4i26d by the,- irs.tiio I~ht hr it ~a th-c poisoned insects
r ski contact with the spra y that killed th,_ frogs and fish wa.s not 4oemne.Bt f'iah and fro'gs wcre still common on _-August 18, 4 day,5s
after ppliction f the ET
Experments nwith DDT for the coto o f certain forestiscswr
conduted by app1lring. the saprayz with ground and tei e quptnt-lCoalt control of the gypsy rith (1;orthetria dispar (L.)) wa ffgd nsal x
p,3r imental1 plots when lijrht cl6sages Iilf tflf I~~_ _eulionQ -Vir apld'ymaso ground equipment either just be._fore the eggs hatched or du rilgtelr season. Very promising results were obtained when DO)T was distrbute r~
airplanes, although experimental work in 19P4was rather limited.. A ; 4i Strind-ird Biplane equipped with a spinner-disk distributing' apparatus a used in tre_;,Ating all plots except one, which was spr-4yed'with a~ PiperCu plane~. The DDT in oil sprays was distributed as _- finely -Aomized mist. Good coverage by, the insecticide wmas obtain, d in mixed hardwood $rQwth we 3i g ,.llons of snray were a pplited p,;r ncre7, and in young plantations with 1 gallon p, r -iore, but gallonage must obviously b~e varied acordin~g to the area, density, -.,rd type of foliage to be covered.
C.oplete control of the:, gypsy m~oth with spray applied lujst beforehtin of the egos and after larvae were partly gro~n, and of the~ green-.stripe maple w-,orm, Anisota rubicunda (F.:)) when larvae were partly gron -wstte by using 5 pnds of' DDT in 5 gallons of oil per acre. Compete controlofth red-headed pine sawfly (.Neodiprion l-contel (Fitch)) was obtained at this dos-age, -.nd also.t ,bou F of WLin 2 gallons of oil per acre.A
imported pine swlDipr-ion frutetorz F) a ls fmtv~
a-t 2 pounds of DIDT per are
In treatments applied from th c 4rplne against the gypsy mnot, thegen striped maple worm, and the rted-headed pine s5awfly, the sprt y was mixed a the, rate of DDT I pou-nd, oyclohexanione 1 pirnt, and Shell horticultural spra base hea-vy oil about 7 pints (enough to :equk.l 1 gallon of mixed spray)4 I the treatments against the imported pine sawfly lo,- pints of xylene were substituted for 1 pint of cyclohex-none Eand the solution seemed perfecly satis f, :ctory. In -the treatment s against~ the sp acc, budworm (Archip s fumnifera-na (Clem.)) the snrLy was mixed at the ratE of DDT1 I lund oyclchx xonze 1 pint, :.nd Maentor No. 29 oil '- to Lhi pints depending, uoo the volumln' of spray y applied per acre,
Late in the season four formulas differing only slightly in c omositi o were -.pplied to young red pine plantation plots. In -thre-e of thEn kcroee was substituted vhtolly or in part for the horticult-ural oil and in the fourth small s-mounto of fish 'oil and motor oil were used, Xylene was use as a solvent in three of the formUl2ts, and kerosene with no other -slvent in the fourth. l these formulas ha~d long residual toxicity and sa me4 pronising.
The 40.acre watershed of a small reservoir in Pittston, Pa. wsteae at the r-te of 5 poutin of DXP in 5 gnllona of oil per acre.'The dy lateafte-r 0.75 inch of rain had falQlen, analysis of Qtr l
the3 reservoir indicated less than I pz.rt of DD in 100 million prsofwtr In the same area- limited observations were jrrrde on the efc fDTo forest fauna in .aworal. 'There wmas no evidece of mctlt fbr ie
but some- of the fish and bullfrogs in the reservoir were kild Us species of insects were gr(-eatly reduced in nmbcer, bu asate h pa
had been -applied enough specimen ns of most sp~cie ramie orpplt
It s blieedthat t~~expeurimentaI work with DDT i~n 194~4 w-Arrants an optmiti attitude toward its use in the future. Many difficulties must be solvd., ut t apears that DDT~ cxri be used as a spray from aircraft at such low osags thant it will be prnctical to use it as a control measure againstcertin -10Oest in~sects.
Figure l.--White standard biplane distributing an oil spray
containing DDT with the spinner disk type of apparatus
over woodland at Wendell, Mass.
Figure 2.-Right-hand unit of spinner-disk distributing apparatus.
UNIVERSITY OF FLORIDA
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