LIBRARY STATE PLANT BOARD July 19 U5 E-665 Tfeited- States Department of Agriculture Agricultural Research Administration Bureau of Entomology and Plant Quarantine TESTS OF DDT AND PYRETHRUM IN OIL SOLUTIONS AND IN EMULSIONS AGAINST THE EARWCRM IN SHEET CORN By R* A* Blahehard and A* F. Satterthwait, Division of Cereal and Forage Insect Investigations f\ *» ■ ' •■• • ••• • Market gardeners in the important sweat-corn-growing sections of Illinois have not favorably considered the application of oil insecticides by the hand-Injection method for control of the com earworm (Heliothis armigera (Hba.)) . Furthermore, this method is too expensive for use on canning corn. Therefore, in I9U3 prelimi- nary tests were conducted with oil- water emulsions containing pyrethrum, in an effort to find a cheaper mixture that could he rapidly and effectively applied to the ears externally as an atomised spray. These tests did not give a high degree of control, apparently "because of the poor physical characteristics of the emulsions* In an effort to improve them, further tests with pyrethrum (0,2 percent pyrethrins) or technical DDT ( 1- triehloro-2 , 2-bis(p-chlorophenyl ) ethane) , in oil solution and in emulsions, were conducted in 19UU in corn planted for canning or for market at Gibson City and Collinsville, 111. The solutions and the emulsions were applied both by injection and at omi station* Experimental Methods The emulsions were mixed by hand in small quantities* This method of mixing is laborious and inefficient, but out of a large number of trials seven satisfactory fast-breaking emulsions and eight stable emulsions^/ were obtained* Injections were made with a small hand injector manufactured for the purpose, at the rate of 0.6 ml* per ear regardless of the type of material* The insecticide was atomized with a small paint spray gun* pressure being supplied from a cylinder of carbon dioxide* The oil solutions and fast-breaking emulsions were atomised at 30 *° 35 pounds pressure, and the heavier stable emulsions at UO .to U5 pounds* Enough material was applied to wet the silks and upper parts of the ears with little or no run-off ♦ The term "stable emulsion" is used in this paper to refer to mixtures that did not separate noticeably* In one instance, at least, a mixture that appeared to be stable when stirred with a glass rod was relatively fast-breaking when made later with an electric mixer. ggJL 26 1945 From 25 to 50 ears were treated with each material in each test. The treatments were applied to some ears "before the silks had wilted and to others immediately afterward* The results were determined when the corn reached the marketing stage* He suit 8 Table 1 shows the data on control of the earworm with the different materials when applied "by atomization and by injection* The number of ears damaged represents those having more than lj-inch tip injury* Comparative amounts of injury to tips of the ears, as indicated by prevention of kernel development, are shown in table 2 for three series of tests conducted at one location* DDT residues resulting from the application of the insecticide in an oil solution, a fast-breaking emulsion, and a stable emulsion were determined "by the Division of Insecticide Investigations and are given in table 3* Sb • 4 ® p d ® •P N P I ° d ® •p » co P d 8 P N «5 «H CO p CO CD E-i ■H CO p o CO CO © o CD o •H p o CO a d o •rl P S* l~t O CO lo r^c\i • * o o to ITv cvj cr* o #4 CP Pi f CO o CO CO P 8* CM C\J o CVJ CO r^vo lf\K\ J* I • I CVJ CX\J? d d CVJ I o o lf\-P P * ill o ITS VS. 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Li to 5 j. ■ ■ I 43 Q J 1 1 O • • • • O •-4 & u to O to in 1 «d 2 rH 5 0 • • • • ■P M 0 rH to a 8 to -p & I i -5 O to P w CO 43 80 1 jected | to EH Atom- ized cd 1 • mnterial 0 (0 to 0) 0 4 to o •H P o to to « to m CM in in CM CM CM o CM CM rH 0) 0 3 •P to in • CM CM ITS CM • rH CM VO to CM CM a o CO to rH ■s +> CO in « O o VO cn in rH • I CM o -P CO 15 o3 ■H VO q mw * o>n rH iH mm • <& CO I I i m in rH f*\ 8 I ! ! o in CM KD VO I i 1 ! { CM «=fr VXi o vo d CM VO VO • CM CM VO s to r— O O rH O in in • • • • • • • • CM IT) 0 vo in CM vo in to to m rH I i I I I CM CM 2 a CM a cm 1— m m cm in • CM rH fH VO «H in O * p\ rH -P ^ 1 BJ w CM AO g O r-i to to P C -rt H to © U -r* a HEh O CO in ■p a CO o CO d I to b CM CM •=1" VO to -p u to to A o - 5 - «d 9 •d ® (13 CP U ft (1) •d cp afilled h 8 a a * Tip loss e, Atom- ized Completely filled ears In- jected A -d o «*-> N Tests In- jected Atom- ized 1 H O • o material Accessory Insecticide CVI ri I LOCO CM r-3 • • iH I • • VO K\. ea cm I d o ■H *» d o CO CM K\ iH •H o o S3 CM CP to CU CM to iH to VO CM CM CM R CM r— vo • in\fc. O OMT\ O W J* CM CM iH rH c o fl o d c?*> « 6 o CO a a CP in to CM CM CXv VO VI- VO in CO VO O CO CM CM CM tM j& t*~\ CO in to CM CO VO CM in c3 CM CM CM CO CM CM CJ 4 a i r— r- P CM CM «2> in ♦ On * cr> in in r— • * o •H rH • • CO CO CM CM Ch CM « CM fl K O O rH CP CPiH CD cp+»cp4»o.ddp a) d