feTATE PLANT BOARD January 1944 *-609 i United States Department of Agriculture * Agricultural Research Administration Bureau of Entomology and Plant Quarantine FIELD TESTS WITH INSECTICIDES TO CONTROL THE EUROPEAN CORN BORER IN EARLY MARKET SWEET CORN AT TOLEDO, OHIO, IN 19^3 By D. D. Questel, Division of Cereal and Forage Insect Investigations Introduction Three fields of early market sweet corn were used in conducting insecticide tests in 19^3 against the first generation of the European corn borer ( Pyrausta nubllalis (Hon. )). The work was divided into (l) tests of experimental sprays and dusts to find a substitute for ground derris, (2) commercial field tests for the purpose of improving application methods, (3) the comparison of sprays and dusts, and (4) the comparison of various dust materials. Experimental Spray Tests The spray experiments were conducted in a field of early Spancross on a light sandy loam in the truck-crop section southwest of Toledo, Ohio. The following materials were tested as sprays: (1) A crude product containing 60 percent 2-chlorofluorene, 4 pounds, dis- solved in 2,000 cc. of "benzene, per 100 gallons of water; (2) ground derris root containing 4.7 percent of rotenone, 4 pounds per 100 gallons of water (standard treatment); (3) ground derris at the same rate for the first two applications, followed "by synthetic cryolite for the last two applications at the rate of 1 pound per 100 gallons of water; (4) ground derris for the first three applications, followed by synthetic cryolite for the last application; (5) phthalonitrile, 4 pounds per 100 gallons of water; (6) synthetic sassafras oil, 1 part to 800 parts of water, plus ground derris root, 1 pound per 100 gallons of water; (7) 6 pounds of spray powder containing 5 percent of DDT per 100 gallons of water; and (8) a nicotine bentonite containing 12.8 percent of nicotine, applied as a spray containing 0.125 percent of nicotine, which is twice the usual recommended concentration. - 2 - The first application was mads on June 21, while the corn was still in the whorl stage and averaged 18 inches in height. Four applications were made, the first three at 5-day intervals. Bains and cool weather caused a 4-day delay in making the fourth application. Dates and amounts of rainfall for the spraying season were as follows: June 28- 0.71 inch; July U, 1.15 inches; July 7. l.Uh inches; and July 10, 0.37 inch. Sodium butylhydroxyphenylbenzenesulfonate (Areskap) was added to all experimental sprays at the rate of 1:2,500 by weight. Treatments were replicated four times. All plots were laid out in random "blocks, each plot being k rows wide and 25 feet long. To save time and materials, all buffer rows were sprayed with derris by using the high- clearance, self-propelled machine. This left only the two middle rows to be treated by hand with the small wheel- barrow sprayer. The spray was applied at 150 pounds' pressure, all areas on the plant where the borers were feeding being thoroughly sprayed. Borer populations in 19^3 ?&& high in the early market sweet corn. The performance of the spray materials is given in table 1. Ground derris spray (standard treatment) gave the highest borer reductions that we have ever obtained with any insecticide, notwithstanding the fact that borer populations in the nontreated plots averaged more than 32 borers per plant. There was no signifi- cant difference between the performance of the standard ground derris treatment and those treatments in which cryolite, at the rate of 1 pound per 100 gallons, was substituted for derris in the last appli- cation or last two applications. Cryolite injured the plants, causing some of the leaves to turn yellow. DDT, 2,2-bis(p~chlorophenyl)-l,l,l-trichloroethane, looked very promising. It reduced the borers 91*9 percent in the plants and 96.1 percent in the ears and did not cause any apparent injury to the corn plants. Higher concentrations of this insecticide might give control*- equal to that with ground derris. a CD 4» U o (jog) © «H rH O U a, o &£> «m d o s I U CO h CD O 2-° © «H Ai O OB fa CD o +> O CO SZS rH ^ P* *H O O O U rH CD f ! t\i CVJ cr> W CTv a\ cr> CO CO VO ITv CO r^ VO IT\ cr> CM VO ir\r<^ s • • • • • • • • VO ITv u^ i-t ITM^- o CVJ rH CTN ■HJ* Pj c^ 43 ,0 O fin 90 9 U U CD CO Vl O Pi P( Op •° § O P| pi o CD O a h CD g P* •a 43 O CD «H CD 4= o 3 52! H o Pl CD .9 Pi CO 4* S o B •a CD CD u Pi 0) Pl o m 4» d CO a 43 Ct) CD Pi o o o oo ooo to ir> to OJ vo vo o CO CACTk r-vo 2 OJ o ^ OJ OJ E>2> 1 CT» C\ f^ OJ CVJ Z> % 3P fcO op VO ^ r- r— OJ to ir\o to r— -d- J- vo p cno q> OJ to VO VO o k\ ir\ ooo J* J" OJVO O OJ O f-« KV^t- h- r^v OJ OJ KN OJ O OJ to OJ OJ OJ to O to • • K\OJ OJ OJ rr\ OJ OJ^t O CTvO OOO • • • OJ o o J- OJ OJ o o CO o CD CD CD CO d © d d £ d O -H O d dd OtI o a o S M d Pl K Pl •H d CD O CD CD O CD «>H CD 43 iH 43 43 Ti 4» ^H 43 o A o o £, o a O Pi 43 U h

d •H CD o O Pi Pi u u p CD 43 CD M O -H Vl rH Pt CD 43 CD Pl © Pi Pl P< p, PJ p, o CO u cd a Pj O CC CD CD O pi CD d IOH hH H -d -d CD p, CO p. ^ o cS CD O ■d «d d »d -d ^ -d o CD U 1 CD Pl § lals C H d OH 3 p, 3 d ^J 43 Pi *-> "3 "rt o o o ooo 1 43 o< u u u (I Kl 1 fi O P^ o o cb e> o oj CO ^ > -6- Commercial Field Tests of Spray and Dusts Applied with a Self-Propelled Boom Sprayer-Duster Tests were conducted in two fields of early Spancross and one field of Earligold to compare spraying with dusting, to compare various dust materials, and to test improvements in application methods. Borer popu- lations in these fields were higher than any encountered "before in in- secticide tests. One field contained an average of 7 9 SS masses per plant before any hatching occurred. This field at harresttime averaged 50 "borers per plant. Very little untreated early market sweet corn near Toledo was sold in 19^3 » owing to heavy "borer damage. Strips h rows wide extending completely across the field, and usually replicated 3 times, were treated with each spray and dust mater- ial. On the date of first application, June 18, the corn was 26 inches high and just "beginning to tassel. High temperature with much hatching "between the second and third applications necessitated a shortening of the spray interval. ill spray treatments were made with k pounds of ground derris root (containing k,f percent of rotenone) per 100 gallons of water, plus wet- ting agent (Areskap) 1 1 2,500. Three solid-cone nozzles per row were used, the apertures "being 3/6H inch for the two outer nozzles and h/&l inch for the center nozzle. Spray dosages averaged approximately 170 gallons per acre per application, applied at a pressure of 150 pounds. Dust treatments consisted of (1) ground derris in pyrophyllite containing 0.5 percent of rotenone, (2) dual-fixed nicotine (h percent nicotine), and (3) a nicotine "bentonite containing 12.6 percent of nico- tine, diluted to 4 percent nicotine with walnut-shell-flour carrier. One derris treatment applied with a fan-case housing having a 1-1/2 inch out- let and tubes leading to the nozzles was compared with another treatment applied with a fan-case housing having a 2-inch outlet and tubes. A high-clearance, self-propelled sprayer and duster, constructed by the Bureau of Plant Industry, Soils, and Agricultural Engineering, was used to apply the materials. The duster was mounted on the same chassis as the sprayer. Two nozzles per row were used. Previous to the dusting season the machine had been calibrated to deliver the desired do sage 8 of the various dusts. Field No. 1 Commercial Test In field No. 1 derris spray was compared with derris dust. It was planned to apply spray with 0.02^ percent of rotenone to these spray plots ,, but owing to an error by the manufacturer in reporting the analysis of one lot of derris the first and third applications in this field received 0.0396 percent of rotenone. The derris-pyrophyllite dust was applied at the rate of 50 pounds per acre per application. For two of the treatments „ the occurrence of rain made it necessary to use 2 days to complete a single application. In all other cases all replicates were treated on the same day. -7- m xi r-i Pi •a •p o CO i d o o Pi H O En kv 0) ■3 EH CO ■P d § co i-h Pi o p«s c Pi P. ® CD «H O Pi PL, O p Pi CO o +» o 9 p- Pi O Eh CM CVJ O ,=*• o o o o o 3^° i-JVO • • I r— o\ I crvr-- ltvvo jd- to • • • • • ^t CT\NVD I*- 60 CT> KVh-CTV • • • • • | o cvi o cvj r— i KM*- o «o CTVVD KM0 OVO 60 h-irir«-\ cu o en rH-=t WMMOOO O LTV 60 VO VX> 60 ^4-^f 60 VD^t O h-OH n-\r*"v60 r*^rHVO KMTlO rH* r-T C\f CvT^f-* 8£& CVI 60 J* SfSa 9 CVJ 60 60 CVJ 8 CVI CVJ 60 O VD QVO CVJ HOOOOVO O O CVI o o H O O r-i iH r* r* r-i r4 «H H fH H OVO o CVJ O rH O rH O ovo o • • • • ••••• • • • O rH O rH 60 ITv CVI CVJ O OON h-C\J r-rH r4 p CD Pi -p d co p d Pi CO CO Pi CO CO X) -d CD (4 CO CD &-g S co -cl 3 Treatment Class No. 1, "borer free or lightly- infested (no side injury) Class No. infest edj sold at a lower price 2, Income per acre Class No. 3» unsalable ears left in field Field No. 1 Derris spray Derris dust No treatment 9,600 6,700 $600 150 63U 1,083 6,81*8 Held No. 2 i/ Derris spray Nicotine "bentonite dust Derris dust Dual-fixed nicotine dust No treatment 9,600 2,592 11,992 ^,992 570 5* 10U 10U 1,152 1,728 2,016 2.687 Field No. 3 Derris spray Derris dust No treatment 9,600 5.S75 ij-SO 196 1,321+ 1.S27 Not counted l/ Smut was extremely heavy in the nontreated and dusted portions of this field. % -11- For purposes of comparison in table h a yield of 800 dozen ears per acre was assumed for the commercial spray treatments, because practically all ears were salable and in a normal year 800 dozen would have been a moderate estimate. Owing to heavy rains and cool weather, however, the stand was poor and the yield below 800 dozen. The numbers of ears per acre given for the dusted and untreated plots are in the same ratio to 800 dozen as the numbers of ears actually harvested in the dust or check plots were to those actually harvested from an equal length of row in the sprayed plots. Harvest data are not so accurate in determining the effects of an insecticide as are dissection data because they show only the numbers of ears Infested and not the degrees of infestation. Although all ears harvested in both the derris and dual-fixed nicotine plots were infested, a comparison of the numbers of borers in the plants and ears given in table 3 shows that derris dust was more effective than the nicotine dusts. Dissection data were obtained prior to harvest data, which probably accounts for the fact that the former indicate the presence of borer-free ears in the dusted plots whereas the latter do not. Some conclusions drawn from the commercial-scale tests are (l) that derris spray was considerably more effective in corn borer control than any of the dust materials used, (2) that derris dusts were more effective than nicotine dusts, (3) that none of the dusts tested were satisfactory when dealing with high borer populations, and (h) that very heavy infesta- tions of the borer can be satisfactorily and profitably con- trolled in early market sweet corn with ground derris spray. Summary The following materials were applied as sprays in small plots in 19*0 to find a substitute for ground derris spray er to lower the cost of treatment: (l) Crude 2-chlorofluorene, (2) derris root (standard treatment for comparison), (3) derris for the first two applications followed by synthetic cryolite for the last two, (k) derris for the first three applications followed by synthetic cryolite for the last application, (5) phthalonitrile, (6) synthetic sassafras oil plus der.-is, (7) DDT, and (8) a nicotine bentonite containing 12.8 percent of nicotine. p^ssa?"-' -12- The derris-cryolite combination gare high control* hut some plant injury was caused hy the cryolite. Both phthalenitrile and the synthetic sassafras oil-derris combination injured the plants. The most promising of the new materials tested was DDT, which gare satisfactory control and no injury to the corn plants. The following dusts were compared in small-plot tests: (l) Cube dust containing 0.5 percent of rotenone, (2) cube dust containing 0.15 percent of rotenone plus 0.75 percent of phenothioxin, (3) cube dust containing 0.15 percent of rotenone without pheno- thioxin, (k) cube dust containing 0.23 percent of rotenone plus 0*73 percent of phenothioxin, (5) cube dust containing 0.25 percent of rotenone without phenothioxin, (6) crude 2-chlorofluorene (5*0 per- cent) dusts, and (7) a 0.25-percent phthalonitrile dust. None of the foregoing dusts prored satisfactory from the standpoint of borer control. Phthalonitrile and crude 2-chlorofluo- rene both injured the corn plants. Phenothioxin wis of no appreci- able value, in the concentrations tested, as a substitute for rote- none in the form of cube dust. Comparisons were made, in three commercial fields, of spray and dust materials applied with a self-propelled sprayer and duster. Borer populations in the nontreated portions of these fields ranged from 2,804 to 4,938 per 100 plants. Very satisfactory control was obtained with ground derris spray in all three fields. Borer reductions produced by the spray treatments ranged from 90.8 to 94.5 percent in the plants and from 94.3 *o 97»3 percent in the ears. Dust treatments in commercial fields produced borer reduc- tions ranging from 37*9 to 78.6 percent in the plants and from 46.1 to 79*9 percent in the ears. With high borer abundance in 19^3 these reductions meant high borer populations remaining in the plants and ears after the dust treatments. Gross returns per acre ranged from $480 to $600 for the spray treatments and from $54 to $196 for the dust treatments. The conclusions drawn from the 1943 commercial tests are as fellowst (1) Derris spray was considerably more effective in corn borer control than any of the dusts used; (2) derris dusts were more effectire than nicotine dusts; (3) none of the dusts tested were satisfactory when dealing with high borer populations; (4) rery heavy infestations of the corn borer can be satisfactorily and profitably controlled in early market sweet corn with ground derris spray. '1J- Pigure 1. — Nontreated strip adjacent to a derris-sprayed strip, photographed at the sane time after harvest in commercial field No. 1 (compare with fig. 2). Toledo, Ohio, 19^3. (Photograph "by- Bureau of Plant Industry, Soils, and Agricultural Engineering). -llj- Figure 2.— Derris-sprayed strip just after harvest in commercial field No. 1 (compare with fig. -1). Toledo, Ohio, 19^3» (Photograph "by Bureau of Plant Industry, Soils, and .Agricultural Engineering.) *> Figure 3»—2ars from the nontreated strip (above) and from the derris- sprayed strip ("below) in field No. 1. These were taken at the time of the fifth and last picking from the sprayed plot and are more irregular and somewhat smaller than the hulk of harvest. No marketable ears were produced on the untreated strip. Toledo, Ohio, 19^3« (Photograph "by Bureau of Plant Industry, Soils, and Agricultural Engineering.) <4*. UNIVERSITY OF FLORIDA Jllllill 3 1262 09228 0048 Jigure U.~ Bars picked from 15 consecutive plants in the nontreated strip in commercial field Eo. 1, showing horer injury to the husks, and small ear 8 caused ty the heavy "borer population in the plants. Toledo, Ohio, 19^3* (Photograph "by Bureau of Plant Industry, Soils, and .Agricultural Engineering.)