UBKAKi 
 STATE PLANT BOARD 
 
 Ma ^ m5 E-659 
 
 United States Department of Agri culture 
 
 Agricultural Be search Administration 
 
 Bureau of Entomology and Plant Quarantine 
 
 JIPBBIMBNTS WITH DDT TOE THE CONTROL 07 THE EUBDPEAN 
 OOHN BOBSR INFESTING SWEET COBN AT TOLEDO, OHIO, IN 19^4 
 
 By 0. H. Batchelder and D« D. Qja.estel» 
 Division of Cereal and Forage Inseot Investigations 
 
 The experiments described in this report were conducted in 
 sweet corn grown near Toledo, Ohio, during l$Uk for the purpose of 
 determining dosage requirements and effectiveness of DDT as an in- 
 secticide for control of the first generation (June-July) of the 
 European corn "borer ( Pyrauata nubllalls (Hon.)). The DDT sprays 
 and dusts were applied with a wheelbarrow sprayer, a self-propelled 
 ground duster, and air-borne dispensing equipment designed for 
 applying dusts and concentrated sprays. Although considered pre- 
 liminary in nature, the experiments have produced information 
 important to further use of this insecticide in field-plot tests 
 and in commercial applications, 
 
 DDT Sprays Applied with Ground Machine (D. D. Questel) 
 
 The following water suspensions of DDT were tested as sprays in 
 comparison with a spray containing rotenone: DDT (technical, 
 undiluted), 10*8 percent of DDT in pyrophyllite, and 5 percent of 
 DDT in an unknown diluent (Gesarol Spray Insecticide). Sodium 
 mono sulfonate of butylphenylphenol (Areskap) was added to all sprays. 
 
 The experimental plota were four rowa wide and 25 feet long in 
 randomized "blocks. All treatment a were replicated four times and 
 each treatment consisted of three applications* For each application 
 approximately 175 gallons of spray per acre were applied with a 
 wheelbarrow sprayer operated by a gasoline engine and applied with 
 a hand-directed nozzle that produced a solid cone of spray. At the 
 time of the first application (June 17) the corn waa ]>6 inches high 
 with 70 percent of the tassels emerging. Additional applications 
 were made on June 22 and 27. Dates and amount a of rainfall for the 
 spraying season were as follows: June 19, 0.21 inch; June 22, 0.10 
 inch; and June 23, 2.13 inches. The results of these tests are given 
 in table 1. 
 
 21 
 
 1/ The self-propelled ground equipment utilized in these experi- 
 ments was designed and built by 7. Irons and staff of the Bureau of 
 Plant Industry, Soils, and Agricultural Engineering. Mr. Irons and 
 his staff also rendered valuable aid in the application of inseotioide 
 materials. 
 
 1945 
 
I 
 
 5 
 
 2 
 
 P. 
 
 o 
 
 s 
 
 1 
 
 s 
 
 1 
 
 B, 
 
 v« d 
 o o 
 
 <H 
 
 • "£ 
 
 d d 
 o o 
 
 ••2 H 
 
 •H Pi 
 P** 
 
 'b 
 
 o 
 o 
 
 I 
 
 o « 
 • d 
 
 is 
 So 
 
 S3 
 
 2 
 
 
 
 • 
 
 
 d« 
 
 d • 
 
 M • 
 
 o u 
 
 
 w4 • 
 
 
 4> Pi 
 
 
 1* 
 
 • 
 
 « O 
 
 ■ 3 
 
 
 *-* P 
 
 Pt 
 
 dS 
 
 d • 
 
 t~t 9 
 
 o -*» 
 
 
 -J 
 
 m 
 
 U H A 
 
 ■•» 
 
 
 1 
 
 d f-t 
 
 M P 
 
 Hi 
 
 • • • 
 
 • Pt • Pj 
 
 o o U ed 
 
 » .o v* c 
 
 
 ■a 
 
 
 4» 
 
 
 O 
 
 • 
 
 ** 
 
 4» 
 
 
 HI 
 
 ^ 
 
 a p 
 
 •** 
 • 
 
 • o 
 
 • 
 
 o 
 
 Vi 
 
 H »H 
 
 d 
 
 
 M 
 
 • U 
 
 
 o • 
 
 
 » p 
 
 I 
 
 
 • • 
 
 
 U • 
 
 
 o u 
 
 
 « *• 
 
 
 d 
 
 
 H 
 
 4» 
 
 d 
 
 o d 
 
 • 
 
 « l> 
 
 •H 
 
 •H 
 
 3 
 
 Pi r-l 
 • O. 
 
 & 
 
 CL, ft 
 
 d 
 
 5 
 
 
 f ^* 
 
 © • 
 
 <H 
 
 o d 
 
 ■P 
 
 H o 
 
 
 a aj 
 
 
 Ou 00 
 
 
 -f» 
 
 I 
 
 
 
 £ 
 
 
 
 -2- 
 
 
 
 CM O 
 
 • • 
 
 ON ON 
 
 • 
 N 
 ON 
 
 o 
 
 . 
 
 .d- 
 
 ON 
 
 1 
 
 onN 
 
 ON ON 
 
 M 
 
 • 
 
 »*N 
 
 ON 
 
 • 
 H 
 
 ON 
 
 1 
 
 *8 * & £ ft 
 
 ft! 
 
 vS k\ 5 
 
 VJD fH 
 
 ITN 
 
 CVJ 
 
 «0 
 
 KN 
 
 00 
 
 00 
 
 ON VO 
 
 Kr 
 
 VO O Jt CVJ vo I 
 
 r-l H •-« fH c-l 
 
 H H i-4 #H H 
 
 -d- «l 
 
 CVJ *0 
 •H ON 
 
 VJO 
 
 8 s « 
 
 -d- 
 
 ON 
 
 £3 & 
 
 o 
 
 (VI 
 
 ON K\ 
 
 KN 
 
 d 
 
 J? 
 
 r 
 
 a & 
 
 d 
 
 Pi O S 
 
 dS*c ob -3 
 
 8 | 
 
 id 
 
 Pi 
 
 O 
 
 0) 
 
 Pi 
 
 o^ 
 
 V» iH 
 • ON 
 
 g~ 
 
 Vi 
 
 V-i 
 
 •r-l O 
 
 •d «^ 
 
 
 t 
 
 4* 
 
 Pi 
 
 Pi 
 
 ■8 
 
 i I 
 
-> 
 
 Owing to the unusually short period during which oviposi- 
 tion took place in these plots, only 3 applications were made; yet 
 excellent control was obtained with these materials, without any 
 apparent injury or other effect on the corn. The spray in which 10.8 
 percent of DDT in pyrophyllite was used as the source of the DDT 
 was outstanding in control of the borer and reduced the population 
 in the plants from I83H to 38 and in the ears from U96 to 4. The mixture 
 readily went into a water suspension, whereas much difficulty was 
 encountered in attempting to put undiluted DDT into suspension. 
 
 DDT Dusts ipplied with Ground Machine (C. H. Satchelder) 
 
 in experiment was conducted to establish the dosage required 
 for application of DDT dust with ground equipment to infested corn. 
 Data of this kind were also considered necessary in connection with 
 the use of DDT in subsequent tests of new types of ground and aerial 
 equipment, for these reasons special attention was giren the mechani- 
 cal adjustment of the duster equipment. 
 
 Precise control in the mechanical operation of the power- 
 operated and self-propelled duster used in this experiment assured 
 uniform dosage by regulation of travel speed, feed rate, ratio of 
 dust to air volume, and physical condition of each hopper load. 
 Dusts containing 0.75 » l»5t 3» a^cL 6 percent of DDT were made from 
 a 10.8 percent DDT-pyrophyllite mixture by the addition of more 
 pyrophyllite. These dusts were applied at the rate of Uo pounds per 
 acre-application to obtain dosages of 0.3, 0.6, 1.2, and 2. U pounds 
 of DDT per acre. No accessory agents were included in the mixtures. 
 
 This experiment was conducted in a' commercial planting of 
 extra-early hybrid sweet corn, Spancross, and the plots were arranged 
 in randomized blocks. All treatments were replicated U times, and 
 each treatment consisted of U applications. An infestation of 10 
 larvae per plant (primary stalk and ears) prevailing at the time of 
 harvest caused severe loss in untreated plots. 
 
 Applications were made on June 18, 25, and 30, end July 5* 
 They would have been started 5 days earlier but for mechanical diffi- 
 culties encountered in assembling the duster equipment. The first 
 application was made when the plants were in late whorl and early green 
 tassel, the second during late tassel, and the last two during silking 
 growth stages. 
 
As ahovm in table 2, "borer reduction increased with each in- 
 crease in dosage without indication of leveling off within the dosage 
 range. Although a dosage of 1.2 pounds of DDT did not provide a 
 sufficiently high degree of control in these experiments, "borer 
 mortality might have been considerably greater end 2.U pounds might 
 have been more than necessary had there been no delay in the explica- 
 tion schedule. 
 
 Table 2. -Borer reduction in extra-early hybrid sweet corn, Spancross, 
 treated in dosage-mortality test of DDT applied in dust form 
 with ground equipment (U replications, UO pounds of mixed 
 dust per acre-application) 
 
 Concen- 
 tration 
 of DDT 
 
 Dosage of 
 
 DDT 
 per acre- 
 application 
 
 Borers per 100 
 plants surviving 
 a , t time of harvest 
 
 In Tin 
 plant sa/ j ears 
 
 Reduction in 
 borers 
 
 In 
 
 plant 
 
 *l 
 
 In 
 ears 
 
 Percent 
 
 Pounds 
 
 Check (untreated) - 
 
 Number Number Percent Percent 
 
 6 
 
 2.U 
 
 91 
 
 19 
 
 91.0 
 
 95.1 
 
 3 
 
 1.2 
 
 277 
 
 90 
 
 72.5 
 
 76.9 
 
 1.5 
 
 .6 
 
 38 
 
 156 
 
 6^.3 
 
 60. 
 
 .75 
 
 .3 
 
 197 
 
 1*5.8 
 
 ^.5 
 
 1007 390 
 
 1/ Primary stalk and its appendages but not including tillers. 
 
 Ears of salable size were graded in three classes: (l) No. 1 and 
 borer-free, (2) salable-infested, having borers in silks or shank but 
 no injuries of kernels or husks, and (3) culled due to borers or to 
 borer injuries of kernels and husk. The yields are summarized in 
 table 3 according to treatment. Borer reduction is reflected in the 
 yields obtained in plots treated at the several dosage levels. 
 Particularly noteworthy are the higher yields in numbers of ears of 
 salable size in treated plots as compared with untreated plots. All 
 dosages more than doubled the number of salable as well as No. 1 and 
 borer-free ears, and the quality of the yield improved continuously 
 with dosage increase. No injury or other effect on the growth of 
 the corn was observed. 
 
- 5- 
 
 Table 3. —Yield increase in extra-early hybrid sweet corn, Spanoross, 
 treated in dosage-mortality test of DDT applied in dust form 
 with ground equipment. (U replications, w pounds of mixed 
 dust per acre-application) 
 
 
 Dosage 
 of DDT 
 per 
 acre- 
 appli- 
 cation 
 
 Xars per 100 plants 
 
 Increase 
 
 in ears 
 
 Distribution 
 of ears of 
 salable size 
 
 Concen- 
 tration 
 of DDT 
 
 Culls 
 due to 
 "borer 8 
 
 Sal- 
 ami e- 
 in- 
 fested 
 
 No. 1 
 and 
 "borer- 
 free 
 
 Total 
 sal- 
 able 
 
 tfo. 1 
 
 and 
 "borer- 
 free 
 
 Culls 
 due to 
 "borers 
 
 No. 1 
 and 
 "borer- 
 free 
 
 Total 
 sal- 
 able 
 
 Percent Pounds Number Number Number 
 
 6 2.H 
 
 3 1.2 
 
 1.5 .6 
 
 •75 .3 
 
 Check (untreated) 
 
 1$ 
 
 s 
 
 66 
 96 
 
 7 
 
 22 
 26 
 26 
 15 
 
 126 
 106 
 
 20 
 
 Per- 
 cent 
 
 280 
 266 
 
 17 I 
 106 
 
 Per- 
 cent 
 
 530 
 U30 
 
 255 
 130 
 
 Per- 
 cent 
 
 10.1 
 
 20.5 
 
 31.2 
 47.S 
 73.3 
 
 Per- 
 cent 
 
 85.1 
 65.S 
 50.3 
 33.2 
 15.3 
 
 Per- 
 cent 
 
 89.9 
 79.5 
 68.8 
 52.2 
 26.7 
 
 DDT in Dusts and in a Concentrated Spray Applied by Airplane 
 
 (C. H. Batchelder) 
 
 Preparations of DDT were dispensed with airplane equipment to deter- 
 mine their suitability and effectiveness when so applied for corn borer 
 control in plantings of sweet corn subject to heavy infestation and damage* 
 The materials used in these tests were a DDT dust, a cube-pyrophyllite dust, 
 and a concentrated spray containing DDT in an oil vehicle. The dusts were 
 applied at a rate of about UO pounds and the spray at about 2.25 gallons 
 per acre-application. There was great variability, however, in the amount 
 of material deposited from the center of the swath laterally in each direc- 
 tion as well as along the line of flight taken by the plane. 
 
 The concentrated spray was assembled in the following proportions: 
 
 Pounds per gallon 
 
 DDT, technical (QNB-A-DDT) O.67 
 
 Solvent, petroleum distillate (Sunoco 7-T) 1*3^ 
 
 White-oil vehicle, Superla grade (125 seconds 
 
 Saybolt) 5.36 
 
 Emulsifying agent (Triton X-100, an aralkyl 
 
 polyether alcohol) .16 
 
 Total 
 
 7.53 
 
-6- 
 
 The petroleum distillate was a low-priced commercial prepara- 
 tion containing olefin! c and aromatic hydrocarbons. This material 
 compared very well with other common solvents in its ability to 
 dissolve DDT and with reference to plant tolerance. The 
 white oil has been used for earworm control and was selected because of 
 its safety and availability. It is believed that grades of white oil 
 with lower viscosity would be Just as satisfactory. The emulsifying 
 agent was included to increase the mobility of residues in the presence 
 of surface moisture; it may not have been necessary. 
 
 The insecticides were applied with a Piper Cub plane carrying 
 interchangeable dusting and spraying equipment. Owing to uneven delivery 
 and also to reduction in deposit laterally from the central rows of the 
 treatment swath by both types of equipment, it wa6 not possible to 
 compute exact delivery rates. Bates of 1.5 pounds of DDT and of 0.5 
 pound of rotenone per acre-application are therefore considered approxi- 
 mate averages for the five central rows of the treatment swath. It is 
 probable that improvements in airplane equipment now in progress will 
 eventually result in more even and better controlled dosages of dusts 
 and sprays. 
 
 Tests in single-strip plots were made in a field providing 
 three flight strips with ample buffer and check areas. The field had 
 been planted with three varieties of sweet corn— Earligold, Whipcross, 
 and Evergreen. These varieties differed in growth rate as well as in 
 rate of infestation and characteristic yields. 
 
 Treatments were applied on June 21, 2k t and 29, and July k. 
 It is of interest to note that, although it was impossible to keep to 
 schedule with the ground duster on account of a muddy field following 
 rain on June 23, the condition of the field was no hindrance to plane 
 operation. 
 
 Beduction of population in the plants and in the ears for a 
 five-row swath, and maximum reduction as obtained in the center row of 
 the swath, on which the average dosage was heavier than it was on the 
 lateral rows, have been summarized in table h. The data show that 
 considerable variation in control occurred according to the variety. 
 In Evergreen DDT in an oil vehicle gave 92 percent reduction of borers 
 in ears in the swath, and 100 percent in the center row of the swath, 
 but in Whipcross it gave only 65 percent reduction in the swath and 
 85 percent in the center row of the swath. This was apparently due 
 to differences in the growth stage of these varieties at the time of 
 treatment and accompanying differences in the development of the 
 infestation. Comparison of borer reductions on Evergreen following 
 applications of DDT in dust and in solution showed the concentrated 
 spray to be superior. It is also noteworthy that an average borer 
 reduction of 89 percent prevailed in the ears of Barligold treated 
 with cube dust. The potentiality of DDT as a corn borer insecticide 
 was shown by the 100 percent protection provided the ears of Evergreen 
 in a central row of the plot treated with the solution of this in- 
 secticide in oil. 
 
- 7 - 
 
 m 
 
 5 I 
 
 ■8 
 
 o 
 
 o 
 o 
 
 r-« ft 
 
 O 
 
 ^ in 
 43 • 
 
 On-' 
 O 
 
 M • 
 .d o 
 
 CD 
 
 • o 
 
 •P 
 
 SI 
 
 AS 
 
 ° § 
 © 
 
 CD fl 
 
 8-^ 
 
 rH -p -n 
 
 CD CD 
 
 "-a 
 
 A3 
 •H O 
 
 b 
 
 o to 
 
 ,d ^1 
 4* o 
 
 eg 
 
 o 
 
 o a 
 
 n 
 
 & 
 
 « 
 
 ft 
 
 CD 
 
 d 
 o 
 
 p 
 o 
 u 
 
 a *d 
 •h d «M 
 
 a o 
 
 «4 A «d 
 
 •p -p d 
 
 o <c p 
 d * o 
 
 'O CO ft 
 CD 
 
 U «h in 
 O • 
 
 * CD 
 
 £ *d 
 
 u 
 o 
 
 T 
 
 •3 
 
 EH 
 
 a 
 
 m ft-p 
 
 m 
 
 ft 
 
 CD 
 
 d 
 
 JUL 
 
 hi 
 
 40 CD 
 
 •d 
 
 .d 
 ■p 
 
 cd 
 
 CO 
 
 «H 
 
 o 
 
 co 
 (c 
 
 o 
 
 inl 
 
 o 
 u 
 ■p 
 d 
 o 
 o 
 
 CD 
 ,0 
 
 d a 
 ■h d 
 
 ■P ,0 
 O tH 
 
 d u 
 
 »d -p 
 
 CD -P 
 
 « CJ 
 
 ft 
 
 CD 
 
 d 
 
 Rr- 
 
 P CD 
 
 fH CD 
 
 d^ 
 M 3 
 
 OH J( 
 « ft+> 
 
 ■P 
 
 d 
 
 § 
 -p 
 
 cd 
 CD 
 U 
 Eh 
 
 8 
 
 t<\ 
 
 
 O 
 
 • 
 
 
 • 
 
 in 
 
 l 
 
 in 
 
 «o 
 
 
 to 
 
 CD 
 
 .d" to 
 
 • • 
 
 10 o 
 
 OMO 
 
 O O 
 i-l 
 
 o o 
 
 • • 
 OMO 
 
 ini-i 
 
 • « 
 
 o o 
 
 • • 
 
 in co 
 
 $ 
 
 m 
 TO 
 
 o in 
 
 • • 
 
 o vo 
 
 
 IfA 
 
 in 
 co 
 
 o 
 10 
 
 
 CD 
 CO 
 
 o 
 
 u 
 o 
 
 in 
 
 V£> 
 
 • 
 rn 
 
 
 
 
 
 
 O 
 
 • 
 
 
 • 
 
 • 
 
 C\J 
 
 •d 
 
 H 
 
 
 
 CM 
 
 3 
 
 .=* 
 
 8) 
 
 ■H 
 
 
 r^ 
 
 
 A 
 
 O 
 
 • 
 
 
 ON 
 CO 
 
 10 
 
 3 
 
 CVJ 
 
 in 
 
 • 
 vo 
 
 K\0 
 
 O 
 
 • • 
 
 • 
 
 ^H 
 
 r*^ 
 
 C\J CO 
 
 r-i 
 
 
 m 
 
 CD 
 
 
 ■P 
 
 
 •H 
 
 
 fcS 
 
 x-% 
 
 ft.d 
 
 •d 
 
 CD 
 
 •• CO ft 
 
 •P 
 
 •3"S fe. 
 
 
 -p ft 
 
 ■P 
 
 «H CO 
 
 1 
 
 d fc d 
 
 .3 P -H 
 
 S«/ 
 
 d 
 
 
 CD ©>£. 
 
 M 
 
 •p in 
 
 CJ 
 
 v/flh«- 
 
 CD 
 
 • 
 
 A 
 
 EH Ot^ 
 
 O 
 
 o o 
 
 • • 
 
 in vo 
 
 in co 
 
 CO «"-* 
 
 t*\ 
 
 & 
 
 CO 
 rH 
 
 .d; 
 
 p. 
 
 •d 
 
 CD 
 
 
 CO 
 
 •d 
 
 CD 
 
 CD 
 
 U 
 
 •P 
 
 4-5 
 
 
 g 
 
 •p 
 
 V^ 
 
 i 
 
 J«l 
 
 g 
 
 % 
 
 
 
 
 O 
 
 ^ 
 
 CM 
 
 •d 
 
 • CD 
 
 CD 
 
 rH -P 
 
 •P 
 
 •H 
 CD r-\ 
 
 2 
 
 d rH 
 
 fn 
 
 8£ 
 
 •P 
 1 
 
 CD ft 
 
 -P O 
 
 V- ' 
 
 O U 
 
 
 u >» 
 
 J^ 
 
 ft 
 
 O 
 
 
 CD 
 
 CD C 
 
 A 
 
 ^> -H 
 
 
 
 CD 
 
 IS 
 
 rH 
 
 w 
 
 
 +3 
 O 
 
 d 
 
 •p 
 
 d 
 
 rO 
 
 CO 
 
 CD 
 
 d 
 
 CD 
 ft 
 
 & 
 
 CD 
 ■P 
 
 »d 
 CO 
 
 M 
 -p 
 
 CO 
 
 rH| 
 
-s- 
 
 The yields of 99 and 100 percent for No. 1 and "borer-free 
 ears obtained with DDT in oil, shown in table 5. indicate higher 
 protection in Evergreen than has been obtained with other insecti- 
 cides. Ears of salable size were graded in three classes as 
 described in the preceding experiments with ground-duster equipment. 
 Dust preparations of DDT and cube provided similar proportions of 
 total salable and No. 1 and borer-free errs, although these treat- 
 ments were applied to different varieties. As might be expected 
 from the lower borer-reduction shown in table 4, the yields of 
 salable and borer-free ears in Whipcross treated with DDT in oil 
 were also lower than those obtained in the later Evergreen variety. 
 The percentage of salable-size ears culled because of borer in- 
 festations was much less in all treated than in untreated plots, 
 and no injury or other effect on the growth of the corn was observed. 
 
-9- 
 
 •8 
 
 1 
 
 a) 
 © 
 u 
 
 s. 
 
 r-l 
 
 o « 
 
 C4 « 
 
 I* 
 
 o • 
 • +» tt 
 
 r-l • 
 
 «5 "3 .O 
 
 1 
 
 ° i 
 
 A 
 
 
 32 
 
 o 
 
 £4 
 
 31 
 
 
 it 
 
 i-t P 
 
 a <h 
 
 o o u 
 
 ft .O %* 
 
 • • ? 
 
 5\» ir\ 
 
 • • • 
 
 52. rt 
 
 H KN 
 
 $£ 3 £ & 
 
 44 
 
 4» 
 
 a) 
 
 Vi 
 
 o 
 
 in 
 
 t 
 
 •8 
 
 o 
 
 t 
 
 o 
 o 
 
 • • • 
 
 •H H 
 
 
 Htr P 
 
 Rr & 
 
 O O ITk 
 
 
 P I 
 
 H 
 
 
 H ITk 
 
 «0 H 
 
 • • 
 
 •0 rR 
 
 evi k\ 
 
 •* -J? 
 
 r-l VO 
 
 £- I 
 
 $ 
 
 3 «. 
 
 CM O 
 
 
 g & 
 
 I R 
 
 £ 
 
 a 
 
 ©0-3 
 
 ■H S 4 
 
 (4 D 9 
 
 a) U 
 
 > -P 
 
 (D 
 
 P 
 
 a) 
 © 
 P. 
 P 
 
 o 
 © 
 
 "p 
 
 at 
 
 1 
 
 © 
 o 
 
 a 
 
 n o 
 a o 
 o 
 
 b frT 
 
 •H Q 
 
 © 
 P 
 
 CO 
 
 a) 
 
 -P 
 
 © 
 
 .G 
 
 • © .— » 
 
 HP "0 
 
 •H © 
 
 © H P 
 
 OH 4 
 
 O >> © 
 
 © a p 
 
 p o a 
 
 3.Sh 1 
 
 a 
 
-10- 
 
 o cj A 
 
 O OS \T\ 
 
 si 2 
 
 • • • 
 
 3 
 
 CO K\ 
 
 • • 
 
 vx> r>- 
 co e\j 
 
 • • 
 
 K\ eg 
 
 O i-4 
 
 
 as 
 
 
 C\J 
 
 <7\ 
 
 tO r- | )*- I 
 
 1—tT* HI ' 
 
 
 o ir> o irt id 
 
 8 ' 
 
 § ' 
 
 •fN J* 
 
 o o ir» o ir\ 
 
 
 8 & 
 
 H 
 
 IS 
 
 e 
 
 o 
 
 c 
 
 o 
 
 a 
 
 co 
 T> 
 
 0) 
 
 ■P 
 m 
 U 
 
 □ 
 
 © 
 o 
 a 
 o 
 o 
 
 
 I 
 
 a) 
 
 u 
 
 « 
 .a 
 
-11- 
 
 S iii'nmaT* y 
 
 In 19UU three applications with ground- sprayer equipment near 
 Toledo, Ohio, at 5-day intervals to early-market sweet corn gave 
 excellent "borer control with three DDT preparations. Of three materi- 
 als tested, 10, 8 percent of DDT in pyrophyllite was outstanding from 
 the standpoint of reducing "borer populations in the plant as well as 
 of the ease with which it could "be put into a spray suspension. This 
 material gave 97*9 percent reduction of "borers in the plant and 99»2 
 percent reduction in the ears, when applied with a wheelbarrow sprayer 
 run "by a gasoline engine and applied with a hand nozzle that produced 
 a solid cone of spray. 
 
 Four applications of dusts containing 0#75» l«5t 3t and 6 per- 
 cent of DDT in pyrophyllite were made 5 to 7 days apart with a ground 
 machine to sweet corn in dosages of 0.3, 0.6, 1.2, and 2.U pounds per 
 acre-application. Borer reduction increased with each increase in the 
 dosage rate, and at the highest rate provided 95 percent reduction of 
 corn borer larvae infesting the ears, even though the applications were 
 begun too late for best results against newly hatched larvae. The 
 yield resulting from treatments applied at a rate of 2.H pounds of DDT 
 per acre-application was graded 89.9 percent salable and 85.1 percent 
 No. 1 and borer-free. 
 
 On the variety Evergreen four airplane applications 3 to 5 days, 
 apart of a concentrated spray containing 8.9 percent of DDT in white 
 oil, at the rate of about 2.25 gallons per acre, provided borer reduc- 
 tions in plants of 98 percent with all ears salable size and borer-free 
 in center rows of the treated swath. DDT in dust form applied by air- 
 plane to the same variety was somewhat less effective than the concen- 
 trated spray. Aerial dust treatments resulted in 82.3 percent reduction 
 of borers in the ears, and a yield 85.6 percent of which was No. 1 and 
 borer-free. 
 
 All treatments resulted in an increase in the number of ears of 
 salable size as compared with the yield of untreated check plots. 
 
UNIVERSITY OF FLORID* 
 
 3 1262 09238 7041 
 
 \