EFFECT OF SOIL APPLICATIONS OF INSECTICIDES I 



seeds were treated with Spergon and planted 6 inches apart in a 

 single row 125 feet long in each plot. Although Fordhook beans 

 are ordinarily harvested green, both varieties were cut between 

 September 14 and 19, dried, and threshed about the second week 

 in October. Threshing was expedited through the use of a special 

 power thresher. 



Ventura Lima Beans 



Periodic inspection of Ventura lima bean plants showed that the 

 application of the insecticides to the soil each year had not affected 

 germination or depressed the growth of the emerging seedlings. 

 In 1949 an excellent stand and exceptionally large yields were ob- 

 tained in all plots. In 1950 the seed-corn maggot (Hylemya 

 cilicrura (Rond.)) caused considerable damage to the seed and 

 plants in the plots treated with ethylene dibromide and in the un- 

 treated plots, but bean production remained high. In 1951 there 

 was no significant difference in numbers of plants or in the yields 

 of lima beans between the treated and untreated plots, although 

 the untreated plots tended to have the best stand and the largest 

 yield. (Table 2.) 



Table 2. — Tolerance of vegetables to insecticides applied annually 

 to the soil prior to planting, 19^9-51 



[Aldrin applied at 4, chlordane and toxaphene at 20, and ethylene dibromide at 54 pounds per acre] 



Crop and insecticide 



Total plants 



Yield 





1949 



1950 



1951 



1949 



1950 



1951 



Ventura lima beans 

 (750 feet of row) : 

 Untreated 



Number 

 1,418 

 1,403 

 1,405 

 1,323 

 1,388 



Number 

 1,020 

 1,261 

 1,126 

 1,105 

 934 

 139 



939 

 1,268 

 1,240 

 1,152 

 1,147 



176 



73 

 74 



77 

 78 

 73 



Number 

 860 

 831 

 746 



849 

 784 



Pounds 

 218 

 217 

 216 

 204 

 214 



Pounds 

 192 

 214 

 199 

 196 

 200 



Pounds 

 189 



Aldrin _ _ 



167 



Chlordane 



166 



Toxaphene 



165 



Ethylene dibromide- __ 

 Error * 



172 



Fordhook lima beans 

 (750 feet of row) : 

 Untreated _ 



1,398 

 1,387 

 1,394 

 1,365 

 1,390 



1,031 



970 

 853 

 937 

 973 



169 

 186 

 173 

 168 

 173 



114 

 145 

 130 

 125 



124 



111 



Aldrin 



101 



Chlordane _ _ - 



97 



Toxaphene 



93 



Ethylene dibromide. __ 

 Error 



120 



Cabbage (180 feet of row): 

 Untreated 



84 

 84 

 84 

 84 

 84 



87 

 85 

 84 

 86 

 85 



172 

 194 

 159 

 150 



186 



196 

 188 

 188 

 183 

 211 



302 



Aldrin 



306 



Chlordane _ __ _ 



292 



Toxaphene 



251 



Ethylene dibromide 



293 



1 Error indicates least significant difference at P = 0.05. Where no figures 

 are given the difference was not significant according to the F test. 



