10 CIRCULAR 926, U. S. DEPARTMENT OF AGRICULTURE 



A statistical analysis of the yield data shows that none of the 

 insecticides affected the growth or productivity of this crop during 

 the 3-year period. Owing to low temperatures in 1950, some of 

 the plants failed to head properly, but otherwise they appeared to 

 be normal in all years (table 2). 



Lettuce 



Lettuce of the Great Lakes variety was seeded in rows 31 feet 

 long on February 15, 1950, and in rows 62 feet long on March 9, 

 1951. Yield figures were obtained by cutting and weighing the 

 heads as they matured. 



In 1950 many of the heads became affected with slime or soft 

 rot and therefore were discarded, but in 1951 only a few heads 

 were affected. In neither year did the insecticides affect the germi- 

 nation or growth of this variety of lettuce. The similarity in yields 

 of the treated and untreated plots confirmed the fact that this crop 

 had not been adversely affected by the~e insecticides (table 2). 



Celery 



From 15 to 21 transplants of the Utah variety of celery were 

 placed in each plot each year, at spacings of 18 to 24 inches. The 

 plants were set out in the latter part of March and were cut about 

 the middle of July. They did not reach the size of commercial 

 plantings because there was no opportunity to irrigate them as 

 frequently. Yields were determined by weighing the entire plants 

 minus the roots. 



None of the insecticides affected the growth or yield of celery 

 in 1949. The applications in 1950 and 1951 also did not signifi- 

 cantly affect the yield, although there was a tendency toward lower 

 yields in the plots treated with toxaphene (table 2) . 



Carrots 



Carrots of the Goldinhart variety were planted each year with 

 a hand seeder in a single row 31 feet long in each plot. No effort 

 was made in 1949 to obtain yield data because of the poor stand 

 in all plots. 



In 1950 wireworms were responsible for fewer plants and for 

 the low yield of carrots obtained in the untreated plots. At har- 

 vesttime 3 percent of the carrots had one or more feeding punc- 

 tures. Some wireworm damage was noted in one of the plots 

 treated with ethylene dibromide, but not in the plots treated with 

 aldrin, chlordane, or toxaphene. As shown in table 2, two applica- 

 tions of toxaphene in the spring and fall of 1949 significantly 

 reduced the yield of carrots in 1950. In 1951, however, the differ- 

 ences in the yield of carrots were within the limits of experimental 

 error (table 2). 



