ANNUAL REPORT, 1936 



55 



The sprays were applied at 5-day intervals beginning with the first appearance 

 of larvae in each field. Four applications were made between June 19 and July 

 3 on each farm. A fifth application was made on July 8 on one farm because 

 the corn there had developed more slowly than in the other field although the 

 insect first appeared on approximately the same date in both cases. The 

 materials tested were ground derris (4 percent rotenone), phenothiazine (thio- 

 diphenyl-amine) and tank-mix nicotine tannate. Each material was used at 

 the rate of 12.5 gallons for the first application, 15 gallons for the second and 

 third, and 25 gallons for the fourth and fifth sprays. 



The results were based on the total yield from both fields, approximately 

 20,000 ears being examined. Nicotine tannate and derris were very effective 

 in reducing corn borer damage. Phenothiazine gave fair control. Its failure 

 to measure up to the other materials is believed to be due to its poor suspension 

 qualities which prevented uniform coverage and protection. None of the 

 materials caused any injury to the corn nor did they render it unsafe as fodder. 

 The yield record from one of the farms is as follows: 



Percentage of Ears Percentage 

 of Ears In- 

 Total Number Grade fested but 

 Treatment* of ears Clean 1 and 2 Infested Salable 



Derris 2,124 95.1 90.0 4.9 57.2 



Nicotine tannate 2,447 92.1 88.4 7.9 53 



Phenothiazine 2,232 89.9 78.8 10.1 48.4 



Check 1,993 77.7 70.4 22.3 45.7 



♦Four plots totaling one-eighth acre for each treatment. 



On each farm the variety tested was Span Cross 2, the earliest variety of 

 yellow sweet corn to mature. Both growers were anxious to secure the full 

 benefit of an early market so that the crop was harvested as rapidly as possible. 

 This allowed a comparatively short time for the infestation of the ears and 

 enabled the check plots to show a much better record than the relative infes- 

 tation warranted. Practically every stalk in the check plots was infested and 

 many contained 6 to 8 borers and were seriously weakened, while comparatively 

 few stalks in the sprayed plots showed the presence of borers. This is indicated 

 in the smaller yield in the check plots, a difference ranging from 1,048 to 3,632 

 ears per acre from the yield in the sprayed plots. It is further supported by the 

 relative percentage of salable infested ears. In the derris and nicotine-tannate 

 plots practically all of the borers found were very small larvae; in many cases 

 they had penetrated only a few of the husks or but a short distance into the 

 base of the ear. In such cases the corn itself was not damaged and much of this 

 type went into the market as Grade 1 or 2. Infested corn from the check plots, 

 however, often contained full-grown larvae, and in a majority of cases the ears 

 were worthless. Both growers were able to command the highest market 

 prices because of their ability to guarantee borer-free corn. On the basis of 

 the price scale prevailing at each picking the sales record for the farm men- 

 tioned above was as follows: 



Treatment Total sales* 



Derris $37.04 



Nicotine tannate 41 .53 



Phenothiazine 36.70 



Check 28.56 



*Sales were from an area of one-eighth acre of each treatment. 



Loss due to 

 borers 



$2.22 

 4.78 

 4.90 

 8.80 



