ANNUAL REPORT, 1937 57 



0.6 percent rotenone ranked next in effectiveness with an 85 percent reduction in 

 beetle population. Calcium arsenate-monohydrated copper sulfate-lime dust 

 10-20-70, and copper oxychloride-clay dust 1-14 (Dupont "A") were nearly as 

 effective but caused slight to moderate burning of the cantaloupe foliage. Cryolite- 

 clay dust 20-80 (Nat. Sulfur Company) and Cryolite Spray (Nat. Sulfur Co.) 

 4 pounds in 100 gallons gave 74 and 73 percent control, but the spray also caused 

 some plant injury. Pyrethrum-clay dust 30-70 and tetra methyl thiuram disulfide 

 (Dupont) 1 pound in 100 gallons, as a repellent, were the least effective treatments. 

 However, the latter material seemed to protect the plants from serious injury in 

 spite of a large number of beetles present. 



Yield records corresponded with the striped beetle control, and the plants treat- 

 ed with cube-clay dust yielded 2.03 harvested fruits per vine compared to 1.35 

 fruits on the untreated vines. Based on yield, pyrethrum-clay dust, thiuram disul- 

 fide spray, and copper-calcium arsenate-lime dust were good, while the copper 

 oxychloride dust was not significantly better than no treatment. 



Control of Cabbage Maggot with Mercury Compounds. In 1937 the infestation 

 by the cabbage maggot at Waltham was the most severe in ten years. Only 1 

 percent of the untreated cabbage plants produced a salable head and 95 percent 

 of them were killed or severely injured. The roots of most of the untreated plants 

 and those having ineffective treatments were attacked by 30 to 40 maggots, and 

 only an abundance of rain which stimulated the growth of secondary roots above 

 the maggot injury prevented a total loss of these plants. 



The first eggs were found on May 7, this being the seventh consecutive \ear 

 when eggs were first found between May 6 and 10 at Waltham. 



Corrosive sublimate, 1 ounce in 10 gallons of water, was applied on May 8, 

 16, and 22, and continued to give good protection. Two applications of this 

 material on Maj* 8 and 16 gave 98 percent commercial control and yielded 82 

 percent large and medium heads. A single treatment on May 16 was more effective 

 than one application on the other dates and gave 80 percent commercial protection 

 with 90 percent satisfactory heads. 



When pure calomel was dusted on the roots at the time of transplanting, 92 

 percent commercial protection was obtained and the yield was high. Calomel 

 mixed 1 — 1 and 1 —3 with clay gave less actual control of the maggot but provided 

 sufficient protection to produce over 90 percent satisfactory heads. Calomel 

 and clay 1—9 gave only 54 percent protection, indicating insufficient toxic action. 



When the roots of cabbage were dipped at transplanting in a suspension of 

 calomel and various adhesive materials, the protection provided by this coating 

 was inadequate. For this purpose, calomel was used at the rate of 16 grams and 

 4.8 grams in a gallon of water. It was apparent that the amount of calomel was 

 insufficient rather than that the method of application was faulty. Among the 

 adhesive materials, laundry starch (1 jounces per gallon) and a synthetic wax 

 soluble in cold water (13^ ounces per gallon) were the most satisfactory, while 

 solutions of liquid rubber, gum arable, and locust bean gum were less effective. 

 When Semesan (10 grams per gallon) was substituted for the calomel, the plants 

 were killed or severely injured, and corrosive sublimate at the rate of 1 ounce in 

 10 gallons of water combined with the adhesive materials was ineffective. 



Results of these and previous experiments indicate that a thorough dusting of 

 the roots of cabbage plants with calomel powder at the time of transplanting gives 

 safe and effective control of the cabbage maggot and can be recommended. 



The cabbage maggot was also a serious pest of radishes at Waltham in 1937. 

 Since the insect attacks the edible part of the radish, injury to this crop is more 

 destructive than injury to cabbage. 



