ANNUAL REPORT, 1944-45 39 



Control of Plum Curculio in Apples. (W. D. Whitcomb, Waltham.) Dosage 

 experiments using %, 1, and 13^4 gallons of spray per 100 square feet of surface 

 area of the tree were continued with special emphasis on the effect of this factor 

 in controlling the plum curculio in a heav^- crop of apples. During the experi- 

 ments 246,000 apples were examined. The results indicated that the IJ^ gallon 

 dosage was definitely more effective and that the % gallon dosage was unsatis- 

 factory. The 1 -gallon dosage was inconsistent, and suggested that the margin 

 was so slight that the results might be affected by factors which were not rrifeas- 

 ured. The influence of dosage on control of the codling moth was even more 

 significantly in favor of the 114 gallon treatment. 



Cryolite again proved less satisfactory than lead arsenate against the plum 

 curculio in apples. 



During the hot weather in late June and early July many dropped apples in- 

 fested with plum curculio larvae were burned b}- the sun. Emergence of larvae 

 from normal apples was 39.4 per 100 fruits; from one-half burned apples, 2.66 

 per 100 fruits; and from completely burned apples 0.20 per 100 fruits. 



Introduction of Parasites of Oriental Fruit Moth in Peach Orchards. (A. I. 



Bourne.) Because of the war emergency it was not possible to conduct the 

 oriental fruit moth parasite-rearing project in 1944. 



Control of Cabbage Maggot. (W. D. Whitcomb, Waltham.) With normal 

 heavy field infestation by the cabbage maggot, untreated plants of the Early 

 Jersey Wakefield and Charleston Wakefield varieties again showed about 25 

 percent less injury, and produced 30 to 50 percent more marketable heads than 

 Golden Acre and Super Curled Savoy varieties. Penn State Ballhead also showed 

 considerable resistance. 



Tar paper pads and 4 percent calomel-talc dust both gave more than 90 per- 

 cent control, and corrosive sublimate solution 1-1280 in two applications was 

 satisfactory with 84 percent control. Talc alone gave no protection, and reduced 

 dosages of 2 percent calomel-talc and corrosive sublimate solution 1-2560 in two 

 applications were unsatisfactory against a very heavy attack. 



The number of eggs laid on each variety in the period May 6-31 varied from 

 29 to 14 per plant, with the largest number being found on Charleston Wakefield 

 which showed the least injury, indicating that resistance results from the ability 

 of the plant to resist injury rather than from any repellent action to the flies 

 during oviposition. 



Biology and Control of the Red Spider Mite on Greenhouse Crops. (W. D. 



Whitcomb, Wm. E. Tomlinson, Jr., and Wm. Garland, Waltham.) Applications 

 of two forms of DNOCHP containing 20 and 13.3 percent of active ingredient 

 respectively killed approximately 97 percent each of the red spider on greenhouse 

 roses when reduced to equal amounts of DNOCHP by using 8 and 12 ounces 

 respectively in 100 gallons of water. This indicates that a definite concentration 

 of DNOCHP is necessary, whether applied in one heavy application or several 

 light applications. Proprietary sprays containing naphthalene and azo-benzene 

 both gave excellent control of red spider but caused injury- to rose foliage. 



A proprietary spray containing the extract of yam bean and one containing 

 B-butoxy-b'thiocyanodiethyl ether were both inconsistent and in general gave 

 unsatisfactory control of red spider on greenhouse roses when used according to 

 manufacturer's directions. 



Control of the Squash Vine Borer. (W. D. Whitcomb, Waltham.) Studies of 

 the susceptibility of different genera of the family' Cucurbitaceae to attack by the 

 squash vine borer showed the Cucurbita maxima was most heavily infested. The 



