ANNUAL REPORT, 1933 35 



that this midge has been observed but not identified at other points in the in- 

 fested area during the last five Aears. The known infested area now covers 

 about 1,0C0 square miles extending from Melrose, Massachusetts, westerly to 

 Westford, Massachusetts, and northerly to Durham and Rye, New Hampshire. 

 Several of the largest commercial orchards in eastern New England are now 

 infested. 



Injury is identified by the presence of tightly rolled leaves on the tips of branches 

 and on water sprouts. The leaves are rolled from the underside upward toward 

 the midvein and parallel to it. In heavily infested specimens the entire leaf forms 

 two tight rolls. All varieties of apples grown in the orchards under observation 

 were infested, but Baldwin, Delicious, and Mcintosh appeared most susceptib'e, 

 while Wealthy was almost immune. The growth of nursery trees and grafts 

 is noticeably delayed and stunted by the activity of this midge, but on bearing 

 trees the size, color, and abundance of fruit were not conspicuousK- affected 

 (luring the present season. 



There appear to be four generations annually, the first midges emerging about 

 June 1, and requiring approximately 5 weeks to complete their life c>cle. The 

 abundance of the third and fourth generations depends on the number of water 

 sprouts available. The eggs, which are laid on the unfolding leaves of terminal 

 growth or water sprouts, hatch in 3 to 5 days, and the tin}- \yhite maggots feed 

 for about 20 days within the tightly rolled leaves. When mature, the maggots 

 are bright orange in color and usually fall to the ground where they spin a small 

 white cocoon just beneath the surface of the soil. Pupation requires 13 to 

 18 days. 



On water sprouts the majority of the infested leaves turn black and fall after 

 the maggots have left them, but on terminal shoots many of the rolled leaves 

 remain throughout the season. 



Two natural enemies, a predatory bug and a parasitic hymenopteron, were 

 reared from leaves infested by the midge, and promise to aid in controlling 

 this pest. 



Biology and Control of the Carrot Rust Fly. (W. D. Whitcomb, Waltham.) 

 As in the two previous seasons, field infestation by the first generation of the 

 carrot rust fly was negligible, and untreated carrots as well as those receiving 

 insecticide applications were practically free from injury. The only infested 

 carrots were found where the plants were watered daily during the oviposition 

 period by overhead irrigation, and only 3 per cent of these were infested. 



Injury by the second generation reached 26 per cent in the untreated plot and 

 was greatest in the plot receiving overhead irrigation, where 32 per cent were 

 infested. This further demonstrates the previously reported theory that cool, 

 damp soil is favorable to this pest. 



Of the dust treatments, which were applied July 31, August 7 and 14, and 

 September 5 and 12, naphthalene was most efficient, with 98 per cent clean car- 

 rots. Soot and two dusts containing derris gave 90 -|- per cent control, and to- 

 bacco and two dusts containing mercury gave 80+ per cent control. Kainit was 

 quite effective, but killed many seedling carrots and caused a poor yield. The 

 treatment of seed with calomel or corrosive sublimate combined with gvpsuni 

 in varying quantities reduced injury 10 to 15 per cent, but the results were not 

 consistent with the amount of mercury used. Seed treated with pure calomel 

 yielded 92 per cent clean carrots. 



Adaptability of Cryptolaemus to Control of Mealybugs in the Greenhouse. 



(W. D. Whitcomb, Waltham.) The Australian Mealybug Destroyer, Crypto- 



