40 MASS. EXPERIMENT STATION BULLETIN 436 



weekly intervals to greenhouse roses indicated that they will not give good com- 

 mercial control of the red spider mite under these conditions. In experiments 

 where a partially satisfactory kill was recorded, a severe infestation developed 

 soon after spraying was discontinued. 



An experimental benzene mixture killed the red spider mite well but caused 

 excessive injury to rose foliage, while an emulsified monochlor naphthalene 

 mixture was both injurious to rose foliage and ineffective against the mite. 



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

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

 Wakefield and the Charleston Wakefield varieties were 94 anxi 88 percent free 

 from injury, indicating considerable resistance compared to Golden Acre and 

 Super Curled Savoy with only 47 and 12 percent of the plants free from injury. 

 On Golden Acre one application of 4 percent calomel-talc dust in a small mound 

 about the stem of the plant gave perfect protection and produced 90 percent 

 salable heads. Corrosive sublimate solution (1 ounce in 10 gallons of water) 

 in two applications gave 95 percent protection. DDT-talc dust containing 5 

 percent DDT, when applied twice at weekly intervals with a hand duster, gave 

 95 percent protection and was more effective than a 3 percent DDT-talc dust 

 applied either with a duster or in a mound around the stem of each plant. A 

 DDT solution containing 1 percent DDT applied in the same way that corrosive 

 sublimate solution was used was quite effective but caused injury to the roots of 

 the plant, apparently due to the action of the solvent rather than of the DDT. 



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

 laborator}' poison studies, spray suspensions containing 2 pounds or more actual 

 DDT in 100 gallons gave reasonable control of the plum curculio. Two pounds 

 of actual DDT in 100 gallons were approximately as effective as 4 pounds of 

 lead arsenate. The time required to kill the beetles and the number of punctures 

 made in sprayed apples decreased consistently as the amount of DDT in the 

 spray was increased, and a spray containing 4 pounds of actual DDT in 100 

 gallons of water (0.5 percent DDT) gave almost perfect protection. Combina- 

 tions of lead arsenate and DDT were generally more effective than equal amounts 

 of either material alone. A combination of 4 pounds of lead arsenate and 2 pounds 

 of actual DDT in 100 gallons was very effective and highly promising for prac- 

 tical use. 



Orchard experiments w'ere greatly limited by a general crop failure following 

 destructive spring frosts, and the infestation of the plum curculio was very heavy. 



Applications of the regular schedule on Golden Delicious apples using wettable 

 sulfur 4 pounds, a sulfated alcohol spreader 2 ounces, with the following materials 

 in each 100 gallons of water gave these results: 



Number of Percent Free 



Material Apples from Stings 



Lead arsenate 4 pounds 1 206S 89 63 



DDT 1 pound J ""' 



Lead arsenate 2 pounds 1 1472 78 47 



DDT 1 pound J "" 



Lead arsenate 4 pounds...- 1231 60.44 



Unsprayed 1 73 4.62 



Apple Maggot Emergence. (W. D. Whitcomb, Waltham.) The emergence of 

 apple maggot flies in orchard cages at Waltham occurred at about the normal 

 time although the first fly was not recovered until July 1 , about two weeks later 

 than in the early season of 1944. The peak of emergence occurred on July 18. 



