68 ^fASS. EXPERIMENT STATION BULLETIN 378 



In spraying experiments on roses in greenhouse benches using 8 differ- 

 ent commercial rotenone preparations, the addition of a neutral copper 

 fungicide decreased the efificiency of the insecticide against the red spider 

 about 5 percent in those materials consisting primarily of rotenone and 

 emulsifier. However, in those preparations in which rotenone was com- 

 bined with other insecticidal ingredients such as thiocyanate or light 

 mineral oil, the additon of a neutral copper fungicide had no significant 

 effect on the red spider mortality. 



In these experiments satisfactory control was obtained after four ap- 

 plications at weekly intervals only with those materials which contained 

 some insecticidal ingredient in addition to rotenone and emulsifier. Ac- 

 cording to counts made 3 to 5 days after each of four applications at 

 weekly intervals, only those sprays which caused a mortality of 50 per- 

 cent or greater prevented the spider population from increasing during 

 the spraying period; and in some cases where the population was held in 

 check during the spraying period, it increased so rapidly after spraying 

 was discontinued that within one week the infestation was greater than 

 after the first application. 



Many of these commercial sprays were more effective at concentrations 

 two to three times greater than recommended by the manufacturers. 



Preliminary experiments on potted rose plants gave promising results 

 from a mixture of tartar emetic, brown sugar and wetting agent, but it 

 was ineffective when the brown sugar was omitted. Indications of plant 

 injury from this material were observed. 



A dinitro dust was very toxic to red spider on both rose and carnation 

 but caused some injury to rose foliage. 



Biology and Control of the Apple Leaf Curling Midge. (W. D. Whit- 

 comb, Waltham.) The apple leaf curling midge, (Dasyneura nmli Kieff.) 

 was generally more abundant than in 1939 and the known infested area 

 was increased to the west and southwest by the discovery of this insect 

 at Ashby and Westboro, Massachusetts. 



In the insectary only one midge fly emerged from 325 maggots which 

 were collected in June, July, and August 1939 and overwintered in sand, 

 but flies emerged in 1940 from 8 to 36 percent of the maggots which were 

 collected in September 1939 and held over winter in the same way. The 

 transformation to flies was 42.42 percent from the maggots collected in 

 June; 27.6 percent from those collected in July; and 13.33 percent from 

 those collected in August. 



The orchard infestation at Westford, Massachusetts, as indicated by 

 the percentage of terminal buds on which eggs were laid, began May 24 

 and reached three distinct peaks on June 4-7, July 16-19, and August 23, 

 when eggs were found on 99 to 100 percent of the l)U(ls. .\fter June 2? 

 practically all new growth is on watersprouts, and on trees where water- 

 sprouts are limited the actual number of eggs is relatively small even 

 though the percentage of buds infested is high. After August 25 only one 

 or two growing tips suitable for ovipositon by the midge flies could be 

 found on a tree. 



The emergence of maggots from rolled leaves was concentrated in two 

 distinct peaks, that of the first generation larvae occurring on June 25 and 

 that of the second generation larvae reaching a maximum on August 2 

 but being spread out over the period July 20 to August 9. Emergence 

 in large numbers occurred only when accompanied by sufficient precipita- 

 tion to thoroughly soak the leaves. 



