40 MASS. EXPERIMENT STATION BULLETIN 315 



and gave good control of thrips. Similar combinations in which Paris green and 

 calcium arsenate were used to replace lead arsenate caused serious injury to the 

 plants. Laboratory tests of different strengths of two rotenone sprays and one 

 pyrethrum-rotenone spray against adult and young-stage thrips gave the fol- 

 lowing results: 



Adult Thrips Young Thrips 



Material Exposure Percentage Exposure Percentage 



(hours) of Kill (hours) of Kill 



Cubor lib.— 50 gal 24 60 



Ku-ba-tox 1—400 24 75 18 90 



Cubor 2 lbs.— 50 gal 24 100 



Ku-ba-tox 1—200 24 100 



Red Arrow 1—200 24 90 



Red Arrow 1—400 24 80 18 85 



Red Arrow 1— 400 1 



4-Dipest 1— 400 J 24 100 



Kaloil 1—400 18 90 



Rotenone Sprays and Dusts for Mexican Bean Beetle. Rotenone sprays and dusts 

 both gave excellent control of larvae of the Mexican bean beetle. The sprays also 

 gave a high percentage of kill of adult beetles. Although in many cases the 

 killing action of the rotenone compounds was not as rapid as that of arsenicals, 

 yet following rotenone applications the insects quickly ceased feeding and dropped 

 to the ground and very few, if any, revived sufficiently to resume feeding. The 

 value of rotenone compounds lies chiefly in the fact that these could be employed 

 after an attack had developed and also could be applied much nearer the time 

 of harvesting the crop than would be possible with arsenicals or fluorine com- 

 pounds. 



Wettable Sulfurs as Substitutes for Lime-Sulfur in Post-Blossom Orchard Sprays. 

 Tests of these materials were continued in cooperation with the Department 

 of Pomology. The tests in the station orchard were duplicated in a commercial 

 orchard near-by. Five standard types of wettable sulfurs were tested in com- 

 bination with lead aresenate, and their relative values compared with the stand- 

 ard combination of lead arsenate-lime-sulfur solution on both Mcintosh and 

 Baldwin. In the pre-blossom and calyx sprays, the lime-sulfur-lead arsenate 

 combination was used. The wettable sulfurs were applied in the first, second, and 

 third cover sprays, and lead arsenate alone in the fourth cover. In addition to 

 the commercial sulfur sprays, a product composed of 300-mesh sulfur and a slight 

 amount of wetting agent was used with lead arsenate in the first three cover 

 sprays. 



While on the whole the season was not of a type to induce severe burning and 

 at the same time was not particularly favorable for scab, yet unmistakable and 

 general burning of foliage was noted following the lead arsenate-lime-sulfur 

 applications. No russeting of fruit was noted. The wettable sulfur sprays in no 

 case caused any foliage injury following any of the three applications. The 

 degree of control of insect pests and diseases from the use of these sprays was 

 measured chiefly on Mcintosh, a variety particularly susceptible to scab, and 

 are as follows: 



