48 MASS. EXPERIMENT STATION BULLETIN 339 



of lime-sulfur 2-100, to give protection up to the time of the first spray of the 

 regular schedule. 



Two new types of colloidal sulfur (paste form) which had shown great promise 

 in preliminary trials the previous year were studied under orchard conditions. 

 A comparison was made of dry lime-sulfur used at standard strength and at a 

 somewhat reduced dosage recommended by the manufacturer in the hope of 

 avoiding foliage injury. 



In all of the above tests liquid lime-sulfur 2-100 was applied in the pre- 

 blossom and calyx sprays and the new materials in the four subsequent appli- 

 cations. Liquid lime-sulfur was applied in one section at 1-50 strength in the 

 pre-pink, 1-75 in the pink, and 1-100 in the calyx applications, in an attempt to 

 secure maximum scab control at the most critical period and at the same time 

 lessen the danger of foliage injury. A wettable sulfur was used in the summer 

 sprays in this section. All of the tests were compared with the standard sprays 

 recommended for the State: lime-sulfur 1-50 in pre-blossom and calyx appli- 

 cations and a wettable sulfur in the four cover sprays. Lead arsenate was used 

 in all the tests: 3 lbs. per 100 gals, in pre-blossom and 3d cover sprays; 4 lbs. 

 per 100 gals, in calyx, 1st and 2d cover sprays; and 2 lbs. per 100 gals, in the 

 4th cover spray. 



On the whole the season was not of a type to induce severe spray burn, and 

 no serious injury was noted in any of the test blocks. A slight amount of 

 marginal burn was noted, however, following the early sprays with lime-sulfur. 

 No burn was observed from summer applications of wettable sulfur. It was 

 hoped that a reduced dosage of liquid lime-sulfur in the pink and calyx appli- 

 cations would prevent spray burn, but this did not prove to be the case, and in 

 the section sprayed with half strength lime-sulfur and wettable sulfur, spray 

 injury was as conspicuous as where lime-sulfur at standard strength was used 

 alone. Reducing the dosage of dry lime-sulfur did not materially lessen the 

 amount of foliage injury but gave satisfactory control of scab. Some russeting 

 of Mcintosh fruit was noted in the sections which received the colloidal sulfurs 

 in summer applications. The relative effectiveness of these sprays in control 

 of scab and insect pests was measured on Mcintosh. The results are as follows: 



Percentage of Fruit Showing 

 Percentage Injury from — 



Material Tested of Clean 



Fruit Scab Curculio Codling 



Moth 



King 59.9 5.1 4.9 16.9 



Linco 81.6 2.1 1.3 6.2 



Lime sulfur (modified) 90.5 0.6 1.2 5.5 



Lime sulfur-post calyx wettable sulfur 92.2 1.1 0.9 2.8 



Lime sulfur-magnetic sulfur, half strength 93.3 1.1 0.4 1.6 



Dry lime sulfur (6 % lbs.) 90.5 1.4 0.7 5.5 



Dry lime sulfur (8 lbs.) 73.6 0.3 10.6 9.9 



Check 3.4 86.1 15.6 14.5 



Derris and Pyrethrum for the Control of Greenhouse Leaf Tier on Snapdragons. 

 In two separate experiments on snapdragons grown in the greenhouse from 

 January to May, commercial pyrethrum sprays diluted 1-200 and 1-400 and 

 applied at approximately 10-day intervals have given good control of the green- 

 house leaf tier. A derris extract containing lj-£ percent rotenone was also sat- 

 isfactory. When the pyrethrum spray was diluted 1-800 the control was poor, 

 evidently due to the low concentration of the insecticide. 



