Control of San Jose Scale With Lubricating Oil. 



11 



Complete eradication of the scale can not be expected with sum- 

 mer treatments with any insecticide. With trees in full foliage it 

 is impossible to cover entirely all parts of the trees with a spray 

 solution. The best results that can be hoped for with a summer ap- 

 I plication are to hold the scale in check until the dormant sprays can 

 ^ be applied. The only time when bad infestations of the scale can 

 be completely cleaned off is during- the dormant season. 



As soon as continued cool weather occurred some tests with late 

 summer sprays were conducted. These were applied on September 

 21 and 22 on trees thoroughly infested with the scale. The appli- 

 cation was made on the Ben Davis variety about a month before the 

 fruit was harvested. The weather remained generally cool after 

 the tests were made. In Table 4 are given the data covering this 

 experiment. 



; Table 4. — Mortality of all stages of the San Jose scale from the use of late 

 r summer sijrays, English d Boles orchard, BentonvUle, ArJc, 1922. 



Plat. 



Inseetioide. 



Lubricating-oil emulsion 



(■Lubricating-oil emulsion. 

 \Bordeaiix 



Liquid lime-sulphur 



{Liquid lime-sulphur 

 40 per cent nicotine sul- 

 phate. 



Check (unsprayed) 



Dosage. 



3 gallons in 100; 2 per cent . 



3 gallons in 100; 2percent. 

 -|-|-oO 



l\ gallons in 50 



ru gallons in 50 



il'toSOO 



Date of 

 applica- 



Date of 

 examina- 

 tion. 



1922 

 Sept. 21 



22 I 



22 1{ 



1922 



Oct. 1 



20 



1 



20 



1 



20 



1 



20 



Num- 



Num- 



ber of 



ber of 



scales 



scales 



dead. 



alive. 



3,025 



79 



2,350 



49 



1,700 



53 



1,550 



51 



1,000 



87 



1,556 



839 



1,000 



31 



1,698 



816 



1,288 



638 



1,566 



839 



Percent 



of scales 



dead. 



P.ct. 

 97.45 

 97.96 

 96.98 

 96.81 

 92.00 

 64.97 

 96.99 

 67.54 



66.87 

 65.11 



Two examinations of scale-infested twigs from the various plats 

 were made, the first 10 days after the spray application and the 

 other about 20 days later. The reason for the first examination was 

 to get an idea of the mortality of the scales, particularly the young 

 crawlers, before the dead bodies were blown away. Plats 1 and 2, 

 2 per cent lul)ricating-oil emulsion plats (a weak Bordeaux being- 

 used with the lubricating-oil emulsion on Plat 2) showed a fair kill of 

 the scales on the dates of both examinations. At the time of the last 

 examination all the young stages of the scale were dead, only a few 

 of the full grown females in protected crevices escaping. A kill 

 of 96 to 97 per cent of the scales during the cool weather of late sum- 

 mer compares favorably with results from a dormant treatment with 

 2 per cent oil emulsion, especially since the foliage hinders thorough 

 work in a summer treatment. Plats 3 and 4, summer-strength lime- 

 sulphur solution plats, lime-sulphur used alone in one and 40 per 

 cent nicotine sulphate added in the other, showed comparatively 

 good killing at the first examination. When these plats were ex- 

 amined about a month after the application, however, they showed 

 approximately the same percentage of dead scales as on Plat 5, the 

 unsprayed check. On October 20, twigs from Plats 3, 4, and 5 were 

 abundantly covered with crawling young, settled scales, and full- 

 grown females. 



