Toxicants and Solids Added to Spray Oil in Control of California Red Scale1

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Abstract
Dry extract of derris root containing 25% rotenone, when added to spray oil by means of a suitable mutual solvent, increased the toxicity of the oil against the California red scale, Aonidiella aurantii. Addition of 1 part of a 5% soln. of derris resins in dibutyl phthalate to 7 parts of medium spray oil used at 2% conc. resulted in a kill of 96.1% of adult [female] red scale on the branches of lemon trees (cf. a kill of 78.8% when the oil was used alone at 2% conc.). Addition of certain finely-divided solids increased the effectiveness of spray oil by causing the oil to be more easily drawn toward the scale insect''s body by capillarity. Addition of 3 lbs. of walnut-shell flour to 100 gallons of spray mixture increased the kill from the aforementioned oil-toxicant mixture from 96.1% to 99.02%.

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