Insecticidal Control of San Jose Scale on Stone Fruits1

Abstract

The following materials applied in the delayed dormant stage gave the best control of San Jose scale (Aspidiotus perniciosus Comst.): Volck Supreme oil used alone at 2 gallons or at 1 gallon in combination with Trithion^® (S-(p-chlorophenylthio) methyl O,O-diethyl phosphorodithioate) at 1 pint, parathion at 1 pound, malathion at 2 pounds, Diazinoni^® (O,O-diethyl O-(2-isopropyl-4-methyl-6-pyrimidinyl) phosphorothioate) at 2 pounds. Ethion-dormant oil combination at 2 gallons gave good scale control. Sevin^® (1-naphthyl methylcarbamate) used alone has not given satisfactory control, but combined with 1 gallon of Volck Supreme oil has given good control of scale. Guthion^® (O,O-dimethyl S-(4-oxo-1,2,3-benzotriazin-3-(4H)- ylmethyl) phosphorodithioate)-oil or dimethoate gave partial control, but was not as effective as the other combinations used. Volck Supreme oil at 1 gallon, used alone, did not give satisfactory scale control. Field studies from 1957 to 1959 have shown that dormant-type oils were more phytotoxic to stone fruit trees than the Volck Supreme oil. However, the Volck Supreme oil was used at a lower dosage with better scale control. With heavy scale infestation, 1½ gallon of Volck Supreme oil is not adequate for good control. All dosages are expressed in amounts per 100 gallons of water and all concentrations of materials are all in terms of the formulations listed in the tables.