Surfactants, or surface acting agents, are often used in conjuction with many classes of pesticides as adjuvants to facilitate the dispersing, spreading, or wetting of active ingredients. The insecticidal and acaricidal effects of soaps and oils as surfactants have been recognized for over 80 years. Silwet L-77, an organosilicone surfactant, was applied to life stages of several arthropod pests of California table grapes. Eggs of grape mealybug, Pseudococcus maritimus (Ehrhorn), and omnivorous leaf roller, Platynota stultana Walsingham, were resistant to 0.1, 0.25, 0.5% (v/v) treatment solutions however, eggs of Pacific spider mite, Tetranychus pacificus McGregor, were highly susceptible with mortality >99.4 % for the 0.1% Silwet L-77 treatment. Mortality of larval and adult stages of cotton aphid, Aphis gossypii Glover, western flower thrips, Frankliniella occidentalis (Pergande), and T. pacificus was >93.8, >98.5, and >99.4% for 0.1, 0.25 and 0.5% Silwet L-77, respectively. Grape mealybug crawlers had 100% mortality when treated with 0.5 and 1.0% Silwet L-77 solutions; however, mortality was only 6.7% when 0.1% Silwet L-77 was applied. When Silwet L-77 was applied to the upper surface of cotton leaves with the lower surfaces infested with A. gossypii, mortality was 24.9, 24.0, and 35.8 % for 0.1, 0.5, and 1.0% Silwet L-77, respectively. 'Thompson Seedless' table grapes did not appear damaged when treated with up to 1.0% of Silwet L-77; however, grapes treated with the 0.5 and 1.0% solutions appeared wetted after removal from cold storage. Grapes dried with the normal bloom on the berries when they reached room temperature.
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