Foliar and Growth Effects of Repetitive Summer Horticultural Oil Sprays on Trees and Shrubs Under Drought Stress

Abstract

A 2% Spray of Sunspray 6E Plus horticultural oil was applied, 2, 3 or 4 times to 52 species and cultivars ot nursery trees and shrubs during the droughty summer of 1988. Phytotoxicity was rated monthly and found to be negligible. Growth effects were evaluated in October. Nine species showed significant differences in growth between treated and untreated plants. All treated plants averaged 1.7 cm more growth than untreated plants.