Horticultural spray oil is one of the most effective treatments to suppress many insect pests that over-winter on trees and shrubs. Oils coat and smother eggs and immature stages of many soft-bodied insects such as aphids and scale insects as well as plant feeding mites. When applied in late winter, oils have minimal impact on beneficial insects that are active during the growing season and help further suppress pest populations.
Today’s oils are more highly refined than ever. This means there is little risk of damaging plants including conifers, broadleaf evergreens and thin bark species that were concerns years ago. In fact, oils are now an integral part of pest management programs with many organic farmers.
Horticultural oils are traditionally applied in late winter just before new growth emerges. However, modern, highly refined oils are also used now during the growing season to suppress active forms of certain pests.
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