dormant spray on ornamentals

Asked January 10, 2019, 9:29 PM EST

We've had such a mild winter and I'd like to get a jump on insect control on ornamentals. I had infestations of aphids and spider mites last year. Are there restrictions on what types of ornamental shrubs can tolerate horticultural oil sprays? When should these be applied?

Washington County Oregon insecticides

1 Response

Thank you for your question. Virtually all pesticides have some sort of regulations, which are found on the labels of the chemicals. But there in no ‘one size fits all’ for insect control for a variety of issues. First, insects have different life cycles, and you can waste time, money and oils by applying at the ‘wrong’ time. So, treatment times vary. Second, applying them when valuable (and often threatened) pollinators are present may jeopardize those populations. And, third, not all insecticides are effective for all “bad” insects. It would be helpful if you were to indicate which plants have (or have had) which insects. Many cannot be prevented, and gardeners need to monitor plants for infestations. And some populations can be controlled by introducing beneficial insects, which control them by eating or laying their eggs in the larvae, becoming parasites and killing them. Nature is amazing!