Whiteflies on geraniums, roses beaded with aphids or spider mites on other ornamental plants – all are examples of nasty pests that, with a little preventive action now, can be reduced or eliminated from the upcoming spring garden. That bit of prevention comes in the form of dormant spraying – it is done during the late winter season, it is relatively inexpensive and easy to do, doesn’t require environmentally harmful pesticides and it is a beneficial part of an overall pest management program.

Dormant spraying is the application of a horticultural oil to a plant when it has no leaves or isn’t actively growing. These types of sprays control a wide range of soft-bodied insects like aphids, immature whiteflies, scales and true bugs, psyllids, thrips, aphid and caterpillar eggs and mites. Horticultural oil is considered a “contact insecticide”- it kills only the insects present at the time of application. These oils break down quickly in the environment and are more toxic to pests than to beneficial insects. Here’s What a Gardener Needs to Know about Horticultural Oils.

Here’s how to do it:

  • Apply with a pump sprayer or hose-end sprayer that is sized appropriately for the number of plants you need to spray.
  • Use a clean sprayer, in good working order and that has not been used for any herbicides.
  • Follow the manufacturer’s directions. 
  • Mix only what you can use – you can’t save the prepared solution for use later.
  • Thoroughly blend the mixture by shaking it. 
  • Wear appropriate protective clothing, and wash hands and face after use when using any garden pesticide. 
  • Select a mild, clear day in mid-winter (January – February) when there is little or no breeze (between 40 and 70° F).

If your garden is plagued by diseases or insects, you may choose to do dormant spraying twice, about four weeks apart, being careful that the last spraying is still while the plants are dormant. 

So take some time now to give your garden a dose of preventive medicine and you’ll be rewarded by fewer unwanted invaders in the upcoming growing season. 

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