At Jericho we recommend the use of dormant oil spray in late fall, through winter, and into early spring. You can us dormant oils as a preventative to help manage many pests on anything from fruit and evergreen trees, to perennial and shrub beds. Dormant oils serve to suffocate insects as they wake from their winters nap.
In a great book, Pests of the West by Whitney Cranshaw, we are reminded that, in the Albuquerque area 80% of our pests winter over and re-animate in the Spring. This winter might be an exception to that, considering the extreme cold we’ve experienced. However, in typical years your dormant oil applications will hinder 80% of the 80% of over-wintering bugs, and can greatly reduce numbers on the bugs you ll have to deal with throughout the growing season.
Applications vary between every 3-4 weeks to an as-needed basis throughout the dormant, green-tip and delayed-dormant stages. The label also lists specific usages during the growing season. However, this product should not be used in temperatures over 80-90 degrees, as it will burn foliage.
All this mumbo-jumbo translates into using much less, if any, harsh chemicals later in the season. I would be remiss to not mention that dormant oil has no affect on insects like stone fruit borers or the coddling moth on apples. That is a whole other article soon to come.
As with any application of any product, chemical or otherwise, read and follow your labels carefully. If you have any additional questions or if the label seems confusing, which sometimes they are, ask your garden center pros for specifics. In some cases you may mix fungicides with the dormant oil to help alleviate certain fungal diseases on specific crops. Again, pay attention to the label to be sure you re choosing the correct products and ask a nursery professional if you re at all unsure.
Find more ideas for preparing for your Spring planting at Jericho’s Planting Calendar.
By Jennifer Timms Hobson, originally published February 11, 2011