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Miss Floribunda: Unusual warm weather awakens aphids

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Posted on: March 7, 2017

Dear Miss Floribunda,

I’ve lived in Hyattsville for 25 years, and I do not recall a February as warm and dry as the one we’ve just had. We usually get a couple of good snowfalls in February. This worries me for a number of reasons, but most upsetting is the sight of aphids already infesting my irises! I am really alarmed to the point that I am considering preemptive strikes in what has been a poison-free garden up to now. Desperate times require desperate measures! My wife suggested I ask your opinion first.

Insecticidal on Ingraham Street


Dear Insecticidal,

You are certainly right that this year’s February is an anomaly. February is usually the snowiest month in our area, averaging five or six inches of snow. In the past 25 years, the Washington, DC, area U.S. Department of Agriculture plant hardiness zone rating, which is based on an area’s mean extreme minimum temperature, changed from 6b to 7a, and many believe that the rating is due for another change. If you like, you can got to and enter your zip code to see your neighborhood rating.  

However, please don’t panic prematurely. You most certainly ought not to upset the balance of your long-established garden ecoculture with poisons. Yes, the aphids have been awakened from dormancy very early by the warmth, but so have the beneficial insects that prey upon them. In the meantime, if you haven’t caught the welcome sight of a ladybug, you can hose the scourge of aphids off your irises with a strong spray of water or manually remove them.

By the way, even the absence of snow has benefits. Insects that bore into the ground to hibernate are protected by snow. One of these is the dreaded Japanese beetle that can decimate rose gardens. As a rose grower, I’ve observed that their presence increases after snowy winters and completely diminishes after winters with little or no snow. And then Hannah Honeywell tells me that honey bees are much happier without snow. Though they slow down in winter cold, honey bees like to periodically leave their hives, and being snowbound could cause sanitation problems. However, a long stretch of unseasonable warmth could indeed disrupt their seasonal chore schedules.

What should give us most cause to worry is the chance that in this volatile season there could still be some hard freezes coming. All the insects that have go into diapause (suspended animation, or dormancy) could be in trouble. These are the majority. When they go dormant in the fall, they produce cryoprotectants, such as glycerol, that work in their cells like antifreeze. Cryoprotectants prevent the formation of destructive ice crystals by lowering the freezing point of the bodily fluids of the insects. Warm weather deactivates this protection, and, of course, awakens the insects. They become active and are not protected if another freeze occurs.   

To discuss this and other gardening concerns, please come to the next meeting of the Hyattsville Horticultural Society at 10 a.m. on Saturday, March 18, at the home of Nina and Jon Faye, 4004 Queensbury Road.




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