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Spruce Spider Mites to Hatch!
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Taken from the P.E.S.T. (Pest Evaluation and Suppressiona Techniques) Newsletter
Dr. David Shetlar (OSU Plant Entomolgist) in partnership with Ohio Nursery & Landscape Association |
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Overwintered spruce spider mite eggs begin to hatch when the Callery pears are in full bloom. This event has already happened in the lower half of Ohio, but I’m never overly concerned about getting out and doing something to control the spring populations of spruce spider mites. In the work that we did here at Ohio State on the biology of this pest, we found that the largest populations occurred in the fall, from October into mid-December.
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Most of the damage you see in the spring, speckled needles turning brown or dropping early, was done last fall. The spring mite populations are often suppressed by periodic heavy rains (sound familiar?). Therefore, I really recommend sampling and/or monitoring the mite activity BEFORE, pulling the trigger on the sprayer. Simply hold a sheet of paper (I use an office tablet even though it has lines on it) under a branch and strike the branch with a stick or pruners, sharply, three times. Needles and other junk will fall onto the tablet. Count to 10, that thousand-one, thousand-two method, and then tilt the tablet vertically to let the debris slide off. Then look on the surface for any dark dots (the size of a period on this page) moving around. Take your index finger tip and squash the dot in a streak. If the streak is an olive-green color, it WAS a spruce spider mite. If the dot and the streak are red, orange, yellowish, or there is no streak, the poor critter was something else. You need 20 to 30 mites on your sheet of paper to consider treating the tree.
Again, we are handicapped for having anything really effective that a homeowner can get and use. Commercial applicators can use Avid, Forbid, Florimite, Hexagon or Sanmite which are all very effective on this mite. None of these are easily available to the homeowner unless they are willing to go online and buy a commercial product (even then, I’d be pretty nervous about untrained folks using Avid due to its toxicity). Horticultural oils would also work, but these can often cause a color shift on glaucous cultivars (ones with the silvery waxy coating on the needles). Insecticidal/miticidal soaps would also work. Both oils and soaps require complete drenching of the plants as they only work by contacting the mite exoskeleton. |
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