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Carole from Carlisle, Pa writes

Can Imidacloprid 0.5G Insecticide be used to prevent insect damage on trees?

My hemlocks have wooly adelgids. Is there a dosing schedule for trees?


The Imidacloprid 0.5G would not be the appropriate product to use for treating trees with wooly adelgids. Dominion 2L would be a much more appropriate product for that application, and typically a systemic treatment is only done once a season/year. When using Dominion 2L as a soil drench for Hemlock Woolly Adelgids you should use 0.2 to 0.4 oz per inch of trunk diameter (D.B.H.) diluted in whatever water volume will provide adequate coverage and penetration into the soil and root zone for your sized tree. The amount of water that is used will vary depending on soil conditions and volumes that are easy for applicators to use. The minimum amount of water that should be used is 1 pint per inch of trunk diameter but you may use 1 quart -1 gallon of water per inch of trunk diameter. Denser soils such as clay do not accept water as readily, so the lower volume of water is suggested.  Since sandy soils can accept more water, using the higher volume of water is preferred. After the soil drench has been applied you should water it in with at east 1/2 inch of water. Note: Water simply acts as a carrier and it is important that even distribution of the product is achieved. Thus, more water may be used if the applicator feels runoff will not occur and proper penetration of the root zone is achieved. Insecticides applied to the soil are taken up by the roots and trans-located throughout the tree or shrub. Root/soil drenches offer the advantage of requiring no special equipment to apply (other than a bucket or watering can). However, surface layers of organic matter, such as mulch or leaf litter, can bind the insecticide and reduce uptake. Before applying drenches, it is important to remove or pull back any mulch or dead leaves so the insecticide solution is poured directly on the mineral soil. It is also important to keep the soil around the tree or shrub moist for the next 7-10 days after applications to encourage uptake.

Answer last updated on: 03/31/2021

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