The Use of Imidacloprid for Aphid Control in Trees
Marianne C. Ophardt
Washington State University Cooperative Extension
Area Extension Agent
Late winter is a good time to apply imidacloprid to shade trees for control of aphids in the coming season. Imidacloprid, know commercially as Merit, is available to home gardeners under the name of ABayer Advanced Garden Tree & Shrub Insect Control Concentrate@. It=s a liquid material that you mix with water in a watering can or bucket and then apply it to the soil at the base of the tree trunk. It=s taken up by the tree and transported to the leaf tissues where it controls a variety of sucking insects, especially aphids. The amount applied is based on the circumference of the trunk at chest height.
It takes a while for the chemical to reach the tops of tall trees... so late winter is a great time to apply the imidacloprid so it will be available when the leaves bud out and the early aphids start feeding. The product is quite expensive and you may have sticker shock after you determine the amount you=ll need for larger trees, but it provides 12 months of control. It=s also more environmentally sound, eliminating the difficulty of spraying the tops tall trees and removing the possibility of spray drift. Beneficial insects are also protected by this method of application.
Imidacloprid is also a good material for season long aphid control in roses. However, the ABayer Advanced Garden 2 in 1 Systemic Rose and Flower Care@ contains fertilizer and a different systemic, disulfoton, that will only be effective for six weeks or less. It=s applied as a granular to the soil. For season long aphid control on roses, use imidacloprid applied to the soil. Just keep in mind that