Sunday, November 16, 2008

Greenhouse, Landscape, Turf, and Nursery - Understanding Systemic and Translaminar Insecticides

Often, we choose an insect control chemical without really knowing how it works or how it is best used. The following is an article on systemic and translaminar insecticides and where they work best.

While many insecticides kill pests by contact activity, some insecticides have either systemic or translaminar properties. Systemic insecticides are pesticides in which the active ingredient is primarily taken up by plant roots and transported throughout the plant, such as the growing points where it can affect plant-feeding pests. Many of our neonicitinoid insecticides such as imidacloprid fall in this catagory when used as a soil drench. Systemics move within the vascular tissues, either through the xylem (water-conducting tissue) or phloem (food-conducting tissue) depending on the characteristics of the material. The water solubility of systemic insecticides determines their movement within plants. Very water soluble materials are readily taken up by plant roots or leaves. Systemic insecticides are most effective on insects with piercing- sucking mouthparts, such as aphids, whiteflies, mealybugs and soft scales because these insects feed within the vascular system. Most of the systemic insecticides have minimal activity on spider mites because spider mites remove chlorophyll and don't feed within the vascular tissues. Systemic insecticides should be applied when plants have an extensive, well-established root system and when they are actively growing.

Translaminar insecticides penetrate leaf tissues and form a reservoir of active ingredient within the leaf. This provides residual activity against certain foliar-feeding insects and mites. Because the active ingredient can move through leaves, thorough spray coverage is less critical to control spider mites, which normally feed on leaf undersides. Insecticides/miticides with translaminar properties include but not limited to abamectin (Avid), pyriproxyfen (Distance), chlorfenapyr (Pylon) and spinosad (Conserve). In general, these types of materials are active against spider mites and/or leafminers.

Adapted from an article by Tina Smith in the December, 2006 section of the New England Greenhouse Update Newsletter.

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