Evaluation of herbicide-coated larvae ofBactra verutana [Lep.: Tortricidae] to control nutsedges [Cyperus rotundus L. andC. Esculentus L.

Abstract

Feeding by 10-day old mid-instar larvae of the native moth,Bactra verutana Zeller, coated with solutions of bentazon [3-isopropyl-1 H-3-benzothiadiazin-4(3H)-one 2,2-dioxide] or glyphosate [N-(phosphonomethyl) glycine], reduced the dry weight of purple (Cyperus rotundus L.) or yellow nutsedge (C. esculentus L.) an average 25% more than did uncoated larvae. The herbicide-coated larvae reduced dry weight by 71% for 4-week yellow nutsedge and by 80% for 2-week purple nutsedge plants within 15 days after release. This integrated approach was apparently not pratical, however, because larvae randomly damaged the non-target crops, cotton (Gossypium hirsutum L.) and turnip (Brassica rapa L.). The more mature larvae killed about 3% of the cotton and 14% of the turnip plants. Newly-emerged larvae were highly sensitive to the herbicides. Mature larvae are less host-specific than are newly-emerged larvae. Therefore, the use of repeated broadcasts of newly-emergedB. verutana larvae is still the best method known for using insects to control nutsedge.