ECONOMICS OF MICROTUS CONTROL IN EASTERN U.S. ORCHARDS

Chemical methods were found to be less expensive for control of voles (Microtus spp.) in orchards than the use of clean culture (combinations of herbicides, mowing, and cultivation). Ground cover sprays of hexachloroepoxyoctahydro-endo-endo-dimethanaphthalene (Endrin) or 2-[(p-chlorophenyl) phenylacetyl-l,3-indandione (Chlorophacinone, CPN, Rozol) required greater equipment and pesticide costs than hand placed or broadcast baits. Since active ingredient rates for ground cover sprayed chemicals may be 100-400 times that for hand placement or broadcast baiting, the costs for any new ground spray will likely be too expensive to be practical. Broadcast baiting, while less labor intensive than hand baiting, was found to be as expensive as hand placement since larger quantities of bait were needed for treatments. The costs for broadcast or hand placed baiting were found to be less for acute toxicants, since the quantity of bait required for a lethal dose is less for acute baits