Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/9/2003
Publication Date: 12/31/2003
Citation: TOEWS, M.D., SUBRAMANYAM, B., ROWAN, J.M. KNOCKDOWN AND MORTALITY OF EIGHT STORED-PRODUCT COLEOPTERANS EXPOSED TO FOUR SURFACES TREATED WITH SPINOSAD. JOURNAL OF ECONOMIC ENTOMOLOGY 96: 1967-1973. 2003. Interpretive Summary: Floor surfaces in warehouses, grain bins, food processing plants, and retail stores are commonly treated by pest management professionals with insecticides to minimize and prevent stored product insect infestation. Spinosad, a naturalyte insecticide with a particularly low mammalian toxicity, has been investigated for use on bulk grains but never as a contact insecticide on floor surfaces. We demonstrated that spinosad has excellent contact activity against 6 of the 8 insect species tested when applied at low rates on common floor surfaces such as floor tile, waxed floor tile, concrete, and steel. This insecticide should be useful for control of insect pests in storage and processing facilities.
Technical Abstract: Contact toxicity of a commercial bacterial fermentation insecticide, spinosad, to adults of eight stored-product coleopterans (beetles) was evaluated on four different surfaces. Aqueous spinosad suspension was sprayed with an airbrush to 30.5 cm2 surfaces of concrete, galvanized steel, unwaxed floor tile, or waxed floor tile to obtain deposits of 0.05 or 0.1 mg (AI)/ cm2. Control surfaces were sprayed with aliquots of distilled water. Approximately 24 h after distilled water or spinosad application, 30 adult beetles were confined, by species, to each panel. Insects on surfaces were exposed for 24 h to assess knockdown at 25ºC and 50% RH, and then were held on food for an additional 24 h to assess mortality. Knockdown and mortality of each insect species on all four surfaces were significantly greater on spinosad-treated surfaces than on surfaces treated with distilled water. Knockdown and mortality of all species on all surfaces was similar at the two spinosad deposit levels. Generally, knockdown and mortality were greater on concrete than on galvanized steel, unwaxed floor tile, or waxed floor tile. Except for Tribolium spp., mortality of all other species exposed to spinosad was 99 to 100%. Tribolium spp. were highly susceptible to spinosad on concrete (98 to 100% mortality); however, on unwaxed floor tile, steel, and waxed floor tile recovery on food following knockdown resulted in only 72 to 92% mortality. Our results suggest that spinosad has excellent contact activity against adults of stored-product insects, especially on concrete, and has potential for use as a general surface, spot, or crack/crevice spray to control insects in empty bins, warehouses, food-processing facilities, and retail stores.