Effects of malathion ULV applied for boll weevil eradication on survival and foraging activity of the red imported fire ant, Solenopsis invicta Buren, in Texas (USA) cotton
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Red imported fire ant, Solenopsis invicta (Buren), is a major pest in the southern USA, though recent studies suggest it may act also as a natural enemy. This study examined how malathion ULV, as applied for boll weevil (Anthonomus grandis grandis) eradication in the southern USA, may impact red imported fire ant survivorship, foraging activity, and predation of lepidopteran pests. Malathion ULV had strong, negative impacts upon fire ant survivorship, foraging, and predation in cotton fields. Malathion ULV was acutely toxic to fire ant under laboratory conditions, and had a strong repellent effect, so reducing foraging activity, in the greenhouse. In the field, fire ant densities on cotton plants treated with malathion ULV were lower for up to 3 weeks after treatment compared to untreated cotton plants. Also in the field, beet armyworm (Spodoptera exigua) egg predation rates were lower in malathion ULV treated plots relative to untreated plots. Overall, the results suggested that boll weevil eradication with malathion ULV negatively impacts red imported fire ant abundance and foraging and predatory activities in cotton fields.