Boric acid, imidacloprid, and thiamethoxam in sucrose aqueous baits had different delayed toxicities to worker Argentine ants, Linepithema humile (Mayr). The concentrations required to produce an LT50 (time required to produce 50% mortality) within 1-4 d were 3.63-0.55% boric acid, 9.2 x 10(-3) to 7.1 x 10(-4)% imidacloprid, and 3 x 10(-4) to 2 x 10(-5)% thiamethoxam. The three toxicants were not repellent. Other laboratory trials showed that 1% boric acid, 5 x 10(-4) to 5 x 10(-3)% imidacloprid, and 1 x 10(-5) to 1 x 10(-3)% thiamethoxam had delayed toxic effects, whereas 0.5% boric acid and < 5 x 10(-3)% imidacloprid did not. Baits that provided an LT50 between days 1 and 4 were considered to have delayed toxic effects. The utility of aqueous sucrose baits and toxicants soluble in such systems and the negative impact of fast-acting toxicants on trail following, recruitment, trophallaxis, and control of Argentine ants are discussed.
The survival and development of the cat flea, Ctenocephalides felis, were assessed at various temperatures and relative humidities (RH). The upper and lower temperature limits for development (egg to adult) were 32 and 13 °C. The length of the developmental period ranged from 14 to 140 days at these temperature extremes. Complete development occurred from 50-92% RH. Immature C. felis reared at 92% RH produced larger adults than those reared at 50% RH. At 27 °C, the minimum RH necessary for greater than 50% survival of the immature stages was egg, 33%; larva, 50%; and pupa, 2%. Adult longevity increased with increasing RH and decreasing temperature.
Control of Argentine ants, Linepithema humile (Mayr), around structures in urban settings requires an extensive and thorough use of existing registered sprays and baits. Barrier sprays must be thoroughly applied at maximum label rates to prevent ants from accessing structures. Although insecticides with systemic activity such as imidacloprid and thiamethoxam may ultimately reduce homopteran food sources for L. humile, quantifying the impact of such reductions has been difficult. Applications of bifenthrin and deltamethrin granules provide short-term reductions. Most commercial baits available for L. humile are not readily consumed by foragers, or they provide too rapid kill of workers. Consequently, none of the baits are consistently effective. Potential new active ingredients for baits such as fipronil, imidacloprid, and thiamethoxam provide about 50% kill within 3 days and are readily accepted by foragers. These toxicants are extremely promising in liquid bait formulations. No single control strategy or treatment has been consistently effective.
Visual inspections and trapping revealed the presence of German cockroaches, Blattella germanica (L.) in 62 of 100 randomly selected commercial food-handling establishments. From live cockroaches trapped in 55 restaurants, 35 strains were established and tested for chlorpyrifos resistance. Poor sanitation and the likelihood of trapping cockroaches were associated. Twenty strains had resistance ratios (RR) as LD50 greater than 10-fold, a value exceeding the pest management threshold level for this insecticide. Resistance ratios were not associated with numbers of cockroaches trapped, the level of sanitation, numbers of different insecticide products used, or the number of treatments per month. Significantly more categories of insecticides (e.g., carbamate, organophosphate, inorganic) were used in restaurants with RR greater than 10 than in those with RR less than 10.
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