Leaf-cutting ants are important pests of forests and agricultural crops in the Neotropical region. Atta sexdens colonies can be composed of thousands of individuals, which form a highly complex society with a single reproductive queen. Successful control of this species is achieved only if the queen is affected. Few data are available on the lethal or sublethal effects of toxic compounds on leaf-cutting ant queens. Azadirachtin has been claimed as an effective biopesticide for insect control, but its action on leaf-cutting ants has been little explored. This study shows that azadirachtin affects oviposition in A. sexdens queens, impairing egg development by decreasing protein reserves. Azadirachtin inhibits the synthesis of vitellogenin, the major yolk protein precursor. The negative effects of azadirachtin on the reproduction of leaf-cutting ant queens suggest a potential use for the control of these insects.

Widespread use of insecticides for the control of urban pests such as ants, termites, and spiders has resulted in contamination and toxicity in urban aquatic ecosystems in different regions of the world. Passive samplers are a convenient and integrative tool for in situ monitoring of trace contaminants in surface water. However, the performance of a passive sampler depends closely on its affinity for the target analytes, making passive samplers highly specific to the types of contaminants being monitored. The goal of this study was to develop a passive sampler compatible with a wide range of insecticides, including the strongly hydrophobic pyrethroids and the weakly hydrophobic fipronil and organophosphates. Of six candidate polymeric thin films, polyurethane film (PU) was identified to be the best at enriching the test compounds. The inclusion of stable isotope labeled analogs as performance reference compounds (PRCs) further allowed the use of PU film for pyrethroids under non-equilibrium conditions. The PU sampler was tested in a large aquarium with circulatory water flow, and also deployed at multiple sites in surface streams in southern California. The concentrations of pesticides derived from the PU sampler ranged from 0.5 to 18.5 ng/L, which were generally lower than the total chemical concentration measured by grab samples, suggesting that suspended particles and dissolved organic matter in water rendered them less available. The influence of suspended particles and dissolved organic matter on bioavailability was more pronounced for pyrethroids than for fipronils. The results show that the developed PU film sampler, when coupled with PRCs, may be used for rapid and sensitive in-situ monitoring of a wide range of insecticides in surface water.