Aerial ultra-low-volume application of naled: impact on nontarget imperiled butterfly larvae (Cyclargus thomasi bethunebakeri) and efficacy against adult mosquitoes (Aedes taeniorhynchus).

We assessed the exposure and acute toxicity of naled, applied aerially as an ultra-low-volume spray for mosquito control, on late instar larvae of the Miami blue (Cyclargus thomasi bethunebakeri) (Comstock and Huntington 1943) (Lepidoptera: Lycaenidae), an imperiled South Florida butterfly. We concurrently evaluated the control efficacy against caged adult female salt-marsh mosquitoes (Aedes taeniorhynchus) (Wiedemann 1821) (Diptera: Culicidae). This 3-yr study was conducted in north Key Largo (Monroe County, FL) beginning in 2006. The field trials incorporated 15 sampling stations: nine in the target spray zone, three in the spray drift zone at varying distances from the target zone, and three in the control zone not subjected to naled spray drift. A total of six field spray trials were completed, three at an altitude of 30.5 m (100 feet), and three at 45.7 m (150 feet). For all trials, the ultra-low-volume application of Trumpet EC insecticide (78% naled) at a rate of 54.8 ml/ha (0.75 fl. oz/acre) was effective in killing caged adult mosquitoes in the target zone. Butterfly larvae survival was significantly reduced in the spray zone compared with drift and control zones. Analysis of insecticide residue data revealed that the mortality of the late instar butterfly larvae was a result of exposure to excess residues of naled. Additional research is needed to determine mitigation strategies that can limit exposure of sensitive butterflies to naled while maintaining mosquito control efficacy.

Host plant selection, larval survival, and reproductive phenology in Megathymus yuccae (Lepidoptera: Hesperiidae).

Our primary objective in this study was to determine the plant level and environmental factors that affect oviposition choice and subsequent offspring survival in Megathymus yuccae (Boisduval and Leconte) on its host plant, Yucca filamentosa L. A preliminary survey suggested that the frequency of pupal eclosion tent presence increased only with host plant height. In an expanded survey conducted during the adult flight period the following spring, we found that plant height increased the probability of oviposition, whereas the density of herbaceous stems and fire damage decreased the probability of egg presence. Similarly, the number of eggs on occupied plants increased with plant height and decreased with fire damage. When we surveyed the plants from the spring 2008 sampling the following winter to determine presence of late-instar larvae or pupae, we found that the probability that at least one larva survived on previously occupied plants decreased with the density of herbaceous stems. These results collectively suggest that larger, unburned Y. filamentosa individuals and those in relatively open areas are more attractive as host plants for oviposition and that larval performance is generally, but not exclusively, consistent with female preference in this system.