High Concentrations of Chlorantraniliprole Reduce Its Compatibility with a Key Predator, Hippodamia convergens (Coleoptera: Coccinellidae).

Diamides are a novel insecticide group that act by disrupting insect muscle contraction. Recommended field rates (FRs) vary greatly among target pests and cropping systems, leading to variable risks for non-target organisms. We evaluated the toxicity of chlorantraniliprole to the predator Hippodamia convergens Guérin-Méneville (Coleoptera: Coccinellidae) by exposure to residues, topical application, and consumption of contaminated food. We also estimated lethal concentrations (LCs) of chlorantraniliprole in two target pests, cotton leafworm, Alabama argillacea (Hübner) (Lepidoptera: Erebidae), and tobacco budworm, Chloridea virescens (F.) (Lepidoptera: Noctuidae), by exposing larvae to treated cotton, Gossypium hirsutum L., leaves and assessed residual activity at various intervals after application to cotton plants. Exposure to dried residues and ingestion of treated moth eggs resulted in similar toxicity to H. convergens, whereas topical application was a less toxic route of exposure. Regardless of exposure route, the LC50s and LC90s obtained for H. convergens were higher than those calculated for the pests. Residues at the upper limit of the LC90 for C. virescens remained effective against this pest for up to 16 d, while exhibiting minor impacts on H. convergens. In contrast, the FR concentration of C. virescens caused significant mortality in H. convergens. The results suggest that the current FR for C. virescens is too high to be safe for H. convergens, and given the LCs observed for this pest in the present study, trials to explore the potential efficacy of lower FRs are justified. Depending on the concentration and route of exposure, this insecticide has the potential to be compatible with H. convergens.

Performance of the Striped Mealybug Ferrisia virgata Cockerell (Hemiptera: Pseudococcidae) under Variable Conditions of Temperature and Mating.

Mealybugs have strong associations with their host plants due to their limitations for dispersal. Thus, environmental conditions and host quality may impact the biological traits of mealybugs. To the best of our knowledge, we are the first to report on the biology of a Brazilian population of the striped mealybug Ferrisia virgata Cockerell (Hemiptera: Pseudococcidae), which has recently been reported to infest cotton in Brazil. We evaluated the development and reproductive performance of F. virgata reared under different temperatures (25, 27, and 28°C) and mating status. The type of reproduction was also studied with insects reared on a factitious host and on cotton plants. Shorter development was obtained at 28°C as follows: nymphs generating males and females exhibited three and four instars with a mean duration of 19.1 and 20.5 days, respectively. The nymphal viability ranged from 77 to 96%, and was highest at 25°C. Females reared at 28°C initiated reproduction earlier (16.4 days), but the reproductive period was similar in all temperatures (∼16.2 days). Females produced more nymphs at 27 and 28°C (440 and 292 neonates) than at 25°C (277 neonates), although they lived longer at 25°C (63 days). Ferrisia virgata females exhibited only sexual reproduction. Thus, only mated females produced offspring, whereas unmated females died without reproducing. Therefore, the studied population of F. virgata exhibited only sexual reproduction with high survival and offspring production when fed cotton. Furthermore, pumpkin is a feasible host for mass rearing this mealybug species in the laboratory, an opening avenue for future studies.