How does thiamethoxam Impact survival of convergent lady beetle and flower bug when exposed via the food chain? 

Erick J Marti­nez Rodri­guez
Staff Researcher
Luis Canas

Neonicotinoids are important insecticides used in agriculture to control plant sap-feeding insects. When applied as drench to the soil, these systemic insecticides move inside the plant providing protection against pests, making them safer to natural enemies such as predators, by minimizing spraying. Thiamethoxam in particular, is a neonicotinoid implemented in many Integrate Pest Management Programs (IPM). Despite its apparent compatibility with biological control, it has been shown that thiamethoxam could move through the food chain towards natural predators; however, the effects it could have on predatory enemies when exposed to thiamethoxam are still poorly understood. Therefore, we aim to evaluate the effects of thiamethoxam on Hippodamia convergens lady beetle and Orius insidiosus flower bug when fed on aphids previously exposed to thiamethoxam-treated plants.  Our hypothesis is that predation of aphids with accumulation of thiamethoxam will impact predator mortality.  To test our hypotheses, we fed aphids on zinnia (Zinnia elegans) and green peppers (Capsicum annumm) for 24 h at 7, 14, 21, 28, 35 and 42 days after thiamethoxam treatment. Aphids were then fed to both predators and survival of predators was recorded every day for the following 7 days. Our results show that convergent lady beetle mortality was not affected by consuming aphids with insecticide. In contrast, insidious flower bug mortality increased when fed with thiamethoxam exposed aphids within the first 21 days after application.