Non-target effects of two sunflower seed treatments on Orius insidiosus (Hemiptera: Anthocoridae)

Systemic insecticides used as seed treatments are generally considered to be safe for natural enemies. However, predatory insects may feed directly on plants or use plant products to supplement their diet. This study examined whether chlorantraniliprole or thiamethoxam might negatively impact Orius insidiosus (Say) (Hemiptera: Anthocoridae) when bugs utilize sunflowers grown from treated seed.

When eggs of O. insidiosus were laid in the stems of treated sunflower seedlings (two-leaf stage), thiamethoxam reduced egg viability and the longevity of females hatching from these eggs, whereas chlorantraniliprole reduced female survival. Thiamethoxam, but not chlorantraniliprole, reduced female fertility in six-leaf-stage plants. Nymphs exposed to thiamethoxam-treated seedlings had reduced survival, delayed development and reduced fecundity as adults, relative to other treatments, whereas chlorantraniliprole delayed oviposition. Nymphs exposed to six-leaf-stage plants did not differ from controls in either treatment. Adults exposed to treated plants expressed no significant differences among treatments for any parameter evaluated for either plant growth stage.

Thiamethoxam treatment on sunflower seeds caused lethal and sublethal effects on O. insidiosus, whereas chlorantraniliprole was not lethal to any life stage, although sublethal effects were evident. The nymphal stage was most susceptible, and insecticidal toxicity diminished with plant development.