Temperature-Dependent Demography of Thrips hawaiiensis (Thysanoptera: Thripidae): Implications for Prevention and Control

Toxicity risk assessment of flupyradifurone for the predatory pirate bug, Orius strigicollis (Poppius) (Heteroptera: Anthocoridae), a biological control agent of Diaphorina citri Kuwayama (Hemiptera: Liviidae)

Diaphorina citri Kuwayama (Hemiptera: Liviidae), commonly known as the Asian citrus psyllid, is a prominent citrus tree pest that serves as a vector for Asian huanglongbing (HLB). The substantial costs incurred by the citrus industry as a consequence of this disease have spurred considerable interest in the combined control of D. citri using insecticides and natural enemies. However, the successful implementation of such integrated pest management strategies is dependent on ensuring the compatibility of using natural enemies in the presence of insecticides. In this regard, we evaluated the lethal and sublethal effects of flupyradifurone on Orius strigicollis (Poppius) (Heteroptera: Anthocoridae), an important predatory biological control agent, in which we assessed the risk of exposure to flupyradifurone under both in- and off-field scenario. The median lethal rate (LR50) value of flupyradifurone against O. strigicollis (9.089 g a.i. ha-1), was found to be significantly lower than the maximum field recommended rate (MFRR, 170 g a.i. ha-1). Additionally, at 0.254 g a.i. ha-1, flupyradifurone was established to significantly prolong the developmental duration of O. strigicollis from the first to third instar nymphs. Although we detected no significant difference in the survival of immature O. strigicollis subjected to 0.064 g a.i. ha-1 and control treatments, survival was significantly lower in 0.127 and 0.254 g a.i. ha-1 treatments. Moreover, whereas there were no significant differences in adult longevity between the 0.127 g a.i. ha-1 and control treatments, we recorded a significant reduction in fecundity. Furthermore, there were reductions in peak life expectancy, reproductive value, finite rate of increase, intrinsic rate of increase, and net reproduction rate in response to exposure to increasing flupyradifurone rate. Additionally, at 0.127 g a.i. ha-1, the mean generation time was significantly longer than that under control conditions. Following simulated exposure to flupyradifurone for 100 days, population of O. strigicollis in the 0.064 g a.i. ha-1 and control treatments were found to be significantly larger than those exposed to 0.127 g a.i. ha-1. On the basis on LR50 evaluations, whereas the risk of exposure risk was unacceptable for O. strigicollis under in-field scenario, it remained acceptable off-field. Nonetheless, the sublethal effect of prolonged exposure to residual flupyradifurone could pose an unacceptable off-field risk to O. strigicollis (e.g., in adjacent habitats). Consequently, the effects of different flupyradifurone exposure scenarios on O. strigicollis should be thoroughly assessed, and reducing the dosage of flupyradifurone could be advantageous for the control of D. citri when combine with augmentative release of O. strigicollis.

Compatibility of six reduced-risk insecticides with Orius strigicollis (Heteroptera: Anthocoridae) predators for controlling Thrips hawaiiensis (Thysanoptera: Thripidae) pests

Contact toxicity assessments of six reduced risk insecticides were carried out to compare their selectivity and sensitivity toward the minute pirate bug Orius strigicollis and its prey Thrips hawaiiensis. Additionally, and their potential exposure risk were evaluated for O. strigicollis. The LR₅₀ value of acetamiprid, emamectin benzoate, cyetpyrafen, and indoxacarb to T. hawaiiensis were 0.126, 2.093, 7.486, and 2.264 g a.i. ha^-1, respectively, far less than the maximum field recommended rate (MFRR) for each. These four insecticides showed higher selectivity for predator and prey with selectivity ratio values of 37.3, 14.8, 22.1, and 119.3, respectively. However, the LR₅₀ value of acetamiprid and emamectin benzoate were lower than MFRR, and unacceptable (approximately unacceptable for emamectin benzoate) risk to O. strigicollis in in-field, and the opposite results were shown in cyetpyrafen and indoxacarb. Although T. hawaiiensis was more sensitive to abamectin than O. strigicollis, the insecticide had poor selectivity for both test insects. The LR₅₀ value of spirotetramat was more than 3 fold MFRR for T. hawaiiensis and O. strigicollis, showing extremely low contact toxicity and selectivity. In general, acetamiprid, emamectin benzoate, cyetpyrafen, and indoxacarb showed high bioactivity against T. hawaiiensis, but only cyetpyrafen and indoxacarb could be well compatible with O. strigicollis, the combination of two insecticides with O. strigicollis indicated a potential strategy for the efficient and safe control of T. hawaiiensis.