Residual action of five insecticides on larvae and adults of the neotropical predators Chrysoperla externa (Neuroptera: Chrysopidae) and Eriopis connexa (Coleoptera: Coccinellidae)

Insecticide mixtures reduce the selectivity enhanced by pyrethroid resistance in a predatory lady beetle

Insecticide mixtures provide various modes of action in a ready-to-use formulation, broadening the range of managed pest species and delaying the development of insecticide resistance. Nonetheless, the insecticides used in the mixture may change the selectivity status for natural enemies obtained when using an individual formulation. Eriopis connexa (Germar), a lady beetle resistant to the broad-spectrum pyrethroid λ-cyhalothrin (EcViR), was exposed to insecticides in both individual and mixture formulations. The insecticides λ-cyhalothrin, chlorantraniliprole, sulfoxaflor, λ-cyhalothrin+dinotefuran, λ-cyhalothrin+thiamethoxam, and λ-chlorantraniliprole+thiamethoxam were tested. Survival of larvae and survival and reproduction of adults were assessed when enclosed with dry insecticide residues obtained at the maximum insecticide recommended rate. Furthermore, concentration-mortality curves were also established for larvae and adults exposed to insecticides with mortality rates exceeding 40%. For 30 days, the number of adults who survived exposure at the larval and adult stages and were still living and reproducing was recorded. The toxicity of the neonicotinoids thiamethoxam and dinotefuran present in the mixture prevailed over the physiological selectivity obtained through the resistance to λ-cyhalothrin. The combination index revealed that adding neonicotinoids to λ-cyhalothrin or chlorantraniliprole was very harmful to the lady beetle. On the other hand, the combination of λ-cyhalothrin with chlorantraniliprole or sulfoxaflor allowed EcViR larvae and adults to survive more than 80%. Therefore, incorporating neonicotinoids into the insecticide formulation nullified the physiological selectivity achieved by E. connexa resistance to λ-cyhalothrin, reducing the potential effectiveness of E. connexa in pest management as an augmentative biological control agent.

Effects of the insecticide flupyradifurone on Anticarsia gemmatalis caterpillar and its predator Podisus nigrispinus

The caterpillar Anticarsia gemmatalis (Lepidoptera: Noctuidae) is a prevalent pest in soybean plantations, managed using both natural and synthetic chemical products. However, the emergence of resistance in some populations emphasizes the need to explore alternative insecticides. Flupyradifurone, a neurotoxic insecticide, has not been previously used for controlling A. gemmatalis. This study evaluated the potential of flupyradifurone in the management of A. gemmatalis. Initially, the toxicity and anti-feeding effects, as well as histopathological and cytotoxic impacts, of flupyradifurone on A. gemmatalis were evaluated. Subsequently, the indirect effects of flupyradifurone on the midgut and fat body of the predator Podisus nigrispinus (Hemiptera: Pentatomidae) were verified. The results indicate the susceptibility of caterpillars to flupyradifurone, with an LC50 of 5.10 g L-1. Furthermore, the insecticide adversely affects survival, induces an anti-feeding response, and inflicts damage on the midgut of the caterpillars. However, flupyradifurone also leads to side effects in the predator P. nigrispinus through indirect intoxication of the caterpillars, including midgut and fat body damage. While flupyradifurone demonstrates toxicity to A. gemmatalis, suggesting its potential for the chemical control of this pest, the indirect negative effects on the predator indicate the need for its controlled use in integrated pest management programs with the insecticide and the predator.

Fitness effect and transcription profile reveal sublethal effect of nitenpyram on the predator Chrysopa pallens (Neuroptera: Chrysopidae)

Although neonicotinoids are widely used and important insecticide, there are growing concerns about their effect on nontarget insects and other organisms. Moreover, the effects of nitenpyram (NIT), a second generation of neonicotinoid insecticides, on Chrysopa pallens are still unclear. Therefore, this study purposed to investigate the acute toxicity of NIT to C. pallens using the spotting method. To examine the potential effects of a sublethal dose of NIT (LD30 , 1.85 ng of active ingredient per insect) on C. pallens, we constructed the life tables and analyzed the transcriptome data. The life table results showed that the period of second instar larvae, adult pre-oviposition period and total pre-oviposition period were significantly prolonged after exposure to sublethal dose of NIT, but had no significant effects on the other instars, longevity, oviposition days, and fecundity. The population parameters, including the preadult survival rate, gross reproduction rate, net reproductive rate, the intrinsic rate of increase, and finite rate of increase, were not significantly affected, and only the mean generation time was significantly prolonged by NIT. Transcriptome analysis showed that there were 68 differentially expressed genes (DEGs), including 50 upregulated genes and 18 downregulated genes. Moreover, 13 DEGs related to heat shock protein, nose resistant to fluoxetine protein 6, and prophenoloxidas were upregulated. This study showed the potential effects of sublethal doses of NIT on C. pallens and provided a theoretical reference for the comprehensive application of chemical and biological control in integrated pest management.