Toxicity assessment of two IGR insecticides on eggs and larvae of the ladybird Eriopis connexa

Abstract

BACKGROUND: Eriopis connexa is an important predator in the Neotropical region, associated with pests of economic relevance on horticultural crops in Argentina. The use of broad-spectrum insecticides could reduce the biodiversity of these natural enemies in agroecosystems and put at risk its conservation. New, selective "risk reduced" insecticides could be an alternative to conventional chemical control to promote sustainable agriculture. The goal of this work was to assess the lethal and sublethal effects of two insect growth regulator (IGR) insecticides on eggs and two larval instars of E. connexa exposed to insecticides. RESULTS: Pyriproxyfen and cypermethrin significantly affected egg hatching by 28.8% and 70.4%, respectively. Pyriproxyfen reduced the survival of larvae that emerged by ≈52% from Day (D3)3 after hatching and caused the lengthening of developmental time for both larval and pupal stages. By contrast, teflubenzuron did not reduce hatching and survival but shortened the developmental time of the pupae stage. Cypermethrin reduced the survival of 2 nd (L 2 ) and 4 th (L 4 ) larval instars by 36.4% and 74.6%, respectively, and lengthened the development time of L 2 . Pyriproxyfen lengthened the development time of L 4 and reduced the fecundity and fertility of females. Teflubenzuron reduced survival of L 2 and L 4 larval instars by 46.9% and 28.6%, respectively, and lengthened the total development time for the larval stage. In addition, teflubenzuron reduced the fecundity and fertility of females. CONCLUSIONS: Both eggs and larvae were susceptible to exposure to IGR, showing lethal and sublethal effects. This study highlights, once again, the higher toxicity of cypermethrin to E. connexa. The toxicity of both IGR insecticides could impair the performance of E. connexa as a biological control agent in agroecosystems.

Sublethal and transgenerational effects of synthetic insecticides on the biological parameters and functional response of Coccinella septempunctata (Coleoptera: Coccinellidae) under laboratory conditions

“…All the tested insecticides reduced the adult emergence, fecundity rates, weight of adults, and survival compared to the control treatment. These results are similar to those from other studies which showed that most of the tested insecticides impaired the reproduction and survival of C. septempunctata and other predators ( Yu et al, 2014 ; Skouras et al, 2017 ; Kang et al, 2018 ; Jiang et al, 2019 ; Noelia et al, 2022 ).…”

A novel allatostatin-A analog, III-2 may particularly regulates juvenile hormone III to influence Spodoptera frugiperda metamorphosis and development

“…Insect growth regulators (IGRs), which include many subcategories of JHAs, chitin synthesis inhibitors, and ecdysone analogs, are a class of specialized insecticides that can obstruct and disrupt the normal growth and development of insect larvae, causing them to perish. They exhibit excellent control over lepidopterans, mosquitoes, white ies, and aphids (Bacci et al, 2007;Gogi et al, 2021;Noelia et al, 2023).…”