How lasting are the effects of pesticides on earwigs? A study based on energy metabolism, body weight and morphometry in two generations of Forficula auricularia from apple orchards

Abstract

Widespread use of pesticides to control crop pests is still the dominant system in apple orchards. Therefore, to avoid adverse side effects, there is a growing interest in promoting alternative methods such as natural enemies. The European earwig Forficula auricularia L. (Dermaptera: Forficuidae) is an effective predator in apple orchards. Pesticide pressure has been shown to divert energy resources which could have a negative impact on life history traits. In this study we assessed (i) whether variations in pesticide exposure could differentially impact energy reserves, body weight and morphometric parameters of F. auricularia, and (ii) whether these effects last or not in the next generation reared under optimal conditions. Individuals from the first generation were collected in late October from organic, IPM and conventional orchards. The next generation was obtained under a rearing program, in the absence of pesticide exposure. Earwigs collected from conventional orchards exhibited lower values for all morphometric parameters compared to those collected in organic orchards. However, a relaxed period without pesticide exposure (in autumn) appears to have allowed the females to recover their energy reserves to ensure reproduction and maternal care. Glycogen contents are the reserves that were more easily restored. However, due to the rearing conditions (food ad libitum), all the earwigs from the second generation exhibited higher body weights and energy reserves than their parents. They finally reached the same level in these parameters regardless of the protection system from which their parents were collected. Sex-specific responses appeared to depend on earwig life cycle.

Arthropods on grapes benefit more from fungicide reduction than from organic farming

“…[71][72][73] Both ants and earwigs play a crucial role in vineyard pest control 38,68,74,75 and tend to be susceptible to pesticides, particularly insecticide applications, in vineyards and orchards. 16,17,35,76,77 Nonetheless, neither ants nor earwigs were affected by reduced fungicide sprayings in our study.…”

“…Ants and earwigs, for example, reproduce in the soil, have high foraging ranges, and may therefore be less affected by fungicide applications in the canopy but rather by soil management 71–73 . Both ants and earwigs play a crucial role in vineyard pest control 38,68,74,75 and tend to be susceptible to pesticides, particularly insecticide applications, in vineyards and orchards 16,17,35,76,77 . Nonetheless, neither ants nor earwigs were affected by reduced fungicide sprayings in our study.…”

Transgenerational effects of pest management strategy on fluctuating asymmetry in the European earwig Forficula auricularia: Being the progeny of a mother who lived in conventional orchards makes you more asymmetric than having a mother who lived in insecticide free orchards.

“…Transgenerational effects have also been observed. Unexposed F1 females whose parents were previously sampled in conventional orchards indeed exhibited a signi cantly smaller femur than those whose parents were sampled in integrated or organic orchards (Le Navenant et al 2021).…”

Exposure to pyriproxyfen (juvenile hormone agonist) does not alter maternal care and reproduction in the European earwig

“…We performed metabolic quantifications following standard protocols previously developed in the European earwig (Suchail et al 2018;Le Navenant et al 2021). First, we homogenized on ice each whole earwig body in 10% low-salt buffer containing 10mM Tri-Hcl (pH 7.3) and 10mM NaCl and then centrifuged for 10 min at 3000 g (Suchail et al 2018).…”