Lethal, sublethal and transgenerational effects of insecticides labeled for cotton on immature Trichogramma pretiosum

Abstract

The egg parasitoid Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) regulates lepidopteran pest populations in cotton crops. However, cotton harbors dozens of pests, and growers rely on multiple insecticide applications to manage these damaging organisms. A harmonious integration of control tactics is required for proper pest management, and the use of selective insecticides (i.e., those promoting effective pest control while causing little impact on natural enemies) ts within this scope. This study aimed to assess the lethal, sublethal and transgenerational effects of insecticides from varying chemical groups on T. pretiosum. The insecticides were sprayed on parasitized host [Ephestia kuehniella (Zeller)] eggs with developing T. pretiosum stages (egg-larva, prepupa and pupa), and biological traits were assessed following adult emergence. Overall, pupae were more susceptible to the insecticides. We found thiodicarb and chlorfenapyr to reduce F0 adult emergence in rates comparable to the positive control (methomyl). Adult F0 deformation was the highest on upyradifurone-treated organisms, and both the F0 parasitism rate and female survival were reduced by the insecticides (except for te ubenzuron). The sex ratio was affected by thiodicarb and upyradifurone. Transgenerational effects occurred on adult emergence, which was reduced on the offspring (F1) of thiodicarb-, chlorfenapyr-, and upyradifurone-treated T. pretiosum. In addition, thiodicarb lessened the F1 sex ratio. Combined, these results indicate that te ubenzuron is the safest insecticide; the other insecticides (especially thiodicarb and chlorfenapyr) are non-selective to T. pretiosum. Field and semi eld studies are required to con rm the harmfulness of thiodicarb and chlorfenapyr towards T. pretiosum.(e.g., temperature, radiation and rainfall) mediate insecticide degradation and potentially reduce their toxicity towards insects (Maia et al. 2016), further studies in semi eld and eld conditions are required to con rm the side effects of thiodicarb and chlorfenapyr on T. pretiosum. Declarations

Transgenerational hormesis and sublethal effects of five key insecticides for controlling Spodoptera frugiperda on its endoparasitoid Cotesia marginiventris

“…However, the female‐to‐male ratio of F 1 C. maginivantris was significantly decreased when F 0 females were exposed to sublethal concentrations of insecticides. The negative impacts of insecticides on the sex ratio of parasitoids have also been reported previously 34,58,62,63 . Furthermore, the reduction in the female‐to‐male ratio even continued into the F 2 generation, which was indirectly exposed to the insecticides, except for the chlorantraniliprole treatment.…”

“…The negative impacts of insecticides on the sex ratio of parasitoids have also been reported previously. 34,58,62,63 Furthermore, the reduction in the female-to-male ratio even continued into the F 2 generation, which was indirectly exposed to the insecticides, except for the chlorantraniliprole treatment. Similar transgenerational suppression on the proposition of females has been observed in Trichogramma galloi Zucchi (Hymenoptera:Trichogrammatidae) with six insecticides, including spinosad, 34 and Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) with thiodicarb.…”

“…Similar transgenerational suppression on the proposition of females has been observed in Trichogramma galloi Zucchi (Hymenoptera:Trichogrammatidae) with six insecticides, including spinosad, 34 and Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) with thiodicarb. 63 Parasitoid female offspring production and sex allocation are attributed to their arrhenotokous (haploid-diploid) sex-determining system. 64 Female offspring develop from fertilized (diploid) eggs, whereas males develop from unfertilized (haploid) eggs, and females store sperm in their spermatheca after mating.…”

Functional response of an egg parasitoid,Trichogramma chilonisIshii to sublethal imidacloprid exposure

“…13,14 Moreover, the assessment of lethal and sublethal effects of insecticides on parasitoids and predators is a center of attention since it has a huge impact on the biological and demographic traits of the bio-agents. 2,[15][16][17][18] The effect can either be stimulating [example: multigenerational sublethal imidacloprid exposure enhanced the fitness traits on Trichogramma chilonis Ishii (Hymenoptera: Trichogrammatidae) 2 ] or reducing [example: transgenerational exposure to sublethal concentrations of chlorfenapyr, thiodicarb, and flupyradifurone reduced the biological traits of Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) 15 ]. In addition, insecticides also intervene in the predator/parasitoid and prey/host interactions.…”

Sublethal Effects of Four Insecticides Targeting Cholinergic Neurons on Partner and Host Finding in the Parasitic Wasp Nasonia vitripennis

“…Therefore, our results suggest that doses of the four insecticides, at which the vast majority of the exposed wasps survive, compromise the important ecosystem function these insects have as natural enemies as well as their applicability in the context of biocontrol. Although this suggestion is supported by previous studies that have also found sublethal effects of these compounds in parasitic wasps (Costa et al, 2023;Gao et al, 2023;Mohammed & Karut, 2021), further experiments under more realistic semifield conditions are needed for a definitive evaluation.…”