Side effects of insecticides applied to cotton on adult Trichogramma pretiosum by three exposure routes

Abstract

BACKGROUND Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) is released in extensive areas cultivated with cotton worldwide, but the use of synthetic insecticides threatens the establishment of augmented populations. Thus, an assessment of insecticides’ effects on T. pretiosum is required to establish their compatibility with mass releases of the parasitoid. We studied in the laboratory the impact of insecticides administered through different exposure routes (direct‐spraying, ingestion and residue contact) on T. pretiosum. Based on their toxicity, the insecticides were rated into four categories (harmless, slightly harmful, moderately harmful and harmful) as per the International Organization for Biological Control. RESULTS The survival, parasitism ability and emergence of the treated adults and offspring (F1 and F2), in addition to the persistence of the toxic effects in semi‐field conditions, were assessed. Teflubenzuron did not reduce female survival and caused a lesser impact on T. pretiosum on both direct‐spraying and ingestion bioassays. In the residue contact bioassay, teflubenzuron and flupyradifurone were rated as harmless and slightly harmful, respectively. The other active substances (chlorfenapyr, thiodicarb and methomyl) were harmful to the parasitoid by all exposure routes and were persistent (with toxicity duration surpassing 30 days). CONCLUSION From these findings, teflubenzuron is the insecticide most compatible with T. pretiosum releases and should be preferred over the other active substances. Further studies with the harmful insecticides (thiodicarb, chlorfenapyr and methomyl) are required to determine their toxicity under field conditions and confirm their incompatibility with T. pretiosum releases.

Selectivity of Insecticides to a Pupal Parasitoid, Trichospilus diatraeae (Hymenoptera: Eulophidae), of Soybean Caterpillars

“…The death of all parasitoids with the insecticide acephate within 24 h confirms the high toxicity of this insecticide [ 16 ]. In addition, the lower survival with insecticides deltamethrin and thiamethoxam + lambda-cyhalothrin is due to the persistence of their dry residues on the leaves and the direct contact of the parasitoid, increasing its mortality over time [ 26 , 31 ].…”

Augmentative Biological Control of Spodoptera Frugiperda Using Trichogramma Species: A Review

“…Methomyl is a pesticide registered for controlling S. frugiperda in many countries, but laboratory tests have shown that it is toxic to T. pretiosum and can remain toxic for over 30 days (Bezuidenhout & Nunkumar, 2017;Costa et al, 2022). However, in a study by Takada et al (2001), T. dendrolimi was not affected by methomyl (Lannate, WP 45%).…”