Selectivity of the insecticide deltamethrin to the parasitoid Palmistichus elaeisis (Hymenoptera: Eulophidae)

Authors: PEREIRA, ELIZANGELA - Universidade Vale, Brasil; SOARES, MARCUS - Universidade Vale, Brasil; CALDEIRA, ZAIRA - Universidade Vale, Brasil; VELOSO, RONNIE VON DOS - Universidade Vale, Brasil; DA SILVA, LUDMILA AGLAI - Universidade Vale, Brasil; DA SILVA, DERLY JOSE - Universidade Federal De Vicosa; DE LIMA SANTOS, ISABEL - University Of Vocosa; DE CASTRO E CASTRO, BARBARA - Universidade Federal De Vicosa; ZANUNCIO, JUSE - Universidade Federal De Vicosa; Legaspi, Jesusa

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/3/2020
Publication Date: 7/24/2020
Citation: Pereira, E.S., Soares, M.A., Caldeira, Z.V., Veloso, R.S., Da Silva, L., Da Silva, D.H., De Lima Santos, I.C., De Castro E Castro, B.M., Zanuncio, J.C., Legaspi, J.C. 2020. Selectivity of the insecticide deltamethrin to the parasitoid Palmistichus elaeisis (Hymenoptera: Eulophidae). Scientific Reports. 10:12395. https://doi.org/10.1038/s41598-020-69200-x.
DOI: https://doi.org/10.1038/s41598-020-69200-x

Interpretive Summary: Defoliator caterpillars cause substantial damage to eucalyptus trees in Brazil. Use of chemicals is one of the management practices to control these insect pests, but this use may have collateral effects on other insects. To assess the impact of a pesticide on non-target beneficial insects, scientists at Universidade Federal dos Vales do Jequitinhonha e Mucuri, Universidade Federal de Viçosa, and Instituto Federal de Mato Grosso in Brazil, in collaboration with scientists at the USDA-ARS, Center for Medical, Agricultural and Veterinary Entomology, Tallahassee, Florida, evaluated the effect of the chemical insecticide, deltamethrin, to a natural parasitoid, in laboratory bioassays. Various doses of deltamethrin were used to expose a laboratory host beetle used to grow the parasitoid on. Results showed that deltamethrin reduced parasitism and the viability of the parasitoid. The results from this study will be useful in developing management strategies against defoliating caterpillars in eucalyptus trees.

Technical Abstract: Insecticides are the main method of controlling lepidopteran pests of eucalyptus plantations and those selective to natural enemies, such as the endoparasitoid Palmistichus elaeisis Delvare and LaSalle (Hymenoptera: Eulophidae), are preferable. The objective of this study was to evaluate the selectivity and effects on biological parameters of the insecticide deltamethrin, registered for the control of defoliator caterpillars of eucalyptus, to the parasitoid P. elaeisis aiming the rational use of this insecticide and its compatibility with parasitoids. The experiment was in a completely randomized design. The treatments were the doses of 0.64, 1.40, 3.10, 6.83, 15.03, 33.05, 72.7 and 160 mg a.i./L of deltamethrin and the control (distilled water) with 10 replications, each with a pupae of the alternative host Tenebrio molitor Linnaeus (Coleoptera: Tenebrionidae) exposed by the immersion method. The parasitism, biological cycle, emergence, longevity, cephalic capsule width and tibia length of the natural enemy were evaluated. Deltamethrin reduced parasitism and the emergence rates of P. elaeisis. The duration of the biological cycle of this parasitoid, emerged from T. molitor pupae exposed to 15.03 mg a.i./L of deltamethrin, was higher. The morphometric parameters of P. elaeisis exposed to the doses of 0.64 and 1.40 mg a.i./L of the insecticide were lower. However, the morphometric parameter values were higher with the doses above 3.10 mg a.i./L than in the control. The parasitism and emergence of P. elaeisis were reduced by the lower deltamethrin doses compared to the commercially recommended one and therefore, this insecticide is not selective for this natural enemy.