Compatibilidade de misturas de produtos fitossanitários recomendados para o meloeiro e sua seletividade sobre Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae)

Abstract

Integrated Pest and Disease Management (IPDM) envisages the use of different control techniques in a simultaneous and harmonic way, that is, integrating them. The aim of this study was to evaluate the compatibility of mixtures of phytosanitary products (insecticides and fungicides) recommended in melon crops and their selectivity for Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae). The experiments were conducted in the Applied Entomology Laboratory (Laboratório de Entomologia Aplicada - LEA) of the Universidade Federal do Ceará (UFC) under controlled conditions. First, the compatibility of the following six mixtures of phytosanitary products was evaluated: 1) Spinetoram + Pyraclostrobin and Fluxapyroxad; 2) Cyromazine + Pyraclostrobin and Fluxapyroxad; 3) Cyproconazole + Spinetoram; 4) Cyantraniliprole + Abamectin + Metiram and Pyraclostrobin; 5) Spinetoram + Azoxystrobin and Difenoconazole; 6) Abamectin + Cyantraniliprole (ready-to-use mixture), and a Control (distilled water). Soon after, the compatible mixtures were used in a bioassay regarding selectivity for T. pretiosum in pre- and post-parasitism. The mixtures corresponding to treatments 1, 2, 3, 5, and 6 did not exhibit change in physical stability; they were compatible. Only treatment 4, involving the mixture with Cyantraniliprole + Abamectin + Metiram and Pyraclostrobin exhibited change in the stability of the mixture after 5 minutes. The pH remained at 6.0 for all the mixtures over the period of evaluation. The treatments affected the mortality of the adult females of T. pretiosum 24 hours after exposure to the treated cards, and mixtures 1, 3, and 5 were most toxic. In pre-parasitism, parasitism and emergence were observed in all the treatments, which allowed all the mixtures to be classified as Class 1 (innocuous to the parasitoid) according to the IOBC. In the bioassay in post-parasitism, effects of the treatments were observed on emergence and on the number of parasitoids per egg at the three ages evaluated (egg, larva, and pupa) of T. pretiosum. The greatest effect on reduction in emergence was observed in the treatments in regard to mixtures 1, 3, and 5. These same treatments had an effect on the number of parasitoids per egg. The treatments did not have an effect on the sex ratio (SR) of the descendants of T. pretiosum at any of the modalities evaluated (pre- and post-parasitism), ranging from 0.46 to 0.63; thus, in general, more females were obtained. The mixtures Spinetoram + Pyraclostrobin and Fluxapyroxad, Cyproconazole + Spinetoram, and Spinetoram + Azoxystrobin and Difenoconazole in the bioassay had the greatest adverse effect on T. pretiosum in pre- and post-parasitism within the parameters evaluated.