Compatibilidade de produtos naturais comerciais a fungos entomopatogênicos e seletividade a Trichogramma pretiosum (Hymenoptera: Trichogrammatidae)

Abstract

In alternative system for production, the use of biological control agents may occur together with the use of natural products. However, information about the effect of natural products on biological control agents are scarce. The objective of this study was to evaluate the compatibility of the entomopathogenic fungi Beauveria bassiana and Isaria sp. with natural products used in alternative system of production as well as the selectivity of the egg parasitoid Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae). For this we used the strains B. bassiana and Isaria sp. and natural products Topneem, Baicao, Orobor®, Compostonat and Rotenat at concentrations recommended by the manufacturer (CR), half (½ CR) and double this one (2CR). To evaluate the compatibility between natural products and entomopathogenic fungi were analyzed parameters: germination, colony forming units (CFU), vegetative growth and number of conidia per colony. The association of natural products with fungi (B. bassiana and Isaria sp.) was evaluated for pathogenicity on the 3rd instar larvae of Anagasta kuehniella Zeller (Lepidoptera: Pyralidae) in a concentration of 1.0 X 108 con./mL. was evaluated daily mortality of A. kuehniella, for a period of 10 days. To evaluate the selectivity of natural products to T. pretiosum these were sprayed on eggs of A. kuehniella available for parasitism by T. pretiosum. For this two tests were performed: (a) free choice, by assessing the percentage of eggs parasitized by T. pretiosum when it can choose from eggs sprayed with the product or sprayed with the witness, and (b) no choice, which consisted of spraying the eggs of A. kuehniella with natural products previously or subsequently to parasitism. We evaluated the number of eggs parasitized, percentage of emergence, longevity and duration of the egg-adult. It was found that for the fungus Isaria sp. germination was affected only by the product Compostonat. The UFCs were not affected by the product Rotenat. For conidia production Topneem products, Rotenat and Baicao reduced this parameter. As for the fungus B. bassiana conidial germination was reduced by only Orobor®. Orobor® products and Baicao reduced the diameter of the colony. For conidia production per colony, all products have reduced this parameter. However, the products did not affect the pathogenicity of the fungus on A. kuehniella. Selectivity for the T. pretiosum products and Baicao Topneem negatively affected parasitism for the free-choice test, how to test no choice. For emergency only product Baicao affected this parameter. It is concluded that natural products tested, although on some biological parameters interfere fungi Isaria sp. and B. bassiana, proved compatible in all concentrations. Natural products Orobor® and Topneem are selective to the parasitoid T. pretiosum. Already Baicao the natural product was classified as slightly harmful for toxicity to the parasitoid adults.