Controle da Mosca-Negra-Dos-Citros Aleurocanthus Woglumi Ashby (Hemiptera: Aleyrodidae) por óleos vegetais e seletividade a Chrysoperla Externa (Hagen) (Neuroptera: Chrysopidae)

Abstract

The citrus black fly is an exotic pest that was introduced in Maranhão territory in the year 2003 and, since then, has worried both researchers and producers of citrus, due to its high dispersal capacity, occurring for countless generations a year, adaptation to the various climatic conditions and high reduction in citrus productivity. Thus, the objective of this work was to control the citrus black fly through the use of cottonseed and degummed soybean oils and to evaluate selectivity of these vegetable oils to a non-target predator. All bioassays were performed at the Laboratory of Entomology/ NBA / CCA of the Maranhão State University (MASU). The predation potential of Chrysoperla externa was determined to verify the predator's ability to consume nymphs (2nd or 3rd instars) of the citrus black fly. Bioassays with different densities (5, 10, 20, 30, 40 and 50) of A. woglumi were performed to determine the average number of nymphs consumed by C. externa first instar larvae during 24h. Subsequently, concentration-mortality bioassays were carried out to determine the lethal concentrations (CL10, CL25, CL50, CL80 and CL90) of the cottonseed and degummed soybean oils to the citrus black fly. Increasing concentrations of cottonseed and degummed soybean oils were sprayed on citrus leaves infested with 3rd instar nymphs of A. woglumi. Additionally, selectivity tests were performed on eggs of C. externa up to 24 hours old. Eggs from this predator were placed in Petri dishes and sprayed with distilled water (control), LC50 from cottonseed and degummed soybean oils. Finally, the toxicological classes of cottonseed and degummed soybean oils were determined on C. externa. The results indicated that 1st instar larvae of C. externa presented a high predation rate on increasing densities of A. woglumi nymphal stages (2nd and 3rd). Additionally, it was possible to prove the toxicity of degummed soybean and cottonseed oils on third instar nymphs of the citrus black fly by determining the lethal concentrations of these vegetable oils. Finally, the selectivity (compatibility) of the degummed cotton and soybean vegetable oils on the biological parameters of C. externa was proved. All the information together is essential for the development of future ecological management programs for the citrus black fly. Key words: Biological aspects, Chrysoperla externa, Predator-prey interaction