Efeito de xenobióticos sobre insetos e a microbiota do solo associados à palma forrageira

Abstract

The palm is recognized as a major forage resources for animal production in the semiarid. However, in recent years, most of palmais North East began to be compromised by the cochineal carmine (Dactylopius opuntiae Cockerell), being necessary control measures that are efficient and that do not affect the activity of the microbiota present in the soil. Thus, the present study aimed to evaluate the effect of xenobiotics applied in the culture of palm infested by D. opuntiae on natural enemies encountered in culture and soil microbes. The study was conducted in an area with palm cv. gigantic (Opuntia ficus-indica) scale-infested cochineal carmine in the region of Caétes – PE. The experimental design was a randomized block with 5 treatments: control (water), detergent + bleach, oil neem, methomyl and thiamethoxam lambda-cyhalothrin, and 3 repetitions. Before application of xenobiotics were conducted eight data collections, to observe the growth of the population of cochineal carmine and distribution of natural enemies. After application of the products, three samples were conducted to quantify the efficiency of xenobiotics and their effect on natural enemies and soil microbes by respirometry microbial, bacterial count and genetic variability of bacteria. For this, were collected soils (0-20cm), the respirometry assessed by monitoring the release of CO2 by the microorganisms for a period of 30 days. In microbiology, was evaluated population density of the bacteria after 24, 48 and 72h of incubation, morphological variability and by staining. Subsequently, we assessed the genetic variability, by molecular techniques, using BOX-PCR. There was increase in the number of colonies of cochineal carmine even after application of xenobiotics, which are not significantly affected natural enemies (IN) present in the culture, as these insects occurred even at low densities, independent of the application of the products. The predatory species of cochineal carmine were observed Zagreus bimaculosus, Cybocephalus sp. and larvae Salpingogaster cochenillivorus, and Z. bimaculosus, considered the most frequent. As to respirometry, there is, in relative terms, the amount of CO2 released from the soil samples was higher in the plots with the application of the insecticide thiamethoxam + lambda-cyhalothrin, relative to the control, not differing from other treatments. Soils treated with water alone (control) and detergent + bleachshowed the largest populations (0.96 and 0.94 x 102 UFC.g-1, respectively). It was observed that soils with water application (control) and detergent + bleach, showed bacteria with slower growth, and the other treatments, with accelerated growth occurred 24h, decreasing from 48 h of incubation. In morphological characteristic (coloration) bacterial colonies predominated white colonies, demonstrating visually low genetic variability. However, the application of molecular techniques (BOX-PCR), revealed high genetic variability between colonies of white coloration analyzed. Demonstrating that given the importance of cactus for semiarid region is of great importance more detailed studies on the effects of xenobiotics on the microbiota and associated insects.