Uso de nanotecnologia e controle biológico conservativo para o manejo de Leucoptera coffeella

Abstract

Chemical control is still the main way to reduce the population of the leaf miner Leucoptera coffeella (Guérin-Mèneville and Perrottet, 1842) (Lepidoptera: Lyonetiidae). The use of nanoclay and the adoption of planting cover crops are tools that can help manage this pest. Thus, the objectives were to evaluate nanotechnology and conservative biological control using eggs of Chrysoperla externa (Hagen, 1861) (Neuroptera: Chrysopidae) combined with different species of cover crops in the management of L. coffeella in coffee plantations. For the study with nanotechnology, three experiments were carried out in a greenhouse in order to evaluate the mortality of L. coffeella caterpillars at 7, 14 and 21 days after application of nanoclays. The nanoclays were synthesized and provided by the Chemistry Laboratory of the Federal University of Viçosa, Campus Rio Paranaíba. The study with cover crops was conducted in two arabica coffee producing regions in the Cerrado of Minas Gerais state, with different coffee varieties and phenological stages. The treatments of experiment 1 were: buckwheat, forage radish, mixed (buckwheat and forage radish), weeds (plants that grew naturally between the rows of the crop) and a dried control, with 4 replications. In experiment 2, two species of cover crops (buckwheat and radish) and weeds were used, with 8 replications. For the study of the use of nanoclays, significant differences were observed for the mortality of L. coffeella in the time of 7 days after application of insecticides. Mortality of L. coffeella was observed in nanoclay treatments with thiamethoxam and Actara 250WG®, and was above what is required by ABPM. There was a significant difference at the 5% probability level by the F Test for the number of leaf miner adults (NLMA), the number of old leaf mines (NOM) and the number of leaf miner eggs (NLFE) only in the experiment 1 with cover crops. All variables evaluated in experiment 2 were not significant. Considering NLMA in experiment 1, the different types of cover crops resulted in a decrease in the number of individuals on the coffee tree, highlighting the use of buckwheat or forage radish between the rows of the coffee crop in reference to the practice of allowing the occurrence of spontaneous plants. Regarding NOM, the adoption of the buckwheat and radish intercropping promoted a reduction in the number of injuries to coffee leaves caused by L. coffeella, compared to the other treatments, in addition to the increase of NLFE in the coffee crop. The use of buckwheat and radish favors the maintenance of C. externa in coffee crops. In addition, the reduction in the number of L. coffeella adults and the decrease in old mines confirms the hypothesis that these species of cover crops helped to promote the biological control of the agent C. externa in the area where experiment 1 was developed. The results of the study suggested that the use of nanoclays associated with thiamethoxam maintained mortality levels of L. coffeella populations above 80%, as well as the use of different cover crops promoted the reduction of damage caused to the coffee crop, in addition to contribute directly to the biological control of the predator C. externa.