Nematoides entomopatogênicos para controle do bicho-mineiro-do-cafeeiro

Abstract

Leucoptera coffeella (Guérin-Mèneville, 1842) (Lepidoptera: Lyonetiidae) is a primary pest in coffee growing capable of reducing production by up to 80%, causing significant economic losses to producers. Chemical control is still the main method used to manage L. coffeella, and due to incorrect use, it has not been proving to be efficient. The method of biological control of L. coffeella is, basically, the adoption of practices that conserve the presence of naturally occurring enemies in crops. Thus, it is necessary to develop new biological technologies that can be applied in crops. In this context, biological control with entomopathogenic nematodes (NEP) shows promise for L. coffeella, in view of the efficiency of NEP in cryptic environments. Thus, the objective of this work was to characterize the effects of NEP on L. coffeella under laboratory conditions, selecting promising isolates for the biological control of this pest. The experiments were carried out at the Laboratory of Pathology and Microbial Control of Insects (DEN/UFLA), under controlled conditions (25 ± 2°C, RH 70 ± 10%, 12h of photophase), using NEP isolates belonging to the laboratory entomopathogens. To assess the pathogenicity of NEP, 1.2 mL of aqueous suspension containing 1,000 infective juveniles (JI)/mL were sprayed on active mines of L. coffeella. The effect of different concentrations of JI suspensions, mortality time and combined applications between the isolates H. amazonensis RSC05 and Heterorhabditis sp. NEPET 11 on L. coffeella larvae. It was found that all NEP were pathogenic to the larvae, with the H. amazonensis RSC05 isolate causing the highest mortality. Larval mortality was proportional to the increase in JI concentration, with LC 50 and LC 90 values for the H. amazonensis RSC05 isolate being 844.20 and 2409.60 JI/mL, respectively, and for the Heterorhabditis sp. NEPET 11, the LC 50 was 708.78 JI/mL, and the LC 90 was 2107.88 JI/mL. In the bioassay of time of exposure to NEP, it was possible to verify that the increase in time increased the mortality of the larvae for both isolates, however the isolate Heterorhabditis sp. NEPET 11 caused higher mortality rates compared to H. amazonensis RSC05. The isolate H. amazonensis RSC05, provided TL 50 of 76.28h and TL 90 of 144.46h, while the isolate Heterorhabditis sp. NEPET 11 presented TL 50 of 73.12h and TL 90 of 140.96h. In the test of combined and individual applications, it was verified that the combined applications were less harmful to L. coffeella larvae, demonstrating competition interaction between the isolates in the adopted concentrations. Thus, it is concluded that nematodes belonging to the Heterorhabditise family are more virulent to L. coffeella larvae than those belonging to the Steinernematidae family, and that combined applications of Heterorhabditis sp. NEPET 11 and H. amazonensis RSC05 do not increase the efficiency of controlling L. coffeella larvae under laboratory conditions.