Controle de Tetranychus urticae Koch com fungos entomopatogênicos. / Control of Tetranychus urticae Koch with entomopathogenic fungi.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2002

RESUMO

Among 45 isolates of hyphomycetes tested against Tetranychus urticae, 8 Beauveria bassiana and 4 Metarhizium anisopliae isolates caused mortality >80 and 90%, respectively, 5 days after inoculation with 5x10 7 conidia/mL. Hirsutella sp. caused 73% mortality at a concentration of 1.7x10 7 conidia/mL. Eighty to 100% of cadavers infected by B. bassiana or M. anisopliae isolates had calcium crystals inside their bodies. Conidia, blastospores and yeastlike cells of five B. bassiana isolates were pathogenic against this pest. Significant differences (P ³ 0.05) were observed among the LC50 s and slopes of dose-mortality lines for the different isolates and infective structures. LC50 values ranged from 4.95x10 6 to 8.21x10 7 cells/mL. There were no significant differences among the infective structures in the two tested variables. However, there were significant differences among the LC50 s with different infective structures within the same B. bassiana isolate. Three fungicide formulations and 24 insecticides and/or mitecides were compatible with B. bassiana including those with the following active ingredients: propamocarb hydrochloride, sulphur, abamectin, acephate,acetamiprid, betacyfluthrin, bifenthrin, cyromazine, deltamethrin, diafentiuron, diflubenzuron, dimethoate, fenpropathrin, fenpyroximate, fenvalerate, imidacloprid, methamidophos, propargite, tebufenozide and trichlorfon. There was large variability in the toxicity of products withing a chemical group and products containing the same active ingredient. B. bassiana was an efficient T. urticae mite control in chrysanthemum (Dendranthema grandiflora), when applied at a concentration of 2x10 8 conidia/mL. Microbial control was better than that provided by chemical pesticides normally used in the greenhouses. With four fungal sprays within 14 days, the mite density was reduced from 1.8 to 0.1 mite/leaf. In strawberry (Fragaria sp.), T. urticae control was lower than in chrysanthemum, with mean density of mites for 21 days after application of 1x10 8 or 5x10 7 conidia/mL at 13 mites/leaflet, compared to 43 mites/leaflet in control plots. The strawberry varieties Campinas and Princesa Isabel had the lowest mite densities, however, these varieties did not affect the efficacy of mite control by B. bassiana. Thus, M. anisopliae, B. bassiana and Hirsutella sp. were the most promissing fungi to be formulated as mycomiticides for T. urticae control.

ASSUNTO(S)

pragas de plantas biological control controle biológico fungos entomopatogênicos entomopathogenic fungi mites crop pests ácaros parasitos de plantas

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