Laboratory evaluation of the effect of the entomopathogenic fungi, hirsutella thompsonii and paecilomyces fumosoroseus, against the citrus brown mite, eutetranychus orientalis (Acari: Tetranychidae)

Abstract

Formulations of the entomopathogenic fungi Hirsutella thompsonii (Fisher) and Paecilomyces fumosoroseus (Wize) Brown and Smith were tested against all stages of this pest under laboratory conditions. Three concentrations: 0.5 × 109, 1.0 × 109, and 2.0 × 109 conidia/ml were sprayed on leaf discs containing larvae, nymphs, and adults, while a single dosage of 1.0 × 109 conidia/ml was sprayed on eggs as ovicide. All the life stages were susceptible to both fungal pathogens at the tested concentrations. Larval and nymphal stages were generally less susceptible than adults. Based on probit analysis, H. thompsonii was the highest virulent with LC50 and LT50 (358, 290, and 146 conidia/ml and 7.78, 7.11, and 6.92 days) and P. fumosoroseus (597, 589, and 339 conidia/ml and 7.49, 7.14, and 4.31 days) for larvae, nymphs, and adults, respectively. However the efficacy of the two pathogens evaluated clearly differs from that of the controls. Compared with controls, egg hatchability was reduced at the different pathogen concentrations used. H. thompsonii at LC50 was more effective against eggs. Also, females in the control laid more eggs than those treated with the fungi. The entomopathogenic fungi H. thompsonii and P. fumosoroseus could be considered as an environmentally friendly alternative for biocontrol of E. orientalis.