Ovicidal activity of two fungal pathogens (Hyphomycetes) against Tetranychus cinnabarinus (Acarina: Tetranichidae)

The carmine spider mite, Tetranychus cinnabarinus, is an economically important pest that devastates varieties of crops worldwide and develops significant resistance to common chemical pesticides, most of which lack ovicidal activity. In the present study, two isolates of entomopathogenic fungi, Beuaveria bassiana SG8702 and Paecilomyces fumosoroseus Pfr153, were bioassayed against T cinnabarinus eggs at 25degreesC under a photophase of 12 : 12 (L : D). Infected eggs on Vicia faba var. minor leaves failed to hatch due to distortion and shrinkage and had fungal outgrowths when maintained under moist conditions. Sprays of B. bassiana conidia to T cinnabarinus eggs (on leaves) at the concentrations of 58, 298 and 1306 conidia/mm(2) (3 replicates per concentration and 35-65 fresh mite eggs per replicate) resulted in corrected egg mortalities of 20.4 +/- 4.2%, 36.0 +/- 7.6% and 64.6 +/- 12.5% (F=43.14, P<0.01), respectively; sprays of P fumosoroseus at 129, 402 and 2328 conidia/mm(2) caused egg mortalities of 16.1 +/- 11.1%, 44.2 +/- 13.3%, and 63.4 +/- 11.7% (F=15.37, P=0.01), respectively. In contrast, natural egg mortalities in blank controls were 7.8% and 10.3% only. Based on probit analysis, the estimates of LC50 with 95% confidential limits were 548 (393-858) conidia/mm(2) 2 for B. bassiana and 914 (625-1550) for R fumosoroseus, respectively. Apparently, both fungal species were capable of infecting T cinnabarinus eggs, but the ovicidal activity of the B. bassiana isolate was greater than that of the P fumosoroseus isolate. This represents the first report on the ovicidal activity of the two entomopathogenic Hyphomycetes against T cinnabarinus.