Field evaluation of Verticillium lecanii (ZIMMERMANN) VIÉGAS as a control agent for Trialeurodes vaporariorum (WEST.) (HOMOPTERA: ALEYRODIDAE) on beans (Phaseolus vulgaris L.)
DOI:
https://doi.org/10.33885/sf.1999.3.877Keywords:
Verticillium lecanii, biological control, whitefly, beansAbstract
The effectiveness of the entomopathogenic fungus Verticillitim lecanii (Zimm.) Viégas as control agent of the
whitefly Trialeurodes vaporarionim (West.) was evaluated on bean, Phaseolus mlgaris L., planted plots by determining
nortality of the pest and the fluctuafion of its population, the yield of the plañís and the damage on infested plants. The
innocuity of the fungus was also ratified on the treated plants. A randomized complete block design was used, three
replicates per treatment in six planted plots of 126 m2 each. Fungal conidia were applied in three of the plots, five times at
15-day intervals with 1012 conidia/ha. The remainder lots were controls without treatment. Average valúes of temperature
and relative humidity were 33°C and 26% during the day, and of 8°C and 96% during the night. The density of the total
population was reduced from the first application of V. lecanii to the end of the study (p<0.05). Fungal applications affected
population dynamics of the whitefly causing, during the fructifying period (75 days), the highest mortality rales in pupal (84.3
and 79.8%), nymphal 2 (72.7%) and nymphal 3 (51.2%) stages. Al 30, 45 and 60 days, ihe mortalily observed for eggs was
of 43.3, 24.8 and 49.8%, respeclively. Al the end of Ihe study, eggs were the most resistant to treatment, no mortality was
found among them. The yield of Ihe fungal applied plañís increased 51.3% as compared lo non-lrealed plants. A higher
amounl of heallhy plañís and wilh slight damage both in flowering (45 and 48% respectively) and fructifying (19 and 59%
respeclively) was found among Ihe ireated plols, whereas Ihe non-lrealed plots yielded plañís with modérale and severe
damage, wilh no recovery tendencies, for Ihe flowering (39 y 19% respeclively) and fructifying (42 y 52% respeclively)
periods. The highest damage was recorded during the fructifying period bolh in ireated (21 and 1% respectively) and nonlrealed
(42 and 52% respeclively) plants. Phylopathogenicity by V. lecanii was nol observed in bean irealed plañís. The
results suggest that y. lecanii is efficacious for the control of the whilefly in open-field bean planlalions, under the
environmental conditions described in this sludy.
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