Nymphicidal and adulticidal action of Beauveria bassiana isolates in whitefly Bemisia tabaci (Hemiptera: Aleyrodidae) in vitro

Abstract

Whitefly Bemisia tabaci is one of the most dangerous and destructive pests for crops in fields and greenhouses. Entomopathogenic fungi have emerged as an effective management method compared to potential disorders created by chemical pesticides, including environmental pollution and development of resistance. Therefore, the bio- control agents (microbial pesticides) provide an alternative to chemical pesticides due to their cheapness and ease of handling with their safe use for farmers and more selective than chemical pesticides. The laboratory study objective was to evaluate the efficiency of the bio-control agent (Beauveria bassiana) in the control of the nymph and adult stages of B. tabaci on cucumber crop. Three concentrations of fungal filtrate of this fungus, 0.25, 0.50, 1.00% conidia mL-1 were used in this study. The results showed high virulent of two tested isolates against the nymph and adult stages of the B. tabaci that different significantly when compared to the control. The mortality rate was increased by elevating the concentration and by increasing in time period of the nymph and adult exposure to fungal filtrates. The 100% concentration for both two isolates (Bb100 and Bb90) was superior from the rest of the concentrations and exhibited the mortality rate in the nymph and adult stages of this pest as 55.55% and 55.55% respectively in nymphs stage, while 52.22% and 51.10% in adult stages. In addition, in the case of effects of time periods on mortality rate after treatment, the highest mortality rate of nymphs occurred after 9 days of treatment, amounting to 84.44% and 66.66% for Bb100 and Bb90 in nymph stage, while 68.88% and 65.55% in adult stage respectively. From the point view of interaction between concentrations and time periods, the highest mortality rate in nymphs was recorded at the concentration of 1.00% after 9 days of treatment amounting to 96.66%, 93.33% for Bb100 and Bb90 respectively and 83.33%, 86.66% in adults respectively. The lowest mortality rate in nymph was 6.66 after 3 days of treatment at the concentration of 0.25% for both isolates in nymph, while in adults were 13.33% and 10.0% for Bb100 and Bb90 respectively.

Keywords

• biological control
• entomopathogenic fungi
• beauveria bassiana
• bemisia tabaci