Novel combination of a biosurfactant with entomopathogenic fungi enhances efficacy against Bemisia whitefly

Abstract

BACKGROUND: Microbial surfactants are multifunctional surface-active molecules that have been overlooked in formulating microbial biopesticides. We report a novel approach using the biosurfactant rhamnolipid (RML) against the destructive cosmopolitan insect pest Bemisia tabaci, as well as the combined action of RML with aerial conidia of two entomopathogenic fungi, Cordyceps javanica and Beauveria bassiana. RML was also tested as a suspension agent to improve the recovery rate of conidia from solid substrate for fungal preparations. RESULTS:The recovery rate of conidia increased dramatically (two to five times) with RML compared with a standard surfactant (Tween 80). Spraying solutions of 0.075% and 0.1% (w/v) RML on B. tabaci third instar nymphs induced 100% mortality within 4 days. Conidial suspensions at 5 × 10 6 conidia/mL amended with RML at 0.01% or 0.05% markedly increased nymphal mortalities and considerably reduced LC 50 . Conidial suspensions of B. bassiana with 0.05% RML added were more effective against whitefly nymphs (87.3% mortality) than C. javanica + RML (51.4% mortality). CONCLUSION:Our results show that this bacterium-based RML improved the recovery rate of hydrophobic conidia, and that mixtures of RML with fungal spore suspensions increased their insecticidal activity.

A Review of the Biology and Control of Whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae), with Special Reference to Biological Control Using Entomopathogenic Fungi

“…The interaction of B. bassiana with other biological control agents, such as Bacillus thuringiensis for the biological control of B. tabaci , were shown to have an antagonistic effect, and mortality greater than 50% was observed over a period of 7 days [ 98 ]. A combination of bacterial biosurfactant with two EPF, Cordyceps javanica and B. bassiana , has recently been found to cause 100% mortality of the third instar nymphs of B. tabaci within 4 days [ 99 ]. Likewise, the combination of B. bassiana and some plant extracts such as neem have shown increased mortality of B. tabaci [ 100 , 101 , 102 , 103 ].…”

A Study on Larvicidal Activity and Phylogenetic Analysis of <i>Staphylococcus epidermidis</i> as a Biosurfactant-Producing Bacterium

“…Today, due to human knowledge about the possibility of contamination and the health threats posed by many common synthetic chemical toxins, much attention has been driven to the production of biotechnology products to promote sustainable agriculture. Although synthetic pesticides can protect crops by suppressing arthropod pests, they have severe hazards for health and the environment because of their toxicological properties and harmful side effects [5,6]. The main problems associated with chemical pesticides are their effects on non-target organisms like humans, pets, beneficial insects, and wildlife, as well as their persistence in nature, which has been often long [7].…”