Characterization of Guazuma ulmifolia Lam. seed gum and its effect on the activity of Metarhizium anisopliae (Metschn.) Sorokin on Bemisia tabaci Genn

Abstract

The present study was conducted to evaluate the functional properties of seed gum of Guazuma ulmifolia (GG) and its effects on the entomotoxic activity of the fungus Metarhizium anisopliae (MET) on whitefly nymphs (Bemisia tabaci). The GG was extracted from mature fruit seeds in distilled water at 60°C and precipitated in ethanol. The quantity of gum extracted from the seed of G. ulmifolia was 67.1 g/kg. This gum showed a dispersion in water of 79.6% and thermal stability. The rheological studies indicated that GG had a non-Newtonian behavior and high viscosity at low concentrations. The swelling index (SI) and water dispersion (WDIS) of GG were determined at different temperatures. The apparent viscosity (µ) of GG was measured using an AR-2000 rheometer. An entomotoxic bioassay was carried out under greenhouse conditions using MET (1x10⁸ conidia mL) suspended in aqueous solutions of GG at 0.2 and 0.5%. These solutions were sprayed on eggplant leaves infested with B. tabaci to evaluate their entomopathogenic effect. The use of GG improved the lethal effect of MET on B. tabaci nymphs by 44.4%. This increase in nymphal mortality caused by MET when combined with GG, suggest that GG could be a good alternative as a carrier and protective agent for entomopathogenic fungi used in pest control.