Applying a saponin complex of Pseudalbizzia inundata (Mart.) Koenen & Duno as surfactants of Beauveria bassiana (Balsamo) Vuillemin conidia to control Bemisia tabaci Gennadius

Biosurfactants secondary plant metabolites, such as saponins, could be an efficient green alternative dispersant for entomopathogenic fungi propagules. This work aimed to evaluate the potential of a saponins’ complex extracted from Pseudalbizzia inundata (Mart.) Koenen & Duno (PSC) to disperse conidia of Beauveria bassiana IBCB66 (Balsamo) Vuillemin (Hypocreales: Cordycipitaceae) as also its’ insecticidal activity against Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae). Despite a negligible effect on fungal germination and mycelial growth at the highest concentration of PSC (1,000 mg L-1), conidia production was significantly inhibited, resulting in a biological index of 52.03 at the higher dose, which characterises PSC as moderately toxic to B. bassiana. However, no effect was detected on the viability of conidia produced in media added with PSC. When applied directly on cowpea leaves, the saponins did not show an insecticidal effect on B. tabaci eggs and nymphs. PSC solution produced an adequate dispersion of B. bassiana IBCB66 conidia, causing nymph mortality higher than 90%, similar to Triton X-100, and adult mortality of 60% with a median survival time (ST50) of 8 days. A probit analysis of dose-effect of IBCB on both surfactants showed no difference between PSC solutions and Triton according to the parallelism test, with LC50 of 2.35 and 1.44 × 107 conidia mL-1 for PSC and Triton, respectively. These findings underscore the potential of PSC as a safe and effective substitute for synthetic surfactants to disperse the conidia of entomopathogenic fungi.