Evaluation of the lethal effect of plant extracts and their synergistic effect with Beauveria bassiana to control the population of Oryzaephilus surinaemensis fed on date palm

Given the compatibility of Beauveria bassiana and plant extracts, it is feasible to increase efficacy of the fungus in microbial control of date storage pests. The aim of this study was to evaluate the interaction of plant extracts and B. bassiana on sawtoothed beetle populations. The vegetative and reproductive parts of myrtle, mugwort, mentha, yarrow, and neem plants were evaluated. The fungal mycelium growth and spore germination were evaluated to checking the consistency of extracted from plants by extract medium mixing method. Then, the compounds toxicity were evaluated individually and conjunction with B. bassiana by bioassay on the adult and larvae of sawtoothed beetle. Studies have shown that mycelial growth and spore germination of B. bassiana occur only in artemisia and neem. The spore germination rate of B. bassiana in neem was higher than artemisia in all concentrations. A concentration equivalent to 1949.4 microliters/liter of neem was required to reduce 50% of the germination of the fungus. The lowest and highest mycelial growth reduction (3.1% and 20.1%) were observed in 250 microliters/liter of neem and 1000 microliters/liter of artemisia, respectively. So, the concentration of neem equivalent of 36679.4 microliters/liter was required for 50% reduction of mycelial growth. The highest compatibility index (T) was 76.89 for 500 microliters/liter in combination with neem and the lowest level consistent with artemisia in 1000 microliters/liter. Both plant extracts had synergistic effect on the pathogenicity of B. bassiana on adult and larva of sawtoothed beetle. However, synergistic effect of neem extract was higher.