Natural infection potential and efficacy of the entomopathogenic fungus Beauveria bassiana against Orosanga japonica (Melichar)

Abstract

Abstract In this study, potential of the entomopathogenic fungi (EPF) isolates from dead samples of Orosanga japonica (Melichar) (Hemiptera: Ricaniidae) was evaluated. Infected specimens with fungi results confirmed that the samples were Beauveria bassiana after morphological and molecular identification. Amplicons produced two haplotypes (h = 2), which included one polymorphic site after sequence and named isolates 1 and 2. Two haplotypes were rooted with MK229193.1, MG345084.1 B. bassiana Genbank samples. Two-year survey results of the EPF effects revealed the highest mortality and natural infection rates in the field. Natural mortality rates varied between 80.35% (Fındıklı-August) and 94.8% (Çayeli-September) in 2018 and between 79.82% (Alipaşa-August) and 97.75% (Fındıklı- September) in 2019. For nymphs, the lowest LT50 value was found at 2.92 days for isolate 1 and 2.56 days for isolate 2, with a concentration of 1 × 106 conidia/ml, using the leaf dipping method. For adults, the lowest LT50 value was found at 3.02 days for isolate 1 and 3.15 days for isolate 2, with a concentration of 1 × 106 conidia/ml, using the direct spraying method. Nymph LT50 values were found a little bit lower than adults. Direct spraying methods results gave a high LT50 value for nymph in contrast to adult. Although the LT50 ratios gave high/low degree in different isolates, methods and life stages, non-significant differences were found between each other’s (p > 0.05). In general, B. bassiana natural infection rates were found high in August and September during the 2 years. Efficacy of the two isolates, which derived from naturally infected O. japonica specimens, increased with concentration. The two isolates can potentially be used for O. japonica integrated management, as a fungal biocontrol agent, but their toxicological effects on beneficial insects, such as honeybees, will need to be determined.

Keywords

• Orosanga japonica
• Beauveria bassiana
• Efficacy
• Natural infection
• Biocontrol