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

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.

Potential of Turkish Beauveria bassiana isolates for the management of the polyphagous planthopper, Orosanga japonica Melichar 1898 (Hemiptera: Ricaniidae)

“…Considering the LT 50 and LT 90 values, B. bassiana isolates were slightly more effective at 25 than at 20 °C, which put forward some B. bassiana isolates as significant candidate organisms for controlling O. japonica in the origin region of the country. Akıner et al (2020) found that the lowest LT 50 values for B. bassiana isolate-1 and isolate-2 were 2.92 and 2.56 days, respectively, for nymphs using the leaf dipping method at (1 × 10 6 conidia ml -1 ). In addition, EPF isolates with a high virulence and good growth characteristics are the basis in pest biocontrol.…”

“…The Eastern Black Sea region receives frequent rainfall and characterized by high humidity and low temperatures throughout the year. These environmental conditions are ideal for the development of EPFs such as B. bassiana and Lecanicillium muscarium Zare and Gams (Ascomycota: Hypocreales) (Akıner et al 2020). Conidia of EPFs need moisture for germination and subsequent sporulation; some even require high humidity to initiate infection.…”

“…The present study showed that all native isolates of EPF isolated from adult cadavers of the pest collected from kiwifruit orchards in Artvin Province (Eastern Black Sea region) were identified as B. bassiana based on the rDNA-ITS sequencing. Akıner et al (2020) reported that the natural mortality rates caused by B. bassiana in the surveys conducted in the areas correct as infested by O. japonica in Rize Province located in the same region were approximately 80-95% and 80-98% in 2018 and 2019, respectively. All tested isolates caused significant mortality against O. japonica adults under laboratory conditions.…”

“…All tested isolates caused significant mortality against O. japonica adults under laboratory conditions. Several previous studies indicated that the EPF were more likely to have ecological compatibility with pests due to their geographical locations and habitats types (Bidochka et al 2002;Akıner et al 2020).…”

“…Documenting EPFs on dead insects in the region, where O. japonica outbreaks occur, is important due to their ability to adapt to their environment. However, the pathogenic activity of native B. bassiana isolates against pests often differs among isolates, indicating the need to evaluate the potential of the Turkish B. bassiana isolates to manage O. japonica (Akıner et al 2020).…”