Lethal concentration and sporulation by contact and direct spray of the entomopathogenic fungus Beauveria bassiana on different stages of Nezara viridula (Heteroptera: Pentatomidae)

Authors: Portilla, Maribel; Zhang, Minling; Glover, James; Johnson, Christopher - Chris; Reddy, Gadi V.P.

Submitted to: The Journal of Fungi
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2022
Publication Date: 11/4/2022
Citation: Portilla, M., Zhang, M., Glover, J.P., Johnson, C.P., Reddy, G.V. 2022. Lethal concentration and sporulation by contact and direct spray of the entomopathogenic fungus Beauveria bassiana on different stages of Nezara viridula (Heteroptera: Pentatomidae). The Journal of Fungi. https://doi.org/10.3390/jof8111164.
DOI: https://doi.org/10.3390/jof8111164

Interpretive Summary: The southern green stink bug, is an herbivore invasive insect responsible of reducing production in soybean and cotton, both quality and quantity. In addition of the plant pathogens transmission, adults and nymphs can injure those crops at any phenological growth stage. Globally, is well known the low susceptibility of N. viridula to pyrethroids and organophosphates; yet chemical control remain the primary tool to manage this pest in most of southern states of U.S., and tropical, and subtropical zones in five continents. The adverse environmental effects of chemical insecticides have increased the interest of microbiological agents over the years. Regardless the pathogen’s slow action, B. Bassiana is well recognized as an essential source of myco-pesticides that are used for numerous insect pest all over the word. Beauveria bassiana, is one of the most common pathogens that occur naturally in North America that could contribute to build a sustainable environment. B. bassiana could be considered a potential non-chemical approach to be adopted for use in an integrated management of the southern green stink bug.

Technical Abstract: The southern green stink bug, Nezara viridula (L.) (Heteroptera: Pentatomidae) is the most signifi-cant pest of soybean worldwide. The present study was conducted to compare the effectiveness of a Delta native strain NI8 of Beauveria bassiana by contact and direct spray on nymphs (2nd to 5th instar) and adults of N. viridula. Water control and four concentrations of B. bassiana were used to evaluate the survival, mortality, and molting percentage, and to estimate lethal concentration (LC50), lethal sporulation (LS50), and resistance ratio (RR50). The greatest reduction in survival was observed on all life stages by direct spray at all concentrations. Mortality and sporulation were positive correlated by concentration, while molting was highly variable with a significantly lower negative correlation on insects that were directly sprayed. Pathogenicity exhibited reduc-tion as young stages developed and emerged to adult. The LC50 (Contact: 612 spores/mm2 Direct spray: 179 spores/mm2) and LS50 (Contact: 1960 spores/mm2 Spray: 3.3x106) values showed that adults of N. viridula were highly resistant than any other life stage when exposed to either contact or direct spray. Fourth instar was the most susceptible (LC50: Contact: 18 spores/mm2 Spray: 23 spores/mm2) (LS50: Contact: 53 spores/mm2 Spray: 26 spores/mm2) followed by second, third, and fifth instars.