Performance of Entomopathogenic Fungal-Based Insecticides against the Citrus Mealybug (Hemiptera: Pseudococcidae) on Coleus (Lamiales: Lamiaceae) Plants under Greenhouse Conditions1

Abstract

The citrus mealybug, Planococcus citri (Risso) (Hemiptera: Pseudococcidae), is an important insect pest of greenhouse-grown horticultural crops. Citrus mealybug causes direct plant damage when feeding on plant leaves, stems, flowers, and fruits, and this damage can result in substantial economic losses. Insecticides are used to manage citrus mealybug populations in greenhouse production systems. Although entomopathogenic fungal-based insecticides are labeled for use against citrus mealybug, there is no quantitative information on their efficacy against this insect pest under greenhouse conditions. Consequently, four experiments were conducted in a research greenhouse at Kansas State University (Manhattan) from 2020 to 2022 to determine the efficacy of three commercially available entomopathogenic fungal-based insecticides on citrus mealybug feeding on coleus, Solenostemon scutellarioides (L.) Codd (Lamiales: Lamiaceae), plants: Beauveria bassiana strain GHA (BotaniGard®, Laverlam International Corp., Butte, MT), B. bassiana strain PPRI 5339 (Velifer™, BASF, Research Triangle, NC), and Isaria fumosorosea Apopka strain 97 (Ancora®, OHP, Inc., Bluffton, SC). The surfactant polyether and polyether-polymethylsiloxane-copolymer (CapSil®, Aquatrols, Paulsboro, NJ) was added to spray solutions to determine whether the surfactant would enhance efficacy. The entomopathogenic fungal-based insecticides, with or without the surfactant, were not effective in managing citrus mealybug populations, with <50% mortality in all four experiments. Our study indicates that entomopathogenic fungal-based insecticides are not effective in managing citrus mealybug populations in greenhouses.

Are Entomopathogenic Fungal-based Insecticides and Insect Growth Regulator Mixtures Effective Against the Citrus Mealybug, Planococcus citri (Hemiptera: Pseudococcidae), Feeding on Coleus, Solenostemon scutellarioides, Plants under Greenhouse Conditions?

“…In conclusion, based on the findings of Herrick and Cloyd (2023) and the findings of the current study, entomopathogenic fungalbased insecticides alone or in mixtures with insect growth regulators are not effective in managing citrus mealybug populations on coleus plants. The temperature and relative humidity must be optimal for germination and infection to occur.…”

“…We found that the entomopathogenic fungalbased insecticides alone and in mixtures with the insect growth regulators tested were not effective in managing citrus mealybug populations on coleus plants under greenhouse conditions. The lack of efficacy may be attributed to the waxy covering protecting citrus mealybugs, which prevents the conidia of the entomopathogenic fungi from attaching to the cuticle (Herrick and Cloyd 2023).…”

“…It has been suggested, although anecdotally, that adding an insect growth regulator to a spray solution may increase the efficacy of entomopathogenic fungal-based insecticides against the citrus mealybug (Herrick and Cloyd 2023). However, the mechanisms responsible for increasing efficacy are unclear.…”

“…Infection and mortality of insects by entomopathogenic fungal-based insecticides takes longer (in days) than commonly used contact insecticides (Zhang et al 2021). Herrick and Cloyd (2023) found that entomopathogenic fungal-based insecticides alone are not effective in managing citrus mealybug populations under greenhouse conditions. However, anecdotal information suggests that mixing entomopathogenic fungal-based insecticides with insect growth regulators may enhance efficacy by increasing hyphal penetration through the insect cuticle (Akbar et al 2005;Hernandez et al 2012;Kivett et al 2016).…”