Another Tool for Combatting Pest Problems in the Greenhouse

Metarhizium brunneum strain F52 is a mycoinsecticide first discovered in 1879 in Russia when E. Metchnikoff discovered a chafer cadaver covered with a green fungal organism. Metchnikoff later found that this fungal organism had insecticidal properties and was responsible for the death of the chafer specimen. The conidia of Metarhizium brunneum strain 52 are green, and when it parasitizes and kills an insect, the conidial growth will envelop the insect after colonization. Because of the green coloration of the conidia, Metarhizium brunneum strain 52 is often referred to in the literature as the "green muscardine" fungus.

Mycoinsecticides, in general, offer growers a bio-based insecticide with low mammalian toxicity. When spores or conidia come in contact with a susceptible insect under the right environmental conditions, the fungal organism will penetrate the insect’s cuticle and then enter the hemolymph of the insect, resulting in the insect's death in 3–7 days. Currently, entomologists have not noted any resistance to mycoinsecticides, but mycoinsecticides can fail if applied under dry, hot environmental conditions or if the conidia or spores do not come in contact with the targeted pest.

Metarhizium brunneum strain F52, now distributed by Lallemand Plant Care and marketed as LALGUARD M52 OD and LALGUARD M52 GR should not be necessarily considered a new product against insect and mite pests, but its re-entrance into the market has given growers another bioinsecticide tool against thrips, spider mites, and other insect pests.

Metarhizium brunneum strain F52 (LALGUARD M52 OD) is currently labeled for managing whiteflies, thrips, mites, and aphids in the greenhouse. LALGUARD M52 OD can be used as a foliar spray, as a dip, or as a drench. When this mycoinsecticide is utilized in this manner the applicator must observe a 4-hour Restricted Entry Interval (REI).  If LALGUARD M52 OD is soil incorporated the REI drops to 0-hours. LALGuard M52 OD is also labeled for use on greenhouse fruits and vegetables and has a 0-day PHI.

There are a variety of mycoinsecticides on the market that should be considered for use in greenhouse systems. The relative effectiveness or efficacy of mycoinsecticides is often linked to the relative humidity levels in the greenhouse after application. Some researchers have observed western flower thrips' mortality rates exceeding 70% on impatiens when the relative humidity in the greenhouse structure was 80% after application.

Mycoinsecticides labeled for use in Pennsylvania greenhouses include:

• Beauveria bassiana Strain GHA (BotaniGard ES, BotaniGard 22 WP, Mycotrol ESO, and Mycotrol WPO) Labeled for managing whiteflies, aphids, mealybugs, leafhoppers, and thrips.
• Beauveria bassiana ANT-03 (BioCeres WP) Labeled for managing plant bugs, whiteflies, aphids, and thrips.
• Beauveria bassiana Strain PPRI5339 (Velifer) Labeled for managing whiteflies, mealybugs, two-spotted spider mites, and thrips.
• Isaria fumosorosea Apopka Strain 97 (Ancora) Labeled for managing insect and mite pests in greenhouses and nurseries.
• Isaria fumosoroseus Strain FE 9901 (NoFly) Labeled for managing whiteflies, thrips, aphids, and mites.
• Metarhizium brunneum Strain F52 (LALGuard M52 OD) Labeled for managing whiteflies, thrips, aphids, and mites.
• Metarhizium brunneum Strain F52 (LALGUARD M52 GR) Labeled for managing black vine weevil and Thrips pupae.