|GOBLE, TARRYN - Cornell University - New York|
|GARDESCU, SANA - Cornell University - New York|
|FISHER, JOANNA - Cornell University - New York|
|HAJEK, ANN - Cornell University - New York|
Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/8/2016
Publication Date: 1/19/2016
Citation: Goble, T.A., Gardescu, S., Fisher, J.J., Jackson, M.A., Hajek, A.E. 2016. Conidial production, persistence and pathogenicity of hydromulch formulations of Metarhizium brunneum F52 microsclerotia under forest conditions. Biological Control. 95:83-93.
Interpretive Summary: We have developed a low-cost liquid culture fermentation method for producing a very stable form the bioinsecticidal fungus Metarhizium called a microsclerotium (MS). When granular formulations of Metarhizium MS are placed in or on soil they germinate to produced spores that infect and kill soil-dwelling insect pests. In an effort to use these MS granules for control of insect pests of trees, MS granules were formulated with hydromulch. Hydromulch is a combination of wheat straw, water, and an adhesive that is sprayed onto freshly sown grass seed to maintain moisture and promote the germination and growth of the seed. In this study, we mixed MS granules with hydromulch and spayed the formulation onto tree bark or wood samples. The microsclerotia granules were shown to persist on tree bark and to produce infective spores for up to 30 days in a forest. These spores infected and killed the Asian longhorned beetles that came in contact with the MS-hydromulch formulation. These studies have shown that MS granules of Metarhizium formulated with hydromulch produce infective spores that persist for 6-8 weeks on tree bark and have potential for use in treating trees for control of the Asian longhorned beetle.
Technical Abstract: Microsclerotia granules of Metarhizium brunneum Petch strain F52 (Hypocreales: Clavicipitaceae) in hydromulch (water, wheat straw, and tackifier) were sprayed onto bark or wood samples during two spray trials in 2013 and six spray trials in 2014. Microsclerotial granules in hydromulch continued to produce many infective conidia overtime in a forest. Hydromulch wood or bark samples exposed on tree trunks for 4–30 d were then evaluated against adult Asian longhorned beetles, Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambycidae), in laboratory bioassays. Conidial densities reached 5.5 × 10**6 conidia/cm**2 after 20–30 d in the field and at these densities, female beetle median survival times ranged from 15.5 to 21.5 d. Males died significantly slower in all spray trials. Viability of field-produced conidia by microsclerotia in hydromulch was recorded for up to 30 d. Increases in temperature, humidity and rainfall were associated with greater conidial production within hydromulch on wood and bark samples. The continued increase in conidial production by microsclerotia in hydromulch over time suggests that reapplication of a potential product in the field might only need to occur after 6–8 weeks.