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Microsclerotia of Metharhizium brunneum F52 applied in hydromulch for control of Asian longhorned beetles (Coleoptera: Cerambycidae)

Goble, Tarryn A., Hajek, Ann E., Jackson, Mark A., Gardescu, Sana
Journal of economic entomology 2015 v.108 no.2 pp. 433-443
Acer pensylvanicum, Anoplophora glabripennis, Metarhizium brunneum, Plantago, adults, bark, bolts, conidia, death, entomopathogenic fungi, fecundity, females, forests, granules, humidity, insect control, insect pests, orchards, oviposition, progeny, sclerotia, straw mulches, water activity, wheat straw
The entomopathogenic fungus Metarhizium brunneum (Petch), strain F52 (Hypocreales: Clavicipitaceae) is able to produce environmentally persistent microsclerotia. Incorporating these desiccation-tolerant M. brunneum F52 microsclerotia (Mb MS) granules into hydromulch [a mixture of water + wheat straw mulch + psyllium tackifier], may represent a novel, easy-to-use and environmentally-friendly mycoinsecticide that can be sprayed onto the trunks of forest or orchard trees to control insect pests. The premise is that hydromulch holds moisture that provides more time for Mb MS to germinate and produce conidia. We tested this formulation against Asian longhorned beetle adults, Anoplophora glabripennis Motschulsky (Coleoptera: Cerambycidae). To test how quickly beetles could be killed, moist and dry bark pieces or filter paper were sprayed with a low dose (~9 Mb MS/cm(2)) of Mb MS-containing hydromulch. Median survival times of beetles exposed to moist bark and filter paper were 17.5 d and 19.5 d, respectively. Beetles exposed to dry bark, which had a lower measured water activity compared to the aforementioned substrates, died significantly slower but median survival time was significantly different from the untreated control. In an attempt to kill beetles faster, moist bark pieces were sprayed with one of three doses of Mb MS-containing hydromulch: low (6-9 Mb MS/cm2); medium (10-19 Mb MS/cm2) and high (20-30 Mb MS/cm2). At high doses, 50% of beetles died in 12.5 d but at lower doses time to death was significantly longer (16.5 d-17.5 d). Mb MS-containing hydromulch sprayed onto striped maple bolts could reduce the overall fecundity of beetles compared with controls. In a two week oviposition period, total beetle fecundity was highest in high-humidity controls in which females produced 18.3 viable offspring compared to 3.9 viable offspring for beetles exposed to Mb MS-containing hydromulch at high humidity. Fecundity in the high-humidity hydromulch treatment however, was not significantly different from the low-humidity Mb MS-containing hydromulch treatment (6.6 viable offspring) or its associated control (8.8 viable offspring). This paper represents the first evaluation of the arboreal application of Mb MS formulated within hydromulch.