Location: Crop Bioprotection Research2012 Annual Report
1a. Objectives (from AD-416):
1) Demonstrate that microsclerotia of Metarhizium anisopliae (Ma) have the ability to control this soil pest; 2) compare efficacy experimental formulations for beetle control; and 3) acquire information to support submission for larger grant opportunity to develop biological control tactics as part of an integrated control program that reduces dependence on chemical insecticides.
1b. Approach (from AD-416):
Samples of Metarhizium anisopliae (Ma) formulations will be prepared at USDA-ARS-NCAUR and provided to the University of California Desert Research and Extension Center near Holtville, CA, for field application and evaluation. The formulations supplied by NCAUR will include (at least) a granule formulation and a hyphal matt formulation containing microsclerotia of Ma. The field study will be conducted at the University of California, Desert Research and Extension Center near Holtville, CA. Treatments will be applied to field grown cantaloupe plots, replicated four times in a randomized complete block design. Experimental treatments will all contain microsclerotia of Ma. Treatments may be applied three times during the growing season. Treatments will be evaluated based on 1) beetle counts form 20 melons per plot, 2) beetle counts on potato pieces placed in the plots after application, and 3) by evaluations of damage to melons at harvest. Additionally, laboratory Petri dish assays will be conducted to evaluate darkling ground beetle infection and mortality by Ma treatments listed below. Additional laboratory bioassays to determine insect infection will be conducted at the University of California, Desert Research and Extension Center near Holtville, CA. Treatments will be applied to adult Darkling Ground beetles in a completely randomized design with 40 replications. Forty beetles will be placed into individual sterilized glass vials with bait, granule, and Ma matt treatments. Treatments will be incubated in the dark at 25° C in a growth chamber. Insect mortality will be assessed on a daily basis. Spore production will be assayed to determine fungal reproduction on beetle hosts, by randomly selecting 5 beetles (out of 40) within each treatment for which there was spore production. Each beetle will be washed with 5 ml of sterile distilled water with 0.1% Triton X-100. Spore production will be determined by hemacytometers counts of dilute solutions. Spore viability will be detemined by plating on 2.5% Noble agar (Becton Dickinson Sparks, MD). Germination will be assessed at 24 h by microscopic observation for spores with germ tubes longer than half the size of the spores.
3. Progress Report:
The Blapstinus beetle is a serious pest of melon production in the Southwest United States. This non-funded cooperative agreement was established to evaluate the potential for using a natural enemy of the beetle, the insect pathogenic fungus Metarhizium brunneum, as a non-chemical control agent. We have previously developed low-cost methods for producing a stable form of Metarhizium called a microsclerotium. Laboratory bioassays showed that microsclerotia of Metarhizium produced spores that successfully infected and killed the target insect pest, Blapstinus beetles. Granular formulations of Metarhizium microsclerotia were developed in our laboratory for field testing by cooperators at the University of California. Data collections to evaluate crop protection by these treatments are currently underway. In addition to field evaluations, field collected beetles were assayed in our laboratory for susceptibility to granular formulations identical to those used in field treatments. Research progress has been monitored by regular electronic and telephone communications. Results from completed experiments have been reported to the California Melon Board, and to the Pacific Branch of the Entomological Society of America. This research project directly supports our research goals related to the development of the Metarhizium microsclerotia technology as a biological insecticide.