Demonstration of a sustainable method of Beauveria bassiana delivery for use against plum curculio

View the project final report

Commodities

• Agronomic: rice
• Fruits: apples, cherries, general tree fruits

Practices

• Education and Training: demonstration, display, on-farm/ranch research
• Pest Management: biological control, integrated pest management, weather monitoring
• Production Systems: organic agriculture

A comparison of entomopathogens for control of plum curculio indicated that the nematode Steinernema riobrave was most effective entomopathogen, but was only effective in sandy soils. Beauveria bassiana may be effective against plum curculio larvae in soils with less sand content, but efficacy remains variable year-to-year and may require micro-sprinkler irrigation.

Introduction:

Plum curculio is a key pest in Midwest tree fruit production. It is a small weevil that lays eggs in young fruit. The larvae develop inside the fruit, causing internal feeding damage, which leads to misshapen, rotten fruit. In conventional cherries, there is zero tolerance for larvae in fruit at harvest, leading to lost crops and a reduction in economic sustainability for farmers.

With conventional pesticides being phased out by the Food Quality Protection Act, newer chemistries, such as the neonicotinoids, insect growth regulators (IGR), pheromones, and sterol inhibitors are being explored as alternatives. These have shown some success in controlling plum curculio, but their use as an OP “replacement” is raising concern among growers with increased residue on finished products and questionable efficacy. The persistence of neonicotinoid and IGR residues provides low-level, long-term exposure that will likely raise potential for resistance development. In addition, these residues impact natural enemy diversity and abundance, reducing benefits from ecosystem services, a key concept in agricultural sustainability.

Biopesticides present reduced risk tactics for both conventional and organic producers. When implemented in conjunction with cultural controls targeting adult pests, the result is a sustainable pest management plan targeting multiple pest life stages.

Increasing interest in biopesticides in both the scientific and grower community is not extending into significantly higher adoption of biopesticides. Challenges including lower efficacy and environmental breakdown make utilization complex. Transitioning to biopesticides requires knowledge of biology, pest density, appropriate environmental conditions and precision in both application timing and rate. Successful completion of our outcomes would help familiarize farmers with these relationships through demonstration.

Of the biopesticides, entomopathogenic fungi (Beauveria and Metarhizium species) and entomopathogenic nematodes (Steinernema and Heterorhabditis species) are recognized for their ease of mass production for augmentative biocontrol. Once established, these fungi can propagate or hibernate, indicating the potential for a multi year impact.

Laboratory tests of both Beauveria and Metarhizium result in high plum curculio larval mortality (Tedders et al. 1982, Alston et al 2005). Infection in overwintered beetles (McGiffen and Meyer 1986, Lafleur et al. 1987) suggests that two windows of opportunity for soil biocontrol of plum curculio exist; summer generation soil life stages and adults in soil habitats surrounding orchards. A modification in formulation and application of hyphomycetes resulting in a granular product drilled into the soil has resulted in better and perhaps less expensive control of soil dwelling life stages of several insect pests (Keller 1992, Nankinga and Moore 2000, Cisneros 2000, Lewis et al. 2002, Dolci et al. 2006, Nelson et al. 2004). The unique method of entomopathogenic fungus delivery for control of the soil-dwelling life stages of weevils offers the opportunity to suppress a pest at a previously untargeted life stage, a major goal of higher level IPM programs throughout the world (Prokopy 1994).

Recently, a SARE grower demonstration trial approached pecan weevil problems with trunk Beauveria spray applications and Metarhizium formulated on fabric trunk bands. Similar adhesive bands impregnated with Beauveria are commercially registered in Japan for control of adult Asian Longhorned beetle on fruit tree trunks (Dubois, 2004). However, the cost of these fabric strips may be prohibitive and the method does not address the susceptible, previously untargeted life stages of weevils within the soil matrix.

Several years of SARE research in Maine found that foliar Beauveria applications for Colorado Potato Beetle (CPB) led to no increase in yield and cited high costs as a prohibitive factor for adoption into integrated potato management. Foliar (Wraight 2002, Poprawski 1997) and soil (Cantwell 1986, Gaugler 1989, Watt & LeBrun 1984) applications of Beauveria have been investigated with deviating, inconsistent results of population suppression.

Short-term outcomes primarily focus on developing the awareness of economic and ecological potential of entomopathogens in the organic tree fruit producing community for suppressing plum curculio populations.

Dissemination of our project results to current members of the entomopathogen industry will encourage investment in organic formulations for orchard use, resulting in ability of a core group of organic growers who have large enough farms to afford any associated risk to adopt the products. The initial adoption by a core group of organic tree fruit growers would lead to the intermediate outcome of broad adoption among all organic tree fruit growers. This would also spill over into minor adoption by conventional growers who are sustainable minded or have major problems controlling plum curculio with the cancellation of the organophosphate Guthion® (azinphosmethyl).