Written by Paige Beuhler and Ines Hanrahan, Washington Tree Fruit Research Commission, March 2025
For 2025, the WA Tree Fruit Research Commission approved $343,581 to help fund five (5) new Apple Crop Protection projects.
2025 New Apple Crop Protection Project Details
Resistance Management for Codling Moth in Organic Pome Fruit
Organization(s): Washington State University, Rutgers University
Principal Investigator(s): Northfield, T.; Nielsen, A.; Gray, D.
Total Funding Amount for All Years: $255,426
Length: 3 Years
The tolerance for codling moth damage is extremely low, elevating it to the primary pest of concern in apples and pears. In the absence of methods to slow resistance, and/or new organic certified control methods, widespread resistance may make organic management impossible in Washington. Unfortunately, codling moths recently evolved resistance to at least two strains of Cydia pomonella granulosis virus (CpGV). Therefore, bioassays are needed to evaluate how widespread resistance is in Washington State. The research team plans to identify at-risk locations and evaluate codling moth resistance to CpGV and other viruses. Grower cooperators will provide spray records that will be used to characterize management approaches. In sites where virus resistance has developed, records will help identify causes of resistance evolution. The team will evaluate resistance in conventional orchards near the organic orchards with virus resistance to evaluate spillover effects and the potential for conventional tools to mitigate resistance spread. Finally, with growers and crop consultants, they will develop a resistance management plan as well as present and discuss the plan widely across the industry.
Objectives:
1) Evaluate Codling Moth resistance in organic blocks.
2) Evaluate resistance spillover in conventional blocks near organic blocks.
3) Develop and disseminate a resistance management plan to slow the spread of virus resistance.
New Codling Moth Pathogens
Organization(s): Washington State University
Principal Investigator(s): Curtiss, RT.; Northfield, T.; Corral, C.
Total Funding Amount for All Years: $349,000
Length: 3 Years
As much as 20% of the apple acreage in Washington state is in organic production. Despite being the primary focus of pest management efforts for at least a century, codling moths are still the key apple pest in Washington and worldwide. Management of codling moths in organic farms relies on effective mating disruption and sprays of the codling moth granulosis virus. However, virus use is not restricted to organic production; farms growing conventionally produced apples for export to markets with restrictive MRLs often turn to viruses to minimize insecticide residues. There is evidence of resistance to codling moth virus in Washington State, consequently leading the team to discover, isolate, sequence, and identify three new entomopathogenic fungal pathogens from a sample of nine field-collected codling moth larvae. The team previously proved that collecting codling moth in bands is a viable method for isolating new fungal pathogens. The research team plans to continue to explore Washington farms for additional fungal pathogens, and/or more virulent strains of the three recently discovered to understand current infection rates. They will be used to infect new codling moth larvae in the laboratory. Those pathogens will be the subject of laboratory selection to achieve higher levels of virulence than currently observed. The new, selected strains of the entomopathogenic fungi already in culture at TFREC (Tree Fruit Research and Extension Center) will be the strains eventually available as biopesticides. The safety of these entomopathogenic fungi to non-target organisms will need to be tested. Their use will contribute to the viability of organic apple production in Washington state, as well as be useful in conventional production in reducing the impact of pesticide residues.
Objectives:
1) Explore – Locate diseased codling moth larvae and adults from Washington apple orchards throughout the state.
2) Isolate – Establish cultures and sequence prospective pathogens that are isolated from those codling moths.
3) Infect – Test the infection potential of pathogens on healthy codling moth caterpillars in lab assays and in field studies.
4) Select – By repeatedly selecting for infection, pathogenicity and virulence may increase with each generation.
5) Share – Provide outreach and education to describe project findings and find an industry partner to commercialize.
New Materials and Delivery System for Fire Blight Control
Organization(s): Washington State University
Principal Investigator(s): Huang, K.; Zhao, F.
Total Funding Amount for All Years: $199,527
Length: 3 Years
Fire blight, caused by Erwinia amylovora, poses a major threat to apple trees, leading to over $100 million in annual losses in the U.S. Infections often occur during bloom or within three weeks after petal fall, with 5% to 10% of Washington orchards significantly affected between 1993 and 2018. Current fire blight management relies heavily on frequent applications of antibiotics. However, overuse of antibiotics raises serious concerns about the development of antibiotic resistance, potentially rendering treatments ineffective and leaving orchards vulnerable. In this project, the researchers plan to evaluate the antimicrobial efficacy of polyamidoamine (PAMAM) dendrimers and silver nanoparticles (AgNPs) against E. amylovora in vitro and in vivo. They will use the commercially available yeast Aureobasidium pullulans (Blossom Protect®) to encapsulate PAMAM dendrimers and generate AgNPs in situ. Combining A. pullulans with these two antimicrobial agents is expected to enhance adhesion to petals and produce a synergistic effect against E. amylovora, leading to high biocidal efficacy at low doses. Upon successful orchard demonstrations, they plan to establish a grower advisory panel with volunteers from the Apple Crop Protection committee to gather feedback on translating these solutions into practical, real-world applications. The success of this project will provide a more effective and sustainable solution for controlling fire blight while reducing environmental impact.
Objectives:
1) To determine the effectiveness of PAMAM dendrimers and AgNPs in inhibiting E. amylovora in vitro and in vivo.
2) To develop a versatile cell-based microcarrier for encapsulating PAMAM dendrimers and enabling in situ generation of AgNPs, aimed at enhancing stability, delivery, and biocidal efficacy.
3) To assess the biocidal efficacy of encapsulated PAMAM dendrimers and AgNPs in controlling fire blight in greenhouse and field trials and to deliver results to growers.
Net Gains: Balancing Codling Moth and Aphid Control Under Drape Nets
Organization(s): Washington State University, United States Department of Agriculture
Principal Investigator(s): Beers, E.; Schmidt-Jeffris, R.; Marshall, A.
Total Funding Amount for All Years: $120,686
Length: 2 Years
Codling moth is the key pest of apples in Washington State and the programs used to control it drive most of the secondary pest problems. The history of codling moth is in large part the history of resistance to the pesticides used against it. While the majority of these have been conventional insecticides, virtually any insecticide can suffer from resistance development. Conventional growers currently have an array of options with different modes of action, but organic growers rely heavily on mating disruption, petroleum oil, and codling moth granulovirus (CpGV). There is growing evidence for resistance development to this group of products in Washington, which results in higher frequencies of spray applications throughout the season. Drape nets represent an alternative to frequent insecticide applications for codling moth control; damage may drop to near zero without any additional insecticidal inputs. In common with other net types, drape nets also reduce damage from sunburn, birds, and hail, providing multiple economic incentives to offset the cost. While the efficacy of nets for codling moth is well-established, there is some evidence that they also have some non-target effects, notably exclusion of predators and outbreaks of woolly apple aphid. Disruption of biological control under nets is one of the issues that must be addressed for this technique. While codling moth control must take precedence, excessive levels of indirect pests will ultimately reduce tree vigor and productivity and cannot be allowed to go unchecked. The team will use a variety of approaches to improve access to important predators and determine if these approaches also maintain control of codling moth, the target pest. They will monitor the entire arthropod community (codling moth, any secondary pests, and natural enemies occurring in the study blocks) to assess the effects of their tested approaches. The ultimate goal is to identify a program that allows drape netting to be used for codling moth without inducing economically significant damage by other pests.
Objectives:
1) Determine if predator-exclusion effects of nets can be mitigated without loss of codling moth control.
2) Determine if predator releases can mitigate aphid pressure under netting.
3) Determine the level of reduction in spray penetration/efficacy caused by netting.
Patulin Risk Assessment and Improved Detection
Organization(s): Washington State University
Principal Investigator(s): Amiri, A.; Leannec, V.
Total Funding Amount for All Years: $103,288
Length: 3 Years
In a previously WTFRC funded research study (Detect Sources of Patulin Contaminations in Processed Apple Products), the team investigated the different fungal species that contaminate both asymptomatic and symptomatic processed apples. The research identified Penicillium spp. and Alternaria spp. as the primary contaminants, alongside secondary pathogens such as Fusarium, Cladosporium, and Mucor spp. A subsample of isolates from P. expansum, Alternaria, Fusarium, and Mucor spp. was evaluated for patulin production on Gala and Honeycrisp apples. The findings indicated varying levels of patulin production by P. expansum and certain strains of Alternaria after both 2 and 5 months of cold storage. Among the isolated Penicillium species, 13 species were identified in addition to P. expansum, which is recognized as an active producer of patulin. The non-expansum species comprised approximately 25% of the recovered Penicillium population, and their ability to produce patulin remains undetermined. Notably, fungal pathogens were isolated from asymptomatic apples, predominantly from the apple cores. While there is currently no evidence of the presence of other thermo-tolerant species in the region, the high diversity of Penicillium spp., which have exhibited significant resistance to current postharvest fungicides (as determined in Understand and mitigate fungicide resistance in Penicilium app), along with the latent infections in asymptomatic fruit may elevate the risks of patulin contamination in processed apple products in WA.
Objectives:
1) Verify the ability of other “non-expansum” Penicillium species to produce patulin in vitro and on apples.
2) Sample additional asymptomatic fruit to corroborate previous findings.
3) Develop and validate a quantitative molecular detection assay for patulin-producing fungi in asymptomatic apples.
4) Develop and validate a dye-based assay for a visual detection of patulin with the naked eye.
Contact:
Paige Beuhler, Administrative Officer
paigeb@treefruitresearch.com
(509) 665 – 8271 ext. 2
Ines Hanrahan, Executive Director
hanrahan@treefruitresearch.com
(509) 669 – 0267
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