In mid-November, nearly 80 field day participants gathered at JSM Organics in Royal Oaks, CA to discuss management of strawberry fields and their arthropod pests and diseases. JSM’s owner, Javier Zamora, welcomed everyone to his farm and the table to share valuable research, practices, conversation and food. This bilingual event offered presentations, Q&A sessions, an interlude where we helped spread cover crop seeds, and a delicious lunch provided by JSM Organics.

Using Non-crop Vegetation to Manage Lygus Bugs in Strawberry - Diego Nieto (Driscoll’s) presented research demonstrating ways growers can reduce pest lygus bug colonization with the use of alfalfa trap crop strips while supporting habitat for beneficial species. In the spring, he marked insects migrating from weeds. Recaptured lygus bug adults were mainly collected in the alfalfa, whereas lygus bug nymphs were found in the strawberries. Three of every four recaptured predatory insects were in strawberries, rather than alfalfa, resulting in a predator-to-lygus ratio of 5:1 in the crop. Hence, the alfalfa strips reduced adult lygus bug migration into the strawberries. Vacuuming the alfalfa in the spring can reduce adult lygus populations. Diego shared complementary research about how native plant hedgerows supports more natural enemies and fewer lygus bugs than weeds, and how proximity to woodland habitat increased the abundance of natural enemies, resulting in an increase in predation of lygus bug nymphs. By incorporating alfalfa strips and native habitat, and using some strategic timing, growers can set the parameters they need to create an ecologically stable system that helps reduce pest pressure and lygus bug colonization in and around strawberry fields.

Plant Species that Optimize Arthropod Pest Biocontrol - Stephen Pryor (WFA) discussed that when fields are surrounded by perennial edge habitat, such as hedgerows, growers may get “free” pest control from generalist predatory arthropods, such as 6-spotted thrips, minute pirate bugs, big-eyed bugs and predatory mites. These predators move into fields as the weather warms and pest populations such as mites, thrips, aphids and lygus bugs start to increase. Beneficial arthropod dispersal, movement and reproduction is further supported when pollen and nectar sources such as sweet alyssum are interplanted within the field. The presence of in-field floral resources is especially important to support a wide variety of parasitoid wasps. In addition to alfalfa mentioned above, annual fleabane can serve as a lygus bug trap crop option. It is highly attractive to lygus bugs and when blooming its flowers attract the parasitoid wasp, Peristinus relictus, which specializes in parasitizing lygus bug nymphs. The key to successful biocontrol is to have blooming species on the farm before pest populations start to build up. Finally, Stephen discussed how grassy row ends and field edges can act as “banker plants” for aphid pest control. Cereal aphid populations, which are not pests of strawberries, can build up in grass species and serve as alternative hosts for parasitoid wasps before pest aphids arrive in the main crop. Once pest aphids are in the strawberries, the banker grass can be mowed to encourage the parasitoids to move into the crop.

Production-Related Research Results - Bill Turecheck (CA Strawberry Commission, CSC) shared the origins of the Commission, and how they facilitate all aspects of strawberry production, advocate for growers through public policy and support research. The CSC has been tracking organic strawberry growers since 2001, when only 1% of strawberries produced in CA were organic. Today there are about 5,300 acres of organic strawberries, which represents about 12% of total production. Bill highlighted the CSC-funded research programs: production research through the Cal Poly Strawberry Center, and CSC’s own grant program which funds research that benefits the strawberry industry, as well as the environment through water quality and nutrient management projects.

Strawberry Soilborne Diseases - Peter Henry (US Department of Agriculture) talked about the different strategies for reducing soil-borne pathogens in strawberries. Rotating with cereals should be a first line of defense. It disrupts the lifecycle of strawberry diseases. If Fusarium and Verticillium wilt are already present, they can be controlled by rotating broccoli and other brassicas with strawberries to simulate beneficial bacteria to attack the pathogens. Verticillium wilt and Macrophomina (not Fusarium wilt) can be managed quite well by anaerobic soil disinfestation (ASD). In the example he gave, rice bran and a wheat cover crop were used as a carbon source. Once incorporated, the field was Growers can use Cal Poly’s free diagnostics screening to help them catch diseases early and use appropriate treatment strategies depending on what they find. 

Disease Resistant Strawberry Varieties- Cindy Lopez (UC Davis) shared how all strawberry fields can be affected by diseases, and that disease susceptible cultivars are still being grown on 50% of the acres in CA. She described five versatile, high-yielding, long shelf-life, Fusarium wilt resistant cultivars that UC Davis developed and released for growers. Cindy’s lab is looking forward to trialing new resistant cultivars next year at JSM Organics.

Using Biodegradable Mulch in Strawberry Fields - Jazmine Mejia-Muñoz (California Marine Sanctuary Foundation, CMSF), shared how plasticulture (covering rows and fields with plastic, and using plastic drip tape) has been an effective practice for strawberry farming because it can produce greater yields, improve chemical application efficiency, and increases water savings. However, the practice is not sustainable, as a significant amount of farming plastics are polluting waterways and the ocean. CMSF is working to find sustainable alternatives. Jazmine discussed a current project where they are testing a strawberry plastic cover that is 90 percent biodegradable. She also discussed working with plastic manufacturers to optimize plastic breakdown. She highlighted collection programs that are available to process separated plastics. JSM Organics uses biodegradable plastics that get disced after the season, and it breaks down within 2-3 years. Additionally, they found that when they rotated strawberries with Brussels sprouts, plastic decomposition happened much quicker.

Avian Pest Control - Jo Ann Baumgartner (WFA) discussed the importance of supporting songbirds for pest control, especially during breeding season when they are feeding their young. Some songbirds, such as Bluebirds and Chickadees catch insects every 5 minutes, feeding their young more than 150 times a day for about 3 weeks. Installing songbird nest boxes on a farm is an easy way to support eight different cavity nesting species, with just one box size, that can provide pest control. Combined with nest boxes, habitat on field edges and throughout the farm will result in many beneficial birds. UC Davis researchers found that farms with semi-natural habitat tends to support more insectivorous birds, including 15 species that eat lygus bugs and other insects that eat plants. They predict that if semi-natural habitat were removed, strawberry costs (crop damage and food safety risk) would increase by 76%, and if semi-natural habitat was added, costs would decrease by 23%.