Biopesticides have garnered a lot of attention recently as farmers turn to alternatives to chemical applications for keeping pests and diseases from damaging their crops. McKenzie Schessl and Samantha Willden, both representing Cornell AgriTech, recently presented “Biopesticides & Controlled Environment Agriculture for Berries” as a webinar.
Willden’s research indicates that raising strawberries in a controlled environment such as a tunnel reduces fruit damage. She compared Dubois Agrinovation plastic film and Warp’s plastic sheeting and found 11% less damage under Warp.
“Mycotrol® performed best under UV-blocking films,” Willden said of the mycoinsecticide (a microbial insecticide derived from fungi). “However, the tradeoffs of using Warp’s UV-blocking film include the plastic is not cut to the correct width. We had to add these holes manually, which is a major labor issue. We really need a new plastic option.”
The UV-blocking plastics are thick and more challenging to manage as well.
Pricewise, the Dubois standard is $0.29/sq. ft. and $0.15 for UV-blocking.
“It could be cheaper if we could get manufacturers to create plastic for low tunnels,” Willden added.
Despite growing in an enclosure, high tunnel strawberries still require pest management.
Willden’s latest experiment involved a June-bearing variety planted in October to focus on overwintering management to see “if the plants required management to avoid spring outbreaks,” she said. Aphids and spider mites are common overwintering pests on high tunnel strawberries.
Willden studied OMRI-approved biopesticide sprays for aphids: Neemix®, PyGanic® and Sil-MATRIX®. “All worked well,” she said.
Neemix and Sil-MATRIX both offered a 94% reduction in aphids. PyGanic provided 96% reduction.
Using predators such as lacewings can also make a difference and even offered the best management compared with other biocontrol agents.
“After three weeks, you’d probably have to reapply again,” Willdren said. “I highly recommend lacewings. You can buy them as eggs or larvae. They were really effective.”
She wants to further study biopesticides. “I’m looking for grower/collaborators,” she said. “If you have pests that are problematic on your controlled environment crops, I’d be happy to support you and answer your questions.”
In light of increased consumer and market interest for fruit produced without multi-site fungicides, McKenzie Schessl, Ph.D. student at Cornell, studied biopesticides in a field trial last year. She explained that worker and environmental safety, along with off-target effects, are the reasons many consumers want to look at biopesticides.
The study was conducted at Cornell AgriTech in Geneva, NY, in double-row, low tunnel-style plantings 12 inches apart. The variety was ‘Albion,’ an everbearing, day neutral strawberry. Researchers planted four replicate plots of 30 plants and conducted three assessments.
From 2021 to 2023, Schessl studied a few diseases of interest, including common leaf spot (Mycosphaerella fragariae). It presents with purple spots with tan/gray centers as the disease matures. It overwinters as mycelium, sclerotia and perithecia and spreads via ascospores, conidia and rain splash.
Gray mold (Botrytis cinerea) is another disease of interest. It causes gray sporulation on fruit and rotting of fruit flesh. The necrotrophic fungi can overwinter as mycelia or sclerotia and spread on wind and rain.
Anthracnose (Colletotrichum acutatum) presents with brown-black spots. A hemibiotrophic fungus, it can feed on both living tissue and dead and decaying tissue within the environment. It feeds on the fruit, runners, petals or crown of the plant.
Schessl studied covered vs. uncovered plots. She timed applications on a weekly schedule vs. using a disease forecasting model of when infection risk was greater than 40%. The Network for Environment & Weather Applications (NEWA) provided forecasting information.
Reducing disease load can help U-pick farms and wholesale growers increase their profits. Photo by Deborah J. Sergeant
Schessl looked at integrated biopesticide vs. conventional Captan® application if the infection risk was moderate. If the infection risk was high, she used a single site fungicide.
In 2021, the rainy, late season caused researchers to apply only nine times for calendar application and six times on the NEWA plot. In 2022, the calendar plot received 10 applications during a moderately rainy season and NEWA plots received five applications. A dry, cool, late season in 2023 meant eight applications, and only three for the NEWA plots.
“Captan was often less effective than biopesticides,” Schessl said.
The research also revealed that tunnels reduced incidence of disease in that cool season and that incidence with the NEWA model was similar to calendar timing, but with fewer applications.
“Covered production is effective at reducing disease,” Schessl said. “If there were rainy or erratic weather seasons, the tunnels can be less effective. It could be because of increased humidity or it could be increased disease pressure that year.”
She added that for wet years, models may call for more applications than in drier years and fewer applications than calendar-driven applications. She thinks that biopesticides are effective when timed appropriately, using models and alternated with single-site fungicides.
In her most recent study on biopesticides, Schessl and her team inoculated strawberry plants at 100% humidity, creating an ideal situation for pathogens so they could see what product came out as effective. The preliminary results showed that the flower infected with Botrytis showed 87% proliferation in the untreated control compared with 23% in those treated with OSO®.
For flowers infected with anthracnose, a fungus, 24% in the untreated control were affected and the treatments tested showed infection at 9% (Blossom Protect™), 10% (Stargus®) and 12% (Sil-MATRIX).
As for infected fruit, those infected with Botrytis showed 90% spread in the untreated control compared with 64% in those treated with Regalia® and 69% with EcoSwing®. The plants infected with anthracnose were 94% affected in the untreated control; the treatments tested showed infection at 65% (LifeGard®) and 82% (Regalia).
“This is where we’d like to tease out what is happening here,” Schessl said. “Sixty-five percent is still very high. We’d like to repeat this study and see if it’s conditions.”
Her group also conducted a post-harvest study with the same biopesticides used in the greenhouse trial. Fifty-seven percent of the harvested strawberries infected with Botrytis were infected in the control group compared with 15% treated with Regalia, 7% with LifeGard and 2% with OSO.
Schessl hopes to repeat the biopesticide trial and also study UV controls of Botrytis and anthracnose, as well as study harvested fruit.
