Blueberry growers can use updated, UF/IFAS web-based tool to fight fungus

Instead of spraying every two or three weeks, Florida blueberry growers can use an updated web-based tool to fight anthracnose fruit rot (AFR) with more precision, thanks to work by UF/IFAS experts.

Blueberries grow throughout much of Florida between December and April. When their flowers and fruit are developing, many farmers use a calendar-based method to spray their plants to protect against AFR, said Doug Phillips, UF/IFAS blueberry Extension coordinator.

Under this method, farmers spray fungicide at regular intervals, typically every 14 to 21 days, which over the course of a season can be costly, Phillips said. UF/IFAS researchers do not know yet how much money farmers might save by using the web tool. That depends on farm size, the products used, and other factors, Phillips said.

The weather-based Blueberry Advisory System (BAS), released on Jan. 31, sends growers alerts that tell them when environmental conditions favor the development of AFR, a fungus that can severely damage blueberries.

“This system allows growers to target their fungicide sprays to those periods when the development of infection is more likely,” Phillips said. “In many cases, this system will decrease spray applications in a given season, while achieving a comparable level of disease control.”

Growers can also use the risk assessments to choose whether to use a less-expensive fungicide when they encounter moderate disease risk, or a more expensive product that may be more effective during high-risk periods, Phillips said.

UF/IFAS tested BAS on nine blueberry farms during the 2018 and 2019 seasons, and results were good. BAS notified growers to spray fungicide when AFR was more likely to develop, and in most cases, they didn’t need to apply the sprays as often, Phillips said.

Data for the AFR risk models come from the Florida Automated Weather Network (FAWN), which has weather stations throughout the state.

UF/IFAS experts have rated the risks for AFR development as “low” (less than 15%), “moderate” (15-50%) or “high” (greater than 50%). Growers who sign up for notifications will receive a text message and/or email when the risk is moderate or high, Phillips said.

The new advisory system works similarly to the Strawberry Advisory System, developed several years ago by Clyde Fraisse, a UF/IFAS agricultural and biological engineering professor, and Natalia Peres, a UF/IFAS plant pathology professor. With the Strawberry Advisory System, growers of that crop spray when they get alerts that anthracnose may be developing.

Fraisse developed the website for the Blueberry Advisory System, Phillips said. Peres evaluated the system in the field trials.

Blueberries are most susceptible to AFR in warm, wet weather, with temperatures between 59 and 81 degrees. Combine those conditions with 12-hour periods of leaf wetness, and you get ideal conditions for AFR to develop, Phillips said.

Rainfall or overhead irrigation can compound the problem by spreading the pathogen to healthy fruit and plants, creating additional opportunities for infection.

The pathogen can also be spread by fruits touching each other and from harvesting machinery and sorting equipment.

Thus, growers can help control the disease primarily by timely application of fungicides.

“Good practices can also help reduce the risk of developing anthracnose fruit rot,” Phillips said. “They include periodic pruning to open the plant canopy, harvesting frequently to avoid overripe berries, and rapid cooling of fruit following harvest.”

For more information, contact Phillips at dal64372@ufl.edu.

Source: University of Florida (Brad Buck)


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