With California’s regulatory vise growing ever tighter on the use of pesticides, the state’s strawberry industry has sought ways to use them only “as a last resort,” as grower Peter Navarro explains.
“We’re always looking to develop ways not to apply pesticides,” such as the use of natural predators, said Navarro, a second-generation Watsonville grower who serves on the California Strawberry Commission.
Recently the industry has received help from computer science students at the University of California, Davis, who worked with agricultural entomologist Christian Nansen to develop a smart phone application to enable strawberry growers to predict spray coverage to control pests.
Many variables affect this coverage, Nansen explains in a university news release. They include weather conditions, tractor speed, spray nozzles, spray volume, boom height and adjuvants, he says.
In a three-year project, Nansen and computer science students Krishna Chennapragada, Gabriel Del Villar and Alexander Recalde developed Smart Spray, designed for both iOS and Android phones to help growers optimize spray applications in their strawberry fields. Chennapragada and Del Villar are now graduates.
The app allows a user to predict coverage under different scenarios, including weather data such as temperature, relative humidity and wind, according to the developers. To measure humidity, the user places a water-sensitive card in the field before spraying, photographs it and uploads it into the app.
“I think Smart Spray is a very helpful tool for growers and advisers as a guide to select spray tips, spray volumes, tractor speed, and other important factors to maximize sprayer coverage,” said Eric Flora, global field development manager of Paso Robles-based Crop Enhancement, Inc. “Using spray cards is the best and simplest way to know if you are penetrating everywhere in the canopy your past target is a problem. Placing cards where the specific pests attack the host gives the best information.”
The app’s development comes as organic acreage in California has steadily grown in the last 20 years, rising to an anticipated 4,170 acres in 2019, although organic yields tend to lag behind those of conventional farms. But UC scientists have pointed out that organic growers still encounter such challenges as nutrient deficiency, for which they are unable to use the controlled-release fertilizers that conventional growers use.
Overall acreage has trended downward, with 25,704 acres statewide projected for 2019, down from 31,640 acres bearing strawberries in 2015, according to the strawberry commission.
As methyl bromide was phased out in 2016 and other fumigants face scrutiny, the commission has funded numerous research projects in recent years, studying alternatives such as using natural sources of carbon to eliminate soil pathogens and sterilizing soil with steam. Other concepts under consideration have included using raised bed troughs and “soilless” fields to avoid soilborne pests and diseases, according to the commission.
In 2017, a team of scientists based at UC-Santa Cruz received a $2.5 million USDA grant to further research biological soil disinfestation, crop rotation and other natural methods for fumigating soil, according to a strawberry commission news release.
“I think the strawberry industry has tried to be innovative in that we stay a step ahead,” Navarro told Western Farm Press. He points to the use of such tools as a bug vacuum to combat lygus bugs, which damage berries.
The Smart Spray project was funded by state, federal and industry grants, including from the California Strawberry Commission and the USDA Agricultural Research Service’s Floriculture and Nursery Research Initiative, according to UC-Davis.
NEARLY 3,000 SPRAYS
The data the app provides is based on nearly 3,000 experimental sprays over three years with different spray rigs, different sizes of crops, different spacing of plants, and under different weather conditions, Nansen explained.
California grows about 88 percent of the nation’s strawberries along California’s coastline from the Watsonville area from San Diego. Strawberries are a year-round fruit in the Golden State, with harvests following the sun.
For more information on the Smart Spray app, access the manual at https://bit.ly/2q3lsL3 or contact Nansen at email@example.com or 530-752-2728.