Water Means Weeds for California Grape Growers

April showers bring May flowers, and weeds and grasses and other yield robbing pests. The increased moisture in California this spring has been a double-edged sword in many ways: the drought pressure has been reduced, but now many vines are standing in water; water restrictions may not be an issue this year, but fungicide applications are being missed due to runoff concerns; vines are budding lusher leaves, but pest pressure is high.

It is likely that weed pressure will also be heavy due to the wet weather. The full scope of weed pressure will not be evident until later this season, but steps can be taken now to prevent grasses and broadleaf weeds from draining yields from vineyards.

“Getting out in front of weeds during wet seasons makes all of the difference,” said Katherine Walker, Technical Service Representative, BASF. “Start with a clean vineyard so grapes can focus on reaching optimal yield and quality.”

A preemergent herbicide application at the start of the season is key to effective weed control. Prowl® H20 herbicide has a proven track record of protecting against strong persistent broadleaf weeds and grasses, especially those germinating in the spring and summertime. It has been proven effective in controlling foxtails, chickweed, ladysthumb and crabgrasses.

The warm weather of previous seasons kept many weeds at bay. Growers wrestled with a few tough, hardened weeds, but this season quantity may be the challenge.

“Though weed pressure has been low in recent seasons due to dry weather, the seed bank in vineyards can be high.” Walker said. “Weed seeds are hearty and can survive for an extended period.”

The seed bank is the reserve of viable weed seeds present on and in the soil, per the Montana State University Extension. Agricultural soils, including vineyards, can contain thousands of weed seeds per square foot. These seeds will germinate with precipitation with some of the first to emerge being shallow seeded broadleaf and grass weeds. This could mean increased weed pest pressure.

An increase of weed pressure means an increase in need for weed management practices. Now is an excellent time to consult with a PCA about how to manage weeds and prevent the development of herbicide resistance. The University of California Agriculture and Natural Resources has created a guide to help growers avoid creating resistant weeds in their permanent crops.

“Managing weeds responsibly ensures that existing chemistries remain effective for many years,” Walker said. “There are limited tools available to control weeds and we need to protect them for future use.

To learn more about controlling weeds responsibly with Prowl H20 herbicide, visit http://agproducts.basf.us/information/solution-guides/grapes/grape-solutions.html or contact your local BASF representative.