Sep 8, 2011

Control weeds this fall to improve fruit crop fields next spring

Fall is a good time to apply residual and systemic herbicides for control of difficult and persistent weeds in perennial crops. Many of the residual herbicides labeled for tree fruit and small fruit are recommended for fall application. Fall application may improve control of difficult perennials, biennials and winter annuals. In addition, fall-germinating annuals, such as horseweed, are vulnerable in the fall. Yellow rocket and dandelion are also controlled more easily in the fall. An application of glyphosate plus a residual herbicide can give two to three months of very good control in the spring.

For optimum quackgrass control, apply Kerb (pronamide) in the fall just before soil freezes. Kerb will suppress quackgrass for about two to three months in the spring. Addition of glyphosate will kill the fall flush of horseweeds, mustards, wild carrots and dandelions. Kerb should be tank-mixed with a PSII inhibitor in the fall, or followed by another residual herbicide in the spring. This will provide good broad-spectrum weed control into July of the following year.

Princep (simazine), Solicam (norflurazon), Casoron (dichlobenil), Sinbar (terbacil) and Chateau (flumioxazin) labels allow for spring or fall application. The Alion (indaziflam) label does not mention time of application. All of these herbicides have long residual activity if applied in the fall. They should be rotated to avoid use of the same mode of action more than once a year, and some combination of pre- and post-emergence herbicides will give the most effective weed control program.

An effective weed control program might include Chateau (PPO inhibitor) plus glyphosate in the fall, followed by a PSII inhibitor (Karmex, Pincep, Sinbar) or Matrix (ALS inhibitor) in the spring. In crops where there is minimal danger of crop injury from glyphosate (i.e., mature apple trees), an application of a foliar-active herbicide during the season will help control most annual and perennial weeds. In crops where glyphosate can cause crop injury (i.e., blueberries), growers may consider the use of Rely (glufosinate), Gramoxone (paraquat), Aim (carfentrazone) or Venue (pyraflufen-ethyl) for application during the growing season.

The Alion label for pome fruit, stone fruit and tree nuts was approved in 2011. Product should be available for the 2012 growing season. Alion gives good control for two to three months of most annuals and some perennials. It tends to be weak on horseweed and common ragweed. Growers who are looking for a different mode of action may try Alion.

There are several other herbicides that are close to registration for fruit crops. Katana (flazasulfuron) is a very active ALS inhibitor (similar to Matrix and Sandea). It provides very good control of most weeds, except field bindweed. Treevix (saflufenacil) should be registered soon for post-emergence control of horseweed and other broadleaves in tree crops. Treevix following Chateau or Alion is a good choice in fields with heavy horseweed populations.

Always read and follow label instructions for all herbicide applications. Current recommendations will be included in the MSU Extension bulletin, 2012 Fruit Management Guide, available late fall at MSU Extension’s bookstore.

By Bernard Zandstra, Michigan State University Extension