Spring herbicide options for Michigan blueberries

Eric Hanson<hansone@msu.edu>, and Bernie Zandstra, Michigan State University Extension, Department of Horticulture - April 03, 2017

Spring is an important time to apply pre-emergent herbicides in blueberries. Here are suggestions on how to choose herbicides and effective combinations.

April is an important time to apply pre-emergent herbicides. Weeds are beginning to emerge and most pre-emergent materials should be applied either before weed emergence or when weeds are just small. In most southern Michigan locations, mid-April is a good time.

There are quite a few materials to choose from. Choose herbicides based on the age of the plants (young plants are less tolerant than older plants), weeds present and soil type. Some pre-emergent herbicides are stronger on grasses or broadleaf weeds, so use combinations that control a broad range of weeds. Also, consider using herbicides with different modes of action (see table below) so that there is less chance weeds will develop resistance to a particular mode of action.

Michigan State University Extension suggests the following spring treatments based on plant age. Rates are in pounds active ingredient (a.i.) per acre.

First-year plantings

For new plants, choose herbicides based on efficacy on weeds and crop safety. The following combinations provide good grass control (Surflan, Prowl, Devrinol, Dual Magnum) and broadleaf suppression (Trellis). These materials need to be applied before weeds emerge. They do not affect emerged weeds. They may need to be followed later in the season with post-emergent grass killers such as Fusilade, Poast or SelectMax.

Surflan (2-4 pounds) + Trellis (0.5-1.0 pound)
Prowl +Trellis (0.5-1.0 pound)
Devrinol (4 pounds) + Trellis (0.5-1.0 pound)
Dual Magnum (0.6-1.3 pounds) + Trellis (0.5-1.0 pound) *If nutsedge is present

Second-year plantings

In addition to the first year options, consider the following programs. Matrix, Solicam and Princep are stronger materials and should be used at their lower labelled rates here. Callisto, Casoron, Dual, Sandea and Sinbar are also labeled for second year plants.

Solicam (2 pounds) + Trellis (0.6-1.0 pound)
Solicam (2 pounds) + Princep (2 pounds)
Matrix (0.063 pound)

Plantings older than two years

There are many combinations that can be used on established blueberries. Consider combinations of products that differ in mode of action and the types of weeds they control.

Chateau (0.19-0.38 pound)
Chateau (0.19-0.38 pound) + Rely (0.9-1.5 pounds) *If marestail is a problem
Solicam (2-4 pounds) + Princep (2 pounds) or Karmex (1.8-3.6 pounds)
Matrix (0.063 pound) + Sinbar (1 pound) or Princep (2 pounds) or Karmex (1.8-3.6 pounds)
Zeus (0.25-0.38 pound) + Rely (0.9-1.5 pounds)
Sandea (0.023 - 0.047 pound) + Solicam (2 pounds) or Sinbar (1 pounds)
Velpar (1-2 pounds) + Solicam (2 pounds) or Surflan (2-4 pounds) *If brambles are present

Application timing

Application times specified on labels are summarized in the chart below. Some labels are very specific; others are not. Velpar and Casoron need to be applied earliest (by early April). Herbicides that do not control emerged weeds need to be applied before weed seeds germinate (Devrinol, Prowl, Surflan, Trellis). Others have some post-emergent activity and can be applied after some weeds begin to emerge (Chateau, Diuron, Matrix, Princep, Sandea, Sinbar).

Herbicide application timing for Michigan blueberries

Application times specified on herbicide labels.

Resistance management

Herbicides kill weeds by disrupting specific processes, and they are classified based on these modes of action. Repeated use of herbicides with the same mode of action will become less effective because tolerant weed species will become established and populations of some species may develop resistance. Blueberry herbicides are grouped below by mode of action. Alternate or combine herbicides with different modes of action.

Modes of action of blueberry herbicides
Herbicide	Mode of action
Karmex, Princep, Sinbar, Velpar	Inhibit photosystem II
Casoron, Trellis	Inhibit cellulose synthesis
Sandea, Matrix	ALS inhibitor
Solicam	Disrupt carotenoid synthesis
Stinger	Synthetic Auxin growth regulator
Surflan, Prowl	Inhibit microtubules (cell division)
Devrinol, Dual Magnum, Kerb	Inhibit VLCFAs (cell division)
Callisto	HPPD inhibitor (pigments)
Aim, Chateau, Zeus	PPO inhibitor (disrupts membranes)
Poast, SelectMax	Lipid synthesis inhibitors
Gramoxone	Photosystem I electron diverters

Drs. Hanson and Zandstra's work is funded in part by MSU's AgBioResearch.

This article was published by Michigan State University Extension. For more information, visit https://extension.msu.edu. To have a digest of information delivered straight to your email inbox, visit https://extension.msu.edu/newsletters. To contact an expert in your area, visit https://extension.msu.edu/experts, or call 888-MSUE4MI (888-678-3464).