Selecting herbicides for tree fruit
Herbicide rotation programs avoid weed resistance and improve weed control.
Bernard Zandstra’s herbicide testing program shows the strengths and weaknesses of individual herbicides.
Fruit growers have a choice among several residual herbicides and postemergence herbicides that are registered for application in tree crops, and they should use several each year to manage the vegetation in the tree strip.
Reliance on too few herbicides can lead to weed resistance to herbicides, proliferation of weed species that are not suppressed by the chosen herbicides, or to a build-up of herbicides in the soil that may result in tree injury, says Dr. Bernard Zandstra, the horticultural weed control specialist at Michigan State University.
Zandstra reported that several new herbicides have been labeled for fruit trees in recent years, and others are in the process of registration. With several active herbicides available for residual weed control, he advises growers to know the modes of action of the various herbicides, and then use herbicides with at least two different modes of action when making applications of preemergence materials in fall and spring. Then rotate herbicides with different modes of action every year. Along with the residual herbicides, he recommends using foliar-active herbicides to kill emerged weeds.
Zandstra spoke to apple and cherry growers at the Northwest Michigan Orchard and Vineyard show in January 2012. He outlined some “model” herbicide programs that fruit growers might use over several years.
Weed control in apples
In apple orchards established for three years or more, Zandstra suggested this three-year program for apples (rates are pounds of product per acre of land treated, not per acre of orchard):
Starting in the spring of year one, apply 1 pound of Sinbar (terbacil)or 3 pounds of Karmex (diuron). Then follow-up in June with a quart of glyphosate and 2 ounces of Venue (pyraflufen-ethyl). In the fall, use 5 ounces of Alion (indaziflam) and 1 quart of glyphosate.
In the spring of the second year, apply 4 ounces of Matrix (rimsulfuron), 3 pounds of Karmex, and glyphosate. In June, apply 1 ounce of Treevix (saflufenacil) and 1 ounce of Venue. In the fall, apply 4 pounds of Solicam (norflurazon) and 1.4 gallons of Casoron CS (dichlobenil), and 1 quart of glyphosate.
In year three, start with 4 pounds of Princep (simazine) plus 4 quarts of Surflan (oryzalin) or Prowl H2O (pendimethalin) in the spring. In June, apply 3 pints of Rely 280 (glufosinate-ammonium) and 1 ounce of Venue. In the fall of year 3, apply 8 to 12 ounces of Chateau (flumioxazin), plus glyphosate.
Zandstra recommends using glyphosate once or twice each year, in spring and in fall, to kill emerged weeds. If no weeds are present, the glyphosate might not be needed. Zandstra also reminded the growers that young trees are susceptible to glyphosate injury, and their stems should not be sprayed. He said that the rotation of herbicides and modes of action is important, not the particular chemical order. You can start a herbicide rotation in spring or fall.
Weed control in cherries
For weed control in cherries, Zandstra recommends use of glyphosate only once each year in the fall.
Here’s his “model” three-year program for cherries:
In the spring, apply 4 quarts of Prowl H2O and 4 ounces of Matrix. Then in June, use 2 ounces of Aim (carfentrazone) plus 2 ounces of Venue. That fall, apply 5 ounces of Alion and 1 quart of glyphosate.
In year two, start in the spring with 2 quarts of GoalTender (oxyfluorfen) and 2 quarts of Surflan. In June, use a quart of Gramoxone (paraquat) and 2 ounces of Venue, but remember that Gramoxone has a 28-day preharvest interval. In the fall, use 6 to 12 ounces of Chateau and a quart of glyphosate.
In the third year, start in the spring with 4 quarts of Prowl H2O and 4 ounces of Matrix. In June, use 2 quarts of Gramoxone and 2 ounces of Venue. That fall, apply 5 ounces of Alion and 1 quart of glyphosate.
Zandstra indicated that growers might want to try Alion for long residual control in apples and cherries. Alion, from Bayer CropScience, is a new herbicide registered for pome and stone fruits, and it will be registered for additional fruit crops in the future. Alion has long residual activity, and is active against weeds that have developed resistance to Karmex, Princep (simazine), glyphosate, and other widely used herbicides, he said.
Sandea (halosulfuron-methyl) is now labeled for preemergence and postemergence control of yellow nutsedge in apples. It also controls pigweeds and most composites. The Sandea label will be expanded to include other fruit crops in the coming years.
Treevix is a new herbicide from BASF that is especially effective against horseweed (marestail). It currently is labeled for apples and pears.
Zandstra reminded the growers that Kerb (pronamide) is an old herbicide that is very effective against quackgrass, especially when applied in the fall. He also said that Select Max (clethodim) is the most effective graminicide for postemergence control of annual bluegrass, which is often a problem in fruit orchards in the spring.
Stinger (clopyralid) may be used postemergence in cherries for control of horseweed, common groundsel, dandelion, Canada thistle, goldenrod, and legumes.
There are several other herbicides being developed for tree fruit, including Mission (flazasulfuron) from ISK Biosciences, Trellis (isoxaben) from Dow AgroSciences, Spartan (sulfentrazone) from FMC, and Pindar (penoxsulam plus oxyfluorfen) from Dow AgroSciences. Zandstra encouraged fruit growers to watch for news that these herbicides are labeled for their crops.