Spring Herbicide Applications

We just finished winter tree fruit meetings during which I talked about some new herbicide registrations.
Spring Herbicide Applications - News


Isoxaben may be very useful to newly planted orchards. Photo: Rob Crassweller

Actually, if you missed the meeting I hope it was because you were out applying your spring herbicides. This winter's mild weather has been ideal for postharvest pre-bud swell herbicide applications. At Rock Springs average soil temperatures have not dipped below freezing the entire winter. For those of you that missed the meeting in your area I thought I would give a brief summary of the material I presented.


Broadworks is a new material labeled for use in stone fruits. It is in WSSA herbicide group 27 and contains the active ingredient mesotrione which is a new mode of action (MOA) for us in tree fruits. If you grow blueberries or raspberries you may have used it on these crops as Callisto where it acts as a pigment inhibitor. It has good pre-emergent and post-emergent activity on many annual broadleves and will suppress Canada thistle, horsenettle and yellow nutsedge if used at higher rates. It is not effective on weedy grasses but will turn weeds like crabgrass and foxtails white.

As a post-emergent application it is most effective on weeds that are 3 inches or smaller in height. It is labeled only for stone fruits that have been established for at least 12 months. A good method of application is to apply in 2 to 3 applications. The first application must be a minimum of 6 oz./A. Second and third applications should be at least 6 weeks after the previous application at 3 oz./A. Do not exceed 3 applications and a total of 12 oz.? in a 12 month period. Use either a non-ionic surfactant (NIS) or crop oil concentrate (COC).

The addition of ammonium sulfate will increase efficacy. The addition of another pre-emergent broad leaf and/or grass herbicide will extend the spectrum of the weeds that will be controlled. If weed seedlings are taller than 3 inches the addition of general burn down post-emergent will be needed. For pre-emergent benefits a minimumof ½ inch of rain or irrigation is needed to move the material into the weed germination zone.

Zeus Prime XC

Zeus Prime XC is a combination of two active ingredients carfentrazone ethyl (commonly known as Aim) and sulfentrazone. Both are in WSSA herbicide group 14. The carfentrazone provides burn down capabilities while the sulfentrazone provides pre-emergent control. Currently it is only labeled for apples with a supplementary label and that have been established at least 3 years in the field. It should not be applied after bud break due to potential damage to young growing tissue. Keep all spray off of growing tissues. Do not rotate with products containing oxyfluofen (Goal), or Chateau which are in the same WSSA herbicide group and could lead to the development of herbicide resistant weed populations.

This product will fit in well with a fall herbicide application with an additional broadleaf and/or grass herbicide. In our trials, the use of Zeus at 6 oz./A plus either Karmex or Alion in a late fall application has given good weed control of a broad spectrum of annual weeds. As with all herbicide applications existing weed cover or trashy vegetation will not be controlled and may reduce the effectiveness of pre-emergent activity.

Pindar GT

Pindar GT is also a combination of two active ingredients oxyfluorfen and penoxsulam; WSSA groups 14 and 2, respectively. Currently it is only labeled on stone fruits in Pennsylvania. Trees must be that are at least 4 years old. The product has a national label for pome fruit but does not yet have a state label for those crops in Pennsylvania. We just established a trial with this product in apples this past November so we do not know about its effectiveness. The addition of the penoxsulem should extend the product's efficacy beyond the general efficacy of oxyfluorfen (Goal products).

To reduce the chance of developing weed biotype resistance do not use this product in a rotation that includes other WSSA group 2 herbicides (Matrix, Solida, Pruvin or Sandea) or WSSA group 14 herbicides (Goal products, Collide, Venue, Aim, Zeus). Pindar has contact, systemic and pre-emergent activity on primarily broadleaf weeds and some grass weeds. It can be applied anytime postharvest but before bud swell in the early spring. Again this would be a good product for use in a fall program of herbicides. In our trial we are looking at 2 and 3 pt./A in combination with oryzalin.


Isoxaben (Gallery, Isoxaben and Trellis) These three products all contain the same active ingredient, isoxaben, and are labeled for all nonbearing tree fruit, nut trees and some small fruit. During the winter meetings I called them the forgotten herbicides because of the restriction to nonbearing orchards. As pictured, they may be very useful to newly planted orchards especially where the soil has been worked or is clean from any plant material after planting and the soil has settled. The first two products are solids and the last is a liquid formulation. Isoxaben controls primarily broadleaf weeds; with the rate used based upon the particular weed species trying to be controlled. It will not control established weeds or grasses.