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Just-After-Budbreak Herbicide Options for Berries

Volume 6 Issue 4

Tim Miller (twmiller@wsu.edu)

See if this sounds familiar: it’s been raining almost nonstop since December, blueberry and raspberry buds are starting to open, and strawberry is actively putting out leaves. But it’s been too wet to spray residual herbicides. Can anything be done at this time?

Spring/Summer Herbicide Options

Strawberry

First, know that there are very few herbicides that can be applied to established strawberries after they begin their late-winter/early-spring growth. Given the current stage of strawberry plant growth, only Stinger (clopyralid) may safely be applied to kill/suppress broadleaf weeds. A number of years ago, the Washington State Department of Agriculture and Dow AgroSciences issued a special local needs (SLN) label for Stinger use in strawberry (WA-030035). This label allows Stinger to be applied in the spring at a rate of 1/3 pt (5.28 fl.oz) of product per acre. Most growers will band it over the strawberry row, although broadcast applications are allowed. Two things to remember: (1) the product must be applied prior to flowering and (2) there is a pre-harvest interval (PHI) of 30 days. Stinger controls a pretty narrow spectrum of broadleaf weeds, but it does generally control annual weeds pretty well, even at this low rate. Common groundsel (Senecio vulgaris), smooth hawksbeard (Crepis capillaris), vetch (Vicia spp.), and pineapple-weed (Matricaria discoidea) are sensitive to Stinger, while growth of annual sowthistle (Sonchus oleracea), bull thistle (Cirsium vulgare), Canada thistle (C. arvensis), dandelion (Taraxacum officinalis), and white clover (Trifolium repens) will be greatly suppressed.
If you have grass weeds, you have a couple of other options: Select Max (clethodim) and Poast (sethoxydim). These should be applied to actively growing grasses, and should be mixed with surfactant prior to application. Note that while both do a good job on most annual grass species, Poast usually only suppresses the perennial quackgrass (Elymus repens). Select Max has a PHI of 4 days, while Poast has a 30-day PHI.

 

 

Vetch (Vicia spp.)

Common Groundsel (Senecio vulgaris)


 

Quackgrass (Elymus repens)

Canada Thistle (Cirsium vulgare)


 

Annual Sowthistle (Sonchus oleracea)

Pineapple-weed (Matricaria discoidea)

Some products can be used following berry harvest at bed renovation, while some are registered for use in newly-planted strawberry:

2,4-D. Certain formulations may be applied during renovation, check the individual labels for which products are registered for use in strawberry and for the directions for their use. This herbicide may cause some epinastic symptoms on the first leaves regrowing from strawberry plants.
Aim (carfentrazone), Gramoxone (paraquat), as well as acetic acid and other natural herbicides. Apply only between strawberry rows to actively growing weed seedlings; any herbicide that contacts the crowns can damage non-dormant strawberry plants. These products will have little lasting effect on established perennial weeds.
Chateau (flumioxazin) can be used 30 days prior to transplanting or between rows at renovation. This herbicide can cause defoliation of sprayed leaves of both strawberry and weeds.
Devrinol (napropamide) can be applied after planting or during renovation. There must be adequate rainfall shortly after application to prevent photodegradation and to activate the herbicide. This herbicide will not control emerged weeds, so strawberries must be clean-cultivated prior to application. On new plantings, some growers apply a partial rate, and follow with another application in the fall.
Prowl H2O (pendimethalin) can be applied between strawberry rows at renovation. Rainfall incorporation or irrigation is necessary to activate the product. This herbicide will not control emerged weeds, however, so row middles must be clean.
Spartan (sulfentrazone) can be applied pre- or post-transplant and after mowing during renovation in summer.
Simazine can be applied at renovation, although most producers tend to use it in the fall.
Sinbar (terbacil) can be used during bed renovation, or later in the fall after newly-planted strawberries have been established for at least 6 months.
As noted above, grass herbicides include Select Max (clethodim) and Poast (sethoxydim). These only control emerged grasses and must be applied with surfactant.

Raspberry and Blackberry.

Herbicides are generally not applied to caneberries after cane burning due to potential for injury to re-growing primocanes. Caneburning product include Aim (carfentrazone), Zeus Prime (sulfentrazone + carfentrazone), Goal (oxyfluorfen), and/or Gramoxone (paraquat). PHI’s for these products vary from 0 days with Aim to 50 days with Goal.
If timed to occur at the same time as caneburning, residual herbicides could be selective enough to apply at that timing, although reduced rates would be advisable since raspberries aren’t fully dormant. These products include Devrinol (napropamide), diuron, Dual Magnum (s-metolachlor), Matrix (rimsulfuron), Sandea (halosulfuron), simazine, Sinbar (terbacil), Surflan (oryzalin), and Zeus (sulfentrazone). Most of these don’t really display postemergence activity, so if weeds are already up and growing, they won’t kill them. So use these in tank mixture, or as sequential applications, with a caneburning product. Note the PHI for all these spring-applied herbicides on the individual product labels to make sure you won’t have problems with illegal residues (they generally range from 15 to 30 days prior to harvest).
Spot treatment of perennial weed patches using a backpack sprayer is possible, and will pay dividends next year. Glyphosate can be wiped on perennial weed growth using a wick applicator. Take care to not accidentally wipe raspberry leaves, however, as severe injury to those canes can result. Contact herbicides such as Gramoxone (paraquat), acetic acid and other natural herbicides may be applied as spot applications, but will have little lasting effect on established perennial weeds.
Grass herbicides include Select (clethodim) and Poast (sethoxydim). These only control emerged grasses and must be applied with surfactant. Poast usually only suppresses quackgrass. Select Max has a 7-day PHI on caneberries, while Poast has a 45-day PHI.

In addition, the following may be used on new plantings of raspberry or blackberry:
Aim (carfentrazone), Gramoxone (paraquat), as well as acetic acid and other natural herbicides. Apply only between caneberry rows to actively growing weed seedlings; any herbicide that contacts the crowns can damage non-dormant caneberry plants. These products will have little lasting effect on established perennial weeds.
Chateau (flumioxazin) can be used after transplanting but before foliage begins growth. This herbicide can cause defoliation of sprayed leaves of both caneberries and weeds.
Devrinol (napropamide) can be applied after transplanting after soil has firmed. There must be adequate rainfall shortly after application to prevent photodegradation and to activate the herbicide. This herbicide will not control emerged weeds, so caneberries must be clean-cultivated prior to application.
Simazine can be applied at transplanting, but lower rates are used than when the product is used in the fall. Rainfall incorporation or irrigation is necessary to activate the product.
Surflan (oryzalin) can be applied after transplanting after soil has firmed. Rainfall incorporation or irrigation is necessary to activate the product. This herbicide will not control emerged weeds.
Trellis (or Gallery; isoxaben) or Snapshot (isoxaben + trifluralin granules) may be used after transplanting after soil has firmed. Rainfall incorporation or irrigation is necessary to activate these products. These herbicides will not control emerged weeds.

Blueberry

Blueberries often benefit from spring herbicide applications, given the bare soil beneath the bushes.
Glyphosate can be wiped on perennial weed growth using a wick applicator. Take care to not accidentally wipe blueberry branches/leaves, however, as severe injury to those bushes can result.
Contact herbicides such as Gramoxone (paraquat), acetic acid and other natural herbicides may be applied as spot applications, but will have little lasting effect on established perennial weeds.
Matrix (rimsulfuron) and Sandea (halosulfuron) may be applied to emerged weeds in established blueberry during the growing season. These products should be applied as a directed spray to emerged weeds in the row, being careful not to overspray blueberry leaves. Apply to dry foliage and allow 6 hours of contact time for best results. PHIs are 21 days for Matrix and 14 days for Sandea.
Callisto (mesotrione) is also available for use in blueberry, but only for a few more days as it is best used prior to bloom. The label suggests caution when considering applications after bloom, as there is a 60-day PHI for Callisto.
Stinger (clopyralid) can be applied either before or after blueberry flowering, and may be more effective on perennials such as Canada thistle if applications are delayed until thistles are a foot or more tall. Stinger has a 30-day PHI.
Grass herbicides include Select Max (clethodim) and Poast (sethoxydim). These only control emerged grasses and must be applied with surfactant. Poast usually only suppresses quackgrass. The PHI for Select Max in blueberry is 14 days, while Poast has a 30-day PHI.
Several products noted above in newly-planted caneberries may also be used in newly-planted blueberry, including Devrinol, Snapshot, simazine, and Surflan. In addition, Solicam (norflurazon) may be applied immediately after planting blueberry plants.

Finally, you should consult the Pacific Northwest Weed Management Handbook for tips on some of these products. You can find it online at https://pnwhandbooks.org/weed/horticultural/small-fruits.