Choosing fall weed management options for strawberries
Fall is a crucial time for post-emergence control of several strawberry weeds. Know how to identify weed species so you can choose the most effective herbicide for your field.
Weeds can be a difficult and season-long problem in years with too much or too little rainfall. Delayed herbicide application in the spring because of wet soils often results in establishment of weeds that are difficult to control during the rest of the season. Fall is an important time for post-emergence control of several strawberry weeds. Late fall is a good time to apply residual herbicides for preemergence control the next spring. Fall application avoids the potential of strawberries greening up before mulch can be removed (because of wet soil) and spring herbicides applied. Most herbicide labels for strawberries require spring or fall application to dormant plants, and application on new growth can stunt or injure the plants.
Row middle management
Weeds emerging in row middles can be managed by cultivation or application of pre- and post-emergence herbicides. Gramoxone Inteon (paraquat) or Aim (carfentrazone) can be used as directed, shielded sprays to burn down weeds in the row middles in the fall. Gramoxone is more effective on larger weeds and grasses than Aim.
Post-emergence grass herbicides such as Poast (sethoxydim) or Select Max (clethodim) are effective against actively growing grasses. Most grasses are past this stage in September, but late applications may be effective against grasses germinating after frost. Roundup (glyphosate) can also be applied to row middles as a directed, shielded spray. Roundup is very damaging to strawberries and should be applied only with a shielded sprayer to control perennials or other hard-to-kill weeds.
Chateau (flumioxazin) is a preemergence herbicide that can be applied to row middles in the fall or spring. Chateau can injure strawberry plants, so only apply as a directed band in row middles. A fall application of Chateau should control weeds for about eight weeks the next season.
Choices of post-emergence herbicides for use in fall are limited. One option for early fall application is Stinger (clopyralid), which controls most weeds in the composite, legume and nightshade families. These include troublesome strawberry weeds such as thistles, clovers, dandelions, common groundsels, oxeye daisies, mayweeds and curly docks. Stinger is effective if applied directly to weeds in the fall when they are still green before a killing frost.
Sinbar (terbacil), Devrinol (napropamide), Ultra Blazer (acifluorfen), Prowl H2O (pendimethalin) and Spartan (sulfentrazone) can be very effective the following year when applied after plants have become dormant in late November or December. Strawberries are more tolerant of these herbicides after they are dormant. An excellent timing is just before mulch is applied. Each product controls a different spectrum of weeds; make choices based on the weeds present.
Generally, Devrinol is active against annual grasses. It has a short residual life of four to six weeks. Sinbar controls most annual grasses and broadleaf weeds. It has fair to good control of quackgrass. It is weak on common groundsel and most pigweeds. Spartan controls several troublesome weeds, including common groundsel, field pansy, mayweed or dog fennel, pineapple-weed or chamomile, several pigweeds, white campion and yellow woodsorrel. It has some yellow nutsedge activity. Prowl H2O may be applied anytime strawberries are dormant. In the fall, apply Prowl just before mulching. It gives good control of most annual grasses and annual broadleaves for about eight weeks the next spring. Prowl does not control yellow rocket or other winter annual mustards. It is weak on most composites.
An effective strawberry weed control program includes fall dormant and early spring applications of residual herbicides, post-emergence grass herbicides during the growing season, post-emergence broadleaf and residual applications at renovation, and fall post-emergence applications. Cultivation at renovation also contributes to the weed control program. Some large annuals and persistent perennials will need to be removed by hand. With some combination of these treatments, growers should be able to maintain their fields with minimal weed infestation for the three- to five-year life of a typical matted row planting.
Learn to identify weed species in order to choose the most effective herbicides for your fields. Excellent books on weed identification are “Weeds of the Northeast” by Uva, Neal, and DiTomaso (Cornell University Press, 1997) and “Weeds of the Midwestern United States and Central Canada” by Bryson and DeFelice (University of Georgia Press, 2010). Current recommendations for herbicides and other pesticides are summarized in MSU Bulletin E-154, Michigan Fruit Management Guide.
Editor’s note: Many of these weeds can be viewed online at MSU’s Identifying weeds in field crops.
Herbicide efficacy on some strawberry weeds (x indicates control).
Dr. Hanson and Dr. Zandstra’s work is funded in part by MSU’s AgBioResearch.