EAST LANSING, Mich. — Strawberry harvest is about finished in Michigan for this year. The period after the last picking of the season is the best time to renovate perennial strawberry (matted row production) fields, which means clearing out the weeds, removing the old foliage and preparing the field for another year of growth. The renovation process includes application of fertilizer, tillage and narrowing of the rows, mowing, and herbicide application. A healthy and weed-free perennial strawberry field should remain productive for four to five years with good renovation and late season practices.
Effective post-harvest tillage and weed control are important for strawberry plant regrowth and fruit production next year. If there are many broadleaf weeds, and especially perennial weeds (dandelion, field bindweed, wild carrot, horsenettle, vetches, and common milkweed), in the field, it may be necessary to apply 2,4-D (Formula 40 or Embed Extra) immediately after the last harvest. If the field has mainly annual broadleaved weeds, the herbicide application can wait until after tillage and mowing.
Broadcast 300 pounds per acre of 20-20-20, or the equivalent amount of NPK, to the field before tillage. An adjustable tiller that straddles the row is the most effective machine for renovation. Narrow the rows to 10-12 inches. A wider original row results in low new-plant density in the middle of the rows next year. The remaining plants in the rows will send out runners that take root, and become the fruiting plants the following year.
The next step is mowing the remaining plants to 4 to 5 inches in height. This should remove most of the existing strawberry foliage, and leave low-growing weeds in the rows. If 2,4-D was not applied previously, it should be applied after mowing if broadleaf weeds are present. A postemergence grass herbicide, such as sethoxydim (Poast), clethodim (Select Max), or fluazifop (Fusilade) should be applied to kill annual and perennial grasses. Include an adjuvant with the grass herbicide. If most of the broadleaf weeds are composites (eg. Canada thistle, dandelion, mayweed, ragweed, groundsel), clopyralid (Stinger) may be used instead of 2,4-D. Stinger has a Michigan 24c label, and is not labeled for this use in all states. Do not include an adjuvant if Stinger is included in the spray mix.
After tillage, apply residual herbicides to control weeds for the rest of the summer. The residual herbicides may be tank mixed with the postemergence herbicides which will help to control already emerged weeds and inhibits germination of most annual weeds during summer. For broad-spectrum, full-season weed control, include two residual herbicides in the post-renovation application. Effective mixes include a primarily grass herbicide (Devrinol, Dual Magnum, Prowl H2O) and a primarily broadleaf herbicide (Spartan, Ultra Blazer). Read labels to determine which weeds will be controlled for your situation. Sinbar is a very effective herbicide, but may stunt strawberry on light sandy soil. Do not use Sinbar on soils with less than 1% organic matter or over 70% sand. Chateau also may be used on strawberry, but should only be applied to aisles between rows. It is most appropriate for strawberry grown on raised beds on plastic mulch.
Spartan, Sinbar, Ultra Blazer, Prowl H2O and Dual Magnum also may be applied in late fall before spreading of straw mulch. An effective herbicide application in fall should provide good weed control through the harvest season the next spring. Check herbicide labels for maximum use rates per acre per year to avoid over-application. You can read labels at CDMS.
There are several generic clopyralid herbicides available. Apply clopyralid in early to mid-fall to control legumes (clover), composites, nightshades (including groundcherry), smartweeds (including prostrate knotweed, red sorrel, and wild buckwheat), and plantains. Another grass herbicide application may be made at the same time. Fusilade is the most effective postemergence herbicide for quackgrass control. Some weeds will escape all of these herbicide applications, and should be removed by hand.
On light soils, another application of 50 pounds nitrogen will give the plants a boost and prepare them for fall dormancy. This should provide more vigorous growth in the spring. Timely irrigation during summer and early fall will promote plant growth and health. This will result in production of many fruit buds and a larger crop the following year. Another application of 50 pounds nitrogen may be needed about May 1 the following year on light soils. If the plants appear to slow down their growth in the spring, apply the extra nitrogen. Over-application of nitrogen may result in excess plant production and reduced fruit production. Every situation is different, so observe your plants regularly in the spring.
— Sushila Chaudhari and Bernard Zandstra, Michigan State University Extension, Department of Horticulture
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