Managing Cover Crops and Declining Sod in Fall

By Blake Jackson

In the fall, foliar-applied herbicides are most effective when plants are actively growing, green, and healthy. Fall is particularly ideal for controlling dandelion, while both fall and early spring are suitable for managing winter annuals such as marestail.

In fallow fields without cover crops, a tank mix of 2,4-D ester (1 pint/acre) + glyphosate (1 quart/acre) + metribuzin (3-5 oz DF/acre) generally provides effective control of marestail, chickweed, henbit, mustards, and dandelion.

Using 2,4-D alone can control many winter annuals but is less effective on chickweed and dandelion compared to a combined herbicide approach. Controlling marestail in the fall is easier as the seedlings and rosettes are small and more susceptible, whereas spring bolting makes control more challenging.

Contact herbicides like Sharpen and Gramoxone and systemic herbicides such as glyphosate, 2,4-D, and dicamba are less active in cold temperatures. Among these, 2,4-D maintains slightly better activity below 40°F, while dicamba is more impacted by cold, making tank mixtures a more effective option.

By November, as foliar herbicide efficacy declines, adding a residual herbicide can improve control. For fields going into soybeans, chlorimuron-containing products (e.g., Canopy, Cloak) are effective, while simazine works well before corn.

Tank-mixing 2,4-D with residual herbicides and including an adjuvant like ammonium sulfate, crop oil concentrate, or methylated seed oil ensures proper uptake.

Cost-effective options such as glyphosate + 2,4-D + metribuzin can control a broad spectrum of weeds while keeping fall burndown expenses low ($5-15/acre).

Cover crops can help reduce winter annual pressure but blends with legumes or radishes limit herbicide use. Small grains like rye or wheat allow herbicide applications, including 2,4-D, dicamba, or Audit 1:1, to manage weeds in the fall or early spring.

Additionally, fall is the optimal time to kill declining sod stands of alfalfa or grass hay. Glyphosate is most effective in the fall, but additional herbicides or tillage may be needed for complete control before planting.

Photo Credit: gettyimages-mvburling