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ISSUE 16  August 22, 2002



As summer draws to an end and school is starting again, lawn care is often low on the priority list. However, there are some fall activities that will greatly benefit the overall health of a lawn and minimize disease problems the following year. Weed control is more effective for many weed species if done in the fall, any time from now until about mid-September, after which time freezing temperatures will limit uptake of herbicide products by the plants. Another benefit of fall herbicide application is that there is greater control of the rosette stage of some perennial weeds produced this time of year. For most broad-leaved weeds, any of the Trimec products will be effective. Confront is also labeled and very effective on many common lawn weeds, but is more difficult to find (try ag chemical retailers) and more expensive. For more information on weed control in lawns, see NDSU Extension Publication, H-1009,


And always read and follow all label instructions carefully.

Fall applications of slow release formulations of nitrogen have proven to be the most beneficial for improving early spring green up and providing better utilization by the grass. These applications are best done the same time as fall weed control, any time from now until about mid-September. It is not a good idea to us a quick release nitrogen formulation any time after mid-July (this inhibits natural hardening off that allows the grass to survive winter), so checking the product label is important. Slow release formulations will typically be labeled as WIN (water insoluble nitrogen) or CRN (controlled release nitrogen), and they may be more expensive than the quick release nitrogen products.

The following cultural practices will also help maintain or improve the condition and health of your grass. Most of the lawns in ND are predominantly cool-season Kentucky bluegrass. These should be maintained at a height of about 2-3 inches; however as temperatures cool off, usually in about October, that height should be kept to about 1.5 inches. Snow mold and powdery mildew are much more likely to occur on lawns that are left longer when snowfall begins. Rake up and remove lawn debris such as clippings and leaf litter to prevent areas covered by this debris being killed, or hot spots for disease development. If soil compaction from children, pet(s), and general traffic is a problem, if you have an accumulation of thatch, or if you have a patch disease such as necrotic ring spot or brown patch, aeration in the fall will promote oxygenation of the lawn roots as well as encouraging naturally occurring microorganisms that break down thatch. This is one of the most important steps in good, basic lawn maintenance, especially on clay type soils, both for disease control as well as promoting a vigorous lawn. Most rental stores have aeration equipment available for a reasonable fee, or you can hire this done by a professional lawn care provider. If you do this yourself, leave the plugs where they fall as they will provide an additional nutrient source when they break down. And the last thing to do before putting all the lawn care equipment away is to have the mower blade sharpened and conditioned so it is ready for spring again. Dulled lawn mower blades shred and tear tender leaf blades which generally adds stress to the lawn and provides an opening for disease-causing organisms.

Cheryl Biller
Plant Diagnostician

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