Dealing with dead spots and other late summer lawn tips

When is the best time to fix dead spots on lawns?

Late summer through early fall (mid-August to mid-September) is the best time to renovate lawns in Wisconsin. According to Dr. John Stier (former UW extension lawn grass specialist), the pleasant air and soil temperatures during this time encourage the germination of the grass seeds. In addition, the soil moisture in early autumn is usually sufficient for the grass seedlings to germinate better. Many annual weed seeds, including crab grass seeds, go into dormancy and do not compete with grass in the fall. Seedlings germinated during this time have ample time to mature and harden before the winter season sets in.

Before taking steps to renovate your lawn, analyze the causative factor behind your lawn waste. Very often disease, insects, weeds, shade, soil compaction and lack of nutrients cause thin lawns and dead spots.

How do I loosen compacted soils in my lawn?

Compacted soils in lawns prevent deeper root growth in the soil and reduce the availability of oxygen. This forces the grass roots to grow on the surface of the soil, making them prone to heat stress and winter injuries, and creating a thin lawn. Core aeration is one of the best ways to loosen the compacted soil. Core aerators remove the soil plugs and improve the flow of oxygen into the soil. This helps with better root growth in the soil. The best time to ventilate is in early autumn. To encourage rapid root growth, plan to fertilize the lawn immediately after aeration.

Another way to loosen compacted soil is to add ¼ inch waste compost for three years with each application in early fall and spring. This improves the quality of your lawn soil and promotes better root growth and density in the grass stand.

Are there organic lawn herbicides to control perennial weeds? How effective are they?

Organic herbicide products that contain ingredients such as iron HEDTA (a chelated iron) and 70 percent or less acetic acid (vinegar) are labeled for use on turf grass. However, these products only affect the foliage of the weeds, and the plants tend to recover in a few weeks. Many organic lawn herbicide spray products require higher application rates and the products must be applied repeatedly (3-4 times per season), especially in the early stage of weed growth, for adequate control. Treating large lawns with organic lawn herbicides can be expensive.

When should I schedule the maggot remedies in my lawn?

Mid to late August is the ideal time to plan maggot control remedies that contain carbaryl (Sevin) or trichlorfon (Dylox) as active ingredients. Young larvae of the Japanese beetles are susceptible to the maggot remedies during this time. Plan the product based on the next rainfall forecast or do some light watering after application. Applying the remedies in mid to late fall or spring is generally ineffective on large maggots.

Vijai Pandian is a horticultural agent / educator for Brown County University of Wisconsin Extension. For questions and advice, contact the Extension Horticulture Helpdesk at 920-391-4615 or [email protected].

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