Answer: One problem could be white grubworms in the soil. Generally, if this is the problem, the area of lawn should have died late alst fall. The entire area of the lawn should be dead, no green sprigs, and the dead grass can be easily lifted in carpet-like sections. This lack of root anchorage is due to the eating off of roots by grubs. What should you do? Actually, the question is?what should you have done last July! The white grub worm (white worm with hard orange head) is the immature stage of the June bug which flies around lights and into your hair in May and June. These June bugs deposit eggs in lawns in early July. An application of granular insecticide approved for grub control at that time will kill the young grubs and save lawns. If this sounds like the problem, visit:
Another problem that weakens areas of lawn grass every fall, and possibly thins the turf significantly is brown patch. Brown patch is a fungal disease that begins in a small area and spreads in a circular pattern. The pattern resembles a balloon being filled with air?it gets larger and larger. Brown patch will only occur on grass that has previously greened in the spring so it cannot be confused with grubs or cold injury. It can also be distinguished from other lawn problems by the presence of dark, smoky rings on the edge of this ever-enlarging ring. There will also be green sprigs of grass within the affected circle.
But suppose you have Brown patch-like symptoms in the heat of summer? Unlike Brown patch that is normally a circular area with the edge of the circle having browning or yellowing grass and the interior of the circle having a more healthy green appearance, this patch disease symptom has brown, dead grass throughout the circle. This summer-patch disease is referred to as Take-All patch. For control measures of Brown patch and Take-All patch, see:
Hope these webpages help you determine just what might be causing the brown patches in your lawn.
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