Answer: I can't tell from your description whether you have random rhizomes dying or if you have straw colored spots in your St. Augustine lawn. Dollar Spot (Sclerotinia homoeocarpa) causes circular straw-colored areas only a few inches across, although spots may merge, resembling large patches. Live blades may have straw-colored
lesions along one edge. The lesion moves across blade, causing tip to dieback. Abundant white fungus growth may be seen in these areas during periods of severe disease development which is evident early in the morning when dew is present. If this is what you have, control by fertilizing as necessary; water adequately. Use an
adequate level of nitrogen, particularly in the spring and early summer. Mow grass at regular intervals. Irrigate turf early in the day to allow the foliage to dry as quickly as possible. Reduce thatch. Irrigate deeply and infrequently to avoid drought stress. Fungicides can help prevent further infection.
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