Homeowners often notice yellow spots developing on their lawn, which detracts from its appearance. Zoysia is a popular turf grass and is subject to a number of damaging pests and diseases. Identifying the cause of yellow spots in your lawn is key to managing insect infestations and diseases and restoring your lawn to good health. Does this Spark an idea?
Identification
Zoysia is a warm-season turf grass that is highly versatile. This turf grass is often used in ballparks, golf courses and in many residential lawns. This grass flourishes in many types of soil, including sandy soil, clay soil and in alkaline soils. Zoysia grass is adapted to many areas of the United States and it grows well in shady locations. However, zoysia does not fare as well in cooler areas. It is very popular in Florida because of its extreme tolerance to drought and salt. Zoysia is tolerant of wear but is susceptible to insects and diseases that can cause it to develop yellow patches.
Disease Causes
Yellow spots in zoysia is most often caused by the fungus Bipolaris tetramera, which is also commonly found in Bermuda grass. This fungus causes a thinning of turf grass, followed by brown spots that run up and down grass stems. Stolons and roots often begin to rot, developing a dark brown appearance. Eventually, yellow lesions begin to form on the lawn. The canopy of the lawn becomes very thin and discolored.
Insect Causes
Insect infestations can cause zoysia to turn yellow in various spots on the lawn. The hunting billbug is a weevil that is also commonly referred to as the zoysia billbug. According to the University of Florida IFAS Extension, the hunting billbug has been reported in Florida, Georgia, Alabama, Arkansas, Kansas, Louisiana, North Carolina, South Carolina, Mississippi, Missouri, Virginia and Texas. The adult form of this pest is a weevil that measures 1/4 to 1/2 inch in length. Hunting billbugs have a curved snout and are gray, reddish-brown or black. The larvae of the hunting billbug is often mistaken for the common white grub and is white with a brown head capsule. This pest is the most commonly recorded destructive pest of zoysia grass and damage appears as small yellow spots on the lawn, which gradually become larger from billbug feeding. Heavy infestations of this pest can kill grass inside the yellow spots, often totally destroying grass roots. Zoysia infested with hunting billbugs can often be rolled back easily and grubs may be easily spotted under the turf.
Control
Keep your zoysia free from stress to maintain good health. Avoid using nitrogen-rich fertilizers and avoid overwatering your lawn, as this encourages fungal growth. Fungicides are available for the treatment of fungal diseases in your zoysia. Avoid mowing your zoysia grass to very low heights. Infestations of hunting billbugs in your zoysia can be controlled by applying insecticides available at your garden center. Roll back a portion of lawn grass to determine if you have hunting billbugs. If 10 billbugs or billbug larvae are found per square foot, insecticides are recommended.
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