Gardening: Rains, yellowing and take-all patch
The recent rains have been a relief for our parched lawns from the spring drought. The high trans-evaporation rate of summer can also put stress on lawns if the rains stop for a length of time. If you turn off your sprinkler system you may have damage from these drought periods. The rain will also cause a population of chinch bugs to hatch and begin feeding along the borders of the damaged, brown areas. The telltale yellowing on a lot of lawns will soon be appearing.
Their presence will appear first as a yellowing of grass blades along the edges of any brown spots you may have or along sidewalks and driveways. The yellow areas will then turn brown causing the spot to spread with the edges of the area remaining yellow. So, if you see yellowing starting to appear in your lawn, especially around the edges of your old dry spots, act immediately or those spots will quickly double in size.
Get down on your hands and knees and at the edge of the damaged area you will see chinch bugs running around in the soil area and on the base of the grass blades. You may have to check several spots before you find them. You can also cut the ends off any can and stick the can through the grass into the soil. Fill it with water and within a few minutes chinch bugs will float to the surface.
Chinch bugs are very small insects about the size of an ant. The young chinch bugs are orange-red specks. The red color changes to brown and then dark brown to black with white wings. They cause damage to St. Augustine grass with the injection of their salivary juices when they suck the sap from the grass.
Good cultural practices are helpful in the management of chinch bugs. Certain practices can drastically reduce the need for pesticide applications. Rapid growth from frequent applications of highly soluble inorganic nitrogen fertilizers increases the chance of chinch bug attack. These attacks can be greatly reduced with minimum applications of slow release nitrogen fertilizers. Prolonged periods of moisture stress can also encourage chinch bug problems. When your lawn begins to turn a bluish-grey color, or the grass blades start curling, water immediately. Chinch bugs lay their eggs in dry areas and wait to hatch with rain. Improper mowing and excessive water or fertilizer can cause St. Augustine lawns to develop a thick layer of thatch or dead material which provides a home for chinch bugs and ties up insecticides thereby reducing control. A little-known fact is that when Floratam, a strain of St. Augustine, lawns are cut at a higher depth, 4 to 5 inches, the blades put out an enzyme which is toxic to chinch bugs. So, stop cutting your lawns so short! You’ll save money on both water and pest control.
Monitor your lawn on a regular basis, especially if the tell-tale yellowish areas appear. You can expect to see this damage begin in the next week or two. Try spot treatments when infestations are first noticed. Treat the off-color area and a buffer zone of ten feet surrounding it. This will help save the beneficial insects which may be present in your lawn. Two of the most helpful predators of chinch bugs are the black big-eyed bug, which looks like a chinch bug but is more robust and has larger eyes, and the earwig with its pincer on its posterior. These predators can be the first line of defense against polluting our environment.
Remember chinch bugs can do a lot of damage in a short period of time so don’t hesitate to act as soon you suspect a problem.
Another cause of yellowing on lawns right now is disease. Last year, around this time, I sent two samples off to the disease clinic at the University of Florida and both came back with three different diseases. Take-all patch, brown patch and grey leaf spot. The take-all patch is the deadliest and is usually caused by stress as mentioned above. One unfortunate reason for stress is the improper use of herbicides in summer to kill weeds in the lawn. It is simply too hot to use them right now and you would be better off working on the health of the grass which will choke out the weeds.
Eileen and Peter Ward have owned a landscape and lawn maintenance company for 35 years. Eileen can be reached at Gswdmarco@comcast.net or 239-394-1413.