Q: I have a St. Augustine...

Q: I have a St. Augustine grass lawn that is wilting in some areas. In the past, such spots ultimately have died. What is causing this condition?--T.W., Whittier A: One of the few insect pests that can damage this tough grass is the Southern chinch bug. Both adult and immature forms feed by sucking plant juices from the grass stems--usually while they’re hidden in the thatch, that tangled mass of dead grass at the base of the blades. Sapped of its juices, the turf wilts and dies out. Yellow spots appear first, to be replaced by dead, brown areas. When you suspect chinch bug damage, you can confirm the pest’s presence by flooding one of the areas between living and dead grass. If they’re there, the chinch bugs will float to the surface. Adult bugs are black with white markings and about an eighth of an inch long. You can control chinch bugs by thoroughly drenching the thatch, their hiding place, with diazinon.

Q: Haven’t I heard that fall is a good time to divide crowded flowering perennials such as iris, phlox and pinks?--F.K., Canoga Park A: Indeed, fall is a good time to divide perennials, although most won’t begin growing until early spring. Therefore, you really have all of fall and much of winter to tend to the task. Use a sharpened spade to split the plants apart if you can’t separate them by hand. While you’re at it, check the roots for signs of disease or nematodes. Any roots showing discoloration, scabbiness, rotted areas or other abnormalities should be discarded. There are various soil fungi that cause crown and stem rot and in doing so produce a white, cottony mold on the affected tissues. In some cases, small, black, seed-like bodies are visible. Structures like those send out the small, trumpet-shaped toadstools that produce the spores that spread the disease. Before replanting, remove all dead leaves, flowers and stems from the plants to minimize disease carry-over as well as breeding and hiding places for insects and snails.