Q. I admit that I'm a bit of a lawn nut. Just when I've spent a small fortune creating a beautiful tall fescue lawn, I'm noticing patches of grass that are turning brown. I fertilize in spring, summer and fall and apply weed killer when necessary. Do you think I have a white grub problem?
A. White grubs are a more common problem in bluegrass lawns. Tug on your brown patches of grass. You have a grub problem if the patches come up without roots attached and if you see 6-8 grubs per square foot of soil. The much more likely problem is a common fungal disease called brown patch that infects tall fescue and was more noticeable during this relatively rainy summer. It is not serious and no fungicide treatment is recommended. Your fertilization program is encouraging brown patch disease. Your lawn only needs to be fertilized in the fall with 2-3 pounds of nitrogen per 1,000 square feet of area.
Q. I have four different types of heirloom tomatoes in my garden that are wilting and dying. The hybrid varieties are doing fine. The strange thing is that I see lots of brown spots on the leaves of the hybrids but hardly any on the heirlooms. What's going on?
A. Some heirloom cultivars seem to have resistance to some leaf diseases, such as early blight. However, most heirloom cultivars are susceptible to fusarium wilt, a devastating disease to which most of the current hybrids are resistant. With a razor blade, shave back the epidermis of a wilted stem to confirm the diagnosis. The cambium layer under the epidermis of a healthy plant should be a light green color. Tan or brown indicates that the water- and food-conducting tubes are blocked with fusarium fungus. Remove and dispose of the infected plants. Fusarium can live in the soil for many years, so you will have to move your tomato bed to another part of the yard or grow your heirloom cultivars in containers.
THIS WEEK'S CHECKLIST
1. Fertilize your zoysia or bermuda grass lawn with 1 pound of nitrogen per 1,000 square feet of area.
2. Remove spent rose flowers to encourage repeat blooms.
Backyard Q&A is by Jon Traunfeld, regional specialist for the Home and Garden Information Center, Maryland Cooperative Extension Services of the University of Maryland. For additional information on these questions, or if you have questions of your own, call the center's hot line at 800-342-2507, or visit its Web site at www.agnr.umd.edu / users / hgic.