I volunteer at a therapeutic riding center where we have a problem with mosquitoes, flies and other insects. Are there any native Texas plants that would help repel insects around our stables? Horse flies are especially annoying this time of year. We would rather not use commercial insect repellents on or around the horses. A.G., Wylie
ANSWER: Plants won't control the insects, but spraying a liquid mixture of compost tea or Garrett Juice with orange oil and broadcasting dry garlic will repel mosquitoes. Garlic also will repel flies, but I have another suggestion that is easy and inexpensive and works well: Hang clear plastic bags filled with water from trees and overhangs. The reflections apparently scare away flies. The bags must be cleaned or replaced after they get dusty. Nontoxic fly traps that use attractants also work well.
QUESTION: I want to plant a tree so that it will cast a shadow on a certain part of my yard and house, but I don't want to plant it where it would interfere with other plantings or be detrimental if the tree fell for some reason. Based on how tall the tree should be at maturity, how can I determine how far the shadow will fall during the hottest part of a Texas summer afternoon? The tree is a lacebark elm. I've looked at mathematical Web sites seeking assistance, but so far no luck. G.A., Crowley
ANSWER: Math is the wrong subject for me. The general rule is to plant deciduous trees on the south and west sides of the structure or area to be shaded in the summer.
QUESTION: I am having problems with what has been identified as Southern corn rootworms or spotted cucumber beetles. Texas A&M University recommends using Dursban, but I don't want to use that stuff. Is there a better option? I tried garlic-pepper tea, but it did not work. These bugs destroyed my garden last year, and I have already seen a few this year. A.C., Hood County
ANSWER: Southern corn rootworms are the larvae of spotted cucumber beetles. Products containing Bt (Bacillus thuringiensis) will control corn rootworms. For cucumber beetles, use a plant oil product such as an orange oil fire ant drench, Eco Exempt or Bioganics. Compost tea or Garrett Juice with neem oil added also will help. (See Resources to obtain handouts.)
QUESTION: I have an insect problem on a schefflera that looks kind of like mealybugs, but I don't see any white fuzz. We had a mealybug problem last year on a lime tree. W.S., Arlington
ANSWER: I think what you see is scale insects and their waste. Spray fire ant mound drench (a mixture of compost tea, orange oil and molasses) or another plant oil product to keep the insects from coming back and to get the plant out of stress.