PHOTOGRAPHY BY KIRTI MATHURA Texas mountain laurel

Q: Every year caterpillars eat the tips of the leaves on my Texas mountain laurel tree. I’ve tried various pesticides, without success. I’ve also cut off the branch tips to remove the caterpillars, but then I don’t get blossoms. Is there some way to permanently rid the tree of these insects?
 
A: The “tent” caterpillar is a common insect that creates weblike tents or silky webs on branch tips of trees and shrubs. The tents provide protection for young larvae, says University of Arizona Maricopa County Cooperative Extension Master Gardener Olin Miller. The larvae feed on nearby leaves and may strip a branch before moving on. It usually is not a serious problem if the plant is otherwise healthy, although it may be unsightly.

The larval stage lasts five or six weeks. Hand-picking works well if you can reach the branches. Bacillus thuringiensis also is effective for killing caterpillars (see next question). However, it isn’t possible to permanently eliminate the caterpillars on your Texas mountain laurel because each year adult moths will appear, looking for good spots to lay eggs. These are night-flying moths attracted to lights, so keep the area around your tree dark at night to discourage their presence. 

Q: What is chewing holes in the leaves of my broccoli, kohlrabi and lettuce plants? I haven’t seen any insects. Are there any organic pest-control methods for this?

A: Look for small green caterpillars, called cabbage loopers, on the undersides of leaves, recommends Maricopa County Cooperative Extension Master Gardener Dick Gross. Their coloration blends with the foliage, so examine stems and the undersides of leaves as well. Once you spot them, they are easy to hand-pick. Bacillus thuringiensis (Bt) is an organic pesticide that disrupts the digestive systems of caterpillars, causing them to starve to death. Follow product directions when applying any pesticide. However, Bt will kill any type of caterpillar, including butterfly larvae, so you may prefer to hand-pick cabbage loopers. More information can be found at Cabbage Looper in the Low Desert at cals.arizona.edu/maricopa/garden/html/t-tips/bugs/looper.htm.
 

Q: My lantana plants seem to thrive for about a year. After I trim them, they become brittle and never flower again. Do they have a dormant stage or a short life expectancy?

A: “In my experience, lantana is fairly long-lived in the Phoenix area,” says Maricopa County Cooperative Extension Master Gardener Olin Miller. However, in colder regions, lantana may be grown as an annual because it doesn’t tolerate cold. In the low desert’s late fall and winter months lantana does not go completely dormant, but there is little, if any, new foliage growth. It may continue to flower a bit, although the blossoms are not profuse at this time. If your lantana needs trimming, do so in January or February. You won’t have to endure the “cut-back” appearance for months before new growth starts in March.