Editor’s note: Kelly R. Jackson’s Garden Corner column is taking on a new format. He now takes questions called into his phone recently at the Christian County Extension Office and answers them in the column.
Question. I found a big wasp making tunnels in my backyard. What are they and how do I get rid of them?
Answer. This time of year, it’s not unusual to find really large wasps making quick trips between the trees and the ground. These are the cicada killer wasps and as the name suggests they prey upon the noisy cicadas making all that racket in the trees. Cicada killers are quite large, up to 1.5 inches long with a wingspan of 3 inches and are marked with distinctive bands of white and yellow on black bodies. Their head and thorax are a rusty red. These insects are generally considered as beneficial as they spend a great deal of time laying eggs on paralyzed cicadas that they bury in underground burrows. They do have a stinger but are very non-aggressive. Seldom is control necessary, but several insecticides are labeled for those instances. Count these wasps among the good guys and let them be.
Q. I have a palm I take outside in the summer and keep indoors during the winter. I just noticed it was covered with scale. What should I do for control?
A. Scales can be found on plant stems and the undersides of leaves of many houseplants. They don’t look like a typical insect. The adults secrete a waxy shell-like covering making them appear like a bump on the plant. Their young are born under this shell and crawl out to settle in new locations on the plant. They feed by piercing the stem and sucking out plant sap. Since houseplants are usually smaller than landscape plants, physical removal, washing the plant, or using cotton swabs with rubbing alcohol to dab on the insects may be all the control methods you need. However several insecticides like bifenthrin and permethrin are labeled for scale. The plants will need to be treated outdoors. Also a few drops of liquid soap to the insecticide can also help the chemical slide under the edges of the scale’s protective shell.
Q. I found a spider web material on my redbud trees. It covers the end of several of the branches. What is that?
A. Fall webworms live communally in silk tents, which they construct at the ends of branches in over 100 species of hardwood trees. Often, there is just a tent or two on scattered trees, and the only impact is unsightly webbing. However, occasional outbreaks can result in significant defoliation and the temporary annoyance caused by large numbers of wandering hairy caterpillars as they leave the tents to pupate. Healthy deciduous trees generally can withstand substantial late season defoliation without significant consequence, so no control measures are needed, even if they are practical. Natural enemies also help to bring populations back to normal levels. If practical, physically remove and destroy the caterpillars and their tents. Insecticides containing Bt or spinosad provide selective caterpillar control, but they work best against small caterpillars, and spray coverage can be a limiting factor if trees are large.
Kelly R. Jackson is the Christian County Extension Agent for horticulture. He can be reached at 270-886-6328 or visit Christian County Horticulture online at www.christiancountyextension.com.