It is summertime, the wonderful time of the year when all the insects of the world gather together in your backyard and completely gobble up your tomatoes, crape myrtles or other prized plants. Let’s talk about a few that are causing problems in Denton County right now.
The almighty grasshopper is back eating everything it can. Cutting down tall weedy areas can reduce populations of hoppers. To protect your vegetables, flowers and maybe even small trees, you can use floating row covers.
Insecticides are most effective on grasshoppers when they are smaller and immature (without wings.) This is especially true for organic insecticides such as bait products containing spores of a protozoan called Nosema locustae. Grasshoppers consuming the bait become infected with the organism which kills the immature grasshoppers. Infected adults often survive but lay fewer eggs. There are several insecticides approved for use in the home landscape or in pastures. Our office can provide you with that information, 940.349.2892 or [email protected]
An interesting insect that we are seeing a lot of right now is the bagworm. They feed on many different types of plants but we tend to see them on arborvitae most frequently. The female bagworm is wingless and lives her whole life in the bag that she makes of silk and leaves. Bagworms hang in the trees like defoliating little ornaments, oftentimes unnoticed until the trees are practically leafless. Bagworms are one of the few pests that can be effectively removed by hand. Because bagworms generally overwinter in the egg stage every bag you remove in the winter holds the potential for hatching 500 to 1,000 eggs the next spring. Another control option besides plucking them by hand is Bacillus thuringiensis, a bacteria, which is especially effective on smaller bagworms. Spinosad is another effective low-impact insecticide.
Our final insect on the panel today is the crape myrtle scale or azalea bark scale. One of the first signs of an infestation is a black, sooty mold coating that appears on the bark of the trunk and branches of crape myrtles. Leaves and limbs may also feel sticky from the honeydew, which is the byproduct of the insect’s feeding.
The scale insect looks like a white to gray, waxy encrustation that can appear anywhere on the plant, but often near pruning wounds. Another identifying characteristic is that a pink liquid “bleeds” from the female scales when crushed. To remove scale from heavily infested plants, use a soft brush and a mild solution of dishwashing soap, to wash the branches removing many of the adults and egg masses and the sooty mold. There are also systemic insecticides that can be used as a drench applied to the root zone of plants such as products containing Imidacloprid (Merit® or Bayer Advanced™ Garden Tree and Shrub Insect Control) and dinotefuran (Greenlight Tree and Shrub Insect Control with Safari).
Janet Laminack, Denton County Extension Agent –Horticulture/Texas A&M AgriLife Extension, 940-349-2883, [email protected]