Recently, we had a substantial increase in a fairly regular visitor, the Say’s stink bug, along with a reoccurrence of the barberry webworm, which shows up here occasionally.
The Say’s stink bug (Chlorochroa sayi) has been seen here before, but this year large numbers have been found from Spanish Valley to Crescent Junction and beyond. This shield shaped bug is one-half inch to three-fourths of an inch long, with white dots from side to side across the green back. On some there appears to be a triangle on the back leading from the white dots to a single dot toward the tail.
Adults overwinter in plant debris and amongst weeds such as Russian thistle and mustard, which abound in our area. The problem with stink bugs is their interest in feeding on desirable plants such as tomatoes and peppers, as well as some fruits. They have piercing sucking mouthparts that they insert in the plant to suck out the juices.
In developing fruits or vegetables this damages that area, which then stops growing or expanding, causing deformations called catfacing. With produce that is almost ripened this area can develop into a hard or corky mass, which damages quality and often taste. While the damage is noticed, often the insect is not – unless you look closely or the number of insects is high. However, if you suspect the insect is present on a plant, try shaking the plant, which causes the stink bugs to drop to the ground. You’ll have to look quickly to see them.
Controls for Say’s stink bugs include keeping their favorite weeds out of the garden, spraying insecticidal soap to kill the young – this won’t kill the adults – and you could spray kaolin clay as a repellent, which can keep the adults at bay. There are heavier duty insecticides if the insect’s numbers get out of control.
The barberry webworm (Omphalocera dentosa) is occasionally seen here, most often on the Fremont’s barberry, or as it is sometimes called, the Fremont’s mahonia. This is an evergreen with spiny toothed, bluish green leaves and small grape-like fruit. This desert shrub is found at elevations from 3,000 to 7,000 feet and can grow to five feet or more in heigh. The Fremont’s barberry is sometimes used in landscapes.
The webworm is a blackish, sometimes brownish, caterpillar that makes webs which sometimes appear as a cylindrical tube with plant debris on the outside, in amongst the twigs. The adult is a grayish-brown moth with a wingspread of approximately two inches. The webworm eats the leaves, and if there are a lot of webworms the plant can be stripped of its leaves fairly quickly. Generally speaking, this isn’t considered a serious pest, but some people have experienced widespread leaf damage on their plants. Control can start by spraying the shrub with water early in the season to disrupt the cycle. If it is already too late in the season, then spray with Bt or spinosad.
Thought for the day: “Just living is not enough,” said the butterfly. “One must have sunshine, freedom, and a little flower.” —Hans Christian Andersen
For more information about these topics, call the Utah State University Extension Grand County office at 435-259-7558 or email Mike Johnson at firstname.lastname@example.org.