The first sighting this year of an insect capable of destroying thousands of acres of rangeland has been reported in the southern Utah area, said a Utah State University entomology professor.
Labops hesperius, commonly known as the black grass bug, began hatching out in the Kanab area this past week, said B. Austin Haws, specialist in injurious and beneficial range insects.With this first sighting, the race is now on. Ranchers in the Kanab area have less than a month to begin spraying or risk losing a substantial amount of already drought-thinned grazing grasses, Haws said.
This first sighting should put other ranchers around the state on alert as well. Substantial numbers in past years have been found in the Fish Lake area and in some of the northeastern ranges of Utah. The bugs seem to thrive best at elevations between 6,000 and 9,000 feet. Crested wheatgrass and intermediate wheatgrass appear to be their favorite host plants, he said.
In 1979 it was estimated that black grass bugs destroyed up to $5.1 million in potential cattle weight gains in Garfield and Kane counties alone, he said.
Black grass bugs, the early birds of the bug kingdom, are about 3/16th of an inch long as adults. They have bulging eyes and whitish buff margins of color around their wings and light markings on their heads, he said.
They are hardy little creatures that hatch in snow water. Moderately cold temperatures play an important part in their development. They have to have cold to hatch, requiring from 30 to 60 days of temperatures between 20 and 30 degrees. Egg survival especially depends upon snowfall, with an ideal snow base of seven to nine inches.
If the snow blows off the ground and temperatures drop much below 20 degrees, the eggs can be killed.
When they first hatch, Haws said the nymphs are less than 1/16th of an inch in length, so it is difficult to spot them. But it is not hard to notice the early damage they cause to nearby grasses.
Because they hatch as soon as the winter snow melts, Haws said they begin feeding on the grasses at their most critical time of growth. The insect population hatches almost at the same time - ithin a small area - and consequently do substantial damage in a short time.
Plants that are attacked by the bugs develop yellow or whitish, irregular spots or patches in the leaves. Eventually the leaves dry and die. These insects do not cut notches or chew holes, he said.
They usually feed with their heads pointing to the ground. The bugs run up and down the stems and leaves, usually starting at the pointed tips of the leaf and feed systematically toward the wider parts of the leaves.
Once the grass blades turn completely yellow, Haws said it is then too late to do anything.
Although several kinds of black grass bugs have been identified in Utah, Haws said it is the Labops hesperius that constitutes the major problem in the state.
He said the first thing ranchers should do is to get any suspicious bugs properly identified. This way they avoid wasting time and money on unnecessary spraying. Bugs can be identified through USU Extension county agents. County agents will also assist in determining when to begin spraying.
Once the black grass bug has been identified, timing becomes everything, he said.
From the time they first hatch, he said the insects should be carefully monitored. Once they have all hatched, spraying should begin before the insects begin developing wings. That can take 19 days or longer, depending on the temperature. The hotter the weather, the faster they develop.
The best spray to use is malathion. It requires only eight ounces per acre.
Haws said if too much time lapses and the insects develop wings, the females are at a mature enough stage to begin laying eggs. They do this by depositing their eggs inside grass stems where pesticides cannot penetrate. Once they reach this point, next year's generation becomes virtually assured.