False chinch bug adults are 1/8-inch long, flattened, grayish bugs, with black or brown markings. Nymphs are smaller and similar in appearance to the adults. The nymphs also have reddish mottling on the abdomen. This is one of the many insects that people refer to as "oat bugs". They use their piercing-sucking mouthparts to feed on a wide variety of plants.
Huge numbers of insects sucking out plant juices and injecting toxins will cause almost any plant to have shriveled, curled, and brown leaves. Horseradish is commonly attacked during droughts and responds to the bug's feeding with frostlike injury to leaf tips and edges. Prolonged feeding by very large false chinch bug populations will kill horseradish plants.
These insects become particularly numerous during droughts and other locally dry situations. Typically they are rarely noticed, but in droughts they band together and move in very large numbers. The bugs have a tendency to sit in large masses on the soil at the base of attacked plants.
Weeds that are spring hosts of the false chinch bug, including canola, cruciferous weeds, or chickweed, may make adjacent irrigated horseradish fields particularly susceptible. Early control of these weeds may help reduce bug buildup at field edges and reduce subsequent invasions into horseradish during drought years. However, weed control during a drought later in the summer may be counterproductive because false chinch bug nymphs have been known to ignore the horseradish and feed on purslane and other weeds within a field. Applications of insecticides in high amounts of water directed at the base of horseradish plants can be effective. The high water amount forces the bugs to crawl through the insecticide, increasing control. During a prolonged drought, repeated applications may be needed to control successive waves of bugs.