Kevin Black, Insect and Plant Disease Technical Manager, Growmark, Inc., recently reported that cereal leaf beetles can be found in low numbers in some wheat fields across southern Illinois. In addition, densities of aphids in these fields were low according to Kevin. He attributed these low pest numbers to the presence of natural enemies hard at work (Figures 1 and 2). Cereal leaf beetles complete one generation per year. The adult is a colorful beetle (3/16 inch long) and has metallic bluish-black wings (elytra) and reddish-orange legs and thorax (Figure 3). Cereal leaf beetle larvae are the primary economic threat due to their feeding on the epidermis tissue of the upper leaves of wheat plants. For approximately a 10-day period, the “sluglike” larvae remove elongated strips of leaf tissue from plants. Severely damaged wheat fields may appear to have a frosted appearance. Larvae appear sluglike (Figure 4) due to the presence of moist fecal material in which they encase themselves. This interesting behavior may enhance their survival by deterring potential predators and parasitoids.
A rescue treatment may be warranted if a combination of eggs and larvae averages 3 or more per stem. Eggs (1/32 inch long) are elliptical and yellowish-orange and typically found near the midvein on upper leaf surfaces. The eggs may be found singly or in short chains.
Producers are encouraged to monitor their fields for cereal leaf beetles and aphids. The presence of parasitized and/or diseased pests (particularly aphids) should be noted before any rescue treatments are applied. As of now, the natural enemies appear to be keeping pest pressure low in many wheat fields.