Hayden Schug, Agriculture Agent | University of Maryland Extension, Charles County | hschug@umd.edu
Ben Beale, Principal Agriculture Agent | University of Maryland Extension, St. Mary’s County | bbeale@umd.edu
Cereal leaf beetle (CLB) is a familiar pest for Maryland wheat growers, and this time of year is ideal for scouting. We often find cereal leaf beetles while scouting for foliar disease like powdery mildew and stripe rust or checking wheat for flowering stage in preparation for fusarium head scab fungicide applications. While both adults and larvae can be present, it’s the larvae (Fig. 1) that cause the most damage. Often mistaken for bird droppings, these larvae feed aggressively on leaf tissue, potentially leading to significant yield loss in wheat if populations are high enough. In Southern Maryland we have found low populations of cereal leaf beetle larvae feeding in wheat throughout most fields. However, only one of these fields met the threshold that would warrant an insecticide application, so it’s important to understand threshold levels.
Adult CLBs (Fig. 2) overwinter in wooded areas and field edges, becoming active as temperatures rise in early spring. They move into small grains and lay distinctive orange or yellowish eggs on the upper surface of wheat leaves, typically singly or in short rows. After hatching, the larvae feed for two to three weeks, chewing narrow, elongated strips between the leaf veins. This results in a “windowpane” effect—thin, transparent patches where only the leaf epidermis remains (Fig. 3). Larvae appear dark and slimy due to a coating of fecal material, though they are actually yellow underneath. When walking through a field with CLB present, a tell tale sign is black stains that appear on pants legs.
Scouting should begin in late March or early April, especially in no-till fields, those near wooded areas, or where there is a history of CLB infestation. When scouting, check 10 tillers at 10 random locations per field and look for larvae, eggs, or adult beetles, which have shiny blue wing covers with reddish thoraxes and legs.
Treatment is recommended when there is one larva per flag leaf after boot stage. If treatment is necessary, insecticides containing pyrethroids such as lambda-cyhalothrin (Warrior) or zeta-cypermethrin (Mustang Max) are effective. Be mindful of insecticide rotation to avoid resistance, and always check pre-harvest intervals.
Scouting and timely management are key to minimizing the impact of cereal leaf beetle. Keep an eye on your fields while out scouting to determine if you need to add an insecticide to your fungicide treatments.
