Cereal Leaf Beetle Larvae are Active in Some Small Grain Fields

We have heard reports that cereal leaf beetle larvae are active in some small grain fields, particularly in wheat in southeastern PA, but oats fields can commonly harbor this pest species. Infestations are difficult to predict and can be very patchy, so scouting is the key to identifying local populations and whether they are large enough to be managed. Cereal leaf beetle eggs and young larvae are orange and relatively to see (Figure 1). As they get older, however, they can be mistaken for slugs as they look dark and shiny because they cover themselves with their own frass, which is the word for insect feces. If you look closely at these shiny animals and see six small legs, you will know you are dealing with cereal leaf beetle larvae and not slugs (Figure 2). Moreover, slugs are nocturnal, so slimy creatures out during the day in small grains have a good chance of being cereal leaf beetle larvae. If young larvae are detected at populations exceeding the economic threshold, cereal leaf beetle is easily controlled with insecticides, but larger larvae are more difficult to control and cause more damage, particularly if they are feeding on the flag leaf. Insecticide treatments are warranted if populations exceed the economic threshold of one larva greater than one-eighth-inch long per stem over a field or a portion of a field. A recently revised fact sheet provides more details on their lifecycle and some images of adults, larvae, and their damage.  For insecticide options, please consult Penn State's Agronomy Guide.