Mourad Louadfel, Bugwood.org
Cereal leaf beetles larvae continue to be active in wheat and oat fields across state (barley and rye can be infested occasionally). Infestations are difficult to predict and can be very patchy, so scouting is the key to identifying local populations that might need to be managed. Cereal leaf beetle larvae can be mistaken for slugs because they can look small, dark and shiny, but if you look closely and see legs, you are not dealing with slugs (Figure 1).
Moreover, slugs tend only to be 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 feed on the flag leaf. Insecticide treatments are warranted if populations exceed the economic threshold of one larva over 0.13 inches long per stem over a field or a portion of a field. A recently published fact sheet provides more details on their life cycle and some images of adults, larvae, and their damage. For insecticide options, please consult Penn State's Agronomy Guide .