Mealybugs have been found causing damage in Northern California. Both nymphs and adults feed with sucking mouthparts and reduce the amount of chlorophyll in the leaves, causing extensive yellowing and browning of foliage, reduced vigor and root damage. Heavy infestations in commercial fields eventually kill the plants. The concealed feeding habit of the Haanchen barley mealybug Trionymus haancheni McKenzie and the fact that the eggs are protected inside the cottony ovisacs would further complicate management attempts and limit insecticide use in barley because insects sheltered under leaf sheaths or ovisacs would be protected from contact sprays. However, insecticide lambda cyhalothrin with a surfactant (Activator 80) applied at tillering stage barley reduced mealybug populations. Biological control with parasitoids and predators has been the most effective and long-lasting management option.