Brownheaded Ash Sawfly - Tomostethus multicintus                          William M. Ciesla, Forest Health Management International, www.ipmimages.org Note: The Blackheaded Ash Sawfly is present in Eastern Montana. HOSTS: Ash. DESCRIPTION: The larvae are pale green and worm-like with dark heads. Adults are small, black wasps. LIFE CYCLE: The brownheaded ash sawfly overwinters as a full grown larva within a cocoon around the base of previously infested ash trees. Pupation occurs in early spring and adult wasps swarm ash trees. Females lay eggs on new leaves, resulting in a slight distortion of these leaves. Emerging larvae feed on leaves, producing small pinhole feeding wounds. Mature larvae can defoliate leaves leaving only the main veins. Larvae mature by early summer, when they shed a papery larval skin that remains attached to the leaf. They then crawl to the ground around the host tree where they form a protective cocoon. There is only one generation per year. CONTROLS: Chemical: Spray with insecticidal soap if >40% of leaves are infested with larvae.
Missoula County Extension Office; Missoula, Montana 59808 - Updated for 2006