Elm Leafminer

Scientific Name: Fenusa ulmi

Leafminers are larvae of sawfly wasps that feed in between the epidermal layers of a leaf. As the larvae feed they consume the plant tissue leaving clear mines that, when they die, turn brown and crispy. Usually by the time the damage is observed, the larvae have already left the leaves and are pupating underground. Control for elm leaf miner needs to be applied before the mines develop. Repeated defoliation by leaf miners can impact the health of infected trees.

Attacks: Red, Siberian, and American elms

What you will see:

• Small whitish spots (haloes) on leaves in May
• Blotch-like mines appear in mid-May
• Mines join together into tan and papery patches
• Mined areas of leaves may fall out and leave holes in the leaf
• Brownish foliage that looks sickly

Life cycle:

• Adults lay eggs in leaf tissue in April and May
• Eggs hatch and larvae begin feeding between leaf layers
• Larvae finish feeding in late May to early June and fall to ground
• Larvae burrow into the soil and build a cocoon to pupate
• Pupae remain underground for the summer, fall and winter

Cultural Management of Elm Leafminer

Cultural practices:

• Increase vigor of tree to recover resources
  • Root Enhancement System®
  • Fertilization with low nitrogen fertilizer

Chemical treatments can be effective and are available for management of elm leaf miner. Follow your Consulting Arborist recommendations.