Common name: Elm flea weevil
Scientific name: Orchestes steppensis (formerly identified at Orchestes alni)
Hosts: The weevil feeds on elms, especially Siberian elm (Ulmus pumila) and lacebark elm (Ulmus parvifolia). Hybrid elms with Asian parentage are also susceptible to this pest.
The elm flea weevil (Orchestes steppensis) has been a pest on elms in the upper Midwest since 2003. This insect is damaging in both the larval and adult stages.
Damage
The adult elm flea weevil chews small pin-head sized holes in leaves, while the larval stage causes blotch-type mines at leaf tips. The damage from elm flea weevil is considered more of an aesthetic problem and will not kill the tree. Extensive feeding, however, can cause severe defoliation which can weaken the tree, making it more vulnerable to other insect or disease problems.
Life Cycle
The elm flea weevil overwinters as adults under loose bark and in leaf litter under infested trees. Adults begin chewing small holes in young leaves in May, usually from the underside of the leaf. Heavy feeding may cause young leaves to turn brown and fall off. The females lay eggs in the mid-vein of the leaf. The larvae hatch soon after and begin to mine in the tip of the leaf. Eventually the mine enlarges to become a blotch. The larvae pupate within the leaf, emerging as adults in late July or early August.
The adult insect is a tiny weevil about 1/16th of an inch long with a long snout. They are reddish brown with black heads and have black spots on their wing covers. Their hind legs are thickened and useful for jumping. They fly when disturbed.
Management
Chemical
Damage caused by the elm flea weevil is often more cosmetic than harmful, and insecticides may not be needed. If needed, insecticide sprays should be applied when the adults begin to feed in spring. If spray application is attempted, a thorough coverage of the foliage, especially the undersides, is critical. Such coverage may be difficult to achieve, especially on tall trees, and special care should be taken to avoid application on windy days when spray may drift to other ornamental plants or food crops nearby.
Systemic insecticides can also be used to manage the elm flea weevil. Since these products can be slow to move through the tree and reach the leaves on which the beetle is feeding, they need to be applied early in the season before extensive feeding begins.
The pesticide information presented in this publication is current with federal and state regulations. The user is responsible for determining that the intended use is consistent with the label of the product being used. The information given here is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement made by The Morton Arboretum.
For more information, contact The Morton Arboretum’s Plant Clinic (630-719-2424 or plantclinic@mortonarb.org).