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Cryptorhynchus lapathi

Adult poplar and willow borer weevil. Photo: Gyorgy Csoka, Hungary Forest Research Institute, Bugwood.
Scientific Name: 
Cryptorhynchus lapathi
Common Name: 
Poplar and Willow Borer
Growing Degree Days (GDD's): 
2271–2806 GDD's, Base 50F, March 1st Start Date (Source: Cornell Cooperative Extension and Robert Childs, UMass Extension.)
Host Plant(s) Common Name (Scientific Name): 
Alder (Alnus spp.)
Bog birch (Betula pumila)
Cottonwood (Populus deltoides)
Poplar (Populus spp.)
River birch (Betula nigra)
Willow (Salix spp.)
Insect Description: 

The poplar-and-willow borer was initially found in the United States in 1882. A non-native insect originally from Europe, this species of weevil spread across the US, including in New England. The timing of the life cycle of this insect varies depending upon geographic location. In the northern most parts of its introduced range, such as British Columbia, it may take 2-3 years for the poplar-and-willow borer to complete its full life cycle. Typically, a single generation occurs per year in much of its introduced range. Pupation occurs in a pupal cell within the host tree, usually in the center of a stem, and most adult weevils emerge by the fall. Adults are the overwintering life stage in British Columbia, passing the colder months in the leaf litter or on the ground nearby susceptible host plants. In the Northeast, it is primarily the larval life stage that overwinters, in different instars (stages) in the sapwood of their host. By the spring and early summer, adult weevils become active on their hosts in British Columbia. In New England, the spring ushers in a period of rapid growth of the overwintered larva, causing it to resume feeding and expel multitudes of frass outside of a hole to the outside of the tree. Frass may be found clinging to the side of the trunk, or sap oozing from the holes created by the growing larvae. Trunks with frequent attacks may have many tunnels that form almost a honeycomb appearance. Pupation occurs in June. Egg laying occurs in July and August, with adult weevils most abundant in New York in August. Eggs are laid in holes or slits found on lenticels, branch bases, or near damaged bark. Eggs are white and tiny and laid for 4-6 weeks, often singly but in groups from 2-4 are possible. Occasionally, an adult weevil will survive through a second winter. Adults are most frequently active in the morning and the evening, and will "play dead" and drop to the ground if disturbed. Larvae are C-shaped in appearance, and 0.24 inches long.  

Damage to Host: 

Adult poplar-and-willow borer weevils feed on green, smooth bark found on shoots. They chew small holes in the bark, and cause minor injury in these locations with this feeding. It is the tunneling of the larvae that is most severe, and in heavy populations can cause the trunk of the host tree to become honeycombed with damage. The bark, trunk, and branches may be impacted. This species prefers to attack young, smooth barked willows. This weevil causes holes in the bark, top die-back, and oozing sap. Expelled frass may also be found. Injury caused by this weevil may be greatest on nursery stock or newly planted young trees. Young trees may be killed or become bushy in appearance from adventitious growth. Young eastern cottonwood may produce rounded, swollen areas in response to larval feeding. These areas eventually are covered in exit or emergence holes from the weevils and scar tissue.


Visually inspect susceptible host plants that are two years or older and more than 1 inch DBH (diameter at breast height; approximately 6 ft. up the trunk). Weekly surveys may be necessary through the growing season. 

Cultural Management: 

Populus tremuloides, quaking aspen, is seldom attacked by this insect. Maintain susceptible hosts to improve overall tree health. Remove and destroy heavily infested plants where appropriate. 

Natural Enemies & Biological Control: 

The larvae of the poplar-and-willow borer may be parasitized by an ichneumonid wasp, Dolichomitus messor, however it is not fully understood to what extent this parasitoid may impact their populations. Ants and birds are also reported as potential predators (Furniss, 1972).

Chemical Management: 

Azadirachtin (NL)

Beauveria bassiana (NL)

Bifenthrin (NL)

Entomopathogenic nematodes (L)

Isaria (paecilomyces) fumosoroseus (larvae) (NL)

Metarhizium anisopliae (robertii) (NL)

Neem oil (NL)

Tau-fluvalinate (NL)


Active ingredients that may be applied systemically include: azadirachtin (injection, soil drench), Metarhizium anisopliae (robertii) (soil drench), and neem oil (soil drench).

Make insecticide applications after bloom to protect pollinators. Applications at times of the day and temperatures when pollinators are less likely to be active can also reduce the risk of impacting their populations.

Note: Beginning July 1, 2022, neonicotinoid insecticides are classified as state restricted use for use on tree and shrub insect pests in Massachusetts. For more information, visit the MA Department of Agricultural Resources Pesticide Program.

Read and follow all label instructions for safety and proper use. If this guide contradicts language on the label, follow the most up-to-date instructions on the product label. Always confirm that the site you wish to treat and the pest you wish to manage are on the label before using any pesticide. Read the full disclaimer. Active ingredients labeled "L" indicate some products containing the active ingredient are labeled for landscape uses on trees or shrubs. Active ingredients labeled "N" indicate some products containing the active ingredient are labeled for use in nurseries. Always confirm allowable uses on product labels. This active ingredient list is based on what was registered for use in Massachusetts at the time of publication. This information changes rapidly and may not be up to date. If you are viewing this information from another state, check with your local Extension Service and State Pesticide Program for local uses and regulations. Active ingredient lists were last updated: January 2024. To check current product registrations in Massachusetts, please visit: .