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Hylobius radicis

Pine root collar weevil larva. Photo: James B. Hanson, USDA Forest Service, Bugwood.
Scientific Name: 
Hylobius radicis
Common Name: 
Pine Root Collar Weevil
Growing Degree Days (GDD's): 
618-912 GDD's, Base 50F, March 1st Start Date (Source: Cornell Cooperative Extension.)
Host Plant(s) Common Name (Scientific Name): 
Austrian pine (Pinus rigida)
Jack pine (Pinus banksiana)
Mugo pine (Pinus mugo)
Red pine (Pinus resinosa)
Scotch pine (Pinus sylvestris) *Most susceptible.
Pitch pine (Pinus rigida)
White pine (Pinus strobus) *Mostly resistant.
Insect Description: 

The pine root collar weevil, Hylobius radicis, is very similar to the pales weevil, H. pales. However, unlike the pales weevil, it will attack both young and older pines. Healthy, open-grown trees, such as those found in nurseries or plantations, are fed upon by this insect. Adults and larvae feed at the root crown of their hosts on the inner bark. Adults are dark brown weevils (1/3 to 1/2 inch in length) with elongated snouts and small patches of pale colored hairs on the elytra (hardened wing covers). Mature larvae are c-shaped, 1/2 inch in length, whitish in color with brown head capsules. Occasionally, adults may be found feeding on the bark of small twigs and branches in the crown at night, particularly near wounds. Adults may also move on the ground from tree to tree at night. Overwintered females emerge in May and begin egg laying, which may last through September (peak egg laying may be in or around mid-to-late June). In a feeding wound in the inner bark of the root collar is where the eggs will be laid. Occasionally, females lay their eggs in the soil just a few centimeters from a root. Females lay on average 18 eggs the first season, and 15 eggs the second. Eggs hatch and the larvae of the pine root collar weevil feed in the bark phloem. Larvae may pass through up to 7 instars (molts). A large build-up of pitch from resin flowing from feeding wounds in the outer and inner bark may be found at the base of the tree and into the surrounding soil. All life stages of the weevil are found throughout the growing season. Pupae are not formed in the typical chip cocoons created by most weevils. Instead, they form a pupal cell in the soil or in the gallery of the bark of the root collar. It may take 2-4 years for infested trees to succumb to the attack by this insect. In fact, it may take almost two years for this insect to complete its life cycle.

Damage to Host: 

Susceptible hosts growing on poor sites are preferentially fed upon by this insect. Larval feeding causes a swollen trunk at the soil line, if in large populations. Bark at base of trunk and soil surface 8 inches from the trunk of susceptible hosts may show signs of activity from this insect. The damage from the pine root collar weevil can be moderate to severe depending upon the site conditions, host plant, and other stressors. Eventually, the entire tree may appear loose in the soil, lean, or perish after several years of yellowing and browning. Trees that are not killed may be weakened and more susceptible to secondary insect attack and breakage in the wind.


Look for black, pitch-soaked soil around the root collar of the tree, especially trees that appear off-color. Rocking smaller trees by hand (when safe) may reveal trees that are loose in the soil. White resin may be present in this area as well. Check for legless, white larvae or pupae beneath the bark at the base of the trunk or nearby in the soil. Pitfall traps baited with both ethanol and turpentine may catch overwintered adult females (Hunt and Raffa, 1989; Rieske and Raffa, 1993). 

Cultural Management: 

Pitch pine is somewhat resistant to this insect, and the pine root collar weevil rarely attacks eastern white pine. Scotch pine is preferentially attacked. Do not plant this host near other pine species, especially in areas where this insect has historically been problematic. In certain situations, removing leaf litter from the base of trees, or the top 1-2 inches of soil may make this area less desirable for adult activity or egg laying. For example, heated soils may be lethal to this insect. Sod layers around the base of trees do not appear to influence infestation by this insect (Maki, 1969).

Natural Enemies & Biological Control: 

Larvae beneath the soil may be protected from certain natural enemies by pitch and the soil itself. Very few reports of larval parasitoids are noted (Coeloides sp.; Finnegan, 1962) (Bracon radicis; Shenefelt and Millers, 1960). Finnegan (1962) also reports 15% mortality of the pupae of this insect following a month of heavy rain. Infrequently, it is reported that carabid beetles may feed upon the adult weevils. Overall, high survival rates of all life stages of this insect are reported, which may mean it is relatively protected from natural enemies.

Chemical Management: 

Acephate (NL)

Azadirachtin (larvae) (NL)

Beauveria bassiana (NL)

Bifenthrin (NL)

Clothianidin (NL)

Entomopathogenic nematodes (L)

Flonicamid+cyclaniliprole (N)

Tau-fluvalinate (NL)

Gamma-cyhalothrin (L)

Isaria (paecilomyces) fumosoroseus (NL)

Lambda-cyhalothrin (L)

Metarhizium anisopliae (robertii) (NL)

Neem oil (NL)

Permethrin (L)


Active ingredients that may be applied systemically include: acephate (injection), azadirachtin (injection, soil drench), clothianidin (soil drench), cyantraniliprole (soil drench, soil injection), 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: .