By Linda Williams, Forest Health Specialist, Woodruff
Linda.Williams@wisconsin.gov, 920-360-0665
Red turpentine beetle and pine root collar weevil both attack pines near ground level. So, how can you identify them and differentiate the damage?
If you prefer the abbreviated version, check out the table below. For more details, read further and be sure to check out the photos.
| |
Pine Root Collar Weevil |
Red Turpentine Beetle |
| Hosts |
Pines |
Pines, tamarack, spruce, fir
|
| Tree size |
Younger pines (generally less than 8 inches diameter at breast height). |
Larger trees (generally greater than 8 inches diameter at breast height)
|
| Location of damage |
Ground level and below |
Lower 1-3 feet of the trunk
|
| Signs and symptoms |
Trees leaning heavily or broken over at the base. Black, pitchy soil at base of tree. Black, pitchy, sunken area at base of tree. |
Scattered trees in a stand decline and die. Pitch tubes near base of tree
|
| Prevention |
Maintain stocking and crown closure to prevent grass and weeds around the base of trees. |
Keep trees healthy
|
| Management |
Remove grass and weeds from base of trees. Prune lower branches to increase air flow. Insecticides may be an option. |
Salvage |
Pine Root Collar Weevil
Damage at the base of young red pine, by pine root collar weevil can weaken it and trees with green needles can suddenly break over. / Photo Credit: Wisconsin DNR
Pine root collar weevil prefers younger pine stands that are open, with grasses or weeds near the bases of the trees to give the insects additional protection. Pine root collar weevil will attack red, jack, scotch and Austrian pine, but rarely white pine.
Pine root collar weevil damages roots and creates a weakened area of the tree at ground level. Damaged trees can break over at ground level if damage is on the trunk or may just lean heavily if roots are damaged and can no longer keep the tree upright.
To look for pine root collar weevil pull the weeds, duff and soil away from the base of the tree and away from the major roots. Infested trees will have black pitch-soaked soil around the base. Removing the bark from the root collar area and from the major roots, will show boring damage from pine root collar larvae just under the bark. The base of the tree may be slightly sunken where weevil larvae have been feeding under the bark.
Management options depend on the age and stocking of the stand when you notice the infestation. Planting at the proper depth and maintaining good crown closure to minimize the amount of grass and weeds around the base of trees can help prevent infestation. If you already have an infestation, eliminating weeds and grass around the base of trees and/or pruning lower branches can increase air flow to dry out the base of the trees and make them less attractive to the weevils.
Looking closely at the base of a tree being attacked by pine root collar weevil shows blackened pitchy dirt around the base of the tree. / Photo Credit: Wisconsin DNR
Red Turpentine Beetle
Pitch blobs near the base of a red pine indicate attack by red turpentine beetle. / Photo Credit: Wisconsin DNR
Red turpentine beetles generally prefer pine trees that are pole-sized and larger. They attack the lower 2-3 feet of the trunk of pines that are under stress, but can also attack stressed tamarack, spruce and fir. The original stressors could be abiotic, such as drought, flooding or fire, could be due to stress from thinning, or from trees being planted too deep or off-site.
Look for pitch tubes around the base of the tree. Adult beetles bore into the bark to lay eggs under the bark, and the tree will start to exude pitch, which the beetles push out to create a blob of pitch called a pitch tube. Pitch tubes will last for many months to years and are a noticeable clue indicating attack.
Larvae feed under the bark. The damage they do can girdle areas, which puts additional stress on the tree. If multiple pitch tubes are noticed at the base of a tree, the damage could be severe enough that Ips bark beetles could attack the tree and kill it.
Red turpentine beetle can also carry the spores of Leptographium root disease and, when introduced to a red pine, the disease can begin to spread through the roots and create expanding pockets of mortality, referred to as Red Pine Pocket Decline And Mortality.
Maintaining tree health is the best way to prevent attack by red turpentine beetles. When stress is severe, and attacks are numerous, salvage of trees may be necessary.
