PINE ROOT COLLAR WEEVIL

Fallen pine tree damaged by pine root collar weevil. 

Photo: Manfred Mielke, USDA Forest Service, Bugwood.org

 Although this is more of a pest in Christmas tree plantations, every once in a while we come across pine root collar weevil damage on landscape trees.

Pine root collar weevil will attack both young and large pine trees. Host trees include Scotch pine, Austrian pine, red pine and occasionally white pine.

The larvae feed in the phloem tissue around the root collar, killing the cambium in the process. This girdling of the tree will eventually cause them to die. Pine trees weakened by root collar weevils may fall over and die one to four years after being attacked. Larvae complete development in June and July and adults emerge from July through September. After emerging, adults will feed on the trees for a short time before moving to sites to overwinter. Adult root collar weevils overwinter in the soil and in bark crevices.

It’s fairly easy to determine if your tree has been killed by pine root collar weevil. Dig around the base of the tree at the soil line. If it is root collar weevil, you will find black pitch-coated bark at the root collar and just beneath the soil. Digging around the tree you might even find yellow-white, C-shaped larvae up to a third of an inch long with an amber brown head.

 Pine root collar weevil damage at base of small pine tree. 

Photo: Steven Katovich, USDA Forest Service, Bugwood.org 

If pine root collar weevil is found then you should check around the base of any other pine trees on your property. Treatments can be made to reduce or prevent root collar weevil damage to your other pine trees.

There are two periods during the growing season when pine root collar control treatments can be applied. The first is with a soil drench around the base of the tree in mid-May. The next control window will be when the majority of emerging adults are active, mid-August to the first week in September. Apply insecticide to the foliage at this time.

Pine root collar weevil (pupal life stage) in its feeding tunnel. 

Photo: Joseph OBrien, USDA Forest Service, Bugwood.org  

GLOBS OF SAP ON PINE TREES

An often unnoticed insect pest that attacks pine trees is the Zimmerman pine moth. This tree borer often goes undetected because homeowners don’t think that the sap on the trunk of their pine tree is unusual. Another problem with finding Zimmerman pine moth damage is that the foliage of the pine tree conceals the damage from view.

Zimmerman pine moth isn’t as damaging as some tree borers in Michigan, but the feeding does disrupt the vascular system of the tree. Because this borer is often present where branches meet the trunk it is not unusual to have pine branches break because of Zimmerman pine moth feeding.

Spraying to control Zimmerman pine moth is done early in the spring. Most borer sprays for this tree insect are done in April, sometimes treatments can extend into early May if we have a cool spring.

You can learn more about Zimmerman pine moth at:
http://www.owentree.com/Zimmerman_Pine_Moth.php

Zimmerman pine moth damage on white pine tree

2016 FOREST HEALTH REPORT

The Michigan DNR has released an updated report on the health of Michigan’s forests. The report includes threats that could come from insect and disease pests.

While some of the pests discussed aren’t common in the landscape, there are several that could affect your landscape trees. Hemlock woolly adelgid, oak wilt and Asian longhorned beetle are three pests everyone in Michigan should be aware of and on the lookout for.

The report can be found at: http://www.michigan.gov/foresthealth

OAK WILT FOUND IN DETROIT

 The discovery of  oak wilt on Belle Isle in Detroit emphasizes the need to prune your oak trees during the dormant season.

Oak Wilt found in Detroit