Control Cankerworms with Tree Banding

Cankerworms in trees can be controlled with a fairly simple method called tree banding. Some cities have control programs in place, but it is possible to maintain the control of cankerworms yourself ,with the same or similar methods they use on their public trees.

What are cankerworms?

Cankerworms are very destructive larvae laid by an adult cankerworm. These worms vary in different shades of green, from dark to light, with stripes down their backs. There are two basic types. One lays its eggs in the spring and one in the autumn. Both varieties have larvae which hatch in spring. They are a particular problem for certain varieties of ash, elm and maple. They are the most destructive in late spring or early summer, in May and June.

The cankerworms make their way up the tree and infect the crown of the tree. They move down the tree on a sticky, messy, silken web. When uncontrolled in areas with many of the affected trees the sticky webs not only create problems for the trees but make a mess on surrounding streets, cars and buildings. If the infestation is bad enough, the streets get a film of sticky substance which can make a destructive mess. (In Winnipeg in 2006, some tree areas did not get banded to prevent the spread of the cankerworms. The webs in some areas made the streets sticky enough that the ground was covered in a gooey surface. You could hear cars driving through it like cars sound driving on wet rainy streets. Car windows had to be cleaned continually. It got tracked inside from walking on the sidewalks and streets. It jammed up roll down windows. It could be felt on your skin and hair. It was coming down so thickly you could watch the webs streaming down like gossamer threads through the air. It didn't take long to have to redo what had already been cleaned up from the messes they created. ) This tiny creature can literally gum up the works woth its sticky silken webs.

The first signs of the infestation to the tree are small holes that appear in the leaves. They progressively feed on the leaves until only the veins of the leaves are left. The trees lose their green. They can grow back the foliage as the season progresses, but the damage caused by the cankerworms may stunt the healthy growth of future leaves.

What is tree banding?

The tree banding keeps the adult cankerworms from climbing the tree to lay their eggs. It is important to encourage others around you to band their trees also. The cankerworms can travel from tree to tree infesting them by flying on the airborne webs, after they are in the crowns of the trees, so even if you have treated your tree/s, if your neighbours haven't, your trees can still get infested with the cankerworms.

If the cankerworms get into the tree's crown and make these webs, then pesticides will work to remove them. It is better to use the tree banding method ,which is less destructive to the environment. They need to be banded by mid March and in September for the two types of larvae. The banding works by using a sticky substance called Tanglefoot applied to the band wrapped around the tree. The Tanglefoot traps
the climbing cankerworms, preventing them from moving further up the tree.

Tree banding is relatively simple to do, although it is messy. Place a strip of foil about 3 inches wide all the way around the tree, about 4 to 5 feet from the ground. Then spread the Tanglefoot on the band all the way around the tree. Make sure you remove leaves or other debris that get caught in the tree banding, to keep the bands working. You do need to put up fresh bands each year and remove old ones that may cause the bark to rot.