CANKERWORM CONTROL

OTHER CONSIDERATIONS

STEP 1 Should I band this year ? 

• The City of Charlotte implemented an aerial spray several years ago which is probably responsible for a drop in the population. The City makes a decision each fall as to whether to spray or not spray.

• If you are living close to a street that the city has black-banded, it is probably best to go ahead and band your trees. 

• If you had very low numbers last year you may not need to band or band a single tree to monitor them.  More than 30 cankerworms in a trap for a large tree is considered high. 

• The cankerworm is native to the U.S. so it could occur anywhere in North Carolina.

STEP 2 Understand the fall cankerworm 

            BIOLOGY                   HOW IT EFFECTS TREES           TYPES OF TREES AFFECTED

                BIOLOGY

• The fall cankerworm (Alsophila pometaria) is a moth native to North America. Its natural range is from Georgia to Nova Scotia and west to Texas. It has a four stage life cycle: egg, pupa, larva (caterpillar), adult.

Eggs, wingless female moths and winged male moths  trapped in cankerworm band	One inch long greenish cankerworm caterpillars. Note different colors and how small they are.

• The first cold snaps in early winter (November, December) cause the adult moths to leave their cocoons in the ground. This usually occurs during the third or fourth week in November.

• The females crawl up any nearby vertical object to lay their eggs. They climb all species of trees, street lights, houses, etc. When climbing trees, the females always climb to the highest branches. 

• This climbing habit is why we place the Tanglefoot bands on the trees. When the females are trapped, we prevent the laying of thousands of eggs. The more traps installed, the greater reduction in the cankerworm population.

• The caterpillars emerge as soon as the leaf buds begin to open in late February and early March. The cankerworm caterpillars are small inch worms, generally 1/2 to 1 inch long. The population often has two colors: a light green and a dark forest green.

• Once hatched, the cankerworm caterpillars immediately feed on the unfolding buds.

• In response, trees will send out new buds and new leaves. The cankerworm may consume several refoliation attempts by the tree in a matter of weeks.

• The cankerworm caterpillar feeding lasts from early March to late April. When the worms have finished, they drop to the ground by threads, burrow into the soil, and form a cocoon.

• A final note is that cankerworms can "balloon" to other trees. They are very light, and can be blown from one tree to another. This is why it is important for neighbors to organize when banding. 

HOW IT EFFECTS TREES

• After mating in December, the female moths crawl up trees such as willow oaks to lay their eggs on twigs and small branches. As the trees leaf out in the spring, the eggs hatch leaving small green caterpillars to feed on the leaves. 

• In most cases, the cankerworm will not kill the trees; however, repeated defoliation can weaken trees, and make them more susceptible to borers and root rot. This is extremely important on large trees because the trees become hazardous from repeated defoliation. 

TYPES OF TREES AFFECTED

• It affects all deciduous trees and shrubs (trees that loose their leaves in fall) 

• It may affect some soft-leaved evergreens like azalea

• Conifers (pine, cedar) and tough-leaved evergreens like magnolia are NOT affected.

• In Charlotte, it seems to prefer the oaks.

• It may kill small trees such as cherry and dogwood in a single year

STEP 3 Distinguish  from other caterpillars 

• Many people incorrectly believe they have cankerworm

• Please use the chart below to determine what you have

• Banding will NOT work for other caterpillars

CATERPILLAR	DESCRIPTION	PHOTOS		season caterpillar appears
cankerworm	1 inch long greenish	see photos in STEP 1		mid-Feb to mid-April
oakworm	2 inch long. Black with two yellow stripes and black horns on head only feeds on oak			July to Sept
tent caterpillar	Forms dense white tents. 1.5 inch black with white stripe along middle Only feeds on cherry, apple, plum			mid-Feb to mid-April
bagworm	brown foliage bags surround caterpillar only affects cedars, junipers, leyland cypress			May to Aug (bag present all year )
fall webworm	makes huge webs that surround entire limbs			July to Sept

STEP 4 Band for cankerworm 

• Apply bands in late November to your large trees, especially oaks.  Small trees can also be banded, however, cankerworms on larger trees can drift to the smaller ones.  

• Remove bands in February.

• Tree banding in late November is an effective way of controlling the cankerworm. By applying a glue barrier to the tree trunk, the wingless cankerworm moths are trapped as they climb the tree. This method is effective only for cankerworms. For best results, trees should not be banded before the third week of November.

• The glue, Tanglefoot, should be applied after most of the leaves have fallen. If the trap becomes clogged with leaves or insects, you should clean it, renew the Tanglefoot or install a new trap. The bands should be removed during the first week in February.

• The following materials are necessary and can be purchased at most hardware and garden stores:

  • Staples, staple gun, disposable elbow length gloves, roofing felt, cotton batting or fiber glass, Tanglefoot (glue) and a putty knife. For small trees you can substitute electrical tape for the staples. Do NOT use nails for any trees !

  • Step 1: Install a strip of cotton or insulation around the tree between the ground and the lowest limb. 

  • Step 2: Position a band of roofing felt or plastic over the strip and attach it to the trees with the staple gun. Avoid using staples on small, young, or thin barked trees. Instead use electrical tape to hold the bands.

  • Step 3: Using disposable gloves and a putty knife, put a film of Tanglefoot (Glue) directly on the band, 1/16" thick. 

STEP 5 Keep trees healthy

• Water Keep trees, large and small, watered once or twice per week by rain or by hand during summer drought. Water from the trunk out to as far as the branches extend. Do not over water. 1 inch of water from a sprinkler or soaker hose is fine.

• Mulching Many of the tree's absorbing roots are in the top few inches of the soil. Grass and other plants compete with the tree roots for water and minerals. Mulch should be no more than 4 inches deep, and should not be placed against the trunk. Mulch should extend for a least 5 feet on each side of the trunk, with more mulch used for larger trees.

• Fertilizing A slow nitrogen release fertilizer with micro-nutrients and a low salt index should be applied in mid-February. Your local garden store or the North Carolina Cooperative Extension Service can help you. Reminder: 10-10-10 is not a good fertilizer for trees. Fertilizer spikes are not effective.

• It may be helpful to obtain advice from a certified arborist. Call the North Carolina Cooperative Extension Service for details.

• Harmful practices Tree topping, improper pruning cuts, soil compaction, soil tilling and disturbance, construction, and new irrigation lines greatly decrease the health of trees.

City of Charlotte monitoring of cankerworm 

• Each December the City of Charlotte has  a number of stations throughout the city in which they count the number of females caught per trap.

• These figures are used to determine the severity of cankerworm attack in the spring. If numbers are high enough they may do an airplane spray. 

• When the Fall Cankerworm populations are high enough to endanger our trees, the city may propose to spray the infested areas air by plane or helicopter. This is done only as a last resort in order to protect our tree canopy and only with the approval of the NC Department of Agriculture.

• The pesticide used is B.T. Baccillus thuriengiensis. This is a naturally occurring bacteria that has been used by organic farmers and gardeners for decades. This natural control has no adverse affects to humans, honey bees, pets, wildlife, fish or groundwater.

• B.T. is sprayed in early spring to kill the Fall Cankerworm. When the caterpillars eat the leaves, the BT will kill the worm within a few days. 

Does the City, County or other Towns help fund banding trees on private property ?

NO 

Homeowner chemical control

• Landscape professionals or homeowners with a sprayer can treat cankerworms. They are easy to kill. Any pesticide registered for caterpillars (and most are) can be used. 

• If you decide to spray, you must treat as soon as they emerge (early March). By late April, you've wasted your time. 

• Astro, Orthene (acephate), Diazinon, and liquid Sevin can be used. 

• If you want to go organic, insecticide soaps or B.T. (dipel, thuricide) can be used. Two applications 5 days apart would be necessary. You must get them when they first emerge. Once they become large, B.T. is ineffective

• Injections can be effective, but is usually expensive and must be repeated each year. 

• Use only an ISA certified arborists with an NCDA pesticide applicator license. 

• For fruit trees, make sure that the product is labeled for caterpillars on fruit trees. 

Why does Charlotte have a cankerworm problem ?

• According to scientific literature, the cankerworm will periodically appear in large numbers but will soon be reduced to normal numbers by natural controls such as birds, insects, enemies, and diseases.

• Unfortunately, Charlotte is now experiencing cankerworms in high numbers. Natural controls have not been adequate to bring the cankerworms to a level that isn't harmful to our tree canopy. Entomologists cannot explain why this is happening to Charlotte but the city's large concentration of old willow oaks may promote the infestation. 

• The next emergence of adults is November with caterpillar emergence in late February. The population has decreased but banding in highly infested areas is still encouraged.

Contacts 

• For questions about trees on private property, contact the North Carolina Cooperative Extension Service at 704-336-2561. 

• For questions about trees on the City of Charlotte right-of-way or questions about spraying by air plane contact the City Landscape Management Office at 704-336-4262.

Recommendations for the use of chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by the North Carolina Cooperative Extension Service nor discrimination against similar products or services not mentioned. Individuals who use chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage and examine a current product label before applying any chemical. For assistance, contact your county North Carolina Cooperative Extension Service agent.