Insect Pests We’re Noticing Now – Cankerworms

If you’ve been outside in the past week or so, you’ve probably noticed little green inchworms. While my 9 year old daughter thinks they’re adorable, they are actually pests called cankerworms. Two species, spring and fall cankerworms, hatch in early spring. The larvae (those inchworms we’re seeing) feed on young leaves before dropping to the ground on a silk thread. The larvae then pupate in leaf litter through the summer. When the adults emerge, the females climb trees and deposit eggs on twigs. Fall cankerworm adults climb in October – November, while spring cankerworm adults emerge in early spring.

While these cankerworms will generally not kill a tree, they can defoliate enough branches to cause the tree to be unsightly, and could potentially weaken trees.

While control of these pests would be difficult and costly at this time of year, banding your trees and applying a sticky substance called Tanglefoot (TM) in the fall can trap the adult females and prevent them from laying eggs. This video from NCSU shows how to apply the bands to a tree. Workshops have been held in Durham during previous fall months, and will be publicized here when scheduled in the coming autumn.

Plant a Tree

If you spend any time on social media, you’ve seen the ice bucket challenges that friends, family, and celebrities have shared online. In his video, actor Vin Diesel issued another challenge to viewers – this time to plant a tree. (Go ahead, look for the video online). If you’re thinking of planting a tree this fall, whether in response to this challenge or because you just want to add to your landscape, take a look at this graphic from Clemson University. Give your new tree a good start by following these planting instructions.


Trees in the Urban Landscape

Trees in the Urban Landscape

Sunday, Jun 22, 2014 3:00pm – 4:00pm 

Where:Durham County Library – South Rgeional Branch, 4505 South Alston Ave. Durham, NC

Trees are wonderful! They provide shade, produce oxygen, enhance our property, and refresh the spirit. Learn which ones to choose, how to plant them, & what errors to avoid. Presented by Gene Carlone, Durham County Extensiion Master Gardener. Class is free, registration is required. Call 919-560-7410

Mulch, But Not Too Much

By now, you may have noticed piles or bags of mulch in landscapes all over the area. Last year, I wrote about some of the reasons why mulch is beneficial (see article here: However, you CAN have too much of a good thing with mulch.

Hardwood or pine bark mulch is a commonly used material in our area. Experts recommend adding a 2-3” deep layer around your plants, which helps to slow water evaporation from the soil, keeps soil temperature more even, and reduces germination of weed seeds, among other benefits. So, if 2-3 inches is good, would more mulch be better? The answer is no. Adding a deep layer of mulch can be harmful to plants. A thick layer of mulch may keep moisture from rain or irrigation from reaching the soil where plant roots are growing, limiting the amount of water the plants can use. During wet periods, a heavy layer of mulch can slow evaporation, keeping the soil waterlogged. Plant roots require oxygen as well as water. A heavy mulch layer can keep roots growing in the soil beneath from getting enough oxygen from the air. Oxygen starved plants will decline over time.


Photo: Cornell University

Trees are frequently victims of overmulching. The practice of piling mulch around trees forming a “volcano” of mulch is common but harmful. As mentioned in the previous paragraph, too much mulch can keep water and oxygen from reaching roots. To compensate, trees may develop roots in the mulch volcano, where oxygen and water are plentiful. These shallow roots grow through the mulched area and can circle the tree. As a tree grow in diameter, the circled roots can strangle the tree, causing decline and death.



A thick layer of mulch around a tree also can trap moisture around its bark.  Like all wood left in wet conditions, the tree bark will begin to rot over time. Decaying bark can be an entry point for fungi and bacteria as well as insects that can further damage the tree. That pile of mulch is the perfect cover for insects and rodents to hide while gnawing on trees, too.

How to KillaTree

To correctly mulch around a tree, keep the mulch a few inches away from the trunk of the tree. Many experts recommend mulching an area 3-4 feet in diameter around a newly planted tree, increasing the diameter as the tree grows.

If parts of your landscaping still have the recommended 2-3” layer of mulch, simply rake the mulch to give it a fresh appearance rather than adding an additional layer. This helps your wallet AND your plants.

-Ann Barnes