Bronze Birch Borer, Verticillium Wilt
June 7, 2007
In this Issue:
What's In Bloom
Insect and Disease Activity
Treatment: imidacloprid (Merit and Bayer Advanced Tree & Shrub Insect Control), neem oil, Bt (Bacillus thuringiensis--Dipel, larvae only)
Treatment: acephate (Ortho Systemic Insect Killer Concentrate, Bonide Systemic Insecticide Liquid), sulfur (Bonide Sulfur Dust, Ferti-Lome Dusting Sulphur), horticultural oil (Ferti-Lome Scalecide), copper sulfate (Bonide Garden Dust, Green Light Rose and Flower Dust), malathion, or Sevin.
Adults lay eggs on birch bark crevices in early summer, and when the larvae hatch, they bore directly into the tree. There the larvae stay until they pupate and emerge as adults either the following first or second spring. The pupal chambers and sometimes the feeding appear as raised swellings under the bark.
Adults are emerging from birch trees now, leaving behind distinctive D-shaped holes on the bark. Look for these holes on your trees to determine if you need to treat your birch trees.
IPM practices to keep your birches healthy include applying adequate water and mulch over the root system, and avoiding pruning during adult flight (late May - late June).
Treatment: Protectant materials are sprayed on the bark and larger limbs to prevent larval entry, so they must be applied before egg laying: acephate (Acecap), permethrin (Hi-Yield products), Systemic insecticides can also be used (Bayer Advanced Tree and Shrub Insect Control) to kill hatching larvae and larvae within the tree.
Treatment: neem oil, horticultural oil, imidacloprid (Merit), carbaryl, or malathion.
Treatment: Controlling with chemicals can be difficult. The best option is to prune out canes and stems with obvious swellings or when they die. Destroy the debris to kill the larvae within.
If you suspect verticillium wilt, there unfortunately is no “cure.” Chronic infections can be managed with careful watering, mulching, fertilization, and pruning (i.e., TLC). If a tree dies from verticillium wilt, remove it and replant with a species that is resistant to the pathogen. These include beech, birch, fir, ginkgo, hawthorn, honeylocust, larch, oak, pine, spruce, sycamore, willow, and others.
Treatment: Make sure water from irrigation does not land on the upper tree canopy; prune out any cankers you find (these are easiest to see in the dormant season); apply a copper fungicide after leaf fall in autumn.
Precautionary Statement: All pesticides have benefits and risks, however following the label will maximize the benefits and reduce risks. Pay attention to the directions for use and follow precautionary statements. Pesticide labels are considered legal documents containing instructions and limitations. Inconsistent use of the product or disregarding the label is a violation of both federal and state laws. The pesticide applicator is legally responsible for proper use.