Guest post by Claire Dunne, Master Gardener and member of the Worland Tree Board.
If it weren't for the damage that scales cause to trees and shrubs, they could be looked upon merely as a marvelous part of nature's wondrous pageantry. However, that's just not the case. Scale insects have the capacity to extract plant sap, a little at a time, slowly reducing the vigor of a tree. A heavy infestation will cause stems and branches to die.
Although different species of scale can be quite different in appearance, most share the common features of being closely attached to the tree on which they feed, are covered with a waxy coating, and do not move around much. Most do not even look like insects. After all, as adults they don't possess the antennae, legs or wings of typical insects. However, scale insects can be devastating.
The method in which scale insects feed is quite different from leaf chewers. Scales are classified as one of the "piercing-sucking" insects. They insert long, threadlike mouthparts known as stylets into plant tissues and extract cell sap. As a result of this feeding, scales secrete a sweet, sticky substance called honeydew, which drops on the surfaces of plants below the infected tree (or cars and picnic tables). The honeydew is attractive to other insects, especially ants and wasps.
Damage from scales is twofold: the aforementioned loss of tissue in the tree canopy, as well as the weakness that they cause. Trees stressed from scale insects become more attractive to borers, spider mites and other insect pests as a result of the stress caused by their feeding.
The lecanium scale is sometimes referred to as the terrapin scale because of its turtle-like appearance. This scale insect occurs on numerous tree species including oak, maple, ash, redbud, fruit trees and linden. Infestations on terminal branches will sometimes kill the new growth.
Mature female scales are convex, oval, usually brown in color, and about 3/16 inch in diameter. Partially grown females overwinter attached to twigs and branches. In the spring they complete development and females give birth to living young. These crawlers migrate to the leaves and settle on the midribs or larger veins. The lecanium scale has only one generation per year. Insecticides should be applied when crawlers first appear in the spring.
Monitor your plants for damage-- adult and crawler stages-- and also for activity of biological control agents. If a scale has taken a shine to your plants, look for the tell-tale signs of honeydew and sooty mold. Look for ant activity. Ants, fond of honeydew, will fight off scale's natural enemies to protect the source. Look closely, with a hand lens: these insects conceal themselves near buds, along veins, in the dark cracks of bark, underneath the leaves.
Crawlers test the sight of even young eyes. Use double-sided sticky tape to capture crawler emergence. As they emerge from their protective cover, they stick to the adhesive tape encircling either side of the infestation. When crawlers are seen, apply soaps and oils, and insect growth regulators.
Adult scales are protected by their "shells" and not affected by insecticides. However, because the crawlers do not yet have a protective cover, they are very vulnerable to insecticides (including alternatives such as soaps and oils). Some scales have extended egg hatch periods and may require repeat applications to achieve satisfactory control.
In addition to treatment at the crawler stage, some scales are vulnerable in their overwintering phase to horticultural oils used as dormant applications. These oils asphyxiate the scales. Oils should be applied in spring before plant bud break (March-April). There are temperature and host restrictions for applying these oils, so read all labels carefully. Thorough coverage is essential for achieving good control.
Here is some additional information about using dinotefuran on pine needle scale from UW Extension Entomologist Scott Schell:
The timing of the dinotefuran treatment in the spring on pine needle scale doesn’t need to coincide with the crawler hatch or activity. It is preferable to treat the tree with product early, before they hatch, though. This prevents any damage on the new needles. Dinotefuran trans-locates in trees faster than imidacloprid (an alternative product) and has given more control on the hard scale insect species experimentally. Imidacloprid is slower to move up into a tree so it is usually recommended to be applied in the fall. Imidacloprid are often not very efficacious on hard scale insects but it does provide decent control on pine needle scale for some reason.
Additional information on managing scale:
UW Extension Horticulture Specialist Karen Panter provides the following tips on Christmas tree care. Click on the image above to read the full bulletin.
For those of you who have a live tree and plan to keep it to plant in the spring, it is important to keep your tree from “waking up” and breaking dormancy. This means that you really should only keep inside for 5 days before storing it in a cold, protected area until the weather warms up enough for planting. Mulch around the base of the tree to protect the rootball from freezing, and water several times throughout the winter until spring arrives.
Additional blog posts on Christmas Cacti and Poinsettias
The Wyoming State Forestry Division recently issued an Emerald Ash Borer (EAB) advisory notice.
While the EAB has been found in trees as close as Boulder, CO, there is still no confirmation of an EAB infestation in Wyoming. At this time, the WSFD does not recommend insecticide treatments or tree removals in anticipation of its arrival.
The EAB is an exotic insect native to eastern Russia, China, Japan, and Korea that was first found in the US in 2002. It is likely that EAB was inadvertently transported to the US in packing crates made of ash wood. EAB can kill any species of ash by chewing on the inner bark, but is especially damaging to Green Ash populations.
They are quite pretty but don't let that fool you! These little bugs have already killed millions of ash trees across the country. Green Ash is one of the four most common trees in towns and parks in Wyoming, and accounts for 20-40% of community trees state wide. An EAB infestation would deal a tremendous blow to Wyoming towns and cities!
The most likely way that EAB could move into Wyoming is through the transport of firewood, raw ash logs, and nursery stock.
If you think you may have an EAB infestation in your trees, or notice signs of boring or other damage, contact the Wyoming State Forestry Division at 307-777-5495.
For more information about EAB you can also visit http://emeraldashborer.info
Spending the time to train and prune your fruit trees will help them develop a strong tree structure, improve fruit quality and quantity, and make it easier to harvest the fruit. Pruning trees when they are small is easy and fast, and you will see the benefits for many years to come.
Bulletins on Training and Pruning
Videos on Training and Pruning
Establishing and Caring for a Home Orchard
Sources for Nursery Stock
There are many sources of nursery stock. Here are two nursery's that sell good quality product. If you are aware of other sources to include on this list please let me know.
Many trees were hit hard this winter, but don't give up on them yet! It may take a season or two to recover, but many of them will bounce back. Make sure they get plenty of water this summer.
The important points to remember are:
More blog posts on Trees and Shrubs.
What kinds of trees and shrubs grow well in the Big Horn Basin, and where can I find more information?
Most of the Basin is in USDA Plant Hardiness Zones 4b and 5a. This is the standard used by gardeners and growers to determine which plants are most likely to thrive at a location based on the average annual minimum winter temperature.
The Wyoming State Forestry Division has several good resources for tree owners, including a Tree Owner's Manual and a tree symptom decoder. I have hard copies of the Manual if you would like to stop by the office and pick one up.
The Washakie Conservation District created a Tree and Shrub Guide for Washakie County which is available on their website or in print. They also recommend purchasing trees through the Colorado State Forest Service Seedling Tree Nursery.
The UW Extension Barnyards and Backyards website has a wealth of information on all things related to rural living, including tree care.
Utah State University has a fun Tree Browser website and app.
There are several fungi that cause most of the foliage diseases of trees in the Populus family (ie. poplar, aspen, and cottonwood) in this area. Fungi will overwinter in dead plant tissue infected in previous seasons, and initiate new infections during the spring during periods of high moisture and warm temperatures (72-79F).
Once an infection has been established fungicide sprays are no longer effective. Early in the spring, trees can be sprayed with a fungicide at bud-break and at 2 week intervals throughout the growing season to prevent new infections.
To prevent fungal leaf spots: