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:
Here are a few tips and resources on managing pests in stored grain from Scott Schell, UW Extension Entomologist, presented at WESTI Ag Days 2016.
Step 1: Keep bins clean and repaired
Step 2: Use residual sprays
Step 3: Store only clean, dry grain
Step 4: Aerate
Step 5: Protect the grain
Step 6: Inspect grain regularly
Guest post from Scott Schell, University of Wyoming Extension Entomologist
It is never too early in the year to think about grasshopper management. We lump all grasshopper species together but only 12 out of the 120 plus species found in Wyoming cause problems on a regular basis. Of that “dirty dozen”, the 4 species in the genus Melanoplus have the greatest ability to increase in population from non-economic levels to crop and garden devastating densities in one year. The worst species in Wyoming’s crops and gardens is Melanoplus bivittatus, the twostriped grasshopper. It can eat its body weight daily and destroy even more leaf area than it consumes. While one twostriped grasshopper alone is not significant, just 30 adults per square yard equals 200 lbs. per acre!
The major grasshopper pest species in Wyoming start hatching from eggs in mid-May and continue hatching all the way to early July. Most available treatments for grasshoppers don’t last very long so effective crop and garden grasshopper control will probably require multiple treatments as the hatch of eggs progresses through the spring.
The good news is that most crop pest grasshopper species concentrate their egg pods in field borders and non–crop areas that are weedy, uncultivated, and don’t get submerged in water. Scout those areas for hatching grasshoppers from mid- May to the end of June and treat them when necessary. This can prevent damage from adult grasshoppers moving into crop fields and gardens later in the summer. It is better to treat grasshoppers away from the crop field or out of the garden than in them. More economical and selective treatments are available for grasshopper control in non-crop habitats. This targeted control also reduces the impact on beneficial insects such as those that pollinate plants.
Stop by the Washakie County Extension office to pick up a "square foot job aid" to help you count and identify grasshoppers in the field.
Grasshopper Control in Gardens and Small Acreages - Colorado Sate University
Community Wide Grasshopper Control - Utah State University
Grasshopper Management (non-chemical methods) - ATTRA
And don't hesitate to call or email me if your have further questions!