Category Archives: Tree Pests

There’s a New Plant Villain in Town Called the Azalea and Rhododendron Lace Bug

Are you wondering why some of your rhododendrons and azaleas are taking on a shabby whitish-yellow look as if some graffiti artist snuck into your yard and airbrushed them with paint while you were asleep? Or maybe you think they sport a pale coat because you neglected to fertilize them, or maybe…. Well, it’s none of the above. These ornamental shrubs look this way because there’s a new villain in town that’s literally sucking the life out of your plants, and it’s called the lace bug, and it’s not going away. Let’s introduce you to your new, not so friendly neighbor is and what you can do about it this pesky little insect.

What is azalea and rhododendron lace bug?

The lace bug is a tiny insect that uses its piercing-sucking mouthparts to suck the sugars of the green chlorophyll out of the leaves of broadleafed evergreen trees and plants. This action causes significant damage to the leaves by reducing their ability to produce food for the plant. If the lace bug infestations is severe, this can weaken a plant thus stressing it to the point where it becomes more susceptible to other pests and diseases. We will discuss what you can do to protect your plants from this bothersome pest.

At one-tenth to three-eighths of inch long, the adult lace bugs are whitish-tan in color with a thorax (body)and transparent wings sculptured with an intricate pattern of veins that resembles lace. There are approximately 140 varieties of lace bugs in North America. The one that feeds primarily on azaleas has smoky brown markings on its wings, which distinguishes it from the pale whitish-tan rhododendron (or rhody) lace bug. The juvenile lace bugs or nymphs, which emerge in the spring, are colorless to black in color, pointed on both ends and may have spines depending upon their age. 

What is the life cycle of the lace bug?

Lace bugs are a hardy creature that can overwinter under bark scales in trees. They also lay eggs along the mid-ribs on the underside of leaves that resemble crusty brown patches. Depending on the temperatures, they can emerge anytime from mid-April to early June. The warmer the spring, the earlier they will hatch.

Adult lace bug

 They primarily spend their lives feeding on the underside of leaves. 

What plants do lace bugs attack?

To this date, here is a list of plants that lace bugs are finding delicious. This list seems to be growing.

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Why Do Mature Trees Suddenly Die?

Why did my mature conifer (cone bearing) or deciduous (trees that lose their leaves in the fall) trees suddenly die? Arborists often get asked this question by grieving tree owners. This question deserves a serious answer, since an unbreakable bond exists between humans and trees, and when that link is unexpectedly broken, there are negative consequences for humans and the environment. This is because trees have such a large impact on our lives and often impact all types of human activities. Moreover, whether we are consciously aware of it or not, our lives are intertwined with trees, and even depend upon them for our survival, and when we lose them there are economic, social and cultural, emotional and environmental consequences. If we understand why trees die, maybe we can proactively help to keep them alive.

So why do trees die? And if we understand the reasons why they die, perhaps through wise and knowledgeable actions on our part, we can help to keep the trees in our lives alive longer. After all, as caretakers of this planet, it is our responsibility to care for the small piece of real estate over which we’ve been given stewardship including the trees on it. Face it, the simple fact is that without trees, all animal and human life will die!

With these things in mind, many years ago, as a tree care professional—in the industry, we’re called arborists—I felt that I was taking out too many trees that I knew were savable. Therefore, I rolled up my sleeves and got the necessary education, credentials, licenses and then purchased the equipment to begin providing plant health care services in my tree care company. Since then, I have saved hundreds, if not thousands of trees from their demise. This has been a rewarding activity for me on many levels.

But along the way, I have found that there is a belief among many of my clients that all trees have a life span and eventually grow old and die. For many people, this seems to explain why their yard tree suddenly died. Yet, in my decades as an arborist, I have found this belief usually to be unfounded. Since there are so many variable factors that contribute to tree mortality, it’s often not easy to determine why a tree has died without conducting extensive and costly forensics. Suffice it to say, many of the factors listed below combine to stress a tree, and if the tree doesn’t possess a sufficient reserve of stored energy to combat its stressors, it will eventually succumb to these stressors. Almost everything that a tree does is in slow motion. It grows slowly, its metabolic processes occur slowly and it usually dies slowly as well. On occasion, a tree dies quickly (in a few weeks or months), but this is rare. Like the rest of us, a tree has a strong survival instinct and wants to live. In fact, it contains many built in mechanisms to insure that it survives come what may. So to say that a tree has a certain life span and then it just dies is a misnomer. True, some trees are able to live for hundreds, even thousands of years, while other trees are relatively short lived, by comparison. But under the right conditions and with the right care, nearly any tree you plant in your yard can outlive you and probably your grandchildren too.

The Reasons Trees Die

So now let’s discuss why trees. The following is a list of some of the more common reasons of tree mortality.

Drought. Like humans and all animal life, plants need water to survive. No water, no life. Trees suck up an immense amount of water out of the soil on a continual basis, especially during the growing season. If they don’t obtain the water they need, the go into stress mode. If this continues long enough, they will slowly die of thirst.

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Did someone shoot your ornamental flowering fruit trees with a shotgun?

Identifying and Treating Flowering Plum, Cherry and Apple Trees Leaf Blights

In the spring and early summer in the Portland and Wilsonville region, do the leaves on your fruiting or ornamental plum, cherry (Prunus spp.) or flowering crab apple (Malus spp.) trees look as if someone was using them for target practice with a shotgun? Are the leaves all peppered with a gazillion small holes? 

Not to worry, your miscreant neighbor doesn’t have a vendetta against either you or your trees. However, an airborne fungal pathogen called coryneum blight or “shothole fungus” is most likely the culprit for the cherry and plum trees. For crabapple trees, a different fungus called apple scab with similar symptoms as coryneum blight is likely the guilty party. 

On the flowering cherry and plum trees, “shothole fungus” (Thyrostroma carpophilum formerly called Wilsonomyces carpophilus) overwinters in dormant infected leaf buds, blossom buds and Continue reading