Like humans and other animals, trees are susceptible to a variety of pests and pathogens. Bacteria and fungi will feed on their tissues, while some viruses will take over a tree’s very cells for their own purposes. And while they aren’t bothered by mosquitoes and similar pests, trees are regularly attacked by aphids, caterpillars and other problematic creatures.
The amount of harm inflicted by these pests and pathogens varies based on a number of factors. Some of these organisms may only cause minor stress for trees, while others can quickly overwhelm a tree’s defenses and cause a rapid death.
The health and species of the afflicted tree are also important factors that play a role in the progression of the disease. Robust, established trees can typically muster an adequately robust response to fight off some pathogens, and some tree species (and cultivars of a given species) are simply more resistant to some bugs and germs than others are.
But one thing is true in all cases: Immediate assessment by a qualified and experienced arborist is imperative.
Many tree pathogens and parasites can be alleviated with prompt action. Even if your trees can’t be treated, you’ll want to take immediate steps to prevent the problem from spreading to other trees and have any terminally afflicted trees removed before they represent a safety hazard.
Signs and Symptoms of Insect Infestation and Disease
- Crown dieback (the progressive death of a tree’s canopy)
- Stunted or slow growth
- Premature color change
- Premature leaf drop
- Poor crop yield
- Misshapen or discolored fruit
- Wilted leaves
- Discolored leaves
- Exudates (liquids or jelly-like substances emerging from the bark)
Unfortunately, many of these symptoms can also indicate other tree health problems. Crown dieback, for example, can occur in response to pests, pathogens or environmental factors, such as root damage or inadequate water. Only an educated tree-care professional can accurately identify the causal organism, which further demonstrates the importance of soliciting professional help anytime your tree exhibits the signs above.
Assessment and Care Regimens: What to Expect
Upon noticing any of the symptoms or signs listed above (or anything else that looks unusual about your tree), you’ll want to contact a professional arborist.
The arborist will visit your property and inspect the tree in question. Often, he or she will also glance at the other trees in the area too. The arborist will catalog the symptoms present, which will help him or her determine what pest or pathogen is present.
Sometimes, a positive identification can be obtained through nothing more than visual inspection. However, some pests and parasites will require the arborist collect samples, which can then be shipped off to a lab for analysis. This usually only takes a few days, but some diagnostic procedures can cause this part of the process to last for a few weeks.
Once the arborist has determined the root of the tree’s struggles, he or she can recommend an appropriate treatment strategy. This may involve things like the selective removal of branches or the application of antibacterial or antifungal medications. In some cases, simple supportive care will allow the tree to fight off the infection on its own.
Complete removal is sometimes the best course of action, but most arborists will consider this a last resort, which should only be undertaken when the odds of recovery are low and the threat of spread high.
Some of the Most Common Tree Pests and Pathogens in Southern California
Southern California’s warm and sunny climate certainly makes the region popular among humans and it allows residents to plant many trees hailing from tropical regions, but it also presents a perfect home for a wide variety of insects and other threats.
Some of the most noteworthy threats include:
à The Asian citrus psyllid(Diaphorina citri) is an introduced insect hailing from Southeast Asia that feeds on the foliage of citrus trees. However, while the feeding damage caused by this insect is problematic, the greater threat is the disease – Huanglongbing or Asian greening disease – that they can carry and transmit.
àPolyphagous shot hole borers (Euwallaecea spp.) are tiny insects that bore beneath the bark of trees, where they feed and deposit eggs. Like the Asian citrus psyllid and some other insects, the bulk of the harm caused by these bugs relates to the diseases it carries with it – a pathogenic fungus (Fusarium euwallacea), in this case.
à Some tree pathogens are flexible enough to attack many different species. But others, such as Xylella fastidiosa — the bacteria responsible for oleander leaf scorch — tend to attack a single species or group of closely related species. This disease can be spread via the activities of several tree-feeding insects, which makes it difficult to prevent or stop.
àThe gold-spotted oak borer (Agrilus auroguttatus) is a small, invasive insect species that attack the oak trees of our region. However, this insect shows a distinct preference for red and intermediate oaks; white oaks are almost never attacked by the insect. The tunnels created by these insects cause massive physical trauma to the trees they attack.
àPalms also fall victim to pests and pathogens, such as theSouth American palm weevil (Rhynchophorus palmarum). Most of the damage inflicted by these insects occurs during the larval stage, as the insects feed on the palm’s tissues. However, they are also associated with the spread of red ring disease, which also causes trouble for palms.
While the organisms listed above are among the most common and noteworthy found in our region, there are hundreds of other invertebrates, bacteria, viruses and fungi that can attack the trees of Southern California.
The Importance of Immediate Action
If you suspect that one of your trees is suffering at the hands of bacteria, fungi or bugs, give your friends at Evergreen Arborist Consultants a call. One of our experienced arborists will visit your property at your convenience and take the steps necessary to identify the causal organism.
From there, we’ll recommend an appropriate treatment, taking into account the tree’s health, the responsible insect orpathogen and the likelihood that the disease will spread. We’ll also factor in your goals and desires, as well as your budget to determine the best possible outcome.
Just remember: Tree pests and pathogens can cause quick and irreparable harm if ignored, so call (213-293-2444) or email us ([email protected]) today to give your trees the best chance at a recovery.