preventative tree care

leaves browning due to vert wilt

Arbor-wellness: Verticillium Wilt

We are seeing more trees this summer that look green and healthy one week and within a few weeks entire branches turn brown and leaves dry up, the most common cause of this problem is verticillium wilt. Verticillium is a soil borne root disease that usually infects through the root as they contact verticillium spores in the soil.

Many trees are susceptible to verticillium including, arborvitae, birch, crabapple, ginkgo, maple, oak, pine, spruce and tuliptree. What makes this disease so difficult is that by the time we typically see damage, the disease has spread too far and tree removal is usually the only option. Once a soil is infected it is very difficult to kill the spores, so it usually remains in the soil indefinitely. However, there are some ways to protect your trees and reduce the chance of infection.

My tree was looked good last week and now this week it has several branches with dead leaves, what’s wrong?

This is most likely verticillium wilt, which is caused by a soil fungus that can lie dormant in the soil for many years. When the roots of susceptible plants grow close to the spores, the fungus germinates and infects the roots of the plants through wounds or natural openings. The fungus spreads into the branches through the plant’s vascular system and at the same time, causes the plant cells to “plug” themselves. Once this happens, water can no longer reach the leaves and they wilt and die, often all along one or branches at a time. It often happens quite suddenly, although in some plants the leaves turn yellow or brown first.

Why is this so prevalent now?

That is a hard question to answer but yes, we are seeing more of this disease this summer and fall. Essentially, our trees are still recovering from the drought of several years back. Their root systems were compromised. The moisture this spring really encouraged new rooting and also encouraged more root diseases overall.

How can I be sure my tree has this disease?

On certain trees – maples and tuliptrees in particular, elongated dead areas of bark, called cankers, may appear on diseased branches or trunks. On most trees with the disease, the sapwood of smaller branches is streaked brown or black, occasionally in other colors too. However, since not every tree exhibits this discoloration, testing a tissue lab may be recommended to confirm the diagnosis.  

Will my tree survive?

Unfortunately, usually not.  There seem to be two forms of the disease, one in which plants die slowly over several years and another where they die rapidly within a few weeks. Trees that show minor branch wilt one year may show more the next year or may not show symptoms again for several years.

Is there anything I can do for the other trees on my property? 

There are ways to help protect your trees, particularly if they don’t show signs of the disease. First make sure the tree is not stressed – proper water and proper feeding are important here. Secondly, there are some good guy fungal species that do battle against this root disease and several others, too. The good guys inoculate onto the roots of a tree and fight and kill these fungal pathogens. (I like to use the analogy of probiotics that help our digestive system stay healthy.) But this process should start before verticillium wilt becomes established in the tree.

Our arborists at Arborwell can recommend a protective program for the trees that are susceptible on your site. Fill out the form below to get in contact with an arborist today!

preventative tree care, Prevention, root disease, tree care, verticillium wilt

Closeup of Psyllids

Arbor-wellness: Psyllids

When large trees lose their leaves in mid-summer, we tend to panic, and often for good reason. We tend to think of water problems or diseases as the main cause, but sometimes it may be a small insect that is hard to spot. Psyllids are small insects that suck plant juices and excrete sticky honeydew on which blackish sooty mold grows. Some species secrete pale or white wax masses, pellets, strands, or coverings called lerps. They affect many species of trees in our region, but the most common are Eucalyptus, peppertree, citrus, acacia, laurel and tipu or rosewood.

My eucalyptus trees are losing lots of leaves, what could be wrong?

There are several reasons why eucalyptus leaves drop their leaves in large amounts. If you see small, whitish “caps” on the leaves, this is a type of “psyllid” called “redgum lerp psyllid”. This is one many psyllid types that are common in our region.

What other damage can psyllids cause?

High psyllid populations reduce plant growth and cause tip damage, discoloration or dieback. Certain species can cause premature leaf drop. Excessive honeydew creates a sticky mess on cars and surfaces below trees.

Do psyllids damage other trees in my landscape?

There are over 160 psyllid species that occurs on landscape plants in California. Each kind of psyllid feeds only on one plant species or one closely related group of plants. Most psyllids native to California are relatively uncommon and rarely become pests. But some can cause extensive damage. These are generally psyllids that have become pests on trees that are originally from other countries. The most important tree damaging psyllids occur on acacia, eucalyptus, olive, peppertree, laurel and citrus.

I’ve heard about citrus trees dying or being taken out, is this the problem with them?

Well, sort of. A relatively new psyllid pest (Asian citrus psyllid) has been introduced into parts of California. The insect itself doesn’t kill citrus trees, but it can introduce a disease called “Citrus Greening” that is essentially fatal to them. If allowed to become widespread, it is feared the California citrus industry will be wiped out. Currently, the agencies involved are heavily involved in scouting, insect control and plant removal efforts in regions that are most affected. Being vigilant about scouting and controlling this pest when found is very critical.

What can I do?

Your Arborwell arborist can identify locations where Asian citrus psyllid, Redgum lerp psyllid (or other types) are doing the most damage and recommend a treatment program to recover your trees and to keep them healthy. They can also recommend a proper plan for citrus trees on your property if you are close to an area affected by Asian citrus psyllid.

Fill out the form below to contact an Arborwell arborist and find out more about Psyllids and what we recommend for preventing damage and for helping trees recover if they have been attacked by high populations of Psyllids.

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Arbor-wellness: Plan for 2020

Prevention Season is Starting

Fall & winter are the most valuable time to protect your trees from next season’s insects and diseases. Whether its sticky sap, borers and bark beetles, or diseases like anthracnose or fireblight, fall or winter are ideal times to protect your trees. When treated now, trees have all winter to move protective products into and throughout their stems, twigs and roots. These products will be ready to work as soon as new growth starts next spring. Many diseases infect as soon as leaves appear, so by NOT protecting now, we are essentially playing catch-up if we don’t protect trees until after they start growing. This also most sense, given the stresses our trees have had to overcome the past several years. Stressed trees are more prone to insects and diseases because their defense systems are weakened and they have a harder time protecting themselves. So along with proper pruning, watering and mulching, protecting against insects and diseases will help them become healthy again.

My trees seem to be struggling still, why is that? 

Well most likely they are still recovering from the stresses of the drought we have had. When trees are stressed, whether it is drought, lack of irrigation, flooding, or whatever stress has occurred, they reduce the output of new leaves and new roots. They don’t produce as much energy storage and they stop producing the compounds (auxins and enzymes) that they use to ward off attacks. Thus, they become more vulnerable to damage from insects and diseases.

Will they die? 

Its hard to determine that without a good evaluation from a certified arborist. That being said, providing extra “help” for them right now is very beneficial to their recovery. Just like a marathon runner that starts out in good shape, if that runner is forced to run back to back to back marathons without the time to recover well, they become more prone to injuries and illnesses. Allowing for proper recovery allows them to run another marathon (another stress) down the road. So, trees need this recovery period too, reduced stress from lack of water, excess heat, over watering and attacks from diseases and insects, so they can build their defense systems again, like we need to recover our immune systems.

How do I help them recover? 

First reduce additional stresses – proper watering, mulching, pruning are key components to helping your trees recover. Second, by proactively protecting a tree from insects and diseases, they have a further chance to build those defense systems. If an insect – like caterpillars for instance, defoliates a tree next spring, that tree has to put new leaves out a second time. The same goes for diseases like anthracnose or fireblight. The energy the tree expends by putting out a second set of leaves prevents it from building up its defense system again, thus prolonging the recover. If this weakened tree is subject to another multi-year drought cycle, the chance of it surviving is even lower.

When is the best time to treat my trees? 

Fall and early winter are the best times by far. This allows ample time for the systemic treatment to completely circulate throughout the tree. It allows the treatment to be ready as soon as spring growing season starts again.  Late winter and early spring are the second-best time. It is still early enough to have the treatment be effective under most circumstances.

What kinds of problems can you control proactively? 

Many of the most common insects and diseases can be suppresses this way.  Insects that produce sap, most boring insects, most scale and thrips, adelgids, caterpillars and twig boring insects for example. As far as diseases go, preventing is so valuable, because by the time you see a disease on a tree, the damage has essentially been done. This is true for fireblight, anthracnose, powdery mildew, root rots like verticillium and phythophera and stem and twig cankers and needle blights on evergreens.  Lastly a nutritional supplement can be applied at the same time. Many times, a tree is stressed in part because of the lack of available nutrients in the soil. We can provide a balanced, organic nutritional supplement that will give your trees a proper feeding. Or better yet, we can sample your soil and replace exactly what your trees need.

Fill out the form below to contact your Arborwell arborist today to help you make a tree protection plan for next year.

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