Are there any P. ramorum-resistant coast live oaks or tanoaks commercially available?

Research has identified coast live oak individuals that may be somewhat resistant to SOD, possibly because of the presence of some chemicals in the bark and phloem.  However, there is no information yet on how genetics and the environment may affect this trait. Tanoak has some mother trees that produce SOD-tolerant seedlings and some that […]

When should I remove a tree?

Tree removal is most likely required if the tree is a hazard to property, people, or places where people congregate (paths, camp grounds, etc.) Bear in mind that individual limbs may be more of a hazard than the failure of the entire tree. A certified arborist should be consulted to determine whether tree removal is […]

What is the Critical Root Zone around a tree?

A tree’s Critical Root Zone (CRZ), sometimes also called the Root Protection Zone (RPZ), is defined as a circle on the ground corresponding to the dripline of the tree. Unfortunately the “dripline” of a tree can be irregular and hard to define. An alternative method of determining this dimension is to measure the diameter of […]

Will fresh wood chip mulch injure the general health of a tamarack tree?

Mulching should not hurt the general health of a tamarack tree; however, make sure the mulch is not piled up against the tree, but rather 1 foot away from the base of the trunk.  The mulch layer should be about 3″- 4″ thick and spread out to the dripline as much as possible for maximum […]

Can the Garbelotto lab analyze wood chips for pathogens?

The lab can, upon request, analyze wood chips at cost ($100 US dollars per sample).  Testing would confirm the presence or absence of any known dangerous pathogens.

Armillaria is slowly killing my Thuja hedge. What is a comparable replacement hedge that will give me the same amount of privacy and be resistant to this fungus?

The first question to ask is what type of irrigation is being used currently on the hedge. Most landscape oak root fungus problems are due to overwatering in summer months. However, Thuja orientalis (=Platycladus orientalis) is quite susceptible to Armillaria even without heavy irrigation as highly susceptible species do not require excessively high soil moisture […]

If the stump of a felled tree is left in place, can the roots to continue to grow?

A lot depends on when the tree is felled. If a tree is cut in winter, it is possible that the root system will experience an additional year of growth. What happens to the root system depends on many variables, including soil type and presence of other trees of the same species adjacent to the […]

My pear tree was looking great. Within a week one of the limbs died and now it looks like the whole tree is dying.

It sounds like your tree is having problems providing enough water to the canopy to keep the foliage and cambium alive. If you are not watering it, that may be the problem. If you are watering it, your tree may have contracted a root disease. In that case, it is important to clear all organic […]

What are the modifications required for drone canopy leaf sampling?

Make sure the prop blades are protected. Modify the tail to include a collection device.  A very sharp blade at a sharp angle allows twigs to be cut off and often to remain caught in the space between the blade and tail. Learn how to drive the drone using the camera. For more on drones […]

What can cause leaf tip scorch on redwood trees?

Leaf tip scorch symptoms on redwood trees are found from the lower to upper canopy and include healthy leaves interspersed with brown and grey leaves or portions of leaves. Grey leaves typically have black margins into the healthy tissue. Such symptoms are typically caused by a fungus called Pestalotiopsis funerea. They are commonly associated with […]

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