Oh Christmas Tree, How Steadfast Are Your Branches

The Destruction that is Climate Change – Tree Loss Continues

The Newest Loser is the White Pine

I’ve been focused most of the last year on the oak and sycamore tree deaths. Well, now I have more bad news to report but to which we can help resolve. The Eastern White Pine is another victim of the Climate Crisis.

As reported by phys.org, the Ecological Society of Australia catalogued a 25% loss of mature trees in a 27 square mile area, the year 2010-2011 in response to extreme drought or the impact of climate change damage. University of Maryland reports a global loss of nearly half a million square miles of forest canopy in a twelve-year period (2000-2012). That’s about 42 square miles loss per year and accelerating. Think about how long it takes you to drive 40 miles, then drive back and forth to make your square. That’s probably around 3 hours of driving. Where is your favorite hiking or nature escape? How long does it take you to get to the boundary of that area and then to the heart of that area? This might give you a visual and hopefully visceral experience of what we are losing in terms of canopy cover.

This map, produced by Google Earth in collaboration with the UMD, shows the amount of tree cover present throughout the US and Mexico, well under 10%. Look at Peru and how much is left, or what is happening in Brazil.

What does this have to do with white pine losses? The eastern white pine (Pinus strobus) is dying from a suite of fungal diseases that once were low-level, chronic. The tree could fight these diseases whether struck by a single pathogen or multiple. What climate change does is complicated and not serviced by sound-bite length descriptions or 270 characters. Or, perhaps, it is more accurate to say, I am not capable of funneling this complexity so effectively. So here we go…first a description of the tree, then a description of the distribution of decline, its history, how climate has turned it from a chronic disease to an acute threat, and finally some mitigation options.

Eastern white pines are an important species in the US (see the areas highlighted in the map below). There are multiple cultivars used in landscaping. The pine can be identified by needles (leaves) numbering 5, rarely three or four, with a blueish green color. Trees are straight-trunked reaching a height of 100ft, with grayish brown bark that begins smooth then becoming deeply furrowed with scaly ridges, at maturity. Cones are elongate (4-8” long) and slender, pendulous on the tree with a long stalk attaching them to the stem. The cone scales are rounded and blunt at the ends. These are the long cones you might find walking down the street or across a golf course that are particularly fun to step on during dry times; crunchy.

Photograph from uwgb.edu

Distribution and History of Decline

Future mapping based on climate change scenarios (some scenarios assume business as it is currently being done while others assume aggressive mitigation of climate damage) can be found through the USFS website (https://www.nrs.fs.fed.us/atlas/tree/future_iv_129.html). Business as usual shows a reduction in white pine abundance of >50% losses in the next decade. That hurts a heart!

In 2009, several diseases were recognized causing needle blight and trunk/stem cankers. According to UMASS extension services, there are four fungal pathogens causing pine needles to prematurely shed but were not causal to death until relatively recently. Research has found successive years of extreme rainfall and drought are resulting in vast swaths of tree death. As trees become less able to repair cells, they become more susceptible not only to disease but other pest attacks.

The Impact of the Climate Crisis on Tree Health

When needles die and drop prematurely the plant is unable to make and preserve sugars used in growth and repair. This includes interference with the trees’ ability to uptake nutrients and water from the soil. Exceptional rainfall through May and July combined with exceptionally high temperatures are fueling what is called the White Pine Needle Disease (WPND) epidemic. It is during these times of year the trees are producing new growth, so to lose that new growth is expensive and causes the tree to use sugar reserves. It’s like tapping into your fat stores while fasting. Short term, not a problem, maybe even healthy, but long term, year upon year, wasting happens. Trees weakened by recurring drought, the new norm of extremely high night-time temperatures, and more extreme rainfall events are thus more susceptible to diseases. They have lost their ability to increase photosynthesis, their needles become lower in nitrogen resources, and all of this leads to a negative feedback in which plant cell growth and repair is compromised to the point of death.

Climate change is often a helpful new norm for plant pests. The increase in average temperatures from May through August is accompanied by peaks in rainfall and humidity – ideal conditions for fungal seeding (sporulation). Also, ideal conditions for weevils and wood boring beetles. Longer hotter spring and summer mean these insects can increase the number of offspring by having more than one generation time. It would be like us being able to reproduce in less than 9 months of gestation. Our population is still growing exponentially. What if the body could mature babies in 3 months; can you imagine the increased steepness of the exponential growth? I recently treated a tree so infested with beetles and weevils; I could hear them chewing throughout the canopy from the base of the trunk to the top. The amount of wood debris and wood frass was astonishing. I had never seen such activity before.

I am not alone in seeing it. Talking to other arborists, specifically Mr. Jay Webster of Marquis Tree Service in MA and Mike Powell from Woodworks Tree Service in NY, this disease is prevalent in their areas and a cause of concern. I also want to recognize and thank these two for providing the bulk of publications informing this blog post. I meet a lot of people in this business who inspire the best in me with their curiosity, intellectual enthusiasm and rigor, and the love they have for what they do. It’s quite a perk and one I expected to have a lot more of when I was an academic. As an arborist – I am enjoying a kind of knowledge camaraderie I can’t be grateful enough for. I digress…

Distribution of White Pine

UMass Extension Services Plant Pathologist, Dr. Nicholas J. Brazee reports that the White Pine dieback disease (WPDD, I just coined this acronym so use with caution) can be identified by:

· Mature trees having straw-colored then browning needles that are premature shed (older seasons needles),

· A few branches can be infected, or the symptoms seen throughout the canopy,

· Newer season needles will continue to be healthy for at least a bit of time,

· Needles yellowing will begin in May and early June with defoliation starting late June and continuing through July,

· Growth decline of the tree will be evident if the tree survives across multiple years,

· Increased insect activity [this is my anecdotal addition].

Weather events and abiotic conditions to use as predictive of the disease (and to help you plan preventative strategies with your Arborist) are:

· Exceptionally high precipitation from May through July,

· Exceptionally high precipitation followed by extended periods of drought stress,

· Above average temperatures from October and extending through early (or all) of December,

· Poor soil conditions (extremely acidic or alkaline; trees’ preferential range is 5.2 to 5.6),

· Increased exposure to air pollution (perhaps no longer a good choice for city landscapes/gardens but still important in rural areas),

· Summer temps >75F,

· High clay soils with poor drainage.

Canker causing fungal pathogens are evident when:

· Resin (white) is streaking down the trunk and/or

· Clustered at the branch-trunk interface,

· The fruiting bodies can be seen by the unaided eye as hairy or eyelash-like protrusions on the trunk.

Treatment Protocols Include:

· Preventative treatment with systemic fungicides and insecticides (insects can transmit the canker causing fungus in addition to the damage their feeding does),

· Ensuring optimal root access to soil resources; no girdling and no mulch touching the trunk,

· Removing infected needles or spraying with a topical fungicide or Cedarcide© to kill the fungal spores,

· Ensuring optimal soil conditions through bio-based fertilizers (deep root fertilization is effective if the proper form of nitrogen is applied many forms readily move through and out of the soil),

· Reducing clay density through soil aeration (chemical and physical),

· Not watering with above ground sprayers, and

· Supplemental watering during long periods of drought, at the trees’ dripline and beyond.

I am often asked if I find disease everywhere and the answer, thankfully, is no. But we are all finding more and more tree diseases because we have created a climate in which pest health is favored over plant health. We exacerbate this with bad, outdated management protocols. It’s important to our health and economies to increase healthy canopy cover. We inform ourselves, demand that those in landscape professions are also informed, and support the Agencies (municipal, state, and federal) who protect our trees.

As always – your comments and suggestions are welcomed. Thank you for all you do as a gardener, arborist, plant lover, sustainability warrior!

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