Every year when summer hits and the weather heats up, the pine death toll rises. Over the last 2 years, we've removed over 1000 dead pines just on client properties in Northern and Southern California metropolitan areas alone.
The Sierras and heavily forested areas of California are experiencing it even worse, with an estimate 129 Million dead pines across the state!
Which pines?
In our urban areas are, these are the 3 species of pine trees primarily affected:
- Monterey Pine, Pinus radiata
- Aleppo Pine, Pinus halapensis
- Mondel Pine, Pinus eldarica
Why is this happening?
There are 3 major factors that are contributing to the sharp decline of pine health:
- Drought Stress
- Pine Pitch Canker
- Bark Beetles
Before we jump to what we can do about it, let's dig a little deeper into each.
DROUGHT STRESS
When trees experience stress, their defenses are compromised, and they become more susceptible to pest and disease. There are many forms of stress a tree can experience in an urban environment -- soil compaction, pollution, drainage issues, root removal, competition with turf -- but in hot summer months, the most impactful stressful element is often from drought.
Drought stressed trees may show symptoms of dieback and yellowing of their needles. The lack of water can also affect soil chemical, physical, and biological activities that are essential for plant and soil health. Thus, both water and soil management are crucial to the trees survival.
PINE PITCH CANKER
Pine Pitch Canker is a disease caused by the fungus Fusarium circinatum. Most pines native to California are susceptible to pitch canker, but chances are, every Monterey pine in California has it. Here's what it can look like:
The fungal spores are spread easily by wind, rain, or carried by insects and beetles. Once a tree is infected, the fungus is generally isolated to each canker or lesion. The infections can then cause girdling, which blocks water and nutrient flow through the tree. This results in needle dieback and canopy defoliation.
The oozing you see is the resin (or pitch) that builds up at the site of the infection. The resin production is the tree's effective defense mechanism against insects and pathogens. Some studies also suggest that the fungus is able to grow inside resin ducts and actually stimulate even more resin production.
Regular fungicide treatments can effectively control Pine Pitch to reduce symptoms.
BARK BEETLES
Bark beetles are opportunistic pests and go after trees too weak to defend themselves. They take advantage of pines weakened through stress and/or disease and wreak havoc. Often, they are the so-called "final nail in the coffin".
If the Pine Pitch Canker is left untreated and doesn't kill the pine, it is likely the bark beetles will come in and finish the job. The bark beetles we see in the urban landscape that most commonly attack our pines are: Engraver Beetles (Ips emarginatus, Ips mexicanus, Ipsparaconfusus, Ips pini, Ips plastographus) and the Red turpentine beetle (Dendroctonus valens).
Ips (engraver) beetles will attack from the top down. They enter into the younger, tender tissue at the top of the trees and you will usually see the top dying first. Red Turpentine Beetles attack on the lower 6 ft of the trunk and you can easily spot their attack sites at the base of the pine.
What can be done?
The proper care and management practices that your pines receive can have a significant impact on its survival during drought periods and seasons when beetle populations are on the rise.
The most effective way to prevent pine death by beetle attack is to maintain tree vigor through adequate watering and good soil management, and to regularly treat Pitch Canker infected pines to suppress fungal activity.
Our Pine Management protocol is an integrated approach to address all 3 factors that lead to the decline of pines which include:
Soil treatment--
- To increase water holding capacity
- For more efficient nutrient uptake
- To remove pollutants (such as soluble salts and Boron) that build up in soil, especially if on reclaimed water and/or during drought periods
Health Treatment--
- To increase density of hair-like roots to promote more efficient water and nutrient uptake
- To slow down canopy growth so the tree can conserve energy and use its resources toward survival
- To thicken needles for increased defense against pest/disease and less evapotranspiration (loss of water through the leaves)
Pitch Canker Treatment --
- A fungicide bark application to help manage and control Pine Pitch Canker
Beetle Treatment --
- A trunk applied barrier spray that is used against borers and effective against new strikers
If you don't know what trees you have, if your pines are "At Risk" or even if your pines may already have some of these issues, then don't hesitate to call us out to you! We will provide a free assessment and inventory of your trees.
Click on the link below to request a visit and one of our Urban Forest Managers will drop in!
References:
http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=18800
http://ipm.ucanr.edu/PMG/PESTNOTES/pn74107.html
https://crops.extension.iastate.edu/cropnews/2017/08/how-drought-affects-soil-health