Pines are a classic choice for the yard, with their stately appearance and evergreen splendor. For the most part, they’re fairly maintenance-free, as well.
Although many conifers are quite resistant to pests and pathogens, they’re still vulnerable to certain issues.
As such, if you have pine trees growing on your property, they may need some special TLC so they don’t succumb to illness or injury. Below are 11 common pine tree problems that you may encounter, as well as how to deal with them.
Table of Contents
Pine Tree Pests
As with any other type of plant, pine trees are vulnerable to many pests that have evolved to specifically prey upon (or otherwise affect) Pinus species.
Although these may also bother other conifers if those are the only ones nearby, they’re more likely to veer towards your beloved pine trees if and when the opportunity arises.
1. Pine Moths
Zimmerman pine moths (Dioryctria zimmermani) are most common on Austrian (P. nigra) and Scotch pine (P. sylvestris), but can be found on numerous pine and spruce species east of the Rockies. They bore into the trees near where the branches meet the trunk.
The adults bore into the trees to lay eggs, and the larvae emerge to feed on the sap and bark. The result is pitting, holes, sawdust, and gummy discharge. Their feeding can cause dead branches and tree tops.
The adults are reddish-brown and gray with zig-zagging marks, while the larvae are off-white or gray. You generally won’t see the larvae unless you dig into the bark, particularly where gummy masses are present.
Once the insect tunnels into the tree, there’s nothing you can do to kill them. They are tucked safely away inside. But, the moment you see caterpillars crawling on the exterior, get to spraying.
Saturate the tree thoroughly in a product that contains the beneficial bacteria Bacillus thuringiensis var. kurstaki (Btk). Monterey B.t. contains this powerful ingredient and is available at Amazon in a quart concentrate.
2. Pine Tree Sawflies
Unlike some of the other pine tree pests on this list, pine sawflies can attack just about any pine species worldwide.
Sawflies aren’t true flies but are members of the Hymenoptera order, which includes bees, wasps, and ants. The females have ovipositors, which are essentially stabby tubes that allow them to poke holes into a surface to deposit their eggs into it.
Braconid wasps use theirs to lay eggs into caterpillars, whereas pine tree sawflies poke their eggs into pine needles. Once the larvae emerge, they munch happily on the needles around them.
This damages the needles badly, causing discoloration and defoliation. Repeated infestations can slow the pine tree’s growth and development and can even result in eventual death.
If you suspect that you’re dealing with pine sawflies, inspect your trees in the late summer or early autumn and look for rows of bumpy brown eggs on the pine needles. Remove and burn them if you find them.
Alternatively, if you see bunches of sawfly larvae on your pines in springtime, prune off the branch and drop the end into a hot water and vinegar solution to kill them. You can also treat your trees with neem oil, insecticidal soap, or Bacillus thuringiensis var. kurstaki (BTK).
3. Pine Bark Beetles
These beetles (Dendroctonus spp.) are very tiny—only three to six millimeters long—and can be very difficult to spot on your trees, mainly because they burrow deep into the bark rather than scuttling around on top of it.
The easiest way to spot an infestation is by looking for brownish-red dust on any pine tree nearby. As the beetles feast on that tasty inner bark, they create “pitch tubes” to eliminate their detritus.
You’ll spot this dust around small holes on the bark’s surface, along with leaking resin from the damage they cause.
If you spot these issues, treat your trees with Cypermethrin (Sylo) or Dominion 2L insecticides to deal with these pine pests.
Should these fail to work, or if the damage is severe, call in an arborist for an evaluation. They can let you know whether the tree is salvageable with more intense insecticide treatments or if it needs to be cut down and burned.
4. Pine Weevils
Pine weevils (Pissodes strobi) are notorious for the damage they cause to white pine (P. strobus) and Jack pine (P. banksiana) trees. When it comes to pine pests, none strike fear into the heart of pine growers as much as pine weevils.
They’re also known as “tip weevils” because the females bore holes near terminal buds (tips) to lay their eggs into, and the larvae then cause damage to the pine tree’s bark from the tips inward.
The damage they cause can lead to “forked” trunks, which are less than ideal for Christmas tree growers. Additionally, the leader stem may develop into a crook or question mark shape.
You can try to deter these weevils by growing your trees under a canopy that offers about 50% shade, as they prefer trees in full sunlight. Additionally, applying bands of sticky tape around branches may help a bit.
There are no products available to treat trees against pine tree weevils, so you’ll either have to prune affected trees aggressively or cut them down and burn them.
5. Porcupines
As far as “pests” go, porcupines are some of the most adorable ones you’ll come across. They don’t intend to harm your pine trees, but well, they get hungry.
In wintertime, pine bark is a staple food for these creatures, and they can do significant damage by gnawing huge swathes of bark off your tasty pine trees. This leaves your trees vulnerable to insect damage and disease and can even traumatize them enough to die of shock.
The best way to deter porcupines is by using aluminum flashing around your trees so they can’t climb them or spraying your pine trees down with hot sauce.
Seriously, they can’t stand the stuff.
Pick up some sriracha on the cheap and hose the tree liberally with it, and they’ll stay away.
Alternatively, you can offer the porcupines other food sources so they aren’t desperate enough to strip off pine bark. Apples, carrots, pumpkins, sweet potatoes, berries, acorns, beech nuts, and chestnuts are top choices for these sweet critters.
Pine Tree Diseases
The types of diseases that may affect your pine tree will depend on the species on your property.
For instance, an issue that may afflict an Eastern white pine (P. stroba) in upstate New York is unlikely to also affect a pinyon pine tree (P. edulis) in New Mexico. Although there are some issues that can affect all Pinus species, others are species-specific.
6. Pine Wilt Disease
This disease is caused by pine wilt nematodes (Bursaphelenchus xylophilus), and generally affects non-native, introduced pine species throughout North America.
Whereas most nematodes affect a plant’s roots, these guys congregate around resin ducts and feed on the surrounding cells. The resin then leaks into the trunk’s xylem (water uptake), essentially preventing the tree from being able to “drink.”
As you can imagine, the trees die quite quickly after this occurs.
Pine wilt disease is spread by vector pine sawyer beetles from the Monochamus genus. These generally bore into dead or dying trees, hence why pine wilt is more common with old trees that may not have much longer to live.
The issue here is that the disease can spread to healthy, younger trees nearby if action isn’t taken quickly.
One of the key signs of this disease is gray or brown wilted needles that remain attached to the tree’s branches. If you see this issue, cut down the tree, burn it immediately, and either remove or burn out the stump.
Then, call in an arborist to inject healthy nearby trees with abamectin to prevent infection.
7. Dothistroma Needle Blight
Take a look at your pine tree’s needles. Are they lusciously green from base to tip? Or do they have brown markings all the way along?
If there are significant brown markings around your needles, you may be dealing with Dothistroma, also called “red needle blight.”
It’s a fungal disease caused by a couple of different ascomycetous fungi: Dothistroma septosporum and D. pini.
This disease thrives in moist conditions and thus affects many different pine species throughout Europe, Canada, and the northern USA.
The first symptom you’ll notice is needle discoloration: the aforementioned bands that start out brown but turn red, followed by yellowing and browning of the entire needle. This is usually followed by premature needle defoliation (needle drop), limb loss, and potential tree death after a few years.
Although there is no cure for this disease, copper-based fungicides have proven effective at reducing its intensity and extending tree life. You can purchase a 16-ounce concentrate of copper fungicide at Amazon.
8. White Pine Blister Rust
White pine blister rust is a pathogen (Cronartium ribicola) that most often targets young, five-needle pine species such as whitebark (P. albicaulis), western white (P. monticola), and eastern white (P. strobus).
It apparently originated in Siberia but made its way over to the Pacific Northwest around 1910 and has been spreading across North America ever since.
The first signs of this disease are diamond-shaped orange swellings on the trunk, which then grow into large orange cankers. These are often covered with white blisters that ooze resin-like pus, which can attract rodents and insects.
The cankers grow to “girdle” (i.e. encircle) either branches or the trunk itself, thus strangling and killing the tree within a few years.
There is no cure for this disease, and it’s recommended that affected trees be cut down and burned to prevent it from spreading.
If you’re keen on avoiding this issue, plant your trees on south- or southwest-facing slopes, and ensure that there are no Ribes species nearby, as these berry bushes and shrubs can carry and spread the pathogen.
9. Annosus Root Rot
Caused by the Heterobasidion annosum pathogen, this root rot is particularly deadly to red pine (P. resinosa), and has wiped out entire pine tree plantations in the USA and Canada. It’s known as “maladie du rond” in French because it affects young trees within a particular radius.
Basically, the blight sets into the freshly cut stump of a tree that’s felled in autumn. Throughout the next couple of years, the fungal hyphae move into that stump’s roots and, from there, into the root systems of healthy trees nearby.
You’ll know that a healthy tree is affected by these if you see basidiocarps growing near their roots (hence the colloquial “root rot” moniker). They tend to be striped pale brown on top, with cream or white multi-pored undersides.
There’s no cure for this pathogen, so prevention is the best course of action. Be very careful to not wound your trees, particularly exposed roots or the trunk close to the soil line.
If and when you cut down a pine tree, apply a borate fungicide to the stump and the roots of surrounding conifers. Should you find that any of your pine trees are dead or dying, cut them down immediately and either apply fungicide to the stump, or dissolve it with Epsom salts.
10. Diplodia Tip Blight
This issue, formerly classified as Sphaeropsis tip blight, is caused by an opportunistic fungal pathogen called Diplodia sapinea. It only afflicts older pine trees—usually over the age of 25—and as you may have guessed, affects the tips of new branches.
As it spreads, it continues to consume the branch from the tips backwards, until they’re bare, browned, and quite haggard.
Although this pathogen won’t kill a pine tree outright, it’ll weaken it and leave it vulnerable to attack.
The aforementioned pine tree beetles are particularly eager to dive in and devour trees that have been damaged by this disease, as they can easily break through damaged bark to get to the tasty cambium within.
Since drought-stressed trees are more vulnerable to Diplodia, try to ensure that yours are well-watered regularly.
Fertilize them to keep them healthy, cut off damaged or blighted shoots immediately, and treat trees with a fungicide if you think the pathogen is spreading. If and when the tree seems too damaged to treat, remove it and burn it.
11. Pine-Oak Gall Rust
Austrian and Scots pine trees are particularly susceptible to this issue, which is caused by Cronartium quercuum f.sp.banksianae.
As you may have guessed by the quercuum classification in there, this pathogen requires both oak and pine trees to complete its life cycle. In spring or early summer, the wind will blow spores from infected oak (Quercus sp.) trees over to new pine tree needles and shoots.
It then moves to larger branches and harasses the surface into creating more larger cells.
This rapid cell multiplication creates a gall around the branch. These galls take a few years to reach full maturity, at which point they burst and release orangey, rust-colored spores.
These infect nearby oak trees, where they form tendril-like structures (telia) on the leaves’ undersides. Over the autumn and winter, these telia will have different spores that they’ll fling onto nearby pine trees once the warm spring weather returns.
The only way to manage this disease is to try to interrupt the reproductive cycle by destroying galls before they can release their spores. Prune out galls if and when you find them, and burn them. Alternatively, if you can’t prune the gall out, cut down the tree and torch it immediately.
