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There are a variety of treatment options which you can learn about in our guide to eradicating aphids.
Mountain Pine Beetles
Mountain pine beetles (Dendroctonus ponderosae) are native to the western United States and have devastated forests in the region.
Historically, these beetles played a beneficial role by feeding on dying trees and accelerating decomposition.
With more drought and higher temperatures, they’ve become a serious problem.
In your own garden, they’re a bit easier to get a handle on, especially if you give your trees a good once-over every few months.
Signs include the presence of quarter-inch black beetles, red sawdust (frass) at the tree base or in bark crevices, and yellowing needles.
If you see any of these signs, try peeling away some bark and look for white larvae or their galleries. They typically only infest wood that’s at least five inches in diameter
The adults lay eggs in the spring. The hatched larvae tunnel into the tree under the bark, where they feed and overwinter. They emerge in the spring to lay eggs, and the cycle begins anew.
Killing the pests can be a challenge because the larvae are protected under the bark. To be effective, you’ll need to take a multi-pronged approach at the right time.
In the spring, apply a pyrethrin-based product like Monterey’s Bug Buster-O, available at Arbico Organics.
Apply according to label directions throughout spring.
When you stop spraying, apply beneficial nematodes, specifically Heterorhabditis bacteriophora, that attack and parasitize larvae.
Arbico Organics carries packets containing five to 500 million live nematodes. Follow application instructions carefully to maintain nematode viability.
Disease
Healthy trees cultivated in appropriate conditions rarely develop diseases.
But overwatering, shady conditions, or excessive humidity can lead to these issues:
Root Rot
Excessively wet soil will inevitably lead to root root. These trees can’t handle wet feet at all.
If your bristlecone pine is exposed to wet conditions regularly, you’ll start to notice overall decline with falling needles and dying branches.
If you dig under the soil and look at the roots, they will be soft and dark.
Unfortunately, there’s little you can do. Stop all irrigation immediately – the tree may recover if damage isn’t severe, but there are no guarantees.
White Pine Blister Rust
The fungus Cronartium ribicola, introduced to North America from Asia in the early 1900s, causes a disease called white pine blight in many pine species.
The disease requires a plant in the Ribes genus to complete its life cycle.
That’s why some states have banned planting species like gooseberries and currants in the past. That’s how bad the disease can be.
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Kristine Lofgren
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