Bark beetles #184880 - Ask Extension

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Bark beetles #184880

Asked May 24, 2014, 1:14 PM EDT

I have bark beetle infestation in pine trees.  I have been told that once the tree starts to have any brown needles at all that there is nothing you can do to save the tree and that once this happens all the beetles have already moved on.  Is this true?  I have 5 acres that are mixed pine (pinon and others) as well as juniper and I am trying to figure out how to keep from losing the whole acreage.

Santa Fe County New Mexico

Expert Response

You are well aware of the drought and the problems it is causing statewide for plants and animals alike. Although water-stressed conifers don't wilt like home garden vegetables do when they don't get enough water, the trees are indeed water stressed, as perhaps indicated by brown tips on needles and olive green color (rather than a richer, deeper green). In a forest situation, trees are growing on variable soil types over rugged terrain. Trees growing on rocky, dry, south-facing slopes may be considerably more water stressed than those growing on deeper, loamy soils in an irrigated park setting. Add mechanical injury, winds, low humidity, root diseases, etc. and it's a wonder that any of our trees are surviving. This is the kind of environment where bark beetles and other wood borers thrive, sometimes to the point of 'out-break.'

It's easier to see on Ponderosas than pinyons, but bark beetles attempting to bore into the trunks, limbs or twigs of their particular hosts succeed in penetrating host defenses best when the host can't get enough water. Specifically, a boring beetle soon chews its way into the resin channels in the bark. If a tree has enough water to keep its resins flowing, the intruder can be trapped, killed and essentially 'removed' from the tree on a gooey pitch tube. However (again), for trees under stress, rarely is just one beetle attempting to chew its way through the bark. A mass attack by particular bark beetles will generally overwhelm the tree's defenses so that it not only has holes through the bark, but very shortly afterward is further challenged by tunneling, ovipositing bark beetle females PLUS their myriad offspring. It doesn't take many 'families' of bark beetles to totally girdle a tree---and often in multiple locations along the trunk and major limbs.

For pinyon, the pinyon bark beetle is likely to have two, maybe three generations annually. When June temperatures occur, tree death becomes obvious very quickly. Needles all over the tree turn red, then yellow and brown before falling from the tree. The trunk is dead, bleaching a little in the sun, but it stays upright until something else takes it down. There are no 'water sprouts' or flushes of growth from below points of major damage like there might be for other (often broadleaf) trees.  

While stress sets the stage for beetle activity, there's another factor at work, too---blue stain fungi, the spores of which are introduced into the host tree by the bark beetle that successfully penetrates the bark. This fungus grows in and plugs the vascular system of the tree. The fungus can feed the beetle larvae while further blocking tree responses to insect infestation. Beetle pupation and emergence then keeps the fungus' life cycle going as fungus spores are dispersed to new host trees.

This is where everything 'hits the fan' so to speak.

The trees have needed water for years; their growth and responses to the environment are minimal when water supply is minimal. Just a bit less over time, and the trees are dead just from that.

Bark beetles respond to stressed trees. People attempt to treat their trees to kill beetles while saving trees. No treatment is a substitute for water, nor will any treatment reverse the cumulative effects of drought stress on tree growth and vitality.

Bifenthrin, carbaryl and permethrin are active ingredients in particular insecticides with 'bark beetles' and 'conifers' (of various kinds) on the label. All are topical treatments; none of them 'soak through' the bark or 'fumigate' beetle tunnels to kill beetles or their other growth stages.

Homeowners attempt to treat their stressed trees with 'over the counter' products. Again, they are no replacement for water. Some people may have some luck if their trees are smaller, young, well cared for and not already infested when treatments begin. It also helps if these people are timely and consistent with their treatment regimens and very thorough with their applications. Even though the treatments they buy have bifenthrih. carbaryl or permethrin as active ingredients, those 'general use' insecticides are not formulated exactly the same as products---with those same AIs' are formulated. These 'Restricted Use" formulations are for licensed applicators to purchase and use for their jobs.

But even those treatments, regardless of formulation, attention to detail, persistence, etc. etc. will treat blue stain fungi. There are no treatments for blue stain fungi. Once the beetles and the fungi are in a host tree, the tree's wood protects the pests.

Yes, if you look hard enough at pesticide labels you will find some active ingredients that are 'systemic,' meaning the host absorbs the active ingredient and may even translocate it within its tissues. Some are 'general use' and available to John Q. Public while others are Restricted Use and available only to licensed applicators. None have activity against blue stain fungi. Further, if bark beetles are in the tree somewhere, the vascular system is cut where those beetle families are located, keeping the active ingredient from going anywhere the beetles are.

So, if the tree is dying or dead, are all the bark beetles gone? Not necessarily...which is the reason why people trying to recycle beetle trees as firewood are advised to totally dispose of those trees as they are cut down---or at least put their firewood into a sunny location, cover it securely on all sides with plastic and solar-treat the wood pile for a couple of years, if possible. Some want to argue that dying and dead trees should be treated as well as those that aren't hurting that badly yet. However, that becomes an act of revenge, rather than control......good money after bad...and the end results will be the same.

So yes, the situation is about as dire as you were advised---but the above should help put that earlier information into context...why things are the way they are, the pros and cons of doing something or not.

It is very easy to spend lots of money on a situation that can go downhill any time. That is definitely true for 5A of forested land. You might think about the location where the house is---and outbuildings---and which trees are 'high value.' Concentrate on your defenses there. Pay attention to State Forestry's programs on making your home site less combustible. Dead and dying trees are basically standing firewood. Remove them, it you can. Surviving trees might have a better chance of getting adequate water from our monsoon season, if that comes to pass, or from irrigation. But where you can't irrigate or afford to spray or have it sprayed, those trees are on their own.. That's tough to accept, but realistic. 

As for the junipers, they are susceptible to different species of wood borers---not the same as the pinyons. However, what you can do for them is pretty much the same as what can be done for the pines---water, protect, spray, remove.

This isn't the best news, for sure. We can't depend on the weather to fix things. From the TV news, we can see what could happen if we got lots of precipitation---all at once in many cases. Too little, too late.

Carol Sutherland Replied May 27, 2014, 2:18 PM EDT

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