Pine Decline in South Carolina

Pine Decline in South Carolina

I am not a scientist or a researcher. Here are my experiences with pine decline and pine mortality.

In 2001, I was called to a landowner’s property because there were patches of longleaf pines dying. The longleaf stand had been burned in March of 2000 with a very hot prescribed fire with char marks as high as 12 feet on some trees. On June 3, 2001, the stand was released with Pronone forest herbicide. Three weeks later, I was called to come identity what was killing the longleaf pines.

The mortality areas were in circles and included very mature to grass stage seedlings. The circles varied in size but some of them were touching and beginning to form figure eights with the mortality pattern. One of the circles had loblolly pines and they, too, had died.

Dr. Larry Nelson, Vegetative Specialist with Clemson Extension came to the site. He did not know why the trees were dying but ruled out Annosum root rot. Experts from the US Forest Service and others were called in. All that could be obtained was that it was not Annosum root rot.

I contacted Dr. Frank Tainter, retired Forest Pathology Professor from Clemson University. He asked that I dig a root of an infected tree and mail it to his home (the root took 3 days to reach his home). His reply was, whatever was there had died (the fungi) and whatever it was, he had never seen before.

A month or two later, I was called to another site where longleaf was dying. Again, there were the high scorch marks of a previous burn and the trees were exhibiting the same symptoms as the first site. This elated me as whatever was causing the trees to die was not an anomaly.

Through contacts throughout the southeast, I received a phone call from Mark Hainds of the Longleaf Alliance. He had heard that what may be causing the trees to die might be Leptographiumspp. and Dr. Lori Eckhardt had done her dissertation and was continuing to research the fungi and associated insects. By the time I located Dr. Eckhardt, she had just been hired by Auburn University.

Since that time, I too have been learning about Leptographium spp and its associated insects.

What causes the tree to get pine decline

At first, it was easy to see the site disturbance that caused stress to the pines so that the Hylastes and other beetles could attack and feed on the root systems. A hot prescribed fire leaving high scorch marks, mechanical disturbances such as removing all understory so that the pine straw can be raked, et cetera. Then it became more difficult to determine the stressor or stressors: drought, not thinning on time, logging in the wet period, too much rain, et cetera.

When the trees become stressed, then they are candidates for pine decline.

Soil types and pine species

Pine decline can be found on most soil types but is observed predominantly on sandy loam, or sandy clay loam and moderately well-drained to well drain soil types.

Leptographium and the associated root feeding beetles can be found in longleaf, loblolly and shortleaf pines. Thus far, it is far less prevalent in slash pine. However, if the slash pine are offsite, then it will be susceptible to stress.

Longleaf is the predominant species that inhabited the lower and upper coastal plains and the lower piedmont area. Loblolly is considered an offsite species where longleaf was native. The research is showing that a lot of the loblolly planted in the longleaf areas are under stress and prone to pine decline.

What to look for if you suspect pine decline.

Luckily, there are a hosts of symptoms that can lead one to suspect pine decline: no last year needles on the lower limbs, curving of the lower smaller branches as if they are drying even if they have needles on them, the top of the tree (top 10-20% crown) has both last year and current year needles. You may see dead trees with or without bark that are broken anywhere from 3 to 25 feet up. Longleaf can exhibit an almost wilting appearance in their needles and sometimes have a grayish green tent. If you see new growth on longleaf that is 3 to 4 inches long and it is August, there is an excellent chance that the tree has pine decline. Sometimes it is isolated trees or appears that way. Sometimes, it is apparent that the trees are dying in large circles. If the stand is left alone, the mortality of these circles spread out and the circles begin to touch forming figure 8’s.

Next step

One day, I was digging roots for someone when a forester commented that the roots were the last frontier of a pine tree. I had never thought of it like that but it may be one reason that pine decline has been misdiagnosed or ignored as the evidence of a beetle attack is below ground.

Digging roots

To dig the roots, take a sharp shovel and dig down around the tree trunk until a large root can be located. Sometimes it may be hard to find on deeper sands. Excavate the root carefully not disturbing the outer bark. When excavating the root, I use both a shovel and a Pulaski depending upon which is needed at the time.

Look carefully as you are digging as there may be evidence that can easily be overlooked such as a dead dried out smaller root or clumps of dirt that have formed around the resin that the root is secreting.

After a root has been located, if there are no signs on the upper side of the root turn it over and look. Sometimes there is a lot more evidence on the underneath side. A main root can be 3 inches to a foot below ground.Excavate about 3-4 feet of the root. Using a Pulaski or ax, cut the root near the trunk of the tree. Generally, if the root has been attacked by Hylastes spp. and other vector insects, the root can be brought up and broken off near the point where it has been uncovered. However, sometimes, large underneath roots may prevent further excavation so a sharp hatchet is needed to cut other roots. Once the root has been removed, it may need to have the dirt removed using water. Clear evidence are marks perpendicular to the root where the Hylastes spp have chewed on the root. The bark beetles feed on the cambium just as the engraver beetles or SPB. Like SPB and other beetles, they release a blue stain fungi while feeding.

“Infected primary roots will have blue –stain and resin soaked lesions caused by Leptographium orOphiostomatoid fungi (L. truncatum, L. procerum, L. terebrantis, G. huntii, G. alacris). This group of fungi is present in the roots because of their association with the various root feeding bark beetles (Hylastes salesbrosus, H. tenuis, H. opacus, Pachylobius picivorus, Hylobius pales, and Dendroctonus terebrans). Just like their above-ground counter parts, these root-feeding insects will vector the Leptographium and Grosmannia fungi or create wounds in the roots that will allow the fungi to enter. Beyond the lesions, the fine roots are either damaged or significantly reduced in number.” (Pine Decline PD090208) (This paragraph was copied but the new current names for two of the fungi replaced the old nomenclature.)

Lesions may have blue-stain but looks black and there may be resin stuck to the root with dirt around it so that it lesions are not readily identifiable. A pocket knife can be used to cut it away the resin pitch from the root.

A little more about the fungi and insects

Leptographium procerum and L. Terebrantis are native with L. Terebrantis being a bit more virulent. Grosmannia huntii and G. alacris are not native to the US and are more virulent. Of the vectors, Hylastes opacus is non-native as well.

Several years ago, Dr. Eckhardt and her research team took samples of the fungi and insects to South Africa to do DNA testing with Dr. Michael J. Wingfield (world authority on Leptographium and Grosmannia). Samples from SC were included from roots and insects mailed to the lab. It was found that the non-native fungi and insect were native to Europe and had also been introduced to South Africa.

What is the next step?

If a forest landowner wishes to know exactly what is in the roots, I send them to Auburn University. I belong to the Forest Health Cooperative, Auburn University. The roots are dug, placed on ice and shipped overnight to AU to prevent drying out. It takes 3 to 4 weeks for the lab to culture the medium to determine which fungus or fungi is present in the roots. The roots are also tested for other fungi which are:P. cinnimomi, (Little leaf) and H. irregulare (formerly H. annosus).

The results gives a landowner an idea of what to do next. For example, one landowner has a silvopasture with about 30 pine sawtimber trees per acre. His pines have L. procerum and he loses about 1 tree per acre per year. On other stands that have the more virulent fungi, the mortality is higher.

Silvicultural Practices to prevent PD

Thin when the trees need to be thinned regardless of the dollar amount. Not thinning when the trees need it places them under stress.

Plant the correct species on the correct soil type to prevent stress.

Keep track (like track hoes) equipment or soil disturbance equipment out of the timber stand.

Do not thin when the tract is wet especially the loam and clay sites.

Make sure that the thinning crew does not skin any trees except the turn trees and they are removed.

Use lower intensity prescribed fires. Back in the old days, especially with longleaf, we used to say the higher the scorch marks the better. Today, using that same burning technique will guarantee pine decline in the timber stand.

If planting in an area with hard pans, pay someone to break the hard pans with a shank plow or other device before planting.

Shorten the rotation age of your timber stand.

All timber owners are going to have to stay on top of their stand and manage it. No longer do we have the option of saying, “I don’t need the money right now; The price of pulpwood is too low; I don’t have the time right now. When your timber stand needs thinning, Thin IT!

If you already have Pine Decline

The first thing you should know is, Do NOT Thin your pines. This is a silvicultural practice for protecting your stand against above ground beetles (SPB, et cetera) but it causes the underground feeders to spread.

Once a tree is severed that has beetles in it, it begins to dry. Drying may take up to 3 years depending upon the soil type. The beetles will leave the drying roots to feed on other trees. About 1.5 to 2 years after a thinning, the landowner will observe dying trees.

Once a stand has pine decline, there is no research that gives an alternative on how to get rid of the insects or stop the fungi. When mortality exceeds pine growth, it is time to clearcut no matter how small the pines are.

Reforestation

The beetles associated with pine decline do not like feeding on seedling roots but they will move to seedling roots when the mature tree roots dry out. Initial feeding vectors the fungi, thus infecting the new seedlings with either Leptogrpahium or Grosmannia or both. Ergo, using our normal time table of clearcut, wait one growing season, site prepare and plant may not work. Because the beetles stay in the root system until it starts drying out, they may still be present when the site is replanted in seedlings. Their roots start drying out and they are looking for food.

There is a longleaf site in Lexington County that had about 900 to 3000 longleaf seedlings in place before the clearcut. This site had Grosmannia huntii and G. alacris. It was the 3rd site that I had seen and it was cultured by AU in 2003. This was my training site for years until the clearcut.

The following growing season, I returned. The seedlings are either dead or stunted with needles only 3 to 4 inches long. The roots were dug and the feeding marks of the Hylastes beetles could easily be seen. There could not be a healthy seedling located on the 50 acres.

Where is pine decline?

The Forest Health Cooperative has documented pine decline in: Aiken, Bamberg, Calhoun, Clarendon, Colleton, Darlington, Lexington, OrangeburgRichland and Sumter counties for both longleaf and loblolly pines through roots that I have mailed. It is becoming very prevalent and I am finding pine decline more often. The ages of stands have been from 17 years old to 60 years old. All have had stressors varying from hot prescribed fires to not being thinned on time, et cetera.

Questions???

There are people who say that Leptographium does not kill trees. It weakens them and other things such as SPB kills the infected pines. Research shows that the fungi does not grow when injected into healthy pines. Also, if the roots have to be shipped over night to keep them from drying out, how does the fungi stay alive when the Hylastes and other root feeding beetles fly above ground?

This is Dr. Eckhardt’s reply to these questions.

Lepto has been inoculated into healthy trees and we have published several papers where we have done so for pathogenicity tests. But when a tree is heathy it can, let's say, hold the fungus at bay, so the resin components act fungistatically. The fungi is still alive but can't really spread. As the tree becomes stressed, the fungus can begin to grow and stress the tree more attracting more insects to come and feed on the root system. The insects will test feed on healthy trees infecting them and then come back and feed more at a later time as the trees become more stressed. We have not had the SPB populations as we have had in the past, so more above ground symptoms are being presented because these weakened trees are not being taken out in a SPB outbreak.

As far as the heat killing the fungus in transport, that is not exactly what happens. The roots need to hold their moisture. When you don't pack with ice or send overnight, the roots dry out and then the fungus is hard to isolate. The beetles body keeps the spores at a constant temperature and keeps them viable so when the beetle feeds and tunnels and the spores wash off in the resin, they can then germinate and grow.(E-mail, 11-20-2014)

Conclusion.

If you have questions about Lepto or any part, please ask me. Even after more than 15 years of research there are still many unknowns about pine decline. If you want me to help you learn what to look for below and above ground, e-mail me or call me at (803) 534-6280; . I will be glad to help.

On May 6th 2015, there will be a meeting in SC on pine decline. Most likely, the meeting will be held at the Edisto Research and Education Center outside of Blackville, SC on US 78.