Guy Meilleur
Addicted to ArboristSite
I'm usually later getting my issues of TCI magazine than other parts of the country. If anyone gets their issue and has a minute to take a look at this article, I'd like to get some feedback on it.
ANY thoughts on the approach, the strategy, the organization of the writing, the conclusions, the future implications, anything. For the Aug Arborist News article on heading cuts I got a little feedback; wish there was more.
The idea of cleaning out wounds and cavities has been controversial on this site and in the overall industry, so I KNOW there's got to be some reaction to this. Also I'm wondering if it's clear what's meant by "sinister symbiosis."
For the :alien: who don't get TCI or get it way late, I'll post the article below in two pieces:
OOZE IN THE NEWS
“Roll out those lazy, hazy, crazy days of summer; those days of soda, and pretzels, and beer!” as Nat King Cole sang way back when. Summer is also the time for other foamy stuff, the kind that has certain insects singing songs of cheer. However, this is not good news for the unfortunate older trees that serve as taverns for moths and hornets and other imbibing creatures. Tree owners who find these frenzied congregations on oozing lower trunks of their older trees often call arborists this time of year. But insecticide is not the answer, because the insects are only a sign of trouble underneath the bark. Oozing slime is a symptom of bacterial infection, and “…warm temperatures are favorable for the development of some bacterial diseases…” as John Lloyd notes in Plant Health Care for Woody Ornamentals.
A coating of polysaccharide, which is called a “slime layer” for obvious reasons, surrounds bacterial cells. When the bacteria multiply, they are forced out of the host plant and ooze down the bark. Dividing as fast as once every twenty minutes, they quickly build up their numbers to as high as a billion per milliliter. A cocktail of bacteria--Pseudomonas, Enterobacter and others--, yeasts and other organisms causes slime flux disease. Whether any of these organisms is particularly pathogenic, or it is simply the physical pressure caused by all of them multiplying that kills the bark, is not clearly understood. Fermentation produces gases such as methane and carbon dioxide, which increases the pressure that ruptures the bark. Many different microorganisms grow in the flux producing an indescribably foul or alcoholic odor that is hard to miss.
Different species of trees have different types of slime flux disease. The type that is found higher up in wounds and crotches of elms and poplars are considered relatively benign. They seldom seem to aggressively damage the bark. What damage occurs is well above ground level and considered correctable. They are located in Zones 2 and 4 as defined in Dr. Kim Coder’s Hazard Tree Evaluation form, published in 1990. On older oaks the disease is quite different; it is typically found between buttress roots. This is Zone 1, where damage and disease are considered critical. Previous physical damage or previous insect injury is seldom noted at infection sites on the trees studied. Like included bark in a crotch, the bark between buttresses seems to be squeezed. One theory is that the tree opens itself up to infection by wounding itself when bark is included, and the bacteria enter from the soil. This is confirmed by Dr. Alex Shigo in Modern Arboriculture: “Included bark between roots and root stubs are common underground infection courts.”
TO ACT, OR NOT TO ACT
The old practice of drilling into the infection and installing a drain pipe to direct the slime flux away from the bark can expand the infection court and worsen the disease. The wet, alkaline conditions at these sites is inhospitable to most decay-causing fungi, so one thought is to leave well enough alone. When armillaria fungus is found along with slime flux, more rhizomorphs are found outside the oozing areas. The “shoestrings” found in the slimy area are few and stunted.. Many insects that are harmless to the living tree—ants, termites, centipedes, sowbugs, for instance—can be found under the dead bark, but there is no reason to go after them. However carpenterworms, Prionoxystus sp., are also active in these infection sites. As Johnson and Lyons report in Insects that Feed on Trees and Shrubs, “Over a period of time the activities of the carpenterworm larvae may prove disastrous to the host tree…” The need to expose and treat this pest calls for the removal of dead bark. Bacterial activity and slime flux on older oaks can and does kill cambium, expanding the diseased area every year. So there is also a clear need for noninvasive methods to preserve the tree.
The first job is to find out which portions of the bark are dead. The first cues are visual; lesions bleeding with blackened sap at the margins of the diseased area. These lesions appear very similar to those caused by infections of fungi such as Phytophthora sp. Auditory cues are gained by tapping with a rubber or plastic mallet outside these lesions. A solid sound indicates living bark over solid wood. Tapping inside the lesions will produce a hollow sound, indicating dead bark. A stethoscope can be used to better hear the sound, but is not often necessary to detect dead bark. The next step is probing these areas with a blunt instrument such as a trowel or screwdriver. Remove all discolored bark down to the wood. In some cases this means removing a lot of bark. If the infection encompasses more than half of the trunk and decay is advancing inward, it is doubtful the tree will remain safe for very long. It is probably best to treat these unfortunate trees with a chain saw at ground level.
Cut around the infected trunk or branch until you come close to healthy cambium. Take care not to cut into healthy bark or wood. Excavation of wounds is still viewed with skepticism in some circles precisely because of the fear that careless digging will result in more damage. When most of the dead bark has been removed, a sharper tool will trim the edges of infected material. In Helping Plants Survive Armillaria Root Rot (November 2003 issue of Tree Care Industry), the author describes the excavation of tissue infected with the fungus Armillaria. Because bacterial infections seem less virulent, and do not cause wood decay like Armillaria does, a more cautious approach to tissue removal seems to be warranted. The goal is to come as close as possible to healthy tissue without cutting into it. A blunt-tipped knife, such as a linoleum knife, can trim the last scraps of diseased bark without scratching the wood. There is no need to trace the wound into an oval, because sap can flow laterally within the cambium. Careful removal of dead bark may reveal the cambial layer, still light in color and adhered to the wood. The more living cambium that is left, the sooner the tree can close its wounds. Rinsing off the last of the debris with a sharp stream of water from the garden hose or better yet a jet of air from a pneumatic tool will finish the excavation work.
ANY thoughts on the approach, the strategy, the organization of the writing, the conclusions, the future implications, anything. For the Aug Arborist News article on heading cuts I got a little feedback; wish there was more.
The idea of cleaning out wounds and cavities has been controversial on this site and in the overall industry, so I KNOW there's got to be some reaction to this. Also I'm wondering if it's clear what's meant by "sinister symbiosis."
For the :alien: who don't get TCI or get it way late, I'll post the article below in two pieces:
OOZE IN THE NEWS
“Roll out those lazy, hazy, crazy days of summer; those days of soda, and pretzels, and beer!” as Nat King Cole sang way back when. Summer is also the time for other foamy stuff, the kind that has certain insects singing songs of cheer. However, this is not good news for the unfortunate older trees that serve as taverns for moths and hornets and other imbibing creatures. Tree owners who find these frenzied congregations on oozing lower trunks of their older trees often call arborists this time of year. But insecticide is not the answer, because the insects are only a sign of trouble underneath the bark. Oozing slime is a symptom of bacterial infection, and “…warm temperatures are favorable for the development of some bacterial diseases…” as John Lloyd notes in Plant Health Care for Woody Ornamentals.
A coating of polysaccharide, which is called a “slime layer” for obvious reasons, surrounds bacterial cells. When the bacteria multiply, they are forced out of the host plant and ooze down the bark. Dividing as fast as once every twenty minutes, they quickly build up their numbers to as high as a billion per milliliter. A cocktail of bacteria--Pseudomonas, Enterobacter and others--, yeasts and other organisms causes slime flux disease. Whether any of these organisms is particularly pathogenic, or it is simply the physical pressure caused by all of them multiplying that kills the bark, is not clearly understood. Fermentation produces gases such as methane and carbon dioxide, which increases the pressure that ruptures the bark. Many different microorganisms grow in the flux producing an indescribably foul or alcoholic odor that is hard to miss.
Different species of trees have different types of slime flux disease. The type that is found higher up in wounds and crotches of elms and poplars are considered relatively benign. They seldom seem to aggressively damage the bark. What damage occurs is well above ground level and considered correctable. They are located in Zones 2 and 4 as defined in Dr. Kim Coder’s Hazard Tree Evaluation form, published in 1990. On older oaks the disease is quite different; it is typically found between buttress roots. This is Zone 1, where damage and disease are considered critical. Previous physical damage or previous insect injury is seldom noted at infection sites on the trees studied. Like included bark in a crotch, the bark between buttresses seems to be squeezed. One theory is that the tree opens itself up to infection by wounding itself when bark is included, and the bacteria enter from the soil. This is confirmed by Dr. Alex Shigo in Modern Arboriculture: “Included bark between roots and root stubs are common underground infection courts.”
TO ACT, OR NOT TO ACT
The old practice of drilling into the infection and installing a drain pipe to direct the slime flux away from the bark can expand the infection court and worsen the disease. The wet, alkaline conditions at these sites is inhospitable to most decay-causing fungi, so one thought is to leave well enough alone. When armillaria fungus is found along with slime flux, more rhizomorphs are found outside the oozing areas. The “shoestrings” found in the slimy area are few and stunted.. Many insects that are harmless to the living tree—ants, termites, centipedes, sowbugs, for instance—can be found under the dead bark, but there is no reason to go after them. However carpenterworms, Prionoxystus sp., are also active in these infection sites. As Johnson and Lyons report in Insects that Feed on Trees and Shrubs, “Over a period of time the activities of the carpenterworm larvae may prove disastrous to the host tree…” The need to expose and treat this pest calls for the removal of dead bark. Bacterial activity and slime flux on older oaks can and does kill cambium, expanding the diseased area every year. So there is also a clear need for noninvasive methods to preserve the tree.
The first job is to find out which portions of the bark are dead. The first cues are visual; lesions bleeding with blackened sap at the margins of the diseased area. These lesions appear very similar to those caused by infections of fungi such as Phytophthora sp. Auditory cues are gained by tapping with a rubber or plastic mallet outside these lesions. A solid sound indicates living bark over solid wood. Tapping inside the lesions will produce a hollow sound, indicating dead bark. A stethoscope can be used to better hear the sound, but is not often necessary to detect dead bark. The next step is probing these areas with a blunt instrument such as a trowel or screwdriver. Remove all discolored bark down to the wood. In some cases this means removing a lot of bark. If the infection encompasses more than half of the trunk and decay is advancing inward, it is doubtful the tree will remain safe for very long. It is probably best to treat these unfortunate trees with a chain saw at ground level.
Cut around the infected trunk or branch until you come close to healthy cambium. Take care not to cut into healthy bark or wood. Excavation of wounds is still viewed with skepticism in some circles precisely because of the fear that careless digging will result in more damage. When most of the dead bark has been removed, a sharper tool will trim the edges of infected material. In Helping Plants Survive Armillaria Root Rot (November 2003 issue of Tree Care Industry), the author describes the excavation of tissue infected with the fungus Armillaria. Because bacterial infections seem less virulent, and do not cause wood decay like Armillaria does, a more cautious approach to tissue removal seems to be warranted. The goal is to come as close as possible to healthy tissue without cutting into it. A blunt-tipped knife, such as a linoleum knife, can trim the last scraps of diseased bark without scratching the wood. There is no need to trace the wound into an oval, because sap can flow laterally within the cambium. Careful removal of dead bark may reveal the cambial layer, still light in color and adhered to the wood. The more living cambium that is left, the sooner the tree can close its wounds. Rinsing off the last of the debris with a sharp stream of water from the garden hose or better yet a jet of air from a pneumatic tool will finish the excavation work.
