Diseases of trees are relatively common, but not commonly catastrophic.Most are caused by fungi, some very specialized, and some much more generalized.
This afternoon I’ll briefly present some information about forest diseases that you should be aware of, and may already know about.I’ll touch on 4 areas of information…Forest diseases realities… just a few thoughts that are broadly true,Diseases you are most likely to encounter… I’ll give a few details about these so you know what to look for and what, if anything, to do,Diseases you will hear about… these are ones that will be in the news or forestry information outlets, but are very unlikely to show up in Arkansas or cause you problems, at least right now; one I’ll mention might.Monitoring tools and information sources… mostly on the web
Most forest diseases won’t affect you in managing your forestland. As I mentioned, there are many, many tree diseases, from obscure to dramatic, so, when one or more shows up, they can be anything from an interesting nuisance to a real concern (rather rare).Treatment options for diseases are, unfortunately, very limited. Management activity to prevent, or minimize damage is generally the only economical option.Monitoring the presence, status, and likely impact of the few most common and dangerous diseases in your general area is something you should do, so you won’t be surprised or unprepared if one shows up on your property.
Well, here’s the short list of diseases that you might encounter on your land, and that could cause you some concern or loss, and that you might be able to do a little something about.I’ll touch on each one and give some brief details, but I’d encourage you to research these further for yourselves so you have more information at hand.
Fusiform rust is generally considered the more serious disease threat to southern pine management.Its caused by an fungus, Cronartiumfusiforme, which is an obligate parasite, always living in intimate contact with its 2 host plants – pines and oaks.It has a complicated life cycle and the damage done to pines is the formation or galls on mainstems or branches that kill or deform them.It’s a serious issue in nursery culture, but regular sprays of systemic fungicide effectively prevents infection there.In outplantings, rust infection occurs in the first few years and can be very high, depending on the current year’s weather, the site conditions, and the susceptibility or resistance of the planting stock.Galls on the main stem of young trees generally result in death or severe deformation. Galls on branches within 12” of the main stem usually grow into the stem in a few years causing a lethal or deforming canker.
To summarize the basic information about rust…Loblolly is less affected than slash; shortleaf is immune; longleaf is pretty resistantRust hazard in southern AR is low to moderate based on analysis of infection levels in FIA dataAt about age 5, determine if you have sufficient stocking of uninfected trees to manage the stand to your projected rotation ageMid-rotation, cankered trees should be removed during thinnings whenever possible to capture volume and improve the standGenetic improvement and nursery culture has greatly reduced disease severity and losses in the region; always plant the best, most resistant stock you can obtain that is suitable for your areaRare in recent years to have catastrophic losses, although it can still happen
This root disease fungus has been re-named again, necessitating a change in common name – now we are calling it Heterobasidion root disease. You may have first learned about it as Fomesannosus, or fomes root rot, or annosum root rot, etc.The fungus is a mild pathogen with saprophytic ability and usually only kills trees on deep, dry, sandy soils after a thinning.
Sporophores of the fungus are produced mainly in the spring and fall, usually under the duff layer at the base of dead or dying trees or on stumps.Airborne spores of the fungus land on freshly-cut stump surfaces, colonize the stump and attached roots and spread by root contacts to nearby healthy trees. On a dry, stressful site, the fungus can continue to colonize the living trees and eventually debilitate or kill them.Small patches of dead trees can develop, as well as individual dead trees, scattered throughout a stand.Sprinkling powdered borax on cut stumps is an effective control, but rarely implemented, probably due to the nuisance factor. There are borax products registered as pesticides for this use. Liquid formulations can also be used. Borax is not recommended at a second or third thinning if root disease is already present in a stand since it can’t be excluded.
Pitch canker is caused by a fungus…It tends to be a wound pathogen, entering a shoot, twig, or branch through physical or insect wounds and causing a resin-soaked canker.Symptoms are wilting, reddening of foliage and shoot and branch dieback distal to the canker.
Copious resin on the bark is usually an indication of the resin-soaked canker underneath. A multitude of these cankers can kill large portions of crowns or entire trees. Ips bark beetles may be attracted to the stressed trees.
Dense stands have sometimes experienced epidemic pitch canker outbreaks, probably due to storm damage or insect damage and high-humidity, closed crown conditions perhaps accompanied by high fertility and rapid growth.
In FL, particularly, with slash pine, but also in MS with loblolly, stands downwind (the exhaust ends) of chicken houses have experience epidemics of pitch canker, primarily due to nitrogen deposition. Disease incidence and damage was most severe on the stand edge closest to the houses and tapered off out to 500 meters or so. Nitrogen deposition was measured and it followed the same pattern in foliage and soil. Stimulated succulent growth is easily wounded during storms and attractive to insect feeding, etc.
Well, the lone hardwood disease I want to mention is oak decline.Actually, this is a complex syndrome, not a single agent-caused malady.It is episodic and we think of it as occurring when one or more predisposing factors are present, such as…An oak decline event or episode is triggered by an event or factor causing severe stress,Followed by the actions of one or more contributing factors, like…; these are secondary agents that become enabled to cause more damage due to the presence of tree stress.
Oak decline is evidenced by a variety of symptoms from foliage yellowing, browning and being retained for a period, defoliation, twig and branch dieback, and mortality.Decline, as its name suggests, is generally progressive over a season or a year or two; but sometimes dieback and mortality can occur rather suddenly.Severely-affected areas may follow soil or topographic patterns or vary according to stand composition.
The insect and fungal contributing factors are the ones we often see and place most blame on, but they are just one component.Armiallaria…Red oak borer populations reached unprecedented epidemic levels in the 1999-2001 decline event in the Ozarks you are probably aware of. These borers…In other areas the 2-lined chestnut borer is a player…
Hypoxylon canker is almost always present on oaks that are damaged or dying from almost any causes, and most pathologists consider it a secondary agent which actually contributes little to branch and tree mortality, rather it quickly colonizes dead and dying tissues.
Well, what about diseases you hear about, but are not likely to encounter. Here are several, and the one that might show up here in the next few years.Pine decline has caused some management problems over in AL and GA and is a little like oak decline in that it is a complex syndrome involving root-feeding insects and root-staining fungi that can contribute to stress and wilt. The agents involved here could probably be found in AR and other parts of the South, but there have not been any clear cases of this problem in the western part of the region yet.Oak wilt – this tree-killing disease is caused by a fungus and is present over much of the South. However, it is relatively rare in AR and you’re just not very likely to see it or have it on your property. If you do, it generally only kills a few trees in a small patch or infection center and then plays out. It does cause extensive mortality of live oaks over in Central Texas and of northern pin oak and other species up in the Lake States.Sudden oak death has caused us much concern since it was discovered killing tanoak, coastal live oak, and California black oak out on the west coast. About 2004, it became apparent that the causal fungus (organism) was also able to infect foliage and shoot of many common nursery ornamentals like camellia and rhododendron. These plants were shipped from infected west coast nurseries to virtually every other state. Survey work since then has documented contamination of quite a number of eastern nurseries as well as a few locations where the organism is moving off-site in drainage water, but nowhere has any infection in oaks or forests been found in the east. Some day it may be, but its not likely right now.Thousand cankers disease of black walnut is another disease issue that first caused problems in the west – interestingly in planted eastern black walnut in western states like CO, NM, CA, ID, OR…
The fungus which causes the cankers and the twig beetle that carries it are both native to the western US, but not pests which have previously been associated with eastern black walnut as a host – they functioned rather benignly on western walnut species causing very little damage. Movement of walnut wood from the west to the east has resulted in both beetles and fungus being introduced to eastern black walnut in TN, VA, PA and OH. The affected areas are still rather localized, but it seems that in spite of quarantines, the disease will show up in more places in the next years and AR certainly has some host material. I don’t know about the size of the walnut industry in AR, but I’m sure there is some. I know it is big in MO and over into IN, etc.
The walnut twig beetle is very small and the fungus was previously undescribed until the issue arose in the west. The beetles actually attack much larger material than twigs and build up over a period of time in individual trees as long as there is suitable material to infest. The fungus is a rather mild pathogen in and of itself, but every beetle attack introduces the fungus and as each little canker expands they begin to coalesce until parts of the tree are girdled and killed. Thus, you need thousands of cankers (and beetle galleries) to cause symptom expression.
Yellowing and wilting foliage, defoliation, and dieback are the primary symptoms followed by mortality.In the east, the full impact of the disease is not yet know, and symptom progression as well as the behavior of the beetle and fungus are being monitored and studied.
And you all know there is a wealth of information on the internet. The most useful sites are displayed here, but, of course, there are many more.
1. Arkansas Forestry Association
October 1-3, 2013
Little Rock, AR
Dale A. Starkey, Plant Pathologist
USDA Forest Service, Southern Region
State & Private Forestry, Forest Health Protection
2. Arkansas Forestry Association ~ October 1-3, 2013 ~ Little Rock, AR
Forest disease realities
Diseases you are most likely to encounter that
could affect your forest management plans
Diseases you will hear about, but are unlikely to
Monitoring tools and information sources
3. Arkansas Forestry Association ~ October 1-3, 2013 ~ Little Rock, AR
Most forest tree diseases won’t affect you in
managing your forestland.
When they do show up, they can be anything from
a very minor nuisance or no real concern (most
often) to a catastrophe (seldom).
Very few effective or economical management or
direct control treatments are available.
You do need to monitor the presence, status, and
likely impact of forest pests in your general vicinity
so as not to be caught unaware.
4. Arkansas Forestry Association ~ October 1-3, 2013 ~ Little Rock, AR
Southern pine diseases
Heterobasidion root disease
5. Arkansas Forestry Association ~ October 1-3, 2013 ~ Little Rock, AR
Slash and loblolly pines
Nursery and young plantations
6. Arkansas Forestry Association ~ October 1-3, 2013 ~ Little Rock, AR
Loblolly is less affected than slash; shortleaf is immune;
longleaf is pretty resistant
Rust hazard in southern AR is low to moderate
At age 5, determine if you have sufficient stocking
Mid-rotation, cankered trees should be removed during
Genetic improvement and nursery culture has greatly
reduced disease severity and losses in the region
Rare in recent years to have catastrophic losses
requiring stand replacement, although it can still
7. Arkansas Forestry Association ~ October 1-3, 2013 ~ Little Rock, AR
Heterobasion irregulare; H. annosum, H. annosus, Fomes
annosum, F. annosus
Disease of thinned pine plantations on deep, sandy
Cut stump surfaces are the infection court
Spread is from dead stumps/roots to nearby living
trees, usually creating small groups of dead trees, or
Mortality peaks about 3-5 years post-thinning
Powdered borax applied to the stumps immediately
after cutting is preventive
8. Arkansas Forestry Association ~ October 1-3, 2013 ~ Little Rock, AR
9. Arkansas Forestry Association ~ October 1-3, 2013 ~ Little Rock, AR
Fusarium circinatum; F. subglutinans, F. subglutinans f. sp.
pini, F. moniliforme var. subglutinans, F. lateritium f. sp. pini
A resin-soaked canker, usually on shoots and small branches
although it can occur on the bole
Generally kills the distal portion; wilting, reddening,
browning of needles
Episodic, weather-related; a common problem in seed
orchards, occasionally in nurseries, outplantings, and
young, dense plantations
Initiated or exacerbated by wounding (eastern pine weevil),
damage, high-N fertilization, plantings on agric. lands
10. Arkansas Forestry Association ~ October 1-3, 2013 ~ Little Rock, AR
Edward L. Barnard, FL DACS, Bugwood.org
Edward L. Barnard, FL DACS, Bugwood.org
11. Arkansas Forestry Association ~ October 1-3, 2013 ~ Little Rock, AR
Thin stands as early as possible
12. Arkansas Forestry Association ~ October 1-3, 2013 ~ Little Rock, AR
Florida Department of Agriculture & Consumer Services
Avoid chicken houses?
13. Arkansas Forestry Association ~ October 1-3, 2013 ~ Little Rock, AR
Episodic, multi-factor syndrome of oaks, hickories
Predisposed by older-age, overstocked (?), stands often on generally
poorer, drier sites, on ridges or with southerly aspects
Triggered by acute drought or defoliation events (east-gypsy moth)
Exacerbated by contributing, secondary agents like borers (red oak
borer) and Armillaria root disease, etc.
Hypoxylon canker is frequently seen, but really contributes little to mortality
Red oaks more quickly and severely affected than white oaks or
Bottomland and stands on higher-quality sites can be affected as well
Oak decline events may last 2 to several years
A useful rule-of-thumb – as stand age eclipses site index, vulnerability to
oak decline increases
14. Arkansas Forestry Association ~ October 1-3, 2013 ~ Little Rock, AR
15. Arkansas Forestry Association ~ October 1-3, 2013 ~ Little Rock, AR
Armillaria root disease
Red oak borer
16. Arkansas Forestry Association ~ October 1-3, 2013 ~ Little Rock, AR
17. Arkansas Forestry Association ~ October 1-3, 2013 ~ Little Rock, AR
Southern pine diseases
Leptographium root disease
Root-feeding weevils and beetles
A tree killer, but not so much in AR
Sudden oak death
Still a CA disease; not in the South or East yet
Pathogen is in ornamental nurseries in the South and drainage
water, but not native vegetation (since 2004)
Thousand cankers disease of black walnut
This one could get here soon and could cause problems
18. Arkansas Forestry Association ~ October 1-3, 2013 ~ Little Rock, AR
Walnut twig beetle (Pityophthoris juglandis) and fungal
canker (Geosmithia morbida); both native to southwestern
U.S. (on AZ and little walnut)
Wilting, dieback, mortality of eastern black walnut planted
in western states like CA, CO, NM, UT
Recently shown up in several areas of the east
Knoxville, TN (2010) – now in 6 counties
Richmond, VA (2011) – now in 7 counties in 2 areas
Bucks County, PA (2011)
Butler County, OH (2013)
Great concern in native eastern black walnut growing
Damage is occurring, but the full impact and rate of spread,
etc. is yet unknown
19. Arkansas Forestry Association ~ October 1-3, 2013 ~ Little Rock, AR
Photos by Ned Tisserat,
Colorado St. Univ.
20. Arkansas Forestry Association ~ October 1-3, 2013 ~ Little Rock, AR
Curtis Utley, CO St. Univ., Bugwood.org
21. Arkansas Forestry Association ~ October 1-3, 2013 ~ Little Rock, AR
Forest Pest Conditions website
Southern Region, Forest Health Protection
Arkansas Forestry Commission website
University of Arkansas Extension website
Your local county forester or extension agent; AFC
forest health specialist