Forest Health Monitoring Review: Fall 2004

• Weather
• Bark Beetles
• Gypsy Moth
• Other Defoliators
• Foliar Oddity
• Sudden Oak Death
• Hemlock Woolly Adelgid
• Funny Fungi
• Voles
• White Pine Mortality
• Acid Update
• Emerald Ash Borer
• Sporax
• Biocontrol of Old
• Fraxinus Favors

Health Watch
Health Watch

Health Primer
Life Under Foot
Multicolored Asian Lady Beetles

Health Update

Weather- It's been a stormy year. One tropical storm (Charley) and four tropical depressions (Gaston, Frances, Ivan, Jeanne) have included the Commonwealth, breaking the record number of four set in 1893. In late August, Gaston dumped up to 11 inches of rain in the greater Richmond area according to some reports. Downtown flooding was severe, interstates 95 and 64 were both closed in sections and five fatalities were attributed to the storm. Funnel clouds and tornadoes were numerous in east-central counties. About 10 days later, Frances brought more flooding, downed trees and power lines and tornadoes in at least nine counties. This was followed by Ivan which spawned tornadoes in at least two counties. Flooding in the greater Roanoke area closed a section of interstate 81.

As mentioned in the last issue, January through March of this year was a bit dry. April was generally warmer and wetter than normal. May precipitation varied among climatic divisions from 79% of normal in the Western Piedmont to 133% of normal in the Southwestern Division. May temperature, on the other hand, was uniformly much warmer than normal - from 5.4 to 6.9 degrees! June temperature was close to normal, but precipitation ranged from 117-181% of normal across the Commonwealth. July was similar, except for the Southwestern Division, which had 81% of normal precipitation. August precipitation exhibited a split between Tidewater plus Piedmont Divisions, which were very much wetter than normal, and the other three divisions, which were considerably drier than normal. August temperatures were slightly cooler than normal across the board. September precipitation ranged from 107% in Tidewater to 320% of normal in the Central Mountains and was roughly twice normal overall. Temperatures were one to two degrees above normal everywhere except the Western Piedmont. October rainfall was about half normal in every division except the Southwestern, which was about normal. Temperatures ranged from near normal in most areas to 3.1 degrees above normal in the Central Mountain and Southwestern Divisions.

Trees are still dying along the path of a severe wind and hail storm on May 9, 2003. Impact was greatest in Amelia and Southampton Counties. Trees in its path were completely defoliated, bruised and root-wrenched or blown down. Many that survived until winter could not rebuild enough crown to survive through 2004.

Bark Beetles-It's a pleasure to report a growing season of relatively few bark beetle problems. Pockets of one to a few infested trees were scattered about, but no large-scale infestations were detected. Engraver beetles, southern pine beetles and black turpentine beetles were all observed in some locations. Even better news is the great response of VDOF field personnel and the landowners they serve to incentives for precommercial pine thinning. This is an excellent, and expensive, practice and we are fortunate to have federal support to offer a cost-share program. About 1600 acres are already treated and nearly twice that have been signed up. These are acres that will be much more productive and much less prone to bark beetle attack. Generous support is expected to continue for at least another two years.

The benefits of precommercial thinning are readily apparent in plot data that John Scrivani recently distributed.

Gypsy Moth- As expected, the gypsy moth left us pretty much alone this year. No suppressionwas necessary, no defoliation met the aerial mapping threshold and no high-density populations have been located that might cause problems next spring. This was particularly helpful in that so few days had suitable weather for conducting aerial surveys. Let’s hope that next spring will be favorable for the fungus disease that has kept the gypsy moth at bay.

Other Defoliators- Early aerial surveys detected heavy fall cankerworm defoliation in the Bentonville area of Warren County and on one small ridge in west central Madison County. Cherry scallop shell moth feeding was obvious in many areas along the crest of the Blue Ridge. Locust leafminer was back to its usual high densities over much of the Commonwealth. Sycamore lacebugs were at higher than normal densities and very widespread. Late in the growing season redheaded pine sawflies were noticed in many coastal plain and piedmont counties, but no extensive defoliation was reported. Earlier in the year, a graduate student from Harvard University collected several species of pine sawflies for a genetics study and received much appreciated specimens and assistance from several VDOF personnel.

Foliar Oddity - At different times this year, very similar leaf peculiarities were reported from Franklin, Dinwiddie and Hanover counties. In the first two cases the effects were mostly on oaks and a few hickories. In Hanover, it was beech. Affected trees produced leaves that were convexly distorted above, somewhat smaller than normal and with a leathery texture. After considerable cogitation, and through a process of elimination, I decided these symptoms must have originated from late, local freeze events that caught individual trees at just the right stage of leaf development to cause injury, but not mortality.

Sudden Oak Death - Cooperative efforts to detect this disease fortunately have come up negative again this year. So far, there is no evidence that Virginia harbors the causal organism, Phytophthora ramorum. Detection surveys, involving VDOF, will continue next season. One new wrinkle will be the inclusion of Cooperative Extension and the Master Gardener program in an attempt to locate homeowners who might have purchased infected host plants from nurseries or other suppliers. Reports of dead and dying oaks increased noticeably following media coverage of the disease threat and I have checked more than the usual number of these oaks. The causal agents continue to be various combinations of old age, past and recent injuries, soil compaction, grade change (addition or removal of soil), drought or flood, defoliation by insects, root disease, hypoxylon decline and twolined chestnut borer. West of the Blue Ridge, oak wilt is an additional possibility.

Hemlock Woolly Adelgid - A survey of Virginia's seven most southwesterly counties this spring and summer failed to find any adelgids on hemlock, except in Tazewell County. The search will continue next spring with support from USFS. Although hemlock mortality is widespread in the rest of the Commonwealth, there are still locations where adelgids have been present for a decade or more without causing much mortality. This holds open the possibility that hemlock might not be extirpated after all. The adelgid was present in Virginia for nearly 30 years before it started killing trees. There is certainly a lot we don't know about site-host-insect interactions.

Voles - Training by Va Tech specialists Jim Parkhurst and Shawn Baker gave selected VDOF personnel a much better appreciation of the reasons that these critters are such pests. Vole damage continues to be a problem in some areas and heavy fescue seems to be one common feature that predisposes sites to high-density vole populations. A remarkable example in my experience occurred in Floyd County recently where voles girdled or damaged large numbers of seven-year-old white pines that were several inches in diameter at the base.

Funny Fungi - So many kinds of fungi have fared so well in the past two years that more than the usual number of folks have taken notice. One commonly encountered is the artillery fungus that inhabits mulch and ejects tiny black spore packets that adhere firmly to siding and cars. They cause a stain and are very difficult to remove. Slime molds can also occur on mulch, first as bright orange or yellow slimy masses, and later as dry powdery coatings. Their effect is merely cosmetic. The startlingly phallic stinkhorn fungi get their name from their form and foul-smelling cap. They're not likely to be overlooked. So-called fairy rings develop from the symmetrical outward growth of soil-inhabiting fungal mycelia from a central point and the subsequent production of fruiting bodies around the perimeter.

The largest living organism ever discovered is reported to be a fungus in eastern Oregon that extends over more than 2000 acres, and a more recent report mentions a species of Armillaria in the Swiss Alps that extends over 86 acres and is believed to be about 1000 years old. A few inquiries have come in concerning bioluminescent fungi. Light from living organisms results from the combination of oxygen with the substance, luciferin, in the presence of the enzyme, luciferase. This occurs in protozoa, insects, crustaceans, and fish as well as fungi. The honey mushroom, Armillaria mellea, is the fungus most commonly seen glowing in decaying wood. Foxfire (from the French, faux, meaning false) is a familiar folk name for this phenomenon.

White Pine Mortality - Thanks to culture work by USFS pathologist, Michelle Cram, we now know that at least some of the white pine mortality we've been attributing to procerum root disease was actually Phythophthora root rot, caused by Phytophthora cinnamomi. Is this a result of two wet seasons or has Phytophthora, been more of a factor than we realized all along? Future experience should provide the answer.

Acid Update - Long-term stream monitoring by University of Virginia scientists reveals continuing acidification of sensitive streams in western Virginia, primarily from sulfur deposition. This is happening despite recent decreases in acidic deposition and evidence for recovery in other regions following implementation of the Clean Air Act amendments of 1990. The problem is most pronounced in watersheds associated with base-poor quartzite and sandstone where calcium and other basic materials are depleted more quickly. Roughly a third of native brook trout streams are affected.

Emerald Ash Borer - A special survey for the emerald ash borer was completed this summer and will be continued in 2005 with support from USFS. A concerted effort to eradicate EAB from Fairfax County, where it was introduced with infested nursery stock from Michigan, was apparently successful. Continuing surveys will attempt to detect any new introductions before the beetle has a chance to become firmly established. The most effective approach is to weaken trees artificially and see if they are attacked. Searching whole trees at random for such tiny beetles is too inefficient.

Sporax - Treating fresh-cut pine stumps with borax to prevent transmission of annosum root rot after thinning is important on high-hazard sites. The only available and legal formulation of borax is called Sporax, and until recently it was not registered in Virginia. We arranged for its registration so DOF could use it to protect stands scheduled for thinning on the new Sandy Point State Forest. It is now an option for anyone who thins pines on deep, dry, sandy soils.

Biocontrol Of Old - The following refers to dragonflies and is from an extensive section on insects in The Fifth Reader of the United States Series by Marcius Willson, Harper & Brothers, New York, 1872: "Yet, when darting rapidly through the air in search of their prey, they are like roving freebooters,d for they feed upon all insects which they can overpower. If several of them be shut up in a house for a short time, they will effectually rid it of flies, musquitoes [sic], and other troublesome household pests." The footnote defines freebooters as "robbers; plunderers."

Fraxinus Favors - It's certainly no surprise that Native Americans used green ash for building materials, utensils and weapons; but infusions of inner bark were also used to fight depression and fatigue, and as a tonic. The Ojibwa cooked scrapings of the inner bark for food, which reportedly tasted like eggs. No mention is made of eating it with green ham. White ash was used more for treating problems such as earache and stomach cramps and as an emetic.

Health Watch

Health Primer

Life Under Foot

Forest soils teem with life. It's a well known and generally underappreciated fact. Although foresters are generally familiar with the physical characteristics and productivity of local soils, few of us have had an opportunity to investigate the lives of soil biota. Most soil organisms are microscopic and are not well studied. In fact, most have yet to be described. We've hardly begun to understand how they interact with each other, with root systems and with their physical and chemical environments. Their vital influence on forest health is axiomatic.

The sizes of soil organisms relate to their microhabitats and their influences on soil properties. They are commonly classified into three size groups: (1) the microfauna and microflora, such as bacteria, fungi and protozoa, (2) the mesofauna, including mites, springtails and several less familiar groups and (3) the macrofauna, such as many insects, earthworms, snails and woodland voles. Of course all soil organisms do not fit neatly into just one of these groups. Some species of nematodes, for example would fall into each size category. The smallest inhabit water films on soil particles, the mid-sized species occupy existing pore spaces and the largest can move soil particles and create their own spaces.

Structure and texture affect the kinds of soil communities that develop. For example, porosity has a key influence on habitat space as well as the movements of air, water, roots and fauna. Clay content is strongly related to soil surface area. It is hard to fathom just how much surface area there is - up to hundreds of square meters per gram of soil depending on particle size and structure! It is these surfaces that are the sites of many chemical reactions involved in carbon and nutrient dynamics.

The cleansing and recycling services of soil biota make them invaluable. Decomposition of organic matter is very much a community affair. Soil fauna are major contributors to the mechanical breakdown of litter, but initial chemical decomposition is largely the work of fungi and bacteria. Few soil animals have enzymes that allow the digestion of plant matter. Forest litter is a mixture of easily decomposed and relatively recalcitrant materials. Thin, calcium-rich dogwood leaves, for instance, break down much more easily than thick, lignified oak leaves. Sugars and starches are readily digested whereas tannins and lignins are utilized directly only by specialized organisms, such as the white rots. Cellulose and hemicelluloses, which account for over half the carbon in plant debris, are intermediate in degradability. Root death probably contributes up to half the carbon added to forest soils annually. Algae in the surface few millimeters can also fix considerable carbon. Nitrogen and carbon in decomposing roots might pass to primary decomposer bacteria and fungi and from them to flagellates and amoebae, next to nematodes and then to mites and on to ants. All the while these organisms are interacting with each other, with living roots and with the mineral soil environment. Root exudates, for example, can stimulate the release of nitrogen from N-fixing bacteria.

Subterranean environments tend to remain humid. Even air-dry soil (2% by weight) has a relative humidity of 98%. Most soil organisms live in a saturated atmosphere and absorb and lose water through their integuments. Temperatures fluctuate less and more slowly in soil than above ground, and freezing does not occur at depth in many latitudes. On the other hand, frost heaving can be a disruptive influence on soil organisms near the surface where freezing occurs.

Microscopic biota confined to soil water films are sometimes referred to as"terrestrial nannoplankton"and include bacteria, yeasts, protozoa, rotifers, nematodes, copepods and enchytraeids. Bacteria are probably the most speciose organisms on Earth and also the most numerous. Most live below ground. Among other things, they make nitrogen available for plant and microbial uptake. Yeasts are single-celled fungi that have enzymes for converting carbohydrates into alcohol and carbon dioxide. Protozoa are a diverse group of single celled or colonial organisms that ingest both living and dead organic particles. They include such groups as the flagellates, amoebae and ciliates and can number up to hundreds of thousands per gram of soil. Usually known as aquatic animals, rotifers sometimes exist in large numbers in both forest and agricultural soils. They are multicellular and have a ciliated wheel-like organ for feeding and locomotion. Nematodes are extraordinarily numerous and diverse in size and feeding habits. Some plant-pest species are familiar, but many other species help suppress pests. Nematodes feed on bacteria and fungi as well as crop plants, and many are predators. Copepods are tiny, cylindrical, filter feeding crustaceans usually associated with aquatic environments and of unknown significance to soil dynamics. Enchytraeids ("potworms"), are small unpigmented worms like miniature earthworms that ingest both mineral and organic particles. They are typically 10-20 mm long and have significant effects on organic matter dynamics and soil structure.

Among the mesofauna, mites and springtails are the most familiar and numerous. There can be hundreds of thousands of individuals and thousands of species per square meter of soil. Mites contribute significantly to organic litter decomposition by grazing on microbes and fragmenting plant detritus. They can store and process a large portion of calcium in the litter. Some species feed selectively on fungi or nematodes and may have important effects on plant pathogens. Chiggers are larvae of a family of mites that feeds on springtails and their eggs. Springtails are tiny insects with worldwide distribution that live both in the litter and throughout the soil profile. They are permanent soil residents unlike many other insects that spend only part of their lives in the soil. Springtails are opportunistic feeders but fungi probably make up a majority of their diets. A European species called the glacier flea is active when temperatures are below freezing. It feeds on pollen grains that have fallen on glacial ice. Snow fleas have similar habits in North America.

Macrofauna such as earthworms, ants and termites have major effects on soil structure as well as litter decomposition. Earthworms ingest a mix of mineral and organic matter that is enriched with gut secretions and colonized by microbes before being ejected as a slurry or pellet. Their activity greatly influences the fragmentation, burial and mixing of plant residues as well as the formation of soil pores and aggregates. More than 3500 species have been described so far, but fewer than a half dozen species are likely to occur in a particular soil and these might not overlap in space. In any one location the earthworms present can be all native species, all exotic species or some combination. Termites are particularly important because the guts of many species are colonized by protozoans that enable the digestion of cellulose and thereby the reduction of woody debris. Other termite species have bacterial and fungal gut symbionts that facilitate the digestion of organic matter. Another group lacks intestinal symbionts and cultures fungi for nutrition. Termite colonies can move huge amounts of soil in the process of nest building, foraging and feeding. Ants are similar to termites in their extensive effects on soil structure. Ants are also major predators of small invertebrates, including mites.

Fungi are pervasive in forest soils, both in function and extent. They degrade organic matter, serve as food for countless other organisms and interact with plant roots in complex ways. Fungal hyphae extend throughout the soil profile and connect its innumerable inhabitants through multifarious networks. One study revealed that an ectomycorrhizal fungus on white pine actually immobilized and infected springtails and these springtails indirectly provided a significant portion of the tree's nitrogen. Another study of fungus-eating mites showed that some species require a nematode"supplement"in order to complete their life cycles. The vital interactions of mycorrhizal fungi and tree roots were covered previously. Plants that don't have mycorrhizae still can have fungal associates but their functions are unknown.

No mention has been made yet of many insects, spiders, centipedes, millipedes, proturans, diplurans, pseudoscorpions, symphylans, pauropods, viruses and other groups that also inhabit forest soils. These organisms are generally less numerous or less studied or perceived to have less of an overall impact on soil dynamics, and I've gone on too long already. Simply put, there's a lot more to forest soils than meets the eye. Next time you're in the woods, consider the priceless activity that's raging under your feet. Soil rocks!

Multicolored Asian Lady Beetles

Current developments in research concerning this exotic nuisance predator were recently summarized in the fall issue of American Entomologist.

After several unsuccessful releases of the multicolored Asian lady beetle, Harmonia axyridis Pallas, an established population was discovered in Louisiana in 1988. From there it spread to much of the United States and southern Canada. It has become a major control agent of some pest aphids and, at the same time, a major pest itself.

The beetles are more than just a seasonal nuisance in homes. They also injure fruit. Grapes are particularly affected (and one beetle in with the grapes is enough to ruin a bottle of wine), but apples, peaches and other fruit are also damaged. They seem to prefer injured fruit for feeding sites, but are also capable of breaking the skin on undamaged fruits. They will break human skin too, and can draw blood if allowed to remain long enough. Both sexes will occasionally bite people. When disturbed the adults exude a malodorous liquid ("reflex bleeding") that stains walls, furniture, carpets and draperies. They can get into food. There have been a few cases of people having allergic reactions to the beetles.

All kinds and colors of houses appear to be susceptible to invasion. Those with woods on one side tend to be slightly more at risk. Proximity to high late-season aphid infestations, air currents and topography also play a part. Chemical communications among the insects is probably a factor too. The adults are attracted to high-contrast linear features like the cracks in cliff faces where they overwinter in natural habitats. Unfortunately, home exteriors are also full of such features (e.g., siding, gutters, downspouts etc.).

The most popular and effective method reported for protecting homes against invasion is application of insecticide to the exterior. The products used most frequently contain the active ingredients cyfluthrin, permethrin or tralomethrin.

Last modified: Monday, 19-Oct-2009 14:40:05 EDT