Forest Health Monitoring Review: Spring 2004

• Weather
• Bark Beetles
• Gypsy Moth
• Other Defoliators
• Fusiform Rust
• Periodical
• White Pine Survival
• Voles
• Pesticide Disposal
• Invaders
• Briefs
• Take Tsuga

Health Watch
Health Watch

Health Primer
Wood Decay
Migration

Health Update

Weather - February through September and November of last year were wet, record-breaking wet. The departure was 20 inches above the long-term average of 42.9 inches, the greatest deviation in the 109-year record. October was drier and cooler than normal in every Climatic Division, although not by a big margin in every case. November precipitation was about normal in Tidewater and from 119-177% of normal elsewhere. Heavy rain on November 19 caused damaging floods in the central and southern mountains. Every Division was also from 4 to 5 degrees warmer that normal. December ranged from normal precipitation in the Southwest to 174% of normal in Tidewater, and every Division was at least a little cooler than normal. January remained cool everywhere, but switched to being consistently quite dry. February was near normal with a slight tendency toward dry and cool. March was uniformly warmer and drier than normal. April was about normal in the Western Piedmont and quite a bit warmer and wetter than normal elsewhere. Early May brought strong winds to much of central and northern Virginia, including uprooted trees, power outages and at least one tornado.

We are still recovering from the impact of last year's many storms. Pine stands heavily defoliated by large, wind-driven hail failed to recover and many hardwoods are recovering slowly, or in some cases, not at all. Blowdown from hurricane Isabel still clutters the forests of eastern Virginia, including the Dismal Swamp where unique stands of Atlantic white-cedar were leveled. Fire hazards will remain elevated for some time.

Temperature was more variable. January and February were cold, March was warmer than normal by an average of 2.8 degrees, and April was about normal everywhere. May ranged from 2.8 degrees above normal in the Southwest to 5.8 degrees below normal in the Western Piedmont. June was quite cool, from 2.1 degrees below normal in Tidewater to 5.3 degrees lower in the Western Piedmont. July was a degree warmer than usual in Tidewater and cooler elsewhere, up to 2 degrees cooler in the Western Piedmont. August was warmer than normal in every Division, up to 2.6 degrees warmer in Tidewater. September ranged from 1.4 degrees warmer in Tidewater to 2.3 degrees cooler than normal in the Western Piedmont.

The April issue covered winter storms. Since then, we've had plenty of additional impact. Some high elevations sustained a late spring freeze that affected emerging foliage and caused confusion during aerial defoliation surveys. On May 5, there was an earthquake (3.9) in central Virginia near Columbia that fortunately caused little damage. On May 9, an extraordinarily powerful storm tore a several-mile wide path from Albemarle County southeast through Southampton and into North Carolina. Straight-line winds of nearly 100 mph, two tornadoes and phenomenal hail caused extensive and severe damage. High quality timber was broken and uprooted in Albemarle, Amelia lost large trees in its court square and for several miles southeast of town, Southampton County sustained major damage to forests and structures from huge hail stones (up to 3 inches or more) blown by high winds. Large areas of pine were killed by loss of growing tips as well as foliage in combination with heavy bark damage. Scattered wind and hail damage occurred along the full path of the storm, affecting parts of 8 or more counties. At least one commercial tree nursery was also heavily damaged.

Flooding in May was widespread and damaging, including human fatality. Many records were set for numbers of rainy days. Woodstock, which is normally one of the driest areas in Virginia, had 23 rainy days in May - 5 more than the previous record set in 1953. Many more precipitation records have been broken since May and local flooding has been a recurring problem. On July 9, a tornado hit in Loudoun County, hail was reported in Bedford and Franklin and winds up to 60 mph caused tree damage and power outages in Richmond and surrounds. On August 26, a hailstorm and possible tornado hit near Richmond, hail and wind damage was reported from Loudoun, Westmoreland and Middlesex and wind damage affected parts of Fairfax and Arlington. The next day a large tent collapsed on Albemarle County fairgoers during driving rain and gusty winds. On September 2nd, strong winds and up to 6 inches of rain caused flooding and power losses around Charlottesville, and hail with damaging winds hit Madison, Stafford, King George and Rockbridge. All this was just the opening act for hurricane Isabel, which roared through on September 17 and 18, leaving behind a huge tangle of downed trees and power lines that kept some folks without electricity for two weeks or more. Tree damage was worst in southeastern counties, but extended northwest into the Piedmont and northern mountains. Shortly after, on September 23, a tornado tracked from Nottoway County northeast through Amelia, northside Richmond, Henrico, Hanover, King William and into the Northern Neck causing additional severe damage and power outages. Total timber losses were estimated by John Scrivani to be $176,760,303 based on average value per acre and estimated percent loss by county.

On October 7, at the request of the Virginia Loggers Association, Governor Warner authorized a temporary waiver of registration, license and weight restrictions for logging trucks operating in hurricane affected counties.

Bark Beetles Last year was a relatively unusual ‘beetle year’in my experience. The historical tendency has been for Virginia to sustain periodic outbreaks separated by years with almost no beetle activity. Last year, we had scattered and moderate infestation levels of both southern pine and engraver beetles. Fortunately, most of the infested timber was salvaged. Occasional reports of beetle activity over the past few months suggest that infestation levels have remained at noticeable levels. Spring trapping results to date from Cumberland and Buckingham indicate that southern pine beetle activity should be static and moderate.

We are fortunate to have received substantial support from the US Forest Service to initiate bark beetle prevention and restoration efforts. In particular this has allowed us to establish a cost-share program to promote pre-commercial thinning of overstocked pine stands. Initial response has been very encouraging and we hope the program will continue to expand. Federal support has also allowed us to accelerate the restoration of longleaf pine where it used to flourish and where it performs better than loblolly. Billy Apperson is leading this effort and has achieved considerable success so far. Increased training and public outreach should help inform the forestry community and landowners about keeping pine forests healthy.

A formulation of the insecticide, Bifenthrin, is now available for use by commercial applicators under the trade name “Onyx”to protect ornamental trees against bark beetles, borers and many other insect pests. Currently, there is no registered and available insecticide against bark beetles or borers in the forest.

Gypsy Moth - We're looking forward to a year of very low gypsy moth populations and no need for a cooperative suppression program. The only treatments will be Slow-The-Spread applications of pheromone along the leading edge of infestation and continued pheromone research applications on the State Forests.

Keep in mind that logs, pulpwood, chips, bark, firewood, mulch, Christmas trees and other forest products moving from the quarantined area into Craig, Roanoke, Franklin, or Henry Counties or points west and south are still regulated. Receiving mills, shippers and loggers need compliance agreements. Training and assistance can be obtained from Jim Zinck (540) 394-2507.

Other Defoliators - According to Kenny Thomas, the weevil that feeds on, and pupates in, yellow-poplar leaves was attracted to his yellow fire shirt in unusually high densities this spring. We'll look for feeding injury from the air when we check for fall cankerworm defoliation. At least one county and a few private landowners are planning to spray against fall cankerworm this spring after one or two years of defoliation. Eastern tent caterpillar has been notably uncommon this spring. Reports of pine sawflies were received from Buckingham, Dinwiddie and Patrick Counties. Light and scattered defoliation by the Virginia pine sawfly has been noticed in several central piedmont counties.

Last year there was an unusual episode of defoliation by the holly looper in Region 2. Not much is known about this inchworm. Reportedly, it overwinters in the Gulf States and migrates north. Feeding was scattered across many counties and some trees were almost completely defoliated.

Fusiform Rust - Last year's extreme weather was presumably responsible for an extraordinary spike in fusiform rust infections. It will be awhile before the full impact is realized. We have no record of this disease occurring at such high levels before. A few plantations in the southernmost coastal plain have had noticeable damage, but not enough to alter management. We have seen it in our nurseries before, but only incidentally. A one-page information sheet has been distributed internally to help us explain this phenomenon to landowners and it's available to anyone on request.

Periodical - Before long, the din of male cicadas singing for a mate will be heard over much of the East. In Virginia, this chorus should be heard in Augusta, Carroll, Clarke, Culpeper, Fairfax, Fauquier, Frederick, Grayson, Lee, Loudoun, Orange, Prince William, Roanoke, Shenandoah, Spotsylvania, Warren, Wise, and Wythe Counties. One couple told me they plan to visit Charlottesville for awhile to escape the noise in northern Virginia. Three species are involved. Emergence usually begins at dusk and it takes them a few days to complete maturation. Egg laying begins in about 2 weeks and the whole episode is over in about 6 weeks. Each female can lay several hundred eggs in twigs, which eventually causes the twigs to die and turn brown. Hatch occurs in 6-10 weeks. Damage to twigs can be prevented on small trees by covering them with cheesecloth. The impact of root feeding by the immature stages is not well quantified. If you get bored, see if you can distinguish and interpret all 5 male signals. Females communicate with wing flicks.

White Pine Survival - A small study to evaluate some of the factors that can contribute to mortality of eastern white pine seedlings was established with local assistance in Augusta, Carroll, Floyd, Franklin, Rockingham and Washington Counties last spring. Results confirmed the importance of preventing desiccation and of controlling sod before planting. Care in the nursery, during transport and by planters can all be critical. White pine seedlings are much less tolerant of careless handling than are loblolly seedlings. The full report is available on request.

Wayne Bowman and John Scrivani have established a study to evaluate herbicide alternatives for controlling sod after planting. The results should be especially useful to those planting white pine. They have also cooperated with growers in another study to evaluate nearly two dozen white pine families for Christmas trees and greenery.

Voles - Continuing local problems with voles is another important reason to plan on controlling sod before planting open fields. Voles can continue to be a seasonal problem until crown closure shades out the grass. Landowners should plan on continual grass control with mowing or chemicals until trees are no longer susceptible.

Pesticide Disposal - VDACS is resuming its excellent pesticide disposal program this year, beginning with the southeastern counties. This effort prevents large volumes of unwanted toxins from being disposed of improperly and saves private individuals much nuisance and expense. Collection months are July, August and November. The late July program will cover Virginia Beach, Chesapeake, Suffolk, Surry, Isle of Wight, Southampton, Norfolk, Portsmouth and Franklin. Collection and disposal are coordinated by Dan Schweitzer.

Invaders - An introduction of the emerald ash borer into Fairfax County last year resulted in the systematic removal and destruction of all ash trees within a half-mile radius of the site. The infested shipment of ash trees from Michigan was in violation of quarantine and resulted in substantial fines, community service and probation for the guilty party. Your help in locating forest stands and recent plantings of ash trees (not seedlings) would be greatly appreciated. We are likely to be monitoring ash for many years and need to develop a base map of significant locations.

Meanwhile, sudden oak death disease was discovered in a southern California nursery that shipped infected plants to nurseries over much of the country, including Virginia.

We will be cooperating with the USFS and other agencies to survey for emerald ash borer and sudden oak death disease this summer. In addition, we'll be searching the southwestern counties to see just how far the hemlock woolly adelgid has extended its range in Virginia.

The exotic pine shoot beetle has been working its way toward Virginia for the past several years and finally appeared in Clarke County last fall. A quarantine is in place to govern the movement of Clarke County pines and certain pine products, including Christmas trees. Questions should be directed to Tom Finn at the VDACS office in Warrenton, 540-347-6380.

Briefs - By far the best way to reduce the probability of getting West Nile virus is to remove artificial and natural water-holding containers from your yard (and perhaps your neighbors' yards).

• Phylogenetic evidence concerning the divergence of body lice (live in clothing) from head lice suggests that humans went around naked much longer than previously thought, and that human lice are of African origin.
• Imported fire ants are occurring in Virginia at increasing numbers.
• The dreaded brown recluse spider is apparently an opportunistic feeder that prefers dead prey and kills only when necessary.
• The praying mantid is the only nonvertebrate symbol of headhunting among the Asmat people of Papua New Guinea.
• Normal clothes washing and drying may not be enough to kill ticks, but one hour of high-heat drying will do the trick.
• Arthropod-borne human diseases such as malaria, dengue, encephalitis and others plagued coastal South Carolina in the early days. Of those born in Charleston from 1720 to 1754, only 19% reached their 20th birthday; and in the pre-Revolution years, 86% of those born in Berkeley County died before the age of 20.
• Eudemonia is a state of happiness whereas dysphoria is a state of anxiety and restlessness.

Take Tsuga - Loss of hemlock to the woolly adelgid is a double tragedy because of hemlock's medicinal properties. Many Native American tribes used various preparations to treat rheumatism, arthritis, skin conditions, cuts, dysentery, venereal disease and other problems. Needles, buds, twigs and bark were used singly and in combinations. Grab some while you can.

Health watch

Health Primer

Wood Decay

Forest decomposers do us a great favor by recycling huge volumes of dead wood. They also cost us huge sums of money through their deterioration of wooden products. Wood decay is of renewed concern since the loss of chromated copper arsenate (CCA) for protecting the lumber used in decks, playground equipment, and most other outdoor applications. The substitutes are more expensive, and require special fasteners, hardware and flashing. Much has yet to be learned about wood decay and its prevention.

Bacteria, insects and other organisms can degrade wood, but wood decay is essentially the realm of fungi. White rots compose the largest group. These fungi can break down all major components of wood –cellulose, hemicellulose and lignin. The group gets its name from bleaching action through oxidation and rapid degradation of lignin, which exposes the whiter cellulose. One sub-group selectively degrades the lignin and hemicellulose first, so the cellulose remains. Considerable research has gone into using these selective fungi in pulping wood for paper production. White rots are associated primarily with decay of
hardwood, but in living trees they also cause heart and sap rot of conifers.

Brown rots remove carbohydrates and leave most of the brownish lignin behind. They comprise roughly ten percent of wood decay fungi and are associated primarily with conifers. Brown rots are responsible for the great majority of decay in wooden structures.

Soft rots tolerate low oxygen levels and occur mostly in moisture-saturated hardwood products. They commonly cause degradation and cavities in secondary cell walls and cause only limited degradation of lignin. Soft rots are not a problem in living trees.

Wood cells absorb water up to what is called the fiber saturation point. Decay fungi require free water, so wood must be above the saturation point for decay to occur. As a general rule, wood kept below 20% moisture content should not decay. This is best accomplished through proper design and construction, except where wood is necessarily exposed to precipitation or soil moisture.

Decay is a highly complicated and variable process because it involves so many kinds of fungi, a variety of wood cell types and changing environments. It is not fully understood. In rough terms, wood is about half cellulose and a quarter each of hemicellulose and lignin. Cellulose, which is linear chains of glucose, is the most abundant organic chemical on earth. Hemicellulose, which includes shorter branched chains of several sugars, exhibits slight differences between hardwoods and conifers. Lignin is a complex polymer with a structure that varies among cell types and species. It gives rigidity to cell walls and is second only to cellulose in its abundance on earth. Wood also contains less than one percent of inorganic minerals, commonly including calcium, potassium, magnesium, manganese, sodium, iron and silica. Familiar wood colors and odors come largely from a wide range of organic compounds, called extractives, which accumulate in the wood after it forms.

Softwoods are composed largely of long, narrow tracheids that provide both support and conduction and are connected by pits. In hardwoods, conduction is provided primarily by short, wide vessel elements connected end to end. Support is provided by short, narrow fibers connected by pits. Both conifers had hardwoods also contain various parenchyma cells for storage and defense. These are oriented radially in rays and, in hardwoods, longitudinally near vessels.

When decay fungi invade wood they usually get started in the rays where thin-walled parenchyma cells have easily assimilated nutrients. From there they move into other cells through pits and lumens, or through bore holes made by specialized small hyphae. Just how fungi break down the lignified cell walls of structural and conducting tissues and absorb decay products is only partly known.

Enzyme molecules are too large to penetrate wood cells, so fungi must use smaller molecules to degrade cell walls before enzymes can diffuse into them. These molecules (glycosylated peptides) are secreted by fungal hyphae into the wood cell lumen where they interact with and penetrate the cell wall and catalyze other reactions. It is believed that resulting oxidation and production of hydroxyl radicals promotes the modification of cellulose and lignin, which enables enzyme diffusion and further degradation of the wood. Iron, manganese and copper probably contribute to some of these reactions. The specifics vary among fungi and are not fully known. Trying to comprehend the details reminds me painfully of huge tuition payments and all those years of classes, which apparently I slept through.

In marine environments, wood is commonly destroyed by shipworms (bivalve mollusks), which bore extensive, closely spaced but non-intersecting burrows. Their economic impact has been staggering (‘billions of clams’). Accounts of damage by shipworms include naval records dating to the third century BC. The fateful fourth voyage of Columbus ended when all four of his ships were destroyed by shipworms, leaving him and his crew stranded on Jamaica. On the plus side, carbon in the wood degraded by shipwoms is sequestered in dissolved bicarbonates and thus has little potential for contributing to global climate change.

Migration

Migration is both familiar and mysterious. Many kinds of organisms engage in these periodic movements to avoid adverse conditions and exploit resources that would otherwise be unavailable. Much has been learned about migratory behavior, and much remains to be discovered.

In his book on the subject (Oxford Univ. Press, 1996) Hugh Dingle devotes considerable space to differentiating migration from other kinds of movement, such as foraging, ranging and dispersal. He also makes a case for extending the concept to include certain plants and fungi. According to Dingle, migration is normally characterized by: (1) specific reallocation of energy, (2) distinctive departure and arrival behaviors, (3) persistent movement (4) travel more or less in a straight path and (5) inhibition of the usual responses to resources. For example, many migratory birds change their feeding habits prior to departure and build up fat reserves. They become restless and fly at night when normally they would be resting. Their flight remains consistently in one direction and they pass up many opportunities to feed and rest along the way.

Not all migration is long-distance, or round-trip or single-generation. Amphibians migrate relatively short distances between aquatic and terrestrial habitats or to hibernation sites, as has been shown for red-spotted newts and wood frogs in Virginia. Some aphids and social insects (e.g., swarming ants, termites and bees) migrate only in one direction, and in the case of aphids, the direction is determined by prevailing winds. The Monarch butterflies we see early in the year are not the ones that left in the fall, but their progeny following the milkweed bloom north from the Gulf where they developed. After their mating season, several kinds of waterfowl migrate to protected sites where they molt and remain flightless for several weeks while growing primary feathers. This is independent of fall migration and often in the opposite direction.

Tumbleweed can be viewed as a one-way migrant. In response to short days it develops special cells in the stem that cause it to break away from its roots and travel with the prevailing winds. Its seed are borne near the center of its globular form rather than on the branch tips so they are likely to travel some distance before dropping. Other plants produce two different seed types, one for local dispersal and another for migration to new habitats.

Because there are migrants among so many disparate organisms, the physiology involved is neither uniform nor simple. Day length, temperature, rainfall, chemical cues, genetically regulated daily and yearly rhythms, age and developmental stage can all interact to cause the changes necessary for migration to occur. There can also be considerable variation among individuals of the same species, and between genders. For example, there are two sub-populations of the green darner dragonfly in southern Canada, only one of which migrates, and some bird species include both year-round residents and migrants. The paths followed and specific destinations can also vary among individuals of the same species.

A subject that has fascinated many of us is the navigational ability of migrants. This too, is complex and variable. Among the cues that various migrants use to find their way are landmarks, location of the sun, brightness and polarization of light, slope of the land, star pattern, chemical signals, echolocation, and Earth’s magnetic field. A bird migrating long distances might be forced by weather and darkness to use several of these cues. Learning and genetic coding are also involved in some cases. Experiments have shown, for example, that naïve juvenile starlings are genetically programmed to fly certain directions and distances and will end up in the wrong place when displaced at the start. Experienced adults of the same species, however, are somehow able to find their way to the correct end point even though they were started in the wrong place. In planetarium experiments, European garden warblers were shown to learn star patterns, and they could be disoriented by a false sky. Any point of light around which other "stars" rotated was used for north-south orientation. It is not known exactly how birds crossing the equator adjust for changes in magnetism and sun movement, but star patterns might be involved. Sun position and plane of polarization, odor and magnetic guidance systems can all be used by migratory species of crustaceans, insects, fish, amphibians and reptiles. Hatchling loggerhead turtles can sense both the direction and strength of Earth’s magnetic field. Some plant-eating mammals follow well-established trails and perhaps odors as well. Many of these same navigational systems are also used for year-round activities such as homing and food finding. Some animals that use sun azimuth are also able to adjust for time of day; others are not.

It is still a mystery where some migrants go. Several species of dragonflies, for example, pass through Virginia, sometimes in mass flights, sometimes individually, but their destination is unknown. The returning dragonflies are of the next generation. There are 15 or so species of eels that migrate between marine and fresh water habitats, but their breeding sites have never been found.

A few migrants on the notables list include: the long-distance-winning arctic tern that migrates between the Arctic and Antarctic (two bad choices in my book), the spiny lobsters that queue up each fall in long lines head-to-tail and move down the Florida straits to warmer water, a European frog that covered more than 9 miles overland in 10 days or less on the way to its overwintering hibernation site, a species of bat in Africa that follows seasonal rains for nearly 1000 miles each year in the Niger River basin and the salmon that return to their natal streams 2-5 years after leaving.

Last modified: Tuesday, 12-Aug-2008 16:45:25 EDT