Christmas Tree Pest Manual (E2676)
November 11, 2015
How to Use This Manual
This manual can help you identify and control damaging Christmas tree pests in the North Central region of the United States. Most of the information also applies to the northeastern states and to the southern portions of the Canadian Provinces that border these states.
You do not have to be a pest specialist to use this information; we wrote the manual in everyday language so that anyone with an interest in Christmas trees can read and understand it. Because it is meant to be a tool and not a textbook, we included only what you need to know to solve pest problems in your nursery or plantation.
In addition to the illustrated pest profiles, you will find plenty of practical advice on
• how to look for and recognize potential pests
• how to select, plant, and care for trees so they are less likely to be damaged by pests
• how to keep pest numbers at harmless levels
These techniques work to discourage pests and prevent them from causing serious damage. We encourage you to read the opening sections of the manual and become familiar with potential pests before they have a chance to build up on your trees.
Carry the manual with you when you inspect your nursery or plantation. If you notice anything out of the ordinary, turn to the "How to Identify and Control Pests" section. This section can help you diagnose tree injury in much the same way that a doctor diagnoses an illness—by working backwards from the symptoms to the cause. All you need to know is the tree species injured and what the injury looks like.
Then simply follow six steps:
1. Decide what kind of injury your tree has.
dead tree and stem/root injury
Turn to the appropriate section in the manual. Check your selection by comparing the injury with the description on the first page of the section.
2. Leaf through that section, checking for your species on the lower outside corners of the pages.
These pages contain photos and descriptions of the pests. The tree species affected by each pest are also listed.
3. Now, sort through the pests that attack your species and find the photos that most closely match the damage you see on your trees.
When you are pretty sure that you have found the culprit, double check it against the "pests that cause similar symptoms" list at the end of each pest description. If you have any doubts about identification, you can send samples of the pest and the injured tree parts to your local pest specialist (see "How to Submit Material for Identification").
4. Finally, review the symptoms and signs listed under "Look For."
You can identify most pests by the clues they leave or by the kind of injury they cause. These symptoms and signs are highlighted in italic type and grouped by the time of year they are most likely to be seen (timing may vary with geographic location). Features visible year around are listed first, without a calendar heading. Pests are also described in terms of their importance, biology, and other characteristics.
5. Decide whether control is needed.
The "Monitoring and Control" section for each pest can help you measure the amount of pest activity on your trees and help you decide how much control, if any, is needed. Before you begin any pest control treatment, ask yourself whether the value of the benefits will exceed the cost of the treatment. In short, will it pay? You may want to contact a pest specialist to help you predict and estimate damage. (See "How to Submit Materials for Identification.")
6. Select control methods.
In the "Monitoring and Control" section for each pest, recommended management and control techniques are divided into a section that provides suggestions to help prevent or reduce pest problems on established seedlings and trees now growing in your nursery or plantation. "Next Crop" controls can help you guard against pest problems on trees the next time you plant.
What is a Pest?
A pest is something that gets in the way of what people want to do. In the Christmas tree business, the goal is to harvest healthy looking, high-quality trees. Insects, diseases, animals, birds, and environmental factors that destroy or damage those trees are therefore considered pests. In their natural settings, these "pests" may be relatively harmless or perhaps even beneficial. In intensively managed nurseries and plantations, however, they can be undesirable and may require prevention or control. The pests in this manual fall into four groups
• fungi and nematodes
• birds and mammals
• environmental factors
The more you know about them, the better able you are to solve pest problems in your nursery or plantation. This section briefly describes how these pests grow, reproduce, and affect Christmas trees. For more information about the biology or characteristics of a given species, see the "How to Identify and Control Pests" section.
Insects and their close relatives, mites, are the most common pests of Christmas trees. This manual lists the major ones, but there are many others that may cause minor injury to your trees.
When abundant, insects can cause costly injury at various times in a tree's growing cycle. Seedlings and young trees are particularly vulnerable because it takes only a few insects to injure or kill them. However, older trees may also be injured when insects are numerous.
Insects damage Christmas trees in many ways. They can chew on or inside the needles or tunnel inside the shoots and trunk. Some insects suck sap from the needles, buds, or stems, weakening or killing the tree. Others cause swellings, or galls to form, and a few spread disease organisms directly or indirectly while feeding.
Insects are one of those unique groups of organisms that change form at least once during their lifetime. This is important to you as a Christmas tree grower because different insect forms cause different kinds of damage. For example, the larval form of one species may cause serious injury to a certain tree species while the adult form is perfectly harmless.
The simplest kind of change, or metamorphosis, starts when a nymph (a miniature copy of the adult) hatches from an egg and then sheds its skin, or molts, several times before maturing into an adult. Pests that have this simple metamorphosis include grasshoppers, thrips, spittlebugs, aphids and mites.
More complex, or complete, metamorphosis proceeds from the egg through larval, pupal, and adult stages. Like nymphs, larvae must molt several times before reaching the pupal stage. Each stage is greatly different in form from previous stages. Common insects with complete metamorphosis are beetles, weevils, moths, midges, and sawflies.
In both cases, the adults mate, produce eggs, and start the process over again. Most Christmas tree insect pests have one generation a year. Some insects and mites, however, may have two or more generations each year.
Fungi and Nematodes
Fungi and nematodes cause disease in trees. A diseased tree may develop abnormal swellings, galls, or deformed needles. Other evidence of disease includes discolored foliage, early needle drop, crooks, wilting, and cankers.
Fungi cause the majority of diseases of Christmas trees. A diseased tree infected with fungi may have a wide range of symptoms, such as abnormal swellings on the branches, discolored needles, needlecast or dropping of needles, pustules or blisters on the foliage, curling of the growing shoots, and cankers. Fungi are simple plants that can live on other living organisms; they do not have food-making chlorophyll of their own.
Fungi reproduce by means of spores — the fungal equivalent of seeds. Spores are produced in a wide variety of fungal "fruitbodies." Some fungal spores are wind-blown and can spread quickly; other spores are carried in rain water and move only as far as raindrops are splashed or blown. Spores can also be transported on equipment, such as shearing knives, and on infected plant material.
Nematodes are members of a group of animals known as roundworms—long, worm-like animals tapered at both ends. Nematodes feed by puncturing tree cells with their hollow feeding tube and sucking out the cell contents. They hatch from eggs and pass through several larval stages when developing. Some nematodes that injure Christmas trees are carried from tree to tree by insects.
Birds and Mammals
Some birds and mammals will also injure Christmas trees. Pine grosbeaks eat buds and yellow-bellied sapsuckers peck holes in tree stems. Although birds usually cause only minor problems, they can sometimes cause enough injury to degrade trees.
Deer nip shoots and seedlings, occasionally causing important damage. Voles, rabbits, and gophers will chew the bark of stems or roots and can readily kill trees. Losses can sometimes be severe.
Some environmental factors that can injure Christmas trees either directly or indirectly are poor soil, extreme weather, and toxic chemicals, such as air pollutants, pesticides, salt, and excessive amounts of fertilizer. Disorders caused by these factors cannot spread from one tree to another like diseases.
A Pest Management Primer
Pest prevention begins before you plant your first tree and extends through harvest time. In fact, everything you do to your plantation, from selecting a species and preparing the site to cultivating, shearing, and beyond, has some bearing on pests.
For many years, pest control meant reaching for the pesticide sprayer anytime a spot or an insect appeared on a tree. Trying to kill every last pest was not only costly, but also environmentally reckless. Today, the goal is to reduce pest losses to a tolerable level by using a variety of control methods. Emphasis is on cultural and biological treatments, supplemented only when necessary by chemicals. Using all available pest control strategies in a complementary way is called IPM— Integrated Pest Management. Four general steps are involved in IPM.
Step 1. Plant the Right Species on the Right Site.
Choosing Your Trees
Ideally, the species you plant should grow well on your site, be somewhat resistant to pests, and give a good return on your investment. Other important traits are form, hardiness, growth rate, and color at harvest time. Scotch pine has been popular because it has many favorable qualities, but also consider several other pines, spruces, firs, and eastern red cedar, especially if your site is better suited to them.
Because Scotch pine was a favored Christmas tree species for many years, several varieties have been developed to enhance certain genetic qualities. Some of these qualities relate to pest resistance. So if you are planning to plant Scotch pine, check with local growers and Extension agents for the pests most common to your area. Then use the table on the next page to select a variety that is most resistant to those pests.
Preparing the Site
Careful site preparation is another essential part of pest management. Poorly prepared planting sites put stress on trees, and stress invariably leads to pest problems.
If you are planting on a new site that has not had Christmas trees on it before, it is usually a good idea to cultivate or treat the site with herbicides to remove vegetation that may compete with the seedlings for light, water, or nutrients. Using herbicides in the fall of the year, before planting, will also leave dead vegetation on the site that will hold the soil and reduce erosion. By controlling weeds and grasses after planting, you can continue to keep competition down, reduce mammal habitat, increase air flow, and destroy alternate hosts— plants that certain insects and diseases live on for part of their lives.
Before planting on a site, you should consider potential pest problems. Are there pests on trees in nearby windbreaks or woodlots? If so, you may want to treat or remove these pest "reservoirs" before planting. If pests in the surrounding areas are difficult to manage, consider planting a tree species that can withstand injury or is resistant to the pests.
Before planting, send soil samples to your extension service or testing firm for analysis. They can tell you if fertilizer or soil treatments are needed to make your plantation more productive. You may even find out that your land needs too much work to make your venture worthwhile.
When replanting a harvested site it is wise to remove or destroy residue, unsalable trees, and old stumps that might lure pests to the site.
A little extra care at planting time will pay off in good survival and growth. Try to avoid planting on sites that are prone to frost or where soils are stony, coarse-textured, or otherwise unsuitable for trees. Such sites invite pest problems. Instead, give your seedlings a head start on good growth by choosing sites that are well matched to the growing needs of the species you have selected.
Spacing is also important. Although some seedling suppliers or Christmas tree guides suggest planting 4'x4' or 4'x5', a better spacing is 5'x6' or 6'x6'. This extra space will give you fewer trees, but will help reduce insect movement and disease spread. Extra wide spacing and access lanes (i.e., 1 or 2 unplanted rows) make shearing easier and allow more room for spray or harvesting equipment.
Plant your seedlings in up- and down-hill rows rather than along the contours of the land. This increases air flow and drainage, allowing trees to dry quickly after rain with less chance of disease spread. It also pays to plant 3- or 4-year-old transplants, if available. These plants are hardier and tend to take root faster and survive better than younger seedlings. When handling seedlings, keep the roots moist to ensure survival and ease transplanting shock.
When you plant, try to spread the roots out in the planting hole to prevent them from growing in a J-shaped curve. Roots grown this way are especially vulnerable to white grubs during the first and second seasons after planting. J-rooted trees also tend to be weak and unstable.
Place seedlings so that the root crown is at or slightly below the surface of the soil at the same level it was in the nursery bed. Pine root collar weevils injure pines more readily when the root collar is more than 2 inches below the ground because an underground "collar" is available for them to girdle.
Step 2. Monitor for Pests
Even if you do a good job in site preparation and planting, insects, diseases, and other pests can still injure your seedlings and trees. Walking through your nursery or plantation on a regular basis to keep track of tree condition, pest abundance, and damage is one of the most important things you can do to maintain healthy trees. If you are observant, you can usually spot the symptoms and signs of distress before widespread damage occurs.
Scouting or monitoring your trees can also help you:
• learn which tree species and varieties are most resistant to damage
• determine whether beneficial organisms are present
• anticipate and prevent pest damage
• gauge how much damage a tree can handle without a loss in grade
• decide whether control is needed
• judge the results of your management decisions.
It is good practice to inspect your trees weekly throughout the growing season and occasionally in winter. Although most pests are active during the warmest season, some diseases are more severe in cool moist weather, and birds and mammals do the most damage in winter when their normal food supply is scarce. When you scout, take notes and make maps of where damage has occurred. This will help you plan next year's scouting and control activities.
Monitoring should begin when your stock arrives from the nursery and continue until harvest. "Hitchhiking" nursery pests are particularly serious because even a few pests can destroy the small plants and quickly spread to other parts of your plantation. To be safe, keep careful records, buy locally grown seedlings, if available, and ask your seedling supplier about guarantees and pestfree certificates.
It also pays to know something about the habits of pests you find on your trees. Certain pests, even when numerous, may not seriously damage a tree if it is large enough. For example, dozens of European pine sawflies can strip most of the needles off a 5-foot pine, but because they eat only old needles, the tree is barely injured and recovers fully in 2 or 3 years. On the other hand, one or two Zimmerman pine moth larvae can kill or severely injure the same 5-foot pine in one season. Naturally, the more "significant" the pest, the more vigilant your monitoring should be. If your first inspection reveals no serious threats, keep at it. The situation can change quickly.
To keep abreast of local pest conditions check into the newsletters and pest monitoring programs available for Christmas tree growers in several states. These programs can provide historical as well as current information on pest problems.
For more information on pest monitoring, contact your county Extension office, your state Department of Agriculture, your state Department of Natural Resources, or the USDA APHIS office in your state or region.
Step 3. Use a Combination of Controls
When faced with a serious pest buildup, your best strategy may be a combination of simple treatments rather than a single drastic action. And, as mentioned before, although chemical control may be used to combat pests, it should only be used as a last resort. In this manual, you will find many good alternatives and supplements to pesticides. Not only are they safer, but in many cases, their effect outlasts the quick-fix of chemical control.
The strategies suggested here will not completely eliminate pests from your nursery or plantation. Instead, these strategies work to bring pest populations down to acceptable levels and keep them there. An acceptable level merely means the trees will not be dead or degraded at the time of harvest. You can keep pests at acceptable levels by practicing prevention and some combination of manual, mechanical, biological, cultural, and chemical control methods.
Most of the methods presented here have been used successfully in Christmas tree fields in the past. However, a few of these suggestions have not yet been extensively tested, so you may wish to try them and see if they work for you. One treatment may work well in one area and not as well in another, so continue trying new treatments or seek help if you have trouble managing a pest. (See "Where to Get Help.")
Manual and Mechanical Control
Hand methods or mechanical devices can be used in small plantings to control pests or to make the environment unsuitable for their survival. For instance, insect pests in low numbers can sometimes be hand picked or knocked off the tree and crushed. Fresh pieces of tree stem can be set out in the plantation to trap certain beetles. Predator calls recorded on tape can be broadcast in the field to drive off bothersome birds. Chipping or burning trees infested with Zimmerman pine moth larvae can prevent attacks on healthy trees. Sometimes these simple controls are all that is needed to discourage costly pest damage.
Natural enemies, such as predators, parasites, and pathogens, can play an important role in pest control. When natural enemies become permanent residents in Christmas tree fields, pests are less likely to increase to damaging levels. The long-term nature of biological control makes it relatively inexpensive as well as environmentally safe.
Biological control can involve introducing beneficial organisms into your nursery or plantation or simply encouraging those that are already in place. These beneficial organisms include lady bugs (which devour aphids and scales by the hundreds), lacewings, spiders, and predatory mites. Parasitic wasps and flies check pest numbers by laying their egg on the body of pest insects. And there are many diseases that can weaken or kill Christmas tree pests.
You can attract beneficial predators and parasites to your fields by leaving edge rows or occasional strips or clumps of certain flowering plants as a pollen and nectar source. Adult parasites of many insects need pollen or nectar for food and will search out pests in your plantation if flowering plants are available. For instance, leaving strips of wild carrot (Queen Anne's lace) will provide food for parasites of the European pine shoot moth.
Some of these beneficial predators and parasites can be bought commercially. For example, a bacterium called Bacillus thuringiensis var. kurstaki ("Bt" for short) that controls many caterpillars is available in liquid form. Bt can be sprayed onto your trees and will kill the caterpillars when they eat the needles. Best of all, the bacterium is not harmful to other nontarget organisms, including humans.
You may be able to buy commercial virus preparations for sawflies (e.g., redheaded pine sawfly), or you can make your own. The recipe is included in the sawfly writeups. Once introduced, a virus persists and affects new generations of sawflies year after year.
Keep predators and parasites working for you by minimizing the use of chemical insecticides. If you must use pesticides, apply the lowest recommended dose. Apply the product at the correct time and minimize pesticide drift to reduce harmful effects on beneficial insects. Also, try to spot-treat pests to further minimize pesticide use. You need not always treat an entire nursery or plantation if only a few trees or small groups of trees have been affected.
Ordinary cultural practices such as weed control, mowing, shearing, pruning, and thinning, help make your nursery or plantation less appealing to pests. If you strategical ly modify and time these operations, you can manipulate pest habitat to prevent and control problems even more effectively. For example, you can discourage mice by mowing the grass they hide in. Pine needle rust can be reduced by removing nearby goldenrod and aster plants. Delaying shearing a few weeks can destroy the European pine shoot moth. Pruning the lower branches from old trees helps control pine root collar weevil, European pine shoot moth, and some disease organisms.
The goal is to make the habitat less favorable so pests will not multiply as rapidly. Sometimes even a slight drop in population can avert a damaging pest buildup and reduce the number of pesticide applications needed for control.
Cultural controls are among the simplest and cheapest methods available because they can complement other management operations, and they are environmentally safe.
Forest and agricultural pests that overwinter, nest, or hide on nursery stock and Christmas trees are often carried into new locations as hitchhikers. Once they enter new areas, these pests can swell to epidemic levels. Lophodermium needlecast is a classic example of a serious fungal disease that moved on nursery stock to many Christmas tree plantations in states where it did not exist previously. New epidemics started when spores released from these newly planted seedlings spread to susceptible trees nearby. Sometimes, the only way to stop the spread of hitchhiking pests is through legal measures, such as quarantines or mandatory inspections.
The gypsy moth and the pine shoot beetle are two important hitchhiking pests to watch for. The gypsy moth is normally a hardwood pest, but frequently lays eggs on the stems and branches of Christmas trees. Look for egg masses of the gypsy moth on the trunks of Christmas tree seedlings and trees. You may find the pine shoot beetle inside shoots or burrowed into the lower stem of pine Christmas trees.
Many pests spend the winter on Christmas trees and may be inadvertently shipped to new areas at harvest time. Some pests, such as the European pine sawfly, can hatch in buyers' homes and become a nuisance. After the holidays, overwintering pests can be carried wherever old or unsold trees are discarded. Therefore, it is good practice to inspect all trees just before harvest to determine if they harbor pests that are regulated by federal or state quarantines. Failure to do so may lead to the introduction of pests into previously uninfested areas, the spread of disease epidemics, and the possible quarantine of valuable trees.
Chemical pesticides can be among the most effective materials used to prevent, destroy, or repel pests, and because of this, they have been used too often in lieu of other control methods. If you must use chemical pesticides, it is important to choose the proper products, timing, and dosages to avoid mistakes.
Improper use of a pesticide might rid your nursery or plantation of a pest, but may very well trigger another more serious problem. Overspraying, for example, often causes mites, aphids, and scales to rapidly build to damaging levels. Heavy dosages, poor timing, and careless application can kill valuable parasites and predators, allowing new pests to gain a foothold in your nursery or plantation. Because of these disadvantages, we stress using chemical pesticides only as a last resort.
To maximize the benefits and avoid the hazards of pesticides, choose formulations that pose the least threat to nontarget species. Adjust and calibrate application equipment so the proper amount of pesticide hits the target, and only the target. Time your treatment to avoid spray drift; windless days, early mornings, and evenings are good times to apply pesticides. We also suggest alternating pesticides to reduce the chances of a pest developing resistance to a particular type of pesticide.
When used as directed and in combination with other controls, pesticides can produce impressive reductions in pest populations. To help you with the proper uses of pesticides, this manual includes information about timing, equipment, and safety. We have purposely left out specific product names and application rates, however, because they change so frequently. Check the label on the pesticide container for application and registration information. University Extension offices and state regulatory agencies can also provide up-to-date information on pesticides registered in your state.
Step 4. Evaluate Your Control Efforts
To be truly effective, pest management should be part of the day-today workings of your Christmas tree operation, from species selection to premarket inspection. This includes regular, careful monitoring, even after a control treatment. By evaluating your treatments, you can decide which management techniques were successful, and which were not. You can then continue using the best techniques and minimize pest damage by design, not by chance.
Symptoms and Signs of Tree Injury
When you are protecting your investment from very small insects, microscopic pathogens, or pests that feed underground, it helps to have an eye for detail. If you know what to look for when inspecting your trees, you can spot a pest problem in its early stages and greatly reduce losses and control costs.
Most likely, you will see the results of pest activity long before you notice the pest. An injured tree will have symptoms such as unusual color, missing foliage, deformed parts, etc. Although these clues may help you diagnose the injury, they may also mislead you. For example, a symptom of one pest may look much like the injury caused by several other pests. To complicate matters further, two or more pests may injure the tree at the same time, producing a new symptom by their interaction. Symptoms also change; yellow foliage may redden, turn brown, or fall off entirely. Therefore, you cannot rely on symptoms alone when you diagnose tree injury.
Reading the signs of the pest as well as symptoms of the host is usually the best way to tell one type of injury from another. Signs are the physical evidence of insect and disease activity and include the pests themselves (eggs, larvae, fruitbodies), their enclosures (webs, cases, cocoons), debris (cast skins, wood slivers, pellets of waste), pitch flow, and associated insects or diseases, such as ants and sooty mold. Sometimes, two different pests will produce look-alike symptoms and leave the same signs. In that case, the pest itself must be examined and identified by you or by a pest specialist. (See "How to Submit Material for Identification.")
The detective work involved in identification becomes more difficult as time passes because both symptoms and signs change. A vigorous tree may mask or outgrow the injury. On the other hand, a weak tree will become susceptible to invading insects and pathogens that can confuse the diagnosis by producing symptoms and signs of their own. Signs such as webs, waste, or cast skins will also breakdown with time.
Therefore, the best time to read a symptom or sign is during the early stages of pest activity. To catch pests in action, start monitoring your trees at planting time and continue to examine them frequently throughout their lives. The following section describes the major symptoms and signs to watch for every time you inspect your nursery or plantation.
Discolored foliage can result from damage to any part of the tree— roots, trunk, branches, or needles. When a single needle or a small group of needles is discolored, damage is usually centered in the individual needles. For instance, needlecast fungi cause banding on the individual needles they infect. However, if an entire section of foliage on a shoot or branch is discolored (flagged), the injury is usually within or at the base of that section. Flagging may also be caused by drought, root injury, or a lack of nutrients—all problems occurring in the soil.
Blackened foliage and/or bark indicates soft scales, aphids, or spittlebugs. A black, sooty mold grows on the sugary "honeydew" and spittle produced by these insects. Needles and shoots covered by the eggs or bodies of insects may also look discolored. In these instances, you can directly identify the insects injuring your trees.
Herbicide damage, air pollution, and winter injury can also discolor foliage. When the whole tree is evenly discolored, the injury is usually on the main stem, root collar, or roots.
Needle loss is a common symptom of many insect and disease injuries. Foliage affected by winter injury or needlecast fungi will die and drop off early. Notched, broken, or hollowed-out needles indicate insect feeding. Insect foliage feeders will strip off clusters of needles, often in a characteristic pattern. Look for the insect or its trass, webs, cocoons, or cast skins on the surrounding foliage and beneath the injury; these are all signs of insect feeding. (See "Insect and Disease Parts and Structures.")
Deformed and Stunted Tissue
Insects and diseases can cause galls, swellings, and other kinds of abnormal growth on needles, shoots, stems, or roots. Past injuries from insects, diseases, or animals may eventually cause excessive branching, forking, and crooking. Stunted shoots are caused by drought and frost damage, insects feeding on shoots and roots, or infection by shoot-blight fungi. Once weakened by injury or stress, trees often grow more slowly. Although economically important, this growth loss may be difficult to detect and diagnose.
When insects feed or tunnel in the shoots, branches, and stems of living conifers, a pitchy substance commonly surrounds or flows from the point where they entered the tree. Canker and shoot blight diseases may cause the same response.
Insects living in dying or dead stems and branches often produce fine sawdust or coarse slivers of wood. Piles of this material may be on the ground or found adhering to the bark.
Insect and Disease Parts and Structures
Insects and pathogens often leave behind evidence. Learning to recognize this evidence can help you find and identify pest populations before damage becomes severe. For example, as insects feed and grow, they must periodically shed their outer skin to accommodate hanges in size. Cast skins of nymphs, larvae, or pupae, as well as old eggs that have hatched, can sometimes be found near the injury. This evidence can often be used to identify the species of insect. Several species of foliage feeders will construct protective bags, webs, or cocoons that are also distinctive. Some wood-boring insects make pupal cells called chip cocoons in the wood where they feed.
Small pellets of waste (frass) left by foliage-feeding insects can often be found near or beneath damaged foliage. Spittlebug nymphs produce white, frothy masses resembling spittle on the twigs or branches of trees. Part the mass carefully to see the small, soft insect.
Fungi produce spores in reproductive structures called fruitbodies. These small structures are formed in the dead tissues of needles, shoots, and stems. Some species of fungi form characteristic sheets of fungal material called mycelial fans (see Armillaria root rot). Keep in mind that fungi found in dead tissues may or may not have killed the tree. Many fungi are secondary agents, which means they invade tissues after the tree has been killed by something else.
In the next section, you will find descriptions and control recommendations for species of insect pests and diseases, grouped by the type of injury they cause. Step-by-step instructions on how to track down a specific pest can be found in the section entitled, "How to Use This Manual."
Where to Get Help
Because so many pests cause look-alike symptoms, it is sometimes difficult to pinpoint the pest causing damage in your nursery or plantation. When in doubt, contact a professional. Your state forester, county Extension agent, or the staff at the plant disease and entomology clinics at your state university are familiar with local insects and diseases and can suggest practical, cost-effective controls. Christmas tree consultants are also available and can provide many of these services.
Some of the best advice may come from other growers who have dealt with a pest problem similar to yours. Joining a Christmas tree growers' association is a good way to connect and compare notes with growers in your area.
How to Submit Materials for Identification
To identify the culprit damaging or killing your trees, your local pest specialist will have to gather clues and examine the evidence. You can help by providing some background information—
• location of plantation
• site conditions (wet, dry, etc.)
• age and species of affected trees
•part(s) of tree damaged
• pattern of damaged trees in plantations (scattered or grouped)
• extent of damage (number of trees or acres affected)
• management history (fertilization, pesticide and herbicide use, etc.)
In addition to these clues, you may need to send damaged plant tissue—foliage, branches, stems or roots—as evidence of insect or disease activity. Include any tissue that contains fungal fruitbodies, such as spore-filled blisters. These are telltale signs of disease.
Look on or around trees for physical evidence of insect activity, such as egg masses, pellets of waste, nests, or the insects themselves. If you spot insects on your trees, send both the damaged plant tissue and the insects to the specialist.
Packing Plant Tissue
To ensure correct identification, ship several examples of each type of injury, and follow these packing tips:
• Fresh plant samples are easier to identify than dry, wilted ones, so keep samples as cool as possible before mailing.
• Foliage—Pack green foliage samples in a plastic bag to keep them from drying out. Put dry paper towels in with the specimen to absorb water that might condense on the inside of the bag.
• Branches and stems—Cut samples at least 10 inches long and place in plastic bags with dry paper towels. Include apparently healthy portions of the same branch or stem section; often the junction of healthy and damaged tissue holds the key to identification.
• Roots—Pack roots in a plastic bag with some soil or litter and keep them cool and moist.
• DO NOT SHIP LIVE INSECTS.
• Moths, butterflies, and beetles— First kill the insects with moth balls or crystals, then place them with egg masses, nests, or frass in jars or boxes. Loosely pack tissue paper above and below the specimens to protect them from damage.
• Soft-bodied insects, egg masses, pupae, and larvae (caterpillars, grubs)—Pack in vials filled with 70 percent alcohol (e.g., rubbing alcohol). Be sure to pad vials well enough to withstand rough handling in shipment.
Related Topic Areas
Deborah G. McCullough