PESTS ON PARADE Many types of organisms can damage trees and shrubs or otherwise be undesirable inhabitants of landscapes. Common pests include insects, mites, snails, vertebrates, weeds, nematodes and pathogens. However, in each of these groups there are many related species that do not harm cultivated plants or are beneficial. In fact, the great majority of organisms in the landscape are desirable components of the ecosystem.

ENVIRONMENTAL PRESENCE Note that the presence of organisms with the potential to become pests may not be cause for alarm. For example, many fungi and other micro-organisms that can cause disease are continually present in the environment. They usually become damaging only when conditions are favorable for disease development or unfavorable for plant growth, such as when poor cultural practices weaken the plant.

Insects, mites, and nematodes that can cause damage when they are abundant can be harmless or even beneficial when their numbers are low. The presence of a few of these plant-feeding pests provides food to maintain the natural enemies that help prevent outbreaks.

USEFUL STEPS Effective, environmentally sound pest management requires considerable planning, knowledge, and observation. Most landscape pest problems can be avoided by taking several steps: 1) choose pest-resistant species and varieties that are well adapted for local conditions; 2) correctly prepare the site before planting; 3) use proper planting techniques, and 4) provide optimum conditions for plant growth. The healthier landscape plants are, the more able they are to resist serious infestations of insects and pathogens.

SEEK ADVICE Take action to prevent problems in established landscapes. Don’t wait until a tree or shrub is severely damaged by pests; the only recourse might be to spray it with a fast-acting pesticide, which normally does not correct the problem permanently.

Learn the potential pest problems and damage symptoms of the plants in your landscape. Remember that each species can have specific insects or diseases that attack it. Don’t be afraid to consult with local plant professionals for information that may be helpful to you.

RECORD KEEPING Examine your landscape plants regularly. Look for pests, damage, and inappropriate cultural practices. It may be a good idea to keep records of any problems you encounter. Learn to recognize when a plant appears abnormal or if pest abundance or damage is approaching levels that require control.

Select control methods that are effective under your growing conditions and least likely to cause adverse effects on the environment. Often more than one method can be employed to give the most reliable control.

PREVENTION BEST ANSWER Prevention is the most important component of landscape IPM. Weed problems can be avoided by good landscape design, proper soil preparation before planting, and mulching. Poor plant choice, improper site design and preparation before planting or incorrect planting methods or maintenance can aggravate or cause most common problems.

For example, many insect and disease problems are caused by poor cultural practices that allow a plant to become weakened to the point where the plant’s ability to ward off these pests is diminished.

IDENTIFYING PROBLEMS Proper identification is essential for choosing the right control actions. Accurate identification of plant problems depends on a combination of knowledge, observation, and available resources. The first step is to know the cultural and environmental conditions required by each plant and check that these are being adequately provided.

Look for differences between the appearance of unhealthy plants and healthy ones of the same species. Patterns of the symptom development in the landscape or within the plant may provide clues to the cause. Obtain information about the recent history of affected plants, weather, the site, and cultural practices.

CONSTANT MONITORING Go out to the landscape on a regular basis and systematically check for pests and damage symptoms. Learn the problems that commonly occur in your area, the stages of common pests and be able to distinguish them from other beneficial organisms. Check regularly for adequate cultural care. Time invested in monitoring can avoid plant damage and reduce the extent of any urgent management actions.

ACTION THRESHOLD A certain number of pest individuals and some amount of damage usually can be tolerated; this concept is fundamental to integrated pest management. The difficulty is in determining the Action Threshold—the point at which some action must be taken to prevent unacceptable damage.

Timing of actions is often critical for effective management. For example, once symptoms become apparent, it is often too late to effectively control many plant diseases. Keep records of pests and the results of management activities. These records will help you to develop action guidelines that work best for your situation in the future.

The pest population or damage level when action must be taken to deter qualitative damage to ornamental plants often depends on people’s attitudes and is commonly referred to as the Aesthetic Threshold. Action and Aesthetic Thresholds may vary, depending on the property owner or client’s preference.

APPROPRIATE ACTION Integrated pest managers must consider the interrelation of cultural practices, environmental conditions, and the biology of plants, pests, and beneficial organisms in order to provide healthy plants. Before applying these methods, determine whether action is needed and likely to be effective.

If it is too late for control to be effective or if the problem is minor or doesn’t threaten plant health, consider taking no action or applying other methods. When action is needed, use more than one method in combination to provide more effective control. There are five control methods used specifically for pest management.

CULTURAL CONTROL Modifications of normal plant care activities that reduce or avoid pest problems. This includes selecting resistant species, proper planting and irrigation methods, and proper pruning methods.

MECHANICAL CONTROL Use labor, materials usually not considered as pesticides, and machinery to directly reduce pest abundance. Examples include using mulch to control weeds, mowing and weed trimmer use, hand pulling weeds, use of sticky materials on trunks to prevent canopy infestation of crawling insects, and pruning to remove foliage infested with insects or disease.

Controls include the thinning of the canopy to improve air circulation and reduce humidity, application of a white interior latex paint to reduce light exposure and prevent sunscald on young trees, covering young trees and shrubs to retain warmth.

BIOLOGICAL CONTROL Biological control is the use of beneficial organisms to control unwanted organisms. Biological control has been used most successfully to control pest insects and mites.

An example is to incorporate natural diseases of the pest such as Bacillus thuringiensis (Bt). The use of insect hormones is another biological control method. Insect pheromones are often used to attract male insects to traps.

CHEMICAL CONTROL Chemical control of insects and diseases is still an important part of maintaining tree health. Temporary control of certain pests is quickly obtained by using the correct pesticide at the right time in an appropriate manner. Pesticides should be selected with regard to minimizing the effect on non-target organisms. Spot spraying is preferred to broadcast spraying and of course follow all label directions.

REGULATORY CONTROL In most states, government restricts the transport of plants or plant products in an effort to deter the spread of unwanted pathogens or insects. Plants and commodities must undergo an inspection before being shipped across state lines to certify that they are free of problems. In some cases, quarantines are placed on states to allow containment of specific insects or diseases.

IPM PROGRAM Many processes are involved with developing and maintaining IPM programs. IPM is not a set of instructions or a list of ingredients, but a collection of information ascertained through knowledge, expertise, experience and the use of resource materials that leads to a determination whether some form of management is necessary. The expectations of the owner are a primary concern and will vary from person to person.

Be prepared to influence expectations with experience and knowledge. Treatments applied merely at the request of the owner, without any other justification, or as an insurance against unknown or possible threats, is not part of an IPM Program.

Editor’s note: Bates is Community Forestry Assistant, Idaho Community Forestry Program, he can be contacted at 888-579-1641 or gabates@cableone.net