Forest Health – Prevention and Treatment of Diseases and Infestations
Setting Up Your Trees for Success
The easiest and most effective way to reduce the impact of insects and diseases that could harm your trees is to reduce environmental stress on the tree. Stresses like drought or poor soil impede your tree’s ability to defend itself against an attack. Trees that are properly maintained and growing under optimal conditions are also less likely to develop costly problems as a result of stress. Tree owners can take simple steps that go a long way toward improving the vitality of their trees and ensure they get the most benefit from their trees in the long-term.
Selecting the right tree for the right place is the most important first step if you wish to choose a tree that has the potential to be enjoyed for generations. A properly selected tree is one that will not be subjected to preventable stresses that could be avoided through careful consideration of site conditions, light and moisture requirements, hardiness, space constraints, and other factors. Learn more about how to select a tree and about tree species recommended for your area before you plant.
Plant Native
Plant Native
Native plants are naturally adapted to our local soils, climate, and wildlife which means less fertilizer, pesticides, and watering. Pollutants such as fertilizer and pesticides are carried away from lawns and gardens when it rains. These pollutants enter storm drains which empty into small streams, then flow into larger streams and eventually downstream to the Chesapeake Bay. Fewer pollutants and improved habitat result in tangible benefits to the people and wildlife of Fairfax County and the Chesapeake Bay through cleaner water and more diverse wildlife. Additionally, native trees are well adapted to cyclical disturbances caused by native forest pests. Native plants even support beneficial insects that prey on forest pests and act as natural controls on their populations. There are many resources available to guide your selection of native trees, shrubs, and herbaceous plants, including Green Spring Gardens, Plant NOVA Natives, Virginia Department of Conservation and Recreation, and Habitat at Home.
Diversity
Diversity
An essential component of a healthy urban forest is its tree diversity which strengthens an urban forest ecosystem against disturbances. Different tree species are host to different pests and vulnerable to different stresses, so more diversity means an urban forest that is more adaptable to pests and diseases, severe storms or climate change. Consider incorporating diversity into your landscape to create an attractive and resilient urban forest.
Unfortunately there are times when it is necessary to remove a tree. A tree may need to be removed because it has become hazardous or there is conflict with infrastructure or competition with other trees. This is an opportunity to plant a more suitable tree and replace some of the benefits lost from tree removal. Native tree and shrub seedlings can be obtained from several local plant resources including Northern Virginia Soil and Water Conservation District, Fairfax ReLeaf, and Earth Sangha.
Maintenance
Maintenance
Regular maintenance will help keep your trees healthy and safe. Trees should be inspected regularly to identify any problems so they can be corrected before they become harmful to the tree or costly to repair. Follow-up care may include pruning, mulching, fertilizing, or soil management. Visit Tree Planting and Care to learn more about tree care and maintenance. If you want expert assistance, consider How to Hire an Arborist who can develop a tree maintenance plan.
Invasive Species
Invasive Species
An invasive species is any organism that has been spread to areas outside its native ecosystem where it can grow and spread quickly causing ecological or economic harm. These invaders thrive because they have no natural predators and outcompete native species for resources such as light and space. Native populations eventually decrease or collapse under pressure from invasive species. Invasive species impact the health and structure of trees and alter natural habitat that native wildlife depend on for shelter and food.
If you’re not sure what steps you should take first to care for your trees, consider hiring a certified or qualified professional who can diagnose problems and perform necessary prescribed treatments. A certified arborist is an experienced professional who has passed an extensive industry-approved examination covering all aspects of tree care. Visit the Tree Removal webpage to learn more about a certified or professional arborist and how to hire an arborist.
Not All Bugs Are Bad
Not All Bugs are Bad
Generally, people perceive insects negatively. Much attention is focused on harmful insects that threaten people of the health of trees. However, there are numerous beneficial insects that provide many functions that are vital to a healthy urban forest ecosystem including pollination, serving as food for birds and wildlife, and control of tree and garden pests. These include bees, ground beetles, parasitic wasps and flies, lacewing larvae, and many more. Often, it’s the lack of natural enemies that allow destructive insect pests to flourish. The Virginia Cooperative Extension has a variety of helpful publications and resources on the topics of insect pest identification and management. If you need help identifying an insect or disease, then try seeking the assistance of a Fairfax Master Gardener.
Integrated Pest Management
Integrated Pest Management (IPM)
Fairfax County follow an integrated pest management (IPM) strategy to accomplish its goals of mitigating and preventing spread of forest pests and diseases in the county. IPM is an ecological approach to pest control which combines multiple strategies including chemical, cultural and biological methods with the goal that chemical control should be the last resort. Successful implementation of an IPM program results in effective control of the target pest while reducing pesticide use and harm to non-target organisms and the environment.
IPM at Home
Residents can begin by evaluating the problems they are having with their landscape and identifying the correct pest that is causing the problem, or if a pest is even the cause of the problem.
Prevention should be the primary goal in IPM. However, when that isn’t possible, cultural controls can be extremely effective and relatively easy to do. Some examples include: water and nutrient management, reducing competition, installing disease/pest resistant cultivars or species, removing weeds, physical removal of pest or infested plants, mulching and proper pruning. Biological control may involve attracting predators or parasitic insects or releasing predators, pathogens or other organisms that may control the target pest.
Finally, chemical controls should only be used if alternative controls have not been effective. Pesticides should not replace alternative controls entirely and are merely another tool in the IPM toolbox. Choosing the right pesticide means having the pest identified, read the label to ensure the pest may be treated with the active ingredient you choose and select an active ingredient as specific as possible to the pest you are treating. For example, Bacillus thuringiensis or Bt has many strains that are specific to mosquitos, beetles and moths/butterflies. For more information please visit Pesticide Environmental Stewardship - Select a Pesticide
Generally, people perceive insects negatively. Much attention is focused on harmful insects that threaten people of the health of trees. However, there are numerous beneficial insects that provide many functions that are vital to a healthy urban forest ecosystem including pollination, serving as food for birds and wildlife, and control of tree and garden pests. These include bees, ground beetles, parasitic wasps and flies, lacewing larvae, and many more. Often, it’s the lack of natural enemies that allow destructive insect pests to flourish. The Virginia Cooperative Extension has a variety of helpful 
