1. they directly impact tree health by feeding of various parts of the plant, or
2. they are transmitters (vectors) of tree diseases from tree to tree.

Most insects are species specific. If a plant is highly susceptible to a certain pest, you should avoid using it in urban settings. Many devastating forest pests in the United States have been introduced from other parts of the world. These pests have no natural enemies here to control them and often the host tree can't defend itself from an non-native invader.

The key to keeping insects and other pests from damaging your trees is proper tree management. Insects attack trees weakened by other agents, biotic/abiotic. These trees are unable to defend themselves as well as a healthy tree. The key to pest management in urban trees involves proper selection, culture and maintenance.

Insects affect the above-ground portion of the tree and can be broken up into three basic categories: chewing insects, sucking insects, boring insects.

• Chewing insects – primarily focus on the leaves and young stems of trees. 
  • Eastern Tent caterpillar and Tussuck moth larvae can defoliate mature trees in about two weeks. 
  • If the tree is healthy, most defoliators are merely a nuisance and the tree will regrow its canopy with little effect. 
  • Repeated defoliations of young or old trees can weaken the tree.
    
• Sucking insects – include scales, mites and aphids. 
  • These insects primarily attach new foliage and stems. Rather than eating plant parts directly, like defoliators, they pierce the epidermal layers of the plant and extract sugars. 
  • These insects produce mostly cosmetic deformities on the tree such as sooty mold, slow growth, tip dieback and galls. 
  • If insects reach high populations, serious damage can occur. 
  • Sucking insects are drawn to healthy, rapidly-growing trees dominated by rapidly-growing, sugar-rich parts.  
  • The best preventative control is culture. 
  • The use of low-nitrogen, slow-release fertilizers will eliminate sucking insect problems.
    
• Boring insects – are of primary concern in southwest Florida. 
  • Adult boring insects can sense stress and attack. 
  • If boring insects choose a healthy tree, the tree will rebuff entry or tolerate and contain damage caused by the attack. 
  • Boring insects use trees to house their eggs. 
  • During the larval stage, the boring insects feed on the living tissues just beneath the bark layer. 
    • This feeding disrupts the water and sugar flow in the tree, damaging living tissues in the trunk.

Pest Signs and Symptoms

Pest control requires diligence on the part of the homeowner. All trees should be inspected every month for the following signs of pests or insects: 

• chewed foliage, twigs or blossoms;
• streaked or mined foliage;
• curling or twisting of leaves;
• dieback of twigs and shoots;
• sawdust or sap leakage from stems;
• sticky honeydew on ground, stems and/or leaves;
• tents, webs or sick masses in crown;
• pitch tubes or gum masses on stems and branches.

Homeowner or managers should establish a tolerance level for pests, based on two thresholds: 

1. defer pest control if you are willing to tolerate cosmetic or aesthetic injury to the plant or
2. set a tolerance or disturbance level beyond which you will resort to a pest management response.  

• Cultural, this includes sanitation, fertilization, irrigation, avoidance and applying proper timing for planting, thinning and pruning.
• Genetic, plant trees that are genetically less susceptible or introduce pests that are avirulent or dilute dangerous insects through inter-breeding.
• Biological, use or introduction of natural enemies, such as predators, parasites, pathogens or competitors to insects that cannot be otherwise controlled by native biological or environmental factors,
• Sanitation, remove infected plant parts and sterilize all pruning and other tools between plants.
• Behavioral, repellants that use confusion or inhibition-chemicals that hinder and prevent infestation, although chemicals should be a last resort in a properly managed landscape.
• Regulatory, through certification, inspection, surveys or quarantines (in the case of viruses and fungi).

For more information on specific insects, borers, mites and other pests visit: