• Bark Beetles -- These insects are usually not the primary problem. They typically attack trees already under stress from some other factor. Bark beetle-infested trees normally cannot be saved.  Emerald Ash Borer: EAB Guide and Invasive Insect list.
  
• Foliage Insects -- Several species of insects can cause foliage damage or loss. Aphids, adelgids, tent caterpillars, sawflies, leaf beetles, and loopers are just a few common examples. Direct control may be possible for ornamental trees but is rarely feasible or necessary in forest stands. Damage is often cyclic, i.e. worse in some years than others. Most trees will recover from this type of insect attack.  Maryland Hardwood Defoliators
• Other Insects and Diseases

• Temperature Extremes -- Sudden heat waves or deep freezes often cause damage. Small trees may be killed. Large trees usually recover.
• Drought -- Extended periods of drought during the growing season can kill or damage trees. Trees on gravely or sandy soils are particularly susceptible.
• High Water -- Poor soil drainage and high water tables during the winter can "suffocate" tree roots. Flooding can also damage or kill trees if water stands for an extended period. 
  
• High Winds -- Storms from the Pacific periodically damage or blow down trees. Check for root disease and hazard trees before the next wind storm. Stands suddenly exposed to wind, such as those at the edge of land clearing or timber harvest areas are susceptible to windthrow. Thinning stands beginning at an early age will help individual trees to resist windthrow.
• Ice and Snow -- Periodically, freezing rain and heavy snow cause excessive damage to trees and forests. Tops and branches are often broken, and whole trees can be bent over or uprooted. Corrective pruning and staking may be required for ornamental trees. Salvage harvesting may be needed in forest stands. Thinning forest stands starting at an early age will help trees withstand ice and snow breakage.
• Overcrowded Stands -- Many forest stands have too many trees per acre. Competition between trees results in small crowns, poor diameter growth, and reduced tree health and vigor. Thinning will help to keep trees healthy and growing vigorously.

Human activities such as excavating, filling, road construction, and timber harvesting can damage trees directly or indirectly by affecting root function or changing soil drainage. Plan to protect trees, and their "root zones" during development or construction activities. Damaged trees may die suddenly or deteriorate slowly. Trees stressed by human-caused damage are often highly susceptible to secondary damage-causing agents such as bark beetles.

People also sometimes unknowingly introduce exotic pests and plants which have the potential to cause extensive damage to Maryland's trees and forests. Invasive Plants List

Both wildlife and domestic animals can damage trees, particularly young seedlings. Use fences to keep horses and cattle away from trees and forest vegetation, particularly along streams. Paper or fabric bud caps, rigid plastic tubing, and repellents can help control feeding damage to trees by deer, rabbits and rodents. White Tail Deer link.

Asian Long Horned Beetle | Emerald Ash Borer | Gypsy Moth | Hemlock Wooly Adelgid | Md Revised EAB Buffer Map

For more information on the Maryland Forest Health, Contact DNR , Email DNR
DNR Health Report | Technical Assistance|

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