Crown Whitefly

• The University of California Integrated Pest Management Program states that crown whiteflies (Aleuroplatus coronata) prefer oak, as well as chestnut, as host trees. Crown whiteflies are small, sap-sucking insects that get their name from the crown-like arrangement of a mealy, white, waxy substance that covers their bodies during their last development stage before maturity. These flies secrete a sticky, dew-like substance that causes the leaves of oak trees to turn yellow, decay and sometimes die. Usually found in groups on the undersides of leaves, crown whiteflies are hard to eradicate once there is a break in their natural biological control.
  
  

Scarlet Oak Sawfly

• The U.S. Forest Service notes the scarlet oak sawfly (Caliroa quercuscoccineae), also known as the slug oak sawfly, is a harmful pest to oak trees. Scarlet oak sawflies skeletonize the leaves of both red and white oak varieties, typically feeding from the upper crown downward. Uncontrolled populations cause devastating defoliation on trees of every size. Damage from scarlet oak sawflies results in stunted tree growth and even the death of heavily effected specimens.
  
  

Lace Bugs

• Lace bugs rob plants of their chlorophyll by feeding on the underside of leaves as both nymphs and adults, which appear as small, brown specimens with lacy wings. The University of Maryland Cooperative Extension notes that several species of lace bugs attack various shade trees, including oak trees. Signs of a lace bug infestation include the appearance of minute white specks on the upper surface of leaves, which later merge forming yellow patches of decay, and the presence of hard, black or brown droppings on the lower leaf surface. Oak orchards heavily infested experience premature leaf drop and the death of smaller or less vital trees.
  
  

Other Pests

• Oak trees are susceptible to a wide variety of insects and pests that are not flies. Pests that wreak havoc on an oak orchard include beetles, borers, worms, weevils, caterpillars, aphids, leafminers and grubs. The U.S. Forest Service offers an extensive list of insects and other pests that can damage oak trees in "Oak Pests: A Guide to Major Insects, Diseases, Air Pollution and Chemical Injury."