Diseases that have no treatment and will kill the tree, and the tree should be removed as soon as possible

Symptoms	When They Appear	Cause	Treatment	Prevention	Notes
One or more limbs dead on an American elm tree	May through early September	Dutch Elm Disease	Treatment involves high costs-fungicide can be used, but may not be effective as the disease is caused by a winged bark beetle	Plant lacebark elms resistant to the disease Remove trees with more than 10% infestation as soon as possible, get rid of wood.
Soft sunken areas on trunks and branches	Anytime	Stem Canker	No treatment	Keep trees in good health, water during droughts to reduce stress, avoid wounding tree	Present in tree many years, becomes harmful when tree is stressed
Pine trees turn gray-green to yellow or brown in a 3-6 week period Trees die.	Midsummer to late fall or late winter to early spring	Pine Wilt	NO cure. Caused by pine wood nematodes moved by wood boring beetles	Plant trees less susceptible. Maintain tree health as it attacks stressed trees	Have tree tested - if pine wilt is present, tree should be removed and destroyed as soon as possible to prevent spread

Deciduous tree pests that are treatable

Symptoms	When They Appear	Cause	Treatment	Prevention	Notes
Small circular spots on upper portion of leaf	May thru October	Leaf Spot	Fungicides, such as Bordeaux mixture can be applied for protection against infection	Prune over thick growth, rake and destroy last years leaves before spring bud break
Chewed holes along edge of leaf, later working toward center	April/May	Cankerworm (Leaf Feeder)	Applying insecticides, such as Tempo in April/May can reduce damage	Apply sticky bands to tree trunks to catch wingless females
Pencil-sized, irregular holes often found on the lower trunk	All Year	Borers	Insecticides, such as Dursban, can be applied to trunk to kill newly hatched larvae in May, June and July	Borers attack weakened trees. Select less susceptible trees, be careful about watering, fertilization. Prune out dead wood on older trees to eliminate food source.	Holes high on trunk in straight lines are probably from woodpeckers or sapsuckers.
Green leaf tissue striped from bottom of leaf	July thru mid October	Skeletonizer larvae	Rarely kills, but can weaken for secondary attack		Spray to kill first brood in May, with insecticide such as Sevin or Tempo
Irregular, scorch-like lesions along the leaf veins	April thru June	Anthracnose	Spray when leaves unfurl with fungicide such as Bordeaux mixture again when they reach full size and two weeks later	Gather and destroy fallen leaves and twigs in fall, prune to allow air circulation
Gray or white powdery substance on upper leaf surfaces	May/June and mid August thru mid October	Powdery Mildew	Spray with fungicide such as Funginex	Plant susceptible species in full sun and space plants and prune to allow air circulation
Leaves slowly discoloring thru the summer, particularly on sycamores	May thru September	Lacebugs	Spray with insecticide, such as Sevin or Tempo, if obvious damage is noticed.		Generally not very deadly or damaging
A webby tent surrounds foliage which is being consumed	June and September/October	Webworms	Use insecticide sprays, such as Sevin or Tempo, or bacterial sprays like Javelin with high pressure to saturate web when webs are small	Prune webs as practical
Leaves stripped, sometimes to point of defoliation on Siberian elms	May thru September	Elm Leaf Beetle	Spray with insecticide such as Tempo to kill first brood in May		May defoliate entire tree but rarely kills, weakens tree for secondary attack
Leaves turn yellow, sometimes develop brown spots and drop off tree	May thru October	Iron Chlorosis	Apply iron chelate in powder form to soil or dissolved in water to foliage or soil	Plant trees that will tolerate the areas soils

Coniferous tree pests that are treatable

Symptoms	When They Appear	Cause	Treatment	Prevention	Notes
Pine needles have reddish brown bands surrounded by yellow bands. Tips of needles turn brown while the rest is green. Needle drop is heavy following heavy dry summers	Early fall	Dothistroma Needle blight	Spray in mid May and again in Mid June or July with copper fungicides or Bordeaux mixture	Collect and destroy infected needles
Dieback of pine branches. New growth is stunted and needles turn brown, a resin is excreted.	Mid June	Diplodia Tip Blight	Spray with copper fungicides or Bordeaux mix between late March and early April. Two applications, a week apart	Remove infected buds when first noticed. Do NOT remove when branches are wet - this may spread the disease
Pine branch tips turn yellow or red brown	Midsummer	Pine Tip Moth	Spray insecticide such as Sevin or Tempo on 20 day intervals between late March through end of June	If noticed, spray the next year in March (3-4 applications) to kill new larvae before they have the chance to bore into branch tips