Tree Diseases in Iowa

Protect Your Trees From Common Iowa Tree Diseases

 

  1. Emerald Ash Borer
    Find Professional Emerald Ash Borer Treatments in Des Moines

    The Emerald Ash Borer is a metallic wood-boring beetle. This beetle normally serves to kill weakened or dying trees as part of natures recycling scheme, however for an undetermined reason this beetle will feed on vigorously growing or weakened Ash trees, it does not discriminate. The Emerald Ash Borer can be incredibly damaging to your tree’s health. The Tree Doctor treats Emerald Ash Borer infestations and we are the only local and privately owned company that has the newest technology in an injection gun. We will determine the DBH (diameter @ breast height) of your Ash tree; using that we will be able to determine the number of injections sites and mL of TREE-Age to inject into the tree. The Tree Doctor uses the only product on the market 99% effective in preventing, curing and eliminating the threat of Emerald Ash Borer infestation.

    For more information on Emerald Ash Borer treatments, symptoms and causes, please visit our Emerald Ash Borer Treatment page.

  2. Oak Wilt
    Trees Affected
    • Red Oak Group (very susceptible)
    • Pin Oak
    • Red Oak
    • Black Oak
    • White Oak Group (more resistant)
    • Bur Oak
    • White Oak
    Cause

    The fungus that causes oak wilt, Ceratocystis fagacearum, invades the water-conducting tissues (xylem) of oak trees. The trees respond to this attack by plugging the xylem vessels with tyloses, which are outgrowths from cells next to the vessels. The tyloses block the normal upward flow of water through the vessels, causing the foliage to wilt and die. In this way, a tree’s own defenses (tyloses) can lead to its imminent death.

    Symptoms
    • First appear in Red Oak late spring early summer and White Oaks mid to late summer
    • Leaf discoloration, dull and bronzed/brown at the tips with sharp distinction of dead and living (green & brown) part of leaf
    • Dark brown or black outer ring of sapwood when bark is peeling
    • Dark brown streaks (vertical) in sapwood of infected branches
    • Isolated dead branches in crown of tree (more common in White Oak)

    Control Strategies

    • Avoid wounds during high-risk period (April 1st – July 1st *high sap)
    • Root graft separation (between infected and healthy)
    • Breaking root grafts – trenching machine or vibrating plow
    • Breaking root grafts – fumigant installation
    • Injecting Fungicide. The fungicide propiconazole (Alamo®) can be injected into oaks to prevent or suppress oak wilt. This is a better preventative than solution or cure
  3. Pine Wilt
    Cause

    The pinewood nematode, Bursaphelenchus xylophilus, a worm- like creature feeds not only on blue- stain fungi that live in the wood of dead and dying pines, but also on the living plant cells surrounding the resin canals, or water-conducting passages, of pines. These nematodes live inside pine sawyer beetles; these beetles are attracted to healthy pines for maturation feeding and dead or dying pines for egg laying. Once the beetle has attached itself to the pine, the nematode leaves the beetle and finds a new home in the tree. At this stage the nematode has effectively transmitted pine wilt to the pine in question.

    Symptoms
    • 90% of Pine Wilt cases affect Scots Pines of 10+ years of age
    • Needles turn grayish green, then tan colored and eventually brown
    • Resin flow ceases as tree health declines
    • Generally starts in scattered branches however spreads to entire tree over time
    • Tree could turn brown at once (rare situation)

    Control Strategies

    • Remove dead or dying pines in the area as sawyer beetles will lay eggs in them
    • Do not trim a healthy pine (in season) near an area where Pine Wilt is known
    • Burn, chip, and completely rid of pinewood, do not have sitting around in piles, etc.
    • Today there are no practical or highly effective management tactics against pine wilt
  4. Dothistroma Needle Blight
    Trees Affected
    • Austrian Pine
    • Ponderosa Pine
    • Mugo Pine
    • Red Pine
    • Scots Pine
    Cause

    Dothistroma needle blight is a product of the fungus Dothistroma pini (also called Mycosphaerella pini). The fungus is active throughout the growing season and can infect any age of needle during wet weather. However, symptoms typically first appear in early fall, although they may not be noticed immediately.

    Symptoms
    • Browning of needles
    • Reddish brown spots or bands on affected needles
    • Needle tips beyond the band dry out and turn brown while base remains green
    • Premature needle dropping
    • Most severely impacted area of tree is at the base

    Control Strategies

    Prevention
    • Avoid planting Austrian pine
    • Provide vigor through watering and mulching
    • Promoting air circulation through appropriate pruning
    • Provide adequate spacing, and proper weeding
    Treatment

    Fungicide sprays may be used if symptoms are found. Sprays should be applied twice in the spring after new growth appears, once in mid-May and again 4 to 6 weeks later. Effective sprays include Bordeaux mixture, copper fungicides, and EBDCs. Spraying may be discontinued when symptoms are no longer found.

  5. Diplodia (Sphaeropsis) Tip Blight & Canker
    Trees Affected
    • Austrian Pine (very susceptible)
    • Ponderosa Pine (very susceptible)
    • Red Pine (less susceptible)
    • Scots Pine (less susceptible)
    Cause

    Dothistroma needle blight is a product of the fungus Dothistroma pini (also called Mycosphaerella pini). The fungus is active throughout the growing season and can infect any age of needle during wet weather. However, symptoms typically first appear in early fall, although they may not be noticed immediately.

    Symptoms
    • Browning of needles
    • Reddish brown spots or bands on affected needles
    • Needle tips beyond the band dry out and turn brown while base remains green
    • Premature needle dropping
    • Most severely impacted area of tree is at the base

    Control Strategies

    Prevention:
    • Avoid planting Austrian pine
    • Promote good air circulation by adequate spacing and weed control
    • Trees may be pruned to improve their appearance, but this does not control the disease
    Treatment

    Spray chlorothalonil, benomyl, thiophanate-methyl, Bordeaux mixture, or other appropriately labeled copper fungicides at bud swell, and then repeat twice at intervals of 10-14 days. This practice does not decrease the likelihood of new infections because a great number of fungal spores are released from diseased cones.

  6. Fire Blight
    Trees & Bushes Affected
    • Apple
    • Pear
    • Crabapple
    • Hawthorn
    • Cotoneaster
    • Quince
    Cause

    Fire blight is caused by a bacterium. The bacterium survives the winter in cankers on infected branches. In the springtime, sticky bacterial ooze formed at the edges of the cankers is carried to healthy plants by insects, wind, and splashing rain. Healthy plants may become infected through blossoms or wounds.

    Symptoms
    • Wilting of leaves
    • Burnt look to leaves, black colored
    • Curling of affected shoots into curved “shepard’s crooks”
    • Cankers (areas of sunken or discolored bark) may develop on limbs
    • Blighted shoots may produce sticky ooze like substance in winter

    Control Strategies

    • Prune infected out of the tree, at least 12” below diseased area to removed all bacteria
    • Plant resistant varieties, pears tend to be more susceptible than apples
    • Bactericidal sprays can be helpful, such as copper sulfate or streptomycin, during the bloom period. However, bactericides are ineffective without proper sanitation
  7. Dutch Elm Disease
    Trees Affected
    • Elm (American Elm)
    Cause

    Dutch elm disease is caused by the fungi Ophiostoma ulmi and Ophiostoma novo-ulmi. This fungi is the original species introduced to the United States and Europe. Ophiostoma novo-ulmi is a more aggressive species that has become more prevalent in recent decades, virtually replacing Ophiostoma ulmi in Iowa. Ophiostoma grows in the xylem (water-conducting tissue) of elms. In an attempt to fight invasion by the fungus, an infected tree will produce gums and cell outgrowths that block its own xylem vessels. Blockage of a tree’s water supply causes the characteristic wilting symptoms.

    Symptoms
    • Wilting leaves on one or a few branches on upper canopy
    • Affected leaves turn yellow, then brown, and eventually fall from tree prematurely
    • Dead leafless branches
    • Smaller than normal leaves the following spring after tree becomes infected
    • Discoloration (dark brown) of xylem (water conducting tissue)

    Control Strategies

    • Prompt, thorough sanitation is vital including trees in parks, fencerows, cemeteries, and other sites as well as in residential areas.
    • Removing sources of the DED fungus and breeding grounds for the beetles is essential.
    • Any tree that has died due to DED should be cut down and destroyed promptly.
    • Branches pruned from infected trees also should be destroyed.
    • All infected wood should be burned, buried, or chipped.
    • Do not store firewood from DED-infected elms with the bark attached, because logs with attached bark provide breeding sites for beetles.
    • Available evidence indicates that wood chips made from DED-infected trees pose no risk of transmitting the disease.
  8. Apple Scab (non-lethal)
    Trees Affected
    • Crabapple
    • Apple
    Cause

    Cool and wet weather are ideal conditions for the development of Apple Scab. Apple scab is caused by the fungus Venturia inaequalis and is spread by two types of spores, sexual spores and asexual spores. Sexual spores are produced on previously infected fallen leaves. The spores spread by wind and splashing rain and provide inoculum for the disease the following year. Asexual spores are produced on the tree during the growing season. They are also spread by wind and rain.

    Symptoms
    • Velvety brown or olive green spots on leaves
    • Older spots on leaves turn dark green to brown or black and develop a rough texture
    • Affected leaves turn yellow and fall prematurely
    • Heavy loss of leaves as soon as early summer
    • Fruit develop similar symptoms to leaves, black, rounded, rough-textured spots
    • Uneven growth of fruit throughout tree

    Control Strategies

    • Plant varieties of crabapple and apple that are highly resistant to scab
    • Fungicide treatment during springtime
    • Remove all fallen leaves or fruit in the fall as infected leaves/fruit are a good source of disease for the following growing season. This decreasing the amount of inoculum
  9. White Pine Blister Rust
    Trees Affected
    • White Pine
    Cause

    White pine blister rust spores germinate on the plant surface and grow into the pine through the stomatal openings in the needles or a through a wound. The fungus then grows into the twig. The infected branch will often swell; after a year or more, the rust forms spores that are contained in blister-like sacks that erupt through the bark of the twig or stem. When the blisters rupture they release bright orange colored aeciospores that infect the alternate host (most commonly gooseberry or currant plants). While hosted on these other plants the rust produces basidiospores that are released in the fall and can infect the pines. The rust is shed from the gooseberry or current plant when the plant naturally drops its leaves in the autumn and the cycle continues.

    Symptoms
    • Spore & canker development
    • Patches of browning bark bordered by yellowish discoloration (first year)
    • Spindle-shaped swelling of infected branch (second year)
    • Canker on main stem (will kill tree above canker)

    Control Strategies

    • No true control strategies
    • Removal of cankers on all branches, especially branches within 4” of the trunk
  10. Girdling Root Syndrome
    Trees Affected
    • Maples
    • Lindens
    Cause

    Girdling roots are caused by nursery and transplanting practices, soil obstructions and unknown factors (e.g. planting trees in a small landscape or in asphault/cement). Girdling roots are usually lateral roots at or slightly below the soil line that cut into at least one side of the main trunk. These roots restrict water and nutrients. Branches will eventually become weakened and the tree may die. If the tree does not die from girdling roots alone it will weaken the tree ability to fight against environmental stresses.

    Symptoms
    • Abnormal abundance of surface roots on or around the trunk of the tree
    • Trunk flare spots
    • Poor growth of tree
    • Premature coloring and falling of leaves
    • Thin or sparse canopy
    • No visible flare at soil surface

    Control Strategies

    • Diagnose and treat immediately, better to treat when tree is young.
    • Do not plant tree in tight or restricted spaces, especially prone trees.
    • If transplanting a prone tree, be sure to use proper equipment to minimize damage to root structure.
    • Cut away any surface roots that may be hindering the water up take or nutrient absorption, however removal of unnecessary roots or too many may impact the health or life of the tree.
  11. Bagworms
    Trees Affected
    • Red Cedar
    • Arborvitae
    • Juniper
    • White Pine
    • Crabapple
    • Honey Locust

    (*Although these are the main trees affected, it has been reported that the bagworms will feed on the leaves and needles of up to 128 different species of tree and shrub.)

    Cause

    Bagworm caterpillars (Thyridopteryx ephemeraeformis) are pests that devour the foliage of several species of fruit, shade and ornamental trees, as well as evergreen shrubs.

    Symptoms
    • Larvae bags form on twigs throughout tree or shrub
    • Holes or bite marks in foliage of tree
    • Visible sighting of caterpillar or moth
    • Discoloration or thinning canopy due to severe infestation

    Control Strategies

    • Inspect tree for bags or pods (contain between 500-1000 eggs) in the fall and cut them off and either burn or soak them in detergent prior to discarding them.
    • Chemical treatment (insecticide) early in the season; Bt (Bacillus thuringiensis), spinosid, azadirachtin (Neem), Sevin, permethrin and many others. The later into the season the less effective this treament will be.