Lexington, Kentucky 40546
      
Nursery Update - A University of Kentucky Cooperative Extension Service update for the Kentucky Nursery Industry
  
By Amy Fulcher, Extension Associate - Nursery Crops
  
University of Kentucky Department of Horticulture
  
Update #12
  
May 7, 2003
  
 
Disease:

Anthracnose
Maple, ash, sycamore, and others are susceptible to anthracose during rainy periods in the spring and summer. Discrete, irregularly shaped areas develop on leaves. The color varies - lesions on Sugar and Norway maple are colored reddish brown while those on Japanese maple are light tan. Anthracnose is generally not a factor in tree health, however, a severe case can cause defoliation.

Source: Diseases of Woody Ornamentals and Trees in Nurseries. Jones and Benson, eds. APS Press.
Photo from Cornell University Publication Anthracnose of Trees and Shrubs
 
Insect:

Flatheaded Appletree Borer (FHAB)
FHAB adults have now emerged from trees in the Ohio River valley. One FHAB borer can kill a tree. The larvae feed initially on phloem in a spiral pattern that often girdles the tree. They affect many species of deciduous trees and shrubs including maple, oak, crabapple, dogwood, pear, tuliptree, sycamore and hawthorn. First year liners and other stressed trees are particularly susceptible.

Growers will want to spray an EC formulation of chlorpyrifos before eggs are laid. United Horticultural Supply's (UHS) Dursban™ TNP is currently labeled for borer control in nurseries as is Chlorpyrifos Pro 4 by Micro Flo. These are restricted use pesticides and are not for borer control in residential areas. Wet the trunk and lower scaffold branches; cover the graft thoroughly.

Source: Insect Borers of Trees and Shrubs. U.K. Pub. ENT-43

Maple Shoot Boring Caterpillar
Maple shoot borer has been detected in nurseries in the Green River and Purchase areas. In the spring, the maple shoot borer adult lays eggs at the base of maple leaf petioles. The newly hatched larvae make a tunnel and bore through the length of the petiole, which becomes swollen. The tip of growth beyond the point of the infestation wilts and dies. Maple shoot borers are most costly when they infest the central leader, requiring that a new leader be trained.

To prevent maple tip borer apply Talstar when the first 2 sets of red maple leaves have emerged. Due to seedling variation reapply in 5-7 days if seedling maples are being grown.

Top: FHAB damage on hawthorn. Middle: Maple shoot borer damage. Bottom: Maple shoot borer larvae.

Source: Commercial Insect and Mite Control for Trees, Shrubs, and Flowers. UT Pub. 1589.

 
Cultural:

Hail Damage
Hail damage is unsightly and provides an entry point for pests, especially fireblight.

Hail injury can cut leaves, defoliate branches, and bruise or break the bark. Hail injury typically occurs on the windward side of the tree. Damage early in the season may cause bruises that aren't easily detected. As the season progresses the bruised tissue splits from the stress of callus growth. New bark will quickly cover small splits. Larger wounds may still be exposed in the fall. Hail damage in the fall may result in twig death due to dessication.

Source: Diseases of Trees and Shrubs. Sinclair, Lyon, and Johnson. Cornell University Press.


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