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Thursday, May 5, 2016

Spring Leaf Drop?

Monday, June 2, 2008

Several calls have come in this past week regarding trees losing leaves and various disease descriptions. While this is very unsightly and a nuisance, there is no need for fear-except for dogwood trees. The culprit is anthracnose which is a bacterial disease that typically can infect trees at this time of year. The cool and damp weather has allowed the disease to proliferate and in some cases be severe. The good news is that generally healthy trees will survive and be fine.

The symptoms of anthracnose are most noticeable in the lower branches.

Typically the top branches are relatively unaffected by the bacterial disease. Common leaf symptoms include dying of the leaf margin tissue on or adjacent to leaf veins. Leaf scorch is different and can be distinguished differently as it is located between veins rather than on or adjacent to veins.

Anthracnose is very host specific-meaning that the bacteria for ash anthracnose will not affect dogwood species and conversely dogwood anthracnose will not have any impact on ash species. There is a typical order that species become impacted. Typically ash are first to show infection symptoms. Green ash is more vulnerable and apt to show infection in mid-to-late April. Sugar maples are next in line to show infection. Maple leaves will curl and turn black. Extensive defoliation may occur in severe cases. Sycamore trees are now becoming heavily infected and are the most seriously impacted tree in Indiana. In many cases, sycamore trees may appear more dead than alive through the spring and early summer months. Sometimes sycamore anthracnose is confused with freeze injury. Newly emerged leaf tissue will suddenly wilt and brown or blacken in color. This stage is commonly referred to as twig blight which results from numerous stem cankers that occur throughout the tree canopy. The leaf blight phase follows the twig blight phase of sycamore anthracnose where the infected area will expand outward to the leaf margin causing leaf distortion.

Other species impacted by anthracnose includes white oaks, dogwood, birch, catalpa, elm, walnut, butternut, hickory and linden. In the white oak leaf symptoms occur along the midribs and veins to the leaf edges and again particularly on the lower branches. Red oak seldom are affected but may be affected by blister leaf, another fungal disease.

Fungicides are typically impractical for larger trees and are of little help by the time one notices the infection. Tree health is not impacted long term. One exception is dogwoods impacted by anthracnose which should be treated in the early spring.

You can contact the local Purdue Extension Office by calling 829-5020 Ext. 14 in Owen County or 448-9041 in Clay County for more information or publication copies regarding this week's column topic or to RSVP for upcoming events. It is always best to call first to assure items are ready when you arrive and to RSVP for programs. While most publications are free, some do have a fee. All times listed are Eastern Time.

Upcoming Events

June 10 Ribeye Steak/ Fallen Officer Owen Community Blood Drive, Spencer 3-6 p.m.

June 12 Ribeye Steak/ Fallen Officer Clay County Blood Drive, Brazil, 3-6 p.m.

June 14 Invasive Plant Workshop (PARP & CCA credit), Pfizer - Terre Haute, 9 a.m.

June 24 Bee Keeping Field Trip-Hunters Honey Farm, 6 p.m.

June 26 Ribeye Blood Drive at YMCA, Brazil, 3-7 p.m.

June 24-28 Clay City Fair

June 28 Ribeye Blood Drive, Clay City Fair

July 6-12 Owen County Fair

July 11-18 Clay County 4-H Fair