The Montgomery County Extension Office has received a high number of calls related to tree issues this past spring and summer. Landowners and homeowners have noted early dropping of leaves, funguses, trees not producing fruit, and a variety of other issues. With the excessively wet spring and summer that we have had here in Indiana, trees may react in negative ways. Some culprits have been identified as Verticillium Wilt and also Brown Rot (discussed at the end of the article).
Homeowners and landowners need to keep an eye on trees that may be dying from weather-related stress, Purdue University tree experts say. Symptoms recently noted on mature oak, tulip and maple trees in Indiana include leaf scorch - the browning of leaves - branch dieback and premature defoliation.
Rosie Lerner, Purdue Extension consumer horticulture specialist, said healthy trees do not die quickly, and there are likely numerous stress factors adding to what is happening to some trees.
"Indiana weather has given us pretty much every extreme in the last few years from extreme heat and drought, to bitter cold and high winds and to floods," Lerner said. "The added stress, especially on urban trees that have compromised root systems, may make them more vulnerable than non-urban trees."
With the water levels in most counties in Indiana this year being above field capacity most of June and July, water stress is likely causing the symptoms, said Kyle Daniel, Extension horticulture program specialist. "Tulip trees and most oaks can't tolerate flooded conditions, but certain maples, like silver maple, can tolerate compacted or flooded soil for a period of time," Daniel said
Lindsey Purcell, urban forestry specialist, wants owners of young and newly established trees to be aware that supplemental watering is essential if there is no rain for an extended amount of time, such as a week.
"These trees do not yet have the substantial root system to obtain water in drier conditions," he said.
Gail Ruhl, plant disease diagnostician, reminds those with trees experiencing these issues that it is crucial not to generalize the main cause of tree dieback but to examine each case with regard to specific symptoms and environmental elements. "Stressed trees are more susceptible to insect and disease. In fact, stressed trees will attract secondary bark- and wood-boring beetles," Ruhl said.
Homeowners wanting to investigate the cause of their tree problems should use the Purdue Tree Doctor app (available at Purdue Extension's The Education Store at www.edustore.purdue.edu and purdueplantdoctor.com) or contact their local extension office (Renee Wiatt, 765-364-6363 or reneewiatt@purdue.edu).
Verticillium wilt is a soil-borne fungal disease that can show up at any time during the growing season. Especially susceptible tree varieties include maple, ash, catalpa, redbud, tulip tree, golden rain tree, Russian olive, smoke tree, and a few others. Because the disease is soil-borne, it enters the tree through the roots of the tree and travels through the vascular system. The disease ultimately affects water movement within the tree, leading braches to wilt and die. Usually, only a few branches are affected at a time but whole trees can be affected simultaneously. Very little can be done once a tree is infected with Verticillium wilt, other than pruning dead braches and watering the tree.
Brown rot is another fungus that can affect trees – namely stone fruit trees (peach, nectarine, apricot, plum, and cherry). Brown rot can cause blossom and twig blight, cankers, and fruit rot on all members of the stone fruit group. Symptoms will typically first appear in the spring as the blossoms become infected. Diseased flowers wilt and turn brown but remain attached to the tree. The fungus may produce masses of tan spores on the dead blossoms. Flower infections may spread to both new growth and spurs, causing cankers and shoot death as the fungus spreads into twigs. Young fruit is normally resistant to brown rot but can become infected through wounds. As fruit matures, it becomes more susceptible to infection. Fungicides, along with removing and destroying fallen and rotted fruit, can help to manage the disease. Pruning out cankers in late winter can also help to manage the disease.