The Morton Arboretum’s Tree Care Quick Facts

THOUSAND CANKERS DISEASE

A deadly disease that has spread from the western states to the East poses a serious threat to Illinois’ black trees. It now is moving into the Midwest, and Illinois owners of black must be vigilant to prevent its spread.

Black Walnut: The fungus is carried by the . It An Important infects the along the insect’s entry hole and in its egg-laying and larval tunnels Illinois Species (galleries). The fungus causes a canker, a A black walnut tree Eastern black walnut ( nigra) is a small, generally circular area of dead bark () large tree, typically growing over 40 feet tissue. When multiple areas are infected tall. It prefers well-drained, slightly elevated they can merge, forming patches of canker floodplain areas but also does well in large enough to girdle tree branches. urban areas. Black walnut is a native tree Multiple dead branches, combined with that grows throughout Illinois, where its insect attack and cankers on the main nuts support a wide range of wildlife. It stem, can kill the tree in a few years. also is valuable for timber; Illinois ranks fourth among the states in production of Identifying a black walnut timber, harvesting roughly Black Walnut 120,000 trees per year with a value of Do you have a black walnut on your more than $18 million. Thousand cankers property? Check your tree for Black walnut disease threatens this market as well as these characteristics: leaf arrangement the black walnut’s value in landscapes Alternate branching: Each branch and natural areas. or bud is set directly opposite the one What is Thousand on the other side of the twig or branch. Cankers Disease? Compound leaves: A single leaf is made up of 11 to 23 small leaflets. Thousand cankers disease (TCD) is Fruit: The round lime-green fruit caused by the interaction of an insect is roughly 3 to 4 inches in diameter. (the ) and a fungus Squirrels and other wildlife love (). The beetle and the black walnuts. fungus are native to the southwestern Chambered pith: If still in doubt, , but were inadvertently remove a small twig and split it to see transported to the East on walnut burls Black walnut the dark pith in the center. A black and logs. TCD has been found in several walnut’s pith consists of eastern states on the highly susceptible distinct chambers. black walnut.

Walnut twig beetle

THE MORTON ARBORETUM 4100 Illinois Route 53 Lisle, IL 60532 • mortonarb.org/plantadvice The Morton Arboretum’s Tree Care Quick Facts

THOUSAND CANKERS DISEASE

Symptoms to Look For Where walnut wood is desired for Symptoms of thousand cankers woodworking, stem and burl sections disease are: from infected or dead trees can be heat- treated to kill any or fungus. The • Yellowing of the leaves wood must be heated to 118 degrees • Wilting leaf appearance for at least 40 minutes. All walnut tree • Thinning of the crown sections cut for use should be completely • Death of large limbs debarked before wood is removed from These symptoms are most evident the site. The removed bark should be during drought periods. burned or buried to prevent further Susceptible Species transmission of the fungus or beetles. Eastern black walnut and butternut appear to highly susceptible to TCD. to Other species, such as English walnut, are Pennsylvania moderately susceptible, while the native Thousand cankers disease was confirmed Arizona walnut appears to be resistant. on August 2, 2011, in Bucks County, Pennsylvania. It is believed that the walnut Illinois Quarantine twig beetle and the fungus arrived in a Against Walnut Wood shipment of logs from Chico, Calif., six To protect black walnuts, the state of to eight years before the infection was Illinois has established a quarantine against noticed. In the 2011 discovery, 10 of the walnut wood from the western states or 56 live walnut trees on the property were from states in the East where thousand found to have both the beetle and the cankers disease has been detected. Walnut fungus. Although the infected trees were wood may only be brought into Illinois if it removed, the beetle had escaped and meets strict requirements. For details, see continues to be found in surveys. thousandcankers.com/state- info.php?state=Illinois. Thousand Cankers Disease in Illinois No Treatment For up-to-date information on this disease Available in Illinois, visit the Illinois Department of There are currently no products produced Agriculture website at agr.state.il.us. or specifically labeled for TCD prevention or management on any walnut species. Research is underway to find a suitable chemical treatment for the beetle and/or the fungus.

THE MORTON ARBORETUM 4100 Illinois Route 53 Lisle, IL 60532 • mortonarb.org/plantadvice