Include a check, payable to the University of Illinois, with the oak-branch sections. The results of the laboratory diagnosis will be mailed as soon as they are known. The process usually takes one to two weeks of lab time. All species and varieties of oak tested to date have been found susceptible to the oak wilt fungus. Back to Top Spread Oak wilt moves from diseased to healthy trees in two ways through root grafts formed between trees and through fresh wounds via sap-feeding insects.
Beetles spread the oak wilt organism by carrying spores to fresh wounds on healthy oaks.
The spores are produced on fungus mats formed beneath the bark of wilt-killed trees of the red oak group and as the beetles crawl over and feed on the fungus mats, the microscopic spores stick to their bodies. The insects then fly to healthy oak trees and feed on the sap oozing from fresh wounds. Squirrels are potential carriers of the wilt fungus, too, but their importance has not been established. Where trees are growing close to one another, their root systems often become intertwined. Thus, the roots of one red oak may graft to the roots of a nearby red oak.