It takes about seven days for the fungus to develop in the lab to the point that a positive confirmation can be made. Occasionally, we hear from clients who thought oak wilt was present when the tree was sampled, but the clinic did not isolate the fungus. The fungus is slow to grow but it is not tricky to isolate in the lab. Assuming a proper sample was taken, the problem may be the sensitive nature of this fungus. Many states report that oak wilt fungus in sampled wood does not survive high mail-truck temperatures.
Many southern states require oak wilt samples to be shipped on ice.
If you have had this problem in the past, consider shipping samples with ice packs in the package and using overnight shipments. We will do our best at this end to get oak wilt suspects in culture as soon as possible. Oak wilt is particularly threatening because there is no complete control or cure once the fungus infects. The fungus infects through fresh wounds and a beetle vector, and it can spread by root grafts between trees. You cannot save the infected tree, but you may be able to save surrounding trees, so a positive diagnosis is important in many cases.