Fresh wounds usually leak sap. The sap attracts insects, including nitidulid beetles that have visited oak wilt spore mats. The overland movement of nitidulid beetles from spore mats on infected trees to wounds on otherwise healthy trees thus creates most new infection centers. Not all nitidulid beetles are vectors of the oak wilt pathogen. In the North, nitidulids in the genera Carpophilus , Colopterus and Epurea are most often associated with both oak wilt spore mats and fresh wounds on healthy oaks.
Nitidulid beetles are primarily responsible for overland spread of oak wilt .
Spore mats can form only within a year after tree death, and only when air temperature and wood moisture are within a certain range. In the northern United States this combination of wood moisture and temperature commonly occurs in spring of the year after the tree dies, or sometimes in autumn of the year the tree dies. The period of time during which mats are formed increases with decreasing latitude. In Texas, mat formation occurs at any time during the year, but is most common in late fall and winter when the weather is cooler and wetter. Spore mats usually do not form on trees smaller than 6 inches in diameter at breast height, although smaller trees can occasionally support mats.