The colonization of Ceratocystis fagacearum fungal mats of different a
ges by Ophiostoma piceae on Quercus spp. was determined in three east-
central Minnesota locations during the spring of 1995. The extent of t
he mat area colonized by O. piceae generally increased with mat age. S
ubsamples per mat yielding the fungus for the three locations averaged
11 to 27% for immature mats, 65 to 72% for mature mats, and 66 to 96%
for aging and declining mats. On a mat-incidence basis, frequencies o
f O. piceae isolation from at least one subsample of an immature mat r
anged from 30 to 53% compared with more than 90% for all other mat age
s in the three locations. The average number of colony-forming units o
f O. piceae per square centimeter ranged from 1 x 10(3) to 1.2 x 10(6)
and increased with mat age. The extent of C. fagacearum recovery from
each mat was lower for aging plus declining mats (P < 0.03) compared
with other ages in two locations. On a mat-incidence basis, frequency
of C. fagacearum recovery from at least one subsample of a mat average
d 99% for all ages of mats in all locations. The interaction between O
. piceae and C. fagacearum on mats, nitidulids, and the oak wound surf
ace is discussed.