Integrated pest management of Ips pini (Col., Scolytidae) populations in south-eastern Montana

Second growth ponderosa pine forests of the Northern Cheyenne Reservation of south-eastern Montana sustained a chronic Ips pini outbreak between 1978 and 1994. Studies determined the emergence and seasonal flight patterns of the scolytids with regards to temporal and spatial distribution of host material as well as population changes during the year. These changes related to the dry-down rate of host material (thinning and logging slash) and the availability of slash; an index of population change (IPC) was developed to estimate seasonal changes in the Ips population from spring to autumn. Principal management components of an integrated pest management system included (1) an emphasis on creating thinning and logging slash between August and December, a time that provides quickly degrading host material for the overwintering Ips population while not providing suitable host material for the subsequent spring flight; (2) restrictions on winter logging as slash produced during this period provided suitable hosts for the first spring flights of I. pini; and (3) restrictions on the use of trap logs or pheromones to lower Ips populations as these materials provide kairomones for the predators (Enoclerus lecontei, Enoclerus spegeus and Temnochila chlorodia) that partition their I. pini host across the spring, summer and autumn.