The California fivespined ips (Ips paraconfusus) is recognized as a significant pest of managed ponderosa pine stands in California. This bark beetle can rapidly increase its populations to outbreak levels since it has two or more generations a year.
Last summer a ponderosa pine plantation in Lane Co. was attacked by the bark beetle. More than 20 young trees (3" DBH) were killed. It appears the Ips population developed in pine slash created by a crew working in a power line right-of-way. The second generation of Ips emerged from the slash and attacked the nearby pines. This is the first known incidence of Ips populations developing in pine slash and attacking young trees in the Willamette Valley.
The scenario of Ips populations developing in thinning slash and then attacking the remaining crop trees could be devastating to Valley pine stands. The recommended timing of slash creation to avoid Ips damage is during the period August - December. Pines dropped during these months will not provide suitable breeding material for the California fivespined ips. Do not create thinning slash during the period January - July since trees cut during these months can produce a dramatic build up of Ips populations.