I am not an expert but I have been working with bark beetles in Ponderosa pine in Arizona for a few years. Some of the signs of beetles here are pitch tubes, these are where the beetle bores in to lay its larva. The trees natural defense is to "flush" the beetles out. A sign of active beetles is when the pitch tubes have red saw dust in them. The IPS Beetle attacks the crown of the tree through fresh slash. The beetles are capable of living in a tree up to seven generations. On my computer at work I have some articles from the Arizona State Land forester and others I will see about sending those this week. I ran a fuels crew for a local fire district, in which I have gotten very familiar with this information due to or work with the state forester and a private forester. If you have anyother questions please write.
Good Luck,
Colin Port
Affordable Fellers LLC
affordablefellers@gmail.com cmp2921@yahoo.com