In particular, this term refers to the manner in which Douglas-fir tussock moth infestations are initiated. A high frequency would be an outbreak every decade.
Hazard is dependent on stand and site factors that are conducive to successful defoliator buildup.
In general, the higher the hazard, the more damage will occur during an infestation. Hazard is based on stand characteristics and climate. Defoliators mentioned in this guidebook normally have six larval instars between egg hatch and pupation. Risk is dependent on the proximity of a defoliator population to the stand in question. The higher the risk, the more likely a stand will be attacked or infested.