bacterium: a microscopic organism, in this case, one which infects insect larvae causing them to become ill and die.
biological control: management of an insect outbreak using insect pathogens or other substances which are natural components of the forest ecosystem.
budmining: early instar larvae enter and consume young buds prior to buds flushing in early spring.
chronic: infestation that is constantly recurring, affecting an area for an extended period of time.
cyclic or cyclical: events which recur in series, that are regularly repeated in the same order.
epicentre: the point from which an infestation begins and radiates. In particular, this term refers to the manner in which Douglas-fir tussock moth infestations are initiated.
frass: solid larval insect excrement.
frequency: the number of repetitions of a periodic process (defoliator outbreak) in a period of time (e.g., in a 25-year period). A high frequency would be an outbreak every decade.
hazard: an estimate of the amount of damage or loss expected should an outbreak of defoliators arise in a stand or area. 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.
incubation period: the time it takes for symptoms of a disease to become apparent in an infected individual.
instar: any post-egg stage initiated or terminated by molting indicating growth stages. Defoliators mentioned in this guidebook normally have six larval instars between egg hatch and pupation.
larva: an individual that emerges from the egg and differs markedly from the adult form. Immature form of an insect that undergoes complete metamorphosis; a caterpillar.
lethal dosage: the amount of ingredient required to cause death of an insect.
mating disruption: the permeation of an area with synthetic pheromone in order to confuse and disorient male moths, thereby reducing their ability to locate and mate with females of the same species.
nucleopolyhedrosis virus (NPV): infectious insect virus, mainly of Lepidoptera and Hymenoptera, characterized by the formation of polyhedra in the nuclui of infected cells; usually fatal.
partial cutting: a silvicultural system in which only selected trees are harvested, and includes seed tree, shelterwood, selection, and clearcutting with reserves.
patch cutting: a silvicultural system that creates an opening less than 1 hectare in size that is designed to manage each opening as a distinct even-aged opening.
peak 4th instar: when the majority of the population sampled are in the 4th instar.
periodicity: the quality of being regularly recurrent (e.g., an outbreak may occur every 8 years).
pheromone: semiochemical released by one individual that modifies the behavior of another individual of the same species.
pupa: the resting, intermediate stage of an insect between the larva and adult.
rasp: to coarsely grind or scrape a surface.
risk: the probability that a tree or stand will be attacked by defoliators. 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.
species specific: pertaining to or limited to one species.
suppression: an aggressive strategy which strives to keep an existing infestation in a stand from spreading. Direct control tactics are used to minimize damage to the affected stand.
tactic: a method or action for accomplishing an end.
tussockosis: respiratory disorder caused by the inhalation of irritating hairs found on the bodies of mature Douglas-fir tussock moth larvae and adults. Some people are incapable of being in the same environment as these insects.
underburn: a light ground fire intended to decrease the density of young Douglas-fir and promote a more diverse species-diverse stand with a higher proportion of seral species, such as ponderosa pine.