Field Guide to Diseases and Insect Pests of Idaho and Montana Forests

Susan K. Hagle – Plant Pathologist,
Scott Tunnock – Entomologist (retired),
Kenneth E. Gibson – Entomologist, and
Carma J. Gilligan – Biological Technician.

U.S. Department of Agriculture, Forest Service, State and Private Forestry, Northern Region, P.O. Box 7669, Missoula, Montana 59807. 1987. Reprint 1990. Publication Number R1-89-54.

Glossary

Abdomen - Body region behind thorax. Usually has 10 segments which bear no legs, but can have appendages at apex.

Bark Beetle - Any beetle which feeds exclusively in the cambial region of stems, or branches, and spends most of its life cycle there.

Blue Stain - Coloration of wood infected by fungi with blue, brown or black hypae; a group of lower fungi (Ascomycetes and Fungi Imperfecti) which cause blue stain.

Brood - All the offspring from eggs laid by one series of parents which mature at about the same time.

Bug - A species in the order Hemiptera-- the "True Bugs".

Callow Adult - Young adult; usually refers to a now adult bark beetle that is light brown and has not emerged from under the bark.

Canker - A definitive lesion on a stem, branch, or root; the cambium of which has been killed.

Chlorotic - Yellow appearance of normally green foliage caused by loss or lack of chlorophyll.

Cocoon - A covering spun or constructed by a larva as a protection to the pupa.

Conk - Fruiting body of a higher fungus (Basidiomycete).

Context - Of a fruiting body; the inner tissues of a fruiting body of a higher fungus (Basidiomycete).

Crawler - The active first instar of a scale insect.

Culture - Process of growing a fungus mycelium, usually on artificial medium.

Decay - Wood decay: process or result of degradation of wood by fungi, bacteria, or yeasts.

Decay Pocket - Pattern of decay characteristic of some fungi in which wood in pocket is more extensively degraded than is the surrounding wood.

Defoliator - An insect which feeds exclusively on foliage.

Egg Niche - Cavities constructed by the female insect into which eggs are deposited.

Elytra - The leathery front wings which serve as coverings to the membranous hind wings. Usually only referred to in the order of beetles.

Flag - Dead shoot or branch on live tree; generally with brown or red needles attached.

Frass - Solid larval excrement.

Fruiting Body - Structure of a fungus which produces spores.

Fungus, plural = Fungi - Group of lower organisms lacking chlorophyll and dependent upon other organisms for source of nutrients.

Gall - Abnormal proliferation of plant tissue stimulated by insect or pathogen attack or abiotic influences.

Gallery - Usually referring to a tunnel or pathway in which an insect lives, feeds, or deposits eggs.

Generation - The development of insects from egg to adult; a brood.

Genus - An assemblage of species agreeing in some character or series of characters.

Gout - An abnormal proliferation of plant tissue.

Gregarious - Living in societies or communities, but not social.

Grub - The larva of a beetle.

Heartrot - Decay restricted to heartwood.

Host - Plant infected or infested by a pathogen or insect.

Hypha - A microscopic filament of fungus cells.

Incipient Decay - Early stages of wood decay.

Infection - The process or result of a pathogen invading host tissue.

Instar - The period or stage between molts during larval development; first instar is the stage between the egg and the first molt.

Laminate Decay - Wood which is decayed more extensively in spring wood than in summer wood and tends to separate into sheets or lamina along annual rings.

Larva, plural Larvae - A young insect in an early stage of development; first instar is the stage between the egg and the first molt.

Lesion - Localized injury caused by a pathogen or insect.

Life Cycle - The time between hatching from the egg and the emergence of the adult from the pupal stage. Most insects have a 1-year life cycle.

Maggot - The larva of a fly.

Metamorphosis - The development of an insect as it goes through different stages from egg to adult. Varies between different groups but is basically of two types; simple and complete. In the simple form (grasshoppers), wings develop externally and there is no pupal stage. In the complete form (beetles) wings develop internally and there is a pupal stage.

Midge - Adults of a group of small 'flies' in the order Diptera.

Molt - The casting of skin between instars.

Mycelium - A mass of fungus hyphae. The vegetative portion of a fungus.

Mycelium Felt - Dense mass of mycelium which takes the form of a thick sheet.

Nuptial Chamber - Usually referring to the chamber beneath the bark of host trees where mating of bark beetles takes place.

Nymph - An immature stage of an insect that does not have a pupal stage.

Overwinter - The act of passing the winter period--usually inactive-- of insect's life cycle.

Oviposition - The act of laying eggs, either singly or in batches.

Pathogen - An organism which causes disease in another organism.

Pheromone - A substance secreted to the outside of an insect's body that serves as a chemical signal between members of the same species. They are usually airborne and act as sex attractants, alarm systems, aggregators, or guides to food.

Phloem - Active, conductive tissue of the inner bark of trees or other woody plants.

Pitch Tube - A mixture of resin, boring dust, and frass on the bark of trees attacked by bark beetles.

Pore - The open end of a tube in which spores of certain higher fungi (Polyporaceac) are produced.

Pore Surface - Surface of a fruiting body of fungi in the family Polyporaccae on which the pores are found.

Progeny - The offspring or brood from eggs laid by an adult.

Proleg - The fleshy unjointed legs of caterpillars and some sawfly larvae; false legs.

Punk Knot - Protruding or unhealed knot of tree with heartrot; knot interior contains a soft decay caused by the heartrot fungus.

Pupa, plural = Pupae - The resting inactive stage between larva and adult.

Puparium - A case formed by the hardening of the next to last larval skin, in which the pupa is formed (flies).

Pustule - Blisters of an infecting fungus which mature into fruiting structures.

Resinosus - Reaction of a tree to invasion by pathogens or insects or abiotic injury which results in flow of resin on outer bark or accumulation of resin within or under bark.

Rhizomorph - Strand of fungus hyphae aggregated together with a protective covering.

Saprot - Decay of sapwood.

Shootborer - Insects which feed and spend the majority of their life cycle within expanding shoots of host plants.

Species, plural = Species - An aggregation of individuals alike in appearance and structure which mate and produce fertile offspring.

Spore - Microscopic reproductive cell or cells. The principal way in which fungi reproduce.

Sporulate - Release spores.

Stage - Any definite period in the development of an insect; egg stage, larval stage, etc.

Sunscald - Cambium damage to thin-barked stem caused by over-exposure to sun.

Symptom - An expression of disease or insect injury as abnormal growth or development of the tree.

Target Canker - A canker in which the pattern of annual growth of the pathogen and callus production by the host results in concentric ridges.

Tendril - Mass of spores in a gelatinous matrix which oozes from a fruiting body in a long curling string.

Thorax - The body region behind the head which bears wings and legs. Divided into three segments: pro-, meso-, and metathorax.

Wingspan - Width of extended wings of those species bearing wings--as opposed to length of wings at rest.

Witches broom - An abnormal proliferation of branches or twigs on a single branch.

Woodborer - Usually referring to beetle species which feed and spend majority of life cycle within the wood of hosts--opposed to those which feed in cambial region or bark.

Zone Line - Thin black or brown line traversing decayed wood; consists of tough fungus tissue which resists invasion by other fungi.

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