Term Definition
accuracy The degree of closeness of a measured or calculated quantity to its actual (true) value.
aesthetic injury level An action threshold for treatment based on aesthetic impacts on a plant
aestivate To enter into diapause during a warm or dry season.
apical dominance In plants, the tendency of an apical bud to produce hormones that suppress the growth of the lateral buds below it on a stem.
basal area (BA) The cross-sectional area of a tree at 1.37 m above ground level; usually accumulated on a per acre basis for all trees and used as an indicator of stand density.
BAF Basal area factor; dependent on the sighting angle arbitrarily selected for a prism used in point sampling; e.g., in the eastern United States a sighting angle of 104.18 min or BAF 10 is commonly used. Any tree tallied within the plot represents 10 ft2 of basal area per acre.
beat sheet A hand-held tool constructed of a square piece of light colored fabric and often supported by a cross frame which is used to catch insects when sampling.
beat stick A pole or stick used to tap/disturb plant material and dislodge insects onto a beat sheet.
binomial sampling A sampling method that involves recording only the presence or absence of members of the population being sampled (such as an insect pest) on a sample unit (such as a leaf), rather than counting the numbers of individuals; presence/absence sampling.
chorion The outer shell or covering of an arthropod egg
codominant A tree with crown forming part of the general canopy level; receiving full sunlight from above and little from the sides.
coefficient of variation A statistical measure of the dispersion of data points in a data series around the mean. It represents the ratio of the standard deviation to the mean, and it is a useful statistic for comparing the degree of variation from one data series to another, even if the means are drastically different from each other.
components of variance When factors being tested are random, a type II ANOVA model is used to determine how much of the variance in an experiment is due to true differences in treatment means, and how much is due to random error about these means.
conspecific An organism belonging to the same species of another.
crown Branches, leaves and reproductive structures extending from the trunk or main stems; highest point of tree.
cultivar A cultivated variety or strain of a plant produced by horticultural techniques and not normally found in wild populations.
d.b.h. Diameter at breast height; the diameter of a tree at 1.37 m above ground level on the uphill side.
degree-days A measurement of thermal units required for growth and development of an arthropod, other cold-blooded animals, or plants. Daily Mean temperature - base development temperature provides degree-days for that day. Add degree-days over many days to get to an accumulated amount that can represent a certain stage of growth specific to that organism.
delta trap A triangular shaped trap with a sticky catch surface often used to attract lepidopteran pest species with a pheromone lure.
density-dependent mortality Rate of mortality that is influenced by increasing population density (either positively or negatively). Ex. The greater the population of a host, the higher the % of hosts parasitized by a parasitoid.
density-independent mortality Rate of mortality that is not influenced by its density (either positively or negatively). Ex. Extreme weather factors can kill a percentage of a population regardless of the population size
diapause A period of genetically controlled arrested development and reduced metabolic rate, during which growth, differentiation and metamorphosis cease.
dominant A tree with crown extending above the general canopy level formed by codominants; receiving full sunlight from above and partly from the sides.
eclose For an insect to emerge from the cuticle of the pupa, the cocoon, or puparium; or in hemimetabolous insects, from the cuticle of the last nymphal instar.
economic injury level The lowest population density of a pest that will cause economic damage; amount of pest injury, which will justify the cost of control.
economic threshold The level of pest population or damage level one needs to treat at to prevent the reaching of the economic injury level.
endemic Native or limited to a specific geographical region.
enumerative sampling plan A sampling plan that incorporates continuous values as sampling measures.
frass Solid larval excrement exuded from the anus.
fundatrix (pl., fundatrices) In aphids, the wingless parthenogenic female that emerges in the spring from overwintering eggs.
gall Abnormal growth of plant tissues stimulated by animal or other biotic organism activity on or in the plant tissue.
gallicola (pl., gallicolae) Gall-forming stages (insects).
hyperbolic curve Any of a set of six functions related, for a real or complex variable x, to the hyperbola in a manner analogous to the relationship of the trigonometric functions to a circle.
immunoassay A technique that uses the binding of antibodies to antigens to identify and measure the presence of certain substances.
indicator plants A species whose presence, absence, or relative well-being in a given environment is indicative of the health of its ecosystem as a whole. The phenological state of plant development can be used to time or synchronize with other biotic activities
instar The period or stage between molts during the larval stage; usually numbered to designate the various periods (typically five or six); e.g., the first instar occurs between egg hatch (eclosion) and the first molt.
integrated pest management (IPM) programs The use of multiple techniques that are effective, economically-viable, and ecologically compatible for maintaining populations below a certain threshold.
intermediate A tree with crown extending into the general canopy level; receiving little direct sunlight from above and none from the side.
leaf plastochron index Way of measuring the age of plants and leaves on a morphological, rather than a temporal time scale.
linear regression Models the relationship between two variables by fitting a linear equation to observed data. One variable is considered to be an explanatory variable, and the other is considered to be a dependent variable. The most common method for fitting a regression line is the method of least-squares. This method calculates the best-fitting line for the observed data by minimizing the sum of the squares of the vertical deviations from each data point to the line.
logarithmic regression Regression done on a log scale. Data may be transformed to a log scale when the variance of Y changes with changing values of X.
logistic regression A regression model for binomially distributed response/dependent variables that is useful for modeling the probability of an event occurring as a function of other factors.
operculum A lid or cover.
oviposition The act of laying eggs.
ovisacs An egg-containing capsule.
parthenogenesis An asexual form of reproduction found in females where growth and development of embryos occurs without fertilization by a male.
pheromone trap Any of various containers baited with sexual scent, used to lure and entrap pests or disrupt mating habits.
precision The degree to which further measurements or calculations show the same or similar results.
prism sampling A point sampling method commonly used to inventory trees in which each tree has a given plot size in relation to it's size. It is easily applied with an optical wedge prism and is appropriate for determining basal area and density, as well as for assessing volume and stand structure.
probit A unit of measurement of statistical probability based on deviations from the mean of normal distribution.
progredientes One of two generations of hemlock woolly adelgid found in late spring developing on hemlock trees. Progredientes are comprised of both wingless (parthenogenic) and winged offspring (sexuparae), which develop simultaneously.
radiograph A photographic image produced on a radiosensitive surface by radiation other than visible light.
raster A data structure for maps based on grid cells.
scouting The monitoring of pest populations and crop development to help growers make sound pest management decisions through knowledge of the pest and natural enemy populations. If used carefully, scouting will help prevent crop damage while eliminating unnecessary pest control treatments.
semiochemical Any substance, produced by an organism that provokes a response in individuals of the same or different species.
sequential estimation a method of estimating a parameter by analyzing a sample just large enough to ensure a previously chosen degree of precision. The fundamental technique is to take a sequence of samples, the outcome of each sampling determining the need for another sampling. The procedure is terminated when the desired degree of precision is achieved.
sequential sampling A sampling method in which the number of samples is not fixed in advance
sessile Attached or fastened, incapable of moving from place to place; attached directly without a stem or petiole.
sexuparae A winged portion of the progredientes generation of hemlock woolly adelgid found on hemlock trees in late spring. Sexupara, when fully developed, will leave hemlocks in search of a spruce species on which to ovioposit. No suitable species is present in North America so this portion of the population dies before sexual reproduction occurs.
sistentes One of two generations of hemlock woolly adelgid found in autumn and winter following a summer aestivation. This is a wingless, parthenogenetic generation that gives rise to progredientes.
stand An arbitrarily determined cohort of trees considered as a single management unit.
stratified sampling Grouping members of the population into relatively homogeneous subgroups before sampling.
strip cruising Where the diameters at breast height (dbh) of all trees within a certain distance of a center line are tallied and the volume of wood on the area sampled and then on the total area of the forest stand are then calculated from these diameter measurements.
Taylor's power law An equation used to relate variance to the mean population size: S2 = aµb, where a and b are constants, a is a sampling parameter while b is an index of aggregation characteristic of the species, s2 is the variance, µ is the mean.
terminal leader The primary shoot of a plant.
transect A path along which one records and counts occurrences of the phenomenon of study (e.g. plants noting each instance).
type I error Rejection of the null hypothesis when it is in fact true.
type II error Not rejecting the null hypothesis when it is false.
vector Mathematical: Mapping data, which is stored as points, lines and/or polygons.
whorl An arrangement of three or more leaves, petals or branches radiating from a single node.
wing trap A type of paper/cardboard based pheromone trap used for sampling insect pests