Ch. 10 Diagnosis and plant disorders

Question 1

abiotic agents

Answer 1

nonliving causes of plant disorders

Question 2

acute

Answer 2

(1) disorder or disease that occurs suddenly or over a short period of time (2) leaves with straight sides tapering to a pointed apex

Question 3

aerobic

Answer 3

having sufficient oxygen; for example, in soil

Question 4

allelopathy

Answer 4

the influence, usually detrimental, of one plant on another, by the release of chemical substances

Question 5

alternate host

Answer 5

one of a number of separate plants of certain obligate pathogens (e.g., rust fungi) or insects (e.g., adelgids) on which successive life stages develop

Question 6

anaerobic

Answer 6

without – or with a restricted supply of – air. Process that occurs in the absence of oxygen

Question 7

biotic agent

Answer 7

living organism capable of causing disease

Question 8

blight

Answer 8

any disease or disorder, regardless of the causal agent, that rapidly kills flower, leaves, or young stems that are then typically retained (i.e., not shed) by the plant.

Question 9

blotch

Answer 9

irregularly shaped necrotic area on leaf, stem, or fruit

Question 10

canker

Answer 10

discrete, localized, usually necrotic area on stems, roots, and branches. Often sunken and discolored. Most canker diseases require laboratory isolation and microscopic examination to be positively identified.

Question 11

chlorosis

Answer 11

whitish or yellowish leaf discoloration caused by lack of chlorophyll. Often caused by nutrient deficiency

Question 12

chronic

Answer 12

disorder or disease occurring or recurring over a very long period of time, typically multiple growing seasons

Question 13

decay

Answer 13

(1) n. the process of decomposition (2) the process of decomposition by microorganisms

Question 14

defoliation

Answer 14

loss of leaves from a tree or other plant by biological, chemical, or mechanical means (as opposed to natural shedding).

Question 15

dieback

Answer 15

condition in which the branches in a tree die from the tips toward the main stem

Question 16

disorder

Answer 16

abnormal condition that impairs the performance of one or more vital functions. Often associated with noninfectious agents or abiotic factors

Question 17

eriophyid mites

Answer 17

mites in the family Eriophyidae. Typically smaller than other mites, requiring higher magnification to see, and often inducing development of leaf galls

Question 18

frass

Answer 18

fecal material and/or wood dust or shavings produced by insects

Question 19

gall

Answer 19

abnormal plant structure that develops in the cells, tissues, or organs of a plant only when it is colonized by certain parasitic organisms such as bacteria, fungi, nematodes, mites, or insects.

Question 20

gummosis

Answer 20

exudation of sap, gum, or resin often in response to disease or insect damage.

Question 21

honeydew

Answer 21

sugary substance excreted by certain insects, including aphids and some scales, when feeding on plants

Question 22

infectious

Answer 22

capable of being spread from plants to result in infection of other plants or organisms

Question 23

necrosis

Answer 23

localized or general death of cells or parts of a living organism

Question 24

nematode

Answer 24

small, often microscopic , unsegmented roundworm. Many are beneficial organisms, but some feed on plant tissues to cause disease or spread viruses

Question 25

noninfectious

Answer 25

disorders that are not caused by a pathogen and cannot be pasesed from one host to another

Question 26

oozing

Answer 26

seeping or exudation from a tree cavity or other opening

Question 27

opportunistic

Answer 27

pathogens or other pests that do not usually attack or infect healthy plants but tend to attack stressed plants

Question 28

pathogen

Answer 28

causal agent of disease. Usually refers to microorganisms

Question 29

phytotoxic

Answer 29

term to describe a compound that is poisonous to plants

Question 29

pest

Answer 29

organism (including, but not limited to, weeds, insects, bacteria, or fungi) that is damaging, noxious, or a nuisance

Question 30

plant disease triangle

Answer 30

conceptual model showing three factors required for plant disease: a susceptible host, a pathogen or an abiotic agent, and a conducive environment

Question 31

scorch

Answer 31

browning and shriveling of foliage, especially at the leaf margin

Question 32

sign

Answer 32

physical evidence of a causal agent (e.g., insect eggs, borer hole, frass, mycelium, fruiting body)

Question 33

skeletonized

Answer 33

leaf-feeding damage caused by insects (skeletonizers), characterized by the loss of tissue between the leaf veins

Question 34

sooty mold

Answer 34

fungus that apperas as a black coating on the surface of leaves, branches, fruits, and other surfaces (including those of buildings), resulting from deposits of sugary excrement from aphids and scale insects

Question 35

spot

Answer 35

discrete, localized, and usually small necrotic area of a leaf or needle, stem, flower, or fruit

Question 36

stippling

Answer 36

speckled or dotted areas in which chlorophyll is absent on foliage

Question 37

stunting

Answer 37

growth reduction of plants or plant parts

Question 38

symptom

Answer 38

plant reaction to a disease or disorder (e.g., spot, wilt, dieback).

Question 39

systemic

Answer 39

(1) when referring to a substance: moving throughout an organism after absorption (2) when referring to a condition, disease, disorder or pest: affecting the entire organism

Question 40

tree stress

Answer 40

factor that affects the health or condition of a tree

Question 41

trunk flare

Answer 41

transition zone from trunk to roots where the trunk expands into the buttress or structural roots

Question 42

vascular discoloration

Answer 42

darkening of the xylem or phloem of woody plants in response to disease, insect boring, or injury

Question 43

vector

Answer 43

(1) in pathology, biotic or abiotic agent that transmits a pathogen.

Question 44

wilt

Answer 44

(1) n. loss of turgor and subsequent drooping of leaves and young stems; a symptom (2) infectious disease caused by a particular agent on a particular host or range of hosts (3) to lose turgor or to wilt

Question 45

witch's broom

Answer 45

plant disorder characterized by a shortening of the internodes and a proliferation of terminal shoots forming a dense, brushlike mass of twigs