Illustrated Glossary of Plant Pathology W

Authors: C.J. D'Arcy, D.M. Eastburn, and G. L. Schumann
(with acknowledgement of contributions from M.C. Shurtleff, P.A. Arneson, F.H. Tainter, and T.A. Evans)

D'Arcy, C. J. , D. M. Eastburn, and G. L. Schumann. 2001. Illustrated Glossary of Plant Pathology. The Plant Health Instructor. DOI: 10.1094/PHI-I-2001-0219-01

NOTE: If you have comments on any term, definition, or image or would like another term or image added to this glossary, please contact Anton Baudoin, Editor-in-Chief, at abaudoin@vt.edu. ALSO NOTE: each defined word is bookmarked for specific reference. To find out more about linking to a particular word, click here.

W | X | Y | Z

walling-off
separation of diseased from healthy tissues by barrier tissues produced by a diseased plant

water-soaked
describing disease symptom of plants or lesions that appear wet, dark, and usually sunken and translucent

water sprout
small, rapidly growing shoot or branch on a large stem, developed from adventitious tissues

white rot (of wood)
type of wood decay resulting from enzymatic action of fungi; it degrades all components of wood, including lignin, leaving the wood light-colored and spongy

white rust
common name usually used for diseases caused by oomycetes in the genus Albugo

whorl
circular arrangement of like parts

wild type
the phenotype characteristic of the majority of individuals of a species under natural conditions

wilt
drooping of leaves and stems from lack of water (inadequate water supply or excessive transpiration);
vascular disease that interrupts normal water uptake

wind break
a row or other grouping of trees or shrubs used to provide protection against the effects of high velocity winds

winterburn
foliar necrosis, often marginal, of plants that retain their leaves in winter due to water deficiency because they cannot take up water from frozen soils

witches' broom
disease symptom characterized by an abnormal, massed, brushlike development of many weak shoots arising at or close to the same point

wood
secondary xylem

wound
injuries to plant tissues that often breach barriers (cuticle, bark, cell walls) that might otherwise exclude pathogens; some pathogens (e.g. viruses) can enter plants only through a wound; wounds may occur from natural growth processes, physical and chemical agents, animals (especially insects), and many human agricultural activities, such as pruning

xylem
water and mineral conducting, food-storing, supporting tissue of a plant

XLB (xylem-limited fastidious bacteria)
bacterial pathogens of plants found only in the xylem, causing wilt, scorch, and stunting symptoms; vectored by insects that feed on xylem fluid; not sap transmissible; require complex culture media

xylem-limited fastidious bacteria (XLB)
bacterial pathogens of plants found only in the xylem, causing wilt, scorch, and stunting symptoms; vectored by insects that feed on xylem fluid; not sap transmissible; require complex culture media

yeast
unicellular ascomycetous fungus that reproduces asexually by budding

yellows
disease characterized by chlorosis and stunting of the host plant

yield
an aggregate of the products resulting from growth or cultivation

zonate
targetlike development of tree canker, characterized by successive, perennial rings of callus; any symptom appearing in concentric rings

zoosporangium
sporangium, or spore case, that bears zoospores

zoospore
fungal spore with flagella, capable of locomotion in water

zygomycetes
a fungus group, also called the Zygomycota, characterized by nonseptate hyphae, sexual zygospores, and sporangiospores produced in a sporangium; common post-harvest pathogens

zygospore
sexual resting spore formed from the union of gametangia in the Zygomycetes

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