Exam I Flashcards
What microorganisms can infect via direct penetration?
Fungi
Hydathode
opening at end of leaf
What microorganisms can infect via natural openings?
fungi and bacteria
Koch’s Postulates
- pathogen must be associated with disease
- isolate suspected pathogen in culture & describe characteristics
- pathogen must be inoculated onto healthy plants of same species and produce same disease
- pathogen must be re-isolated from inoculated plants and have characteristics identical to step 2
When did Koch’s postulates come about?
mid-1800’s
Winter Burn
occurs when leaves want to transpire but the roots are still frozen; usually affects conifers; usually affects one side
Frost-Cracks
woody parts expand and crack
Frost band
similar to russetinf
Frost heaving
occurs when repetitive patterns of freezing and thawing cause the clay to expand and sever the vascular system
Blossom end rot
caused by a deficiency in Calcium
Etiolation
caused by a deficiency in light. results in weak, long stems, and smaller, chlorotic leaves.
Iron deficiency
tips of branches and leaves chlorotic and necrotic
Nitrogen deficiency
old growth chlorosis
Phosphorus deficiency
purplish discoloration
Potassium deficiency
pale, necrotic spots around margin
What is an example of a disease complex
crown rot of alfalfa. plant initially has mechanical damage done that allows a secondary pathogen to enter.
Four plant disease control methods
exclusion, eradication, host resistance, direct protection
1912
first quarantine laws introduced in US
1957
Federal Plant Pest Act
Four quarantine categories
- restricted: usually inspect/treat seeds
- post-entry period: can enter after quarantine
- completely prohibited: not allowed
- unrestricted: dead specimens allowed
Evasion
a method used to control plant disease where the plant is grown in particular geographic or regions or at particular times in order to avoid pathogen. (i.e Barley Yellow Dwarf, Black Rot of Cabbage)
disinfectant
used when pathogen is INSIDE seed; bayleton
disinfestation
used when pathogen is OUTSIDE seed; captan, thiram
Protectant
used when pathogen may not be present-preemptive; captan, thorium.
Temp required to kill ALL microorganisms in heat treatment
176 F
Temp required to kill fungi in heat treatment
100-130 F
Temp required to kill bacteria in heat treatment
140-160 F
1885
Millardet discovers first fungicide after spraying grapes w/ Copper sulfate and lime.
Bordeaux mixture
3:1:100 CuSO4:Lime:H20; first fungicide
heterocyclic compounds
interferes w/ proteins; Capatan
Agrobacterium
gram negative, rod shaped with 1-4 flagella; colonies are slimy on carb media, non pigmented and smooth. soil inhabitants
Clavibacter (corynebacterium)
Gram positive, slightly curved rod, generallynon-motile
Erwinia
Gram negative, several flagella; facultative anaerobes: amylovora-no pectic enzymes, necrotic or wilt disease. carotovora-produces pectic enzymes, causes soft rot
Pseudomonas
gram negative, common inhabitants of soil, H2O, marine. Fluorescent-produce yellow/green diffusible fluorescent pigments on low iron media. Nonflourescent- no pigments
Xanthomonas
gram negative straight rods, polar flagellum. colonies usually yellow. all are plant pathogens, usually found only on plant/plant material.
Xyella
Gram negative, straigh rods, no flagella. no pigments, small colonies. habitat is in xylem
Streptomyces
gram positive and filamentous. colonies has smooth surface that may become powdery. variety of pigments, used for abx
Lethal Yellowing of Coconut Palm
CA: Mollicute
S: premature coconut drop, yellowing/death of lower leaves, top of tree falls off
D: plant hopper
C: remove and burn palms, plant resistance, tetracycline
Western X Disease of Cherry
CA: Mollicute
S: enlarged stipules, die back of branches, small, flat, pointed, bitter greenish/white cherries
D: Grafting, leafhoppers
C: plant resistance, remover infected trees, remove chokecherries from around orchards, disease free buds
Bacterial Wilt of Alfalfa
CA: Clavibacter michiganense pv insidiosum
S: stunting, yellowing of leaves, wilting and browning of vascular tissue
Resting Stage: alfalfa seed and live or dead plants
Control: crop rotation, resitance
Black Chaff of Wheat
CA: Xanthomonas campestris pv tranlucens
S: water soaked lesions, become necrotic spots/streaks
Resting Stage: Straw or winter wheat
D: lead contact, sprinkler, wind/rain, seed
C: uninfected seed, reduce irrigation
Bacterial Ring Rot of Potato
CA: Clavibacter michiganense pv sepedonicum
S: late in growing sense, chlorides, upward necrotic leaves, creamy mass of bacterial juice in vascular tissue
R: infected tubers, machinery, sacks
D: Infected seeds, knives
C: certified seeds, disinfect equipment using sodium hypochlorite
