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.