Plant Disease Basics 1 Flashcards
What is Phytopathology?
Phyto=Plant
Pathos= Suffering
Logia= Study
What are the two factors that cause disease?
Biotic factors: Infectious Pathogens.
Abiotic factors: Non-infectious and Non-living. This causes more than 50% of the plant problems.
What are the four ways to distinguish between biotic and abiotic stress?
-Signs and symptoms
-Environment History
-Soil characteristics
-Weather conditions
What is the difference between Signs and Symptoms?
Symptoms are the effects of the disease on the plant and Signs are the evidence of the presence of disease. Signs are only present in biotic factors.
What are the 7 common nutrition deficiencies and How do they affect the plant?
Iron: Intra-veinal chlorosis appears on newer leaves and eventually the leaves yellow and die.
Calcium: Stunted growth of newer leaves
Nitrogen: Light green upper leaves.
Potassium: Yellowing of tips and Edges.
Phosphorus: Dark leaves.
Manganese: Yellow spots and/or elongated holes.
Magnesium: Lower leaves turn yellow from the inside.
What is nutrient toxicity?
Giving your plant excessive amounts of minerals.
How do high salt levels effect plants?
It can cause yellowing
How does extreme weathers effect plants?
Frost- Affects sensitive organs or kills entire plants.
Heat Injury-Symptoms of scorching.
What are three things that need to be present for biotic stresses to occur?
-Pathogen
-Favorable environment
-Susceptible Host
What are the two classifications of fungi?
Parasites and Saprophytes
What are some symptoms of plant disease caused by fungi?
- Leaf spots, Leaf curling
- Galls, wilts
-Canker, Stem and root rots
What are the two symptoms of plant disease caused by bacteria?
-Bacterial blight
-Bacterial spots
What is the difference between saprophytes vs. Parasites
Saprophytes get their nutrients from dead organic matter and Parasites get their nutrients from other organisms.
How many plant pathogenic bacteria are known?
about 1600 but only 100 are known to cause plant disease as most are facultative parasites.
Give examples of plant viruses.
Most mosaics, barley yellow dwarf, and potato leaf roll.
What are viruses?
Viruses are minute effective particles that can multiply and reproduce only in living cells and cause disease
What is phytoplasma?
It is classified as a bacteria but lacks a cell wall. It is an obligate parasite (can only survive within its host).
Where does phytoplasma reside?
It lives in the phloem of the plant. This bacteria is transmitted by phloem feeding insect (leaf hopper).
What makes plants parasitic?
Their inability to produce chlorophyll.
How many plant species are known to be parasitic?
More than 2500.
What are Nematodes?
They are microscopic roundworms that extract the nutrients out of the roots of plants.
What are 4 symptoms of nematodes attacking the plants?
Stunted growth, yellowing, wilting, knot like growth in roots.
What are the four symptoms caused by gram-negative bacteria?
- Spots and Blights
- Rots
- Galls
- Vascular wilts
What is the one symptom of gram-positive bacteria?
Common scab
What are the four host plants for bacterial leaf streaks?
- What
- Barley
- Triticale
- Rye
How much yield can bacterial leaf streak reduce?
40%
What are some signs of BLS?
- Appearance of water-soaked leaves that develop into narcotic legions.
- Bacterial Ooze on leaf surface.
How does BLS spread?
Through rain splashes
Where do the symptoms of BLS show?
On the flag leaves
What is black chaff?
This is when the BLS reaches up the plant on the grain and creates purple to black legions.
What are the 3 favorable crop conditions for BLS?
- Temp. 15-30 C
- High humidity and free moisture.
- Favored by crop injury
When is BLS most noticeable?
At flag leaf stage.
How does the BLS pathogen survive?
- They can survive on weedy grasses.
- Can survive in the seed.
What are some ways of controlling BLS?
- Use of certified seeds.
- Excluding weed hosts and rotating to a non-host.
- Resistant cultivars.
What kind of bacteria causes Goss’s bacterial wilt and leaf blight in Corn?
Gram positive bacterium
Where does Goss’s bacterial wilt and leaf blight overwinter?
It overwinters in corn and several grasses.
