OTPS (Alabama)
Disease - Answer -Abnormal function caused by a continuously irritating agent and expressed by
noticeable symptoms
Requirements for disease - Answer -(1) disease agent; (2) susceptible plant; (3) favorite environment
Symptom - Answer -The visible effect produced in or on a plant by the presence of pathogen or disease
agent
Sign - Answer -An indication of a disease from direct visibility of the pathogen
Examples of Disease Symptoms - Answer -Spots, blights, cankers, diebacks, stunting, chlorosis, galls,
root-knot, wilt.
Disease Agents - Answer -(1)Living and (2) Non-living
Living Disease Agent - Answer -: Fungi, Bacteria, Viruses, Viroids, Mycoplasmas, Nematodes, Parasitic
Higher Plants, Protozoa
Non-living Disease Agent - Answer -Environmental factors, Nutrition, Pollution, etc.
, Fungi: small organisms (Kingdom Mycetae) - Answer -8000 species cause plant disease ii. Cause over
80% of plant disease iii. Consist of microscopic filaments called hyphae iv. Reproduce by spores v.
Identified by spores and reproductive structures vi. Survive as parasites and saprophytes vii. Spread by
wind/rain/insects
Bacteria: primitive microscopic organisms (Kingdom - Prokaryotes) - Answer -i. 200 species cause plant
disease ii. Microscopic, one-celled organisms iii. Reproduce by binary fission iv. Survive as parasites/
saprophytes v. Infect plant wounds/ natural openings vi. Spread by wind/ insects
Viruses: submicroscopic structures - Answer -i. 500 + cause plant disease ii. Submicroscopic organisms
iii. Obligate parasites iv. Nucleic acid and protein coat v. Replicate within the host cell vi. Infect plants
through wounds vii. Spread by insect/seed/animals
Nematodes: small round worms (Kingdom - Animal) - Answer -i. Round worms - plant parasites are
microscopic ii. Need live host to survive iii. Use stylet to feed on plant cells iv. Most plant nematodes
feed on roots v. 4 Juvenile stages and adult form and over-winter egg stage vi. Generation time 30 days
(1-5 generations/yr.) vii. Spread by soil transport
Disease Control Principles - Answer -i. Exclusion ii. Eradication iii. Protection iv. Resistance
Disease Control Practices/Methods - Answer -i. Cultural: modifications in planting, soil fertilization,
irrigation, soil preparation, etc. ii. Chemical: most are protective sprays; some chemicals provide
eradication iii. Genetic: plant resistant varieties or cultivars iv. Biological
Field Diagnosis Observe Plants carefully - Answer -1. Check foliage for spots, yellowing, mosaics,
marginal burns, growth abnormalities, insect damage 2. Examine stems and crowns for internal
discoloration, external discoloration, fungal structures, bacterial ooze. 3. Examine roots for
discoloration, swelling, stunting, absence of secondary roots
Field Diagnosis Considerations - Answer -recent weather, chemicals/fertilizers applied, soil conditions,
insect problems, animal damage disease, nematodes, patterns of the damage
Collecting/ Packages Mailing Samples Collecting - Answer -1. If spots, collect affected plant parts 2. If
poor growth, collect whole plants 3. Include development stages of the problem 4. Include damage but