WI Pesticide Applicator Test Questions and Answers verified

Define plant disease and what causes disease. - Plant disease is any harmful change in the physiology and/or structure of a plant caused by the continuous irritation of a primary causal agent (pathogen). List examples of plant pathogens. - 1. Fungi 2. Oomycetes 3. Nematodes 4. Bacteria 5. Viruses 6. Phytoplasmas 7. Viroids How is fungi spread? - Wind, rain splash, or insect vectors How is Oomycetes spread? - Wind, rain splash, Transfer of infested soil (for example on equipment tires) How is Bacteria spread? - Rain splash, insect vectors, and on tools How is Phytoplasmas spread? - Only by insect vectors (principally leafhoppers) How are Viruses spread? - Insect vectors, mechanical transmission (rubbing of infected leaf onto another leaf by equipment), some are seed borne, vegetative propagation. How are Viroids spread? - mechanical transmission, vegetative propagation How are Nematodes spread? - Transfer of infested soil (for example on equipment tires), in infested planting stockWhat are four prerequisites for plant disease to occur? - 1. A pathogen population capable of causing the disease. 2. A host that is susceptible to infection by that pathogen population. 3. Environmental conditions that favor disease development. 4. Sufficient time for disease to actually develop. What are clues that help you determine whether a problem is caused by an abiotic agent (non living thing) or a pathogen (living thing)? - Caused by an abiotic agent if... 1. The problem appears suddenly 2. The problem is in a uniform pattern 3. More than one plant species is affected Caused by a pathogen if... 1. The problem starts small and gradually increases in size and severity over a period of several days. 2. Observe a gradual cange from healthy to dead or damaged areas. 3. Randomly distributed in the field. 4. Disease affects only one plant species. List examples of abiotic agents that induce plant injury. - 1. Temperature extremes 2. Soil moisture extremes 3. Reduced oxygen levels 4. Unfavorable light conditions 5. Naturally occurring toxic chemicals 6. Salt 7. Soil compaction 8. Deficiency, excess, or imbalance of soil nutrients 9. Pollutants 10. Frost11. Lightning, hail, and wind 12. Phytotoxic spray mixtures 13. Nitrogen burn 14. Pollutants What factors contribute to the need for chemical control? - 1. Other control practices are unavailable or inadequate. 2. The plant has high aesthetic value or its use allows little tolerance for disease. 3. Quality is reduced by even a low level of disease. 4. A sudden and unexpected disease outbreak occurs.