CPH Plant Diseases and Pathology 2

Question 1

Phytophthora root rot is most severe in landscapes when:

Accepted Answer

Soils are poorly drained with prolonged saturation

Answer

Phytophthora species are oomycetes (water molds) that produce motile zoospores requiring free water in saturated or flooded soils to infect plant roots.

Question 2

Black spot (Diplocarpon rosae) on roses is best managed through a combination of which two strategies?

Accepted Answer

Removing infected leaves and applying fungicides preventively

Answer

Black spot is managed by removing and disposing of infected leaves to reduce inoculum and applying protectant or systemic fungicides before infection occurs.

Question 3

Crown gall, which produces tumor-like growths at or near the soil line on woody plants, is caused by:

Accepted Answer

Agrobacterium tumefaciens (bacterium)

Answer

Crown gall is caused by Agrobacterium tumefaciens, a bacterium that transfers a segment of its Ti plasmid DNA into plant cells, triggering uncontrolled cell proliferation.

Question 4

Anthracnose diseases of ornamental trees are primarily caused by which group of pathogens?

Accepted Answer

Coelomycetous and hyphomycetous fungi

Answer

Anthracnose diseases are caused by fungi such as Colletotrichum, Apiognomonia, and Discula species that produce acervuli and infect young leaves and shoots in wet spring weather.

Question 5

Which of the following best describes a 'systemic' plant disease?

Accepted Answer

A disease that spreads throughout the entire plant via vascular tissue

Answer

Systemic diseases spread throughout the plant via xylem or phloem, meaning the pathogen or its products move beyond the initial infection site to affect the whole plant.

CPH - Certified Professional Horticulturist Practice Test

CPH - Certified Professional Horticulturist Practice Test

CPH Plant Diseases and Pathology 2