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

Soils are sandy, dry, and low in organic matter

Answer

Plants are grown in full sun with low humidity

Answer

Soils are slightly acidic with high nitrogen levels

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

Soil drenching with systemic insecticides and deep watering

Answer

Overhead irrigation and foliar fertilization

Answer

Heavy pruning in midsummer and applying copper sulfate in fall

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

Rhizoctonia solani (fungus)

Answer

Tomato ringspot virus

Answer

Pratylenchus penetrans (nematode)

Question 4

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

Accepted Answer

Coelomycetous and hyphomycetous fungi

Answer

Obligate bacterial pathogens

Answer

Phytoplasmas transmitted by leafhoppers

Answer

Cyst nematodes in the root zone

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

A disease confined to a single leaf or stem lesion

Answer

A disease that only affects root tissue below the soil line

Answer

A disease caused by multiple pathogens acting simultaneously

Question 6

The term 'necrosis' in plant pathology refers to:

Accepted Answer

Localized or widespread death of plant tissue

Answer

Abnormal cell enlargement resulting in gall formation

Answer

Yellow discoloration of leaves due to chlorophyll loss

Answer

Distortion of leaves or stems from hormonal imbalance

Question 7

Copper-based fungicides and bactericides are commonly used in horticulture primarily because copper:

Accepted Answer

Is toxic to fungal and bacterial cells while having low mammalian toxicity at label rates

Answer

Stimulates plant immune responses and strengthens cell walls

Answer

Provides foliar micronutrient correction alongside disease control

Answer

Degrades rapidly in soil, leaving no residue on harvested crops