CPH Plant Diseases and Pathology

Question 1

Powdery mildew on ornamental plants is caused by which type of organism?

Accepted Answer

Fungus

Answer

Powdery mildew is caused by obligate fungal pathogens in the order Erysiphales, which produce the characteristic white powdery coating on leaf surfaces.

Question 2

Fire blight, which causes a characteristic 'shepherd's crook' wilting of shoot tips on apple and pear trees, is caused by which pathogen?

Accepted Answer

Erwinia amylovora (bacterium)

Answer

Fire blight is caused by the bacterium Erwinia amylovora, which infects flowers and young shoots, causing the distinctive scorched, shepherd's-crook symptom.

Question 3

Dutch elm disease is caused by which type of pathogen, and is primarily spread by which vector?

Accepted Answer

Fungus spread by bark beetles

Answer

Dutch elm disease is caused by the fungus Ophiostoma ulmi (and O. novo-ulmi) and is spread primarily by native and European elm bark beetles.

Question 4

Which of the following best describes a 'biotroph' in plant pathology?

Accepted Answer

A pathogen that requires living host tissue to complete its life cycle

Answer

Biotrophs are pathogens such as powdery mildews and rusts that must obtain nutrients from living host cells and cannot complete their life cycle on dead tissue.

Question 5

Verticillium wilt causes yellowing and wilting of foliage primarily by:

Accepted Answer

Colonizing and blocking the xylem vessels, restricting water flow

Answer

Verticillium dahliae colonizes the xylem vessels of host plants, where the fungal mycelium and produced gels physically block water transport, causing wilting.

CPH - Certified Professional Horticulturist Practice Test

CPH - Certified Professional Horticulturist Practice Test

CPH Plant Diseases and Pathology