ISA Pest and Disease Diagnosis 3

Question 1

What is the characteristic sign of Dutch elm disease in an infected tree?

Accepted Answer

Flagging of branches with brown, wilted leaves that curl inward

Answer

Dutch elm disease, caused by the fungus Ophiostoma, produces characteristic branch flagging where leaves wilt, turn brown, and curl inward. This often appears first in the upper crown.

Question 2

Which insect pest creates D-shaped exit holes in ash trees?

Accepted Answer

Emerald ash borer

Answer

The emerald ash borer (Agrilus planipennis) creates distinctive D-shaped exit holes approximately 3-4mm wide when adults emerge from beneath the bark of ash trees.

Question 3

What diagnostic technique involves removing a section of bark to examine underlying wood for discoloration patterns?

Accepted Answer

Bark tracing

Answer

Bark tracing involves carefully removing bark sections to examine the cambium and sapwood underneath for patterns of discoloration, canker margins, or insect galleries that aid in diagnosis.

Question 4

Which of the following conditions is most commonly misidentified as a disease but is actually caused by environmental stress?

Accepted Answer

Leaf scorch

Answer

Leaf scorch — browning of leaf margins — is frequently caused by environmental stress factors such as drought, salt exposure, or root damage, and is often mistakenly attributed to disease.

Question 5

What is the primary vector for the spread of oak wilt from tree to tree over long distances?

Accepted Answer

Nitidulid (sap) beetles carrying fungal spores

Answer

Nitidulid beetles (sap beetles) are the primary overland vectors of oak wilt. They are attracted to fungal mats produced on killed red oaks and carry spores to fresh wounds on healthy trees.

(ISA) ISA Certified Arborist Practice Test

(ISA) ISA Certified Arborist Practice Test

ISA Pest and Disease Diagnosis 3