Certified Arborist Test Tree Diagnosis and Treatment 1

Question 1

Which symptom pattern most reliably distinguishes oak wilt from other causes of rapid crown decline in red oaks?

Accepted Answer

Rapid wilting and bronzing of leaves beginning at the leaf margins and progressing from branch tips toward the trunk, often killing the tree within a single growing season

Answer

Oak wilt (Bretziella fagacearum) in red oaks causes a characteristic symptom called 'flagging' — leaves bronze rapidly from the margins inward and wilt while still attached. The disease moves through root grafts and xylem so quickly that red oaks typically die within weeks to months of symptom onset, a pace that distinguishes it from slower decline causes like compaction or drought.

Question 2

An arborist observes sunken, discolored bark lesions on a stressed honeylocust with an amber, gum-like exudate at the margins. The inner bark beneath the lesion is brown and water-soaked. What is the most likely diagnosis?

Accepted Answer

Cytospora canker, a stress-related fungal canker that invades weakened or wounded tissue

Answer

Cytospora canker is a common stress-related fungal disease in honeylocusts and many other species that enters through wounds or winter injury. The sunken, resin-soaked lesions with water-soaked inner bark are classic. Hypoxylon canker produces a distinctive metallic stromata crust rather than amber exudate, and Armillaria signs appear at the root collar, not mid-trunk.

Question 3

What is the primary mode of transmission for fire blight (Erwinia amylovora) from tree to tree, and which tissue type shows the pathognomonic 'shepherd's crook' symptom?

Accepted Answer

Pollinating insects carry the bacterium to blossoms during wet spring weather; shepherd's crook forms on infected shoot tips

Answer

Fire blight bacteria are spread primarily by bees and other pollinators that visit infected blossoms during warm, wet spring conditions — optimal spread occurs above 65°F with rain or high humidity. The infection moves into young shoot tissue, where the wilting and darkening of the terminal growth produces the characteristic downward curl called a shepherd's crook at the tip of the shoot.

Question 4

A mature sugar maple shows progressive dieback of branches in the upper crown combined with heavy seed production, early fall coloration, and epicormic sprouting along the lower trunk. These signs together are consistent with which condition?

Accepted Answer

Maple decline syndrome, a multi-factorial stress condition often linked to soil compaction, drought, and foliar diseases acting together

Answer

The constellation of symptoms — upper-crown dieback, heavy mast production (a stress response), early senescence, and epicormic sprouting — is the classic presentation of maple decline, a complex disorder driven by cumulative stressors such as soil compaction, road salt, drought, and repeated defoliation by pests or pathogens. No single pathogen produces this exact multi-symptom pattern, which is the key to distinguishing decline from a primary infectious disease.

Question 5

Phytophthora root rot is frequently misdiagnosed as drought stress in landscape trees. Which combination of diagnostic observations most reliably differentiates Phytophthora infection from simple moisture deficit?

Accepted Answer

Wilting that does not recover after irrigation, discolored (reddish-brown) inner bark at the root collar, and decline symptoms that worsen in chronically wet or poorly drained soils

Answer

Phytophthora spp. are water molds that thrive in saturated soils, so symptoms paradoxically worsen in wet conditions rather than improving with irrigation. The tell-tale sign is reddish-brown discoloration of the inner bark just at and below the soil line (the root collar), often with a distinct boundary between healthy and dead tissue. Drought stress typically improves after watering and lacks the root-collar lesion, while white mycelial fans indicate Armillaria, not Phytophthora.

Certified Arborist Test Practice Test

Certified Arborist Test Practice Test

Certified Arborist Test Tree Diagnosis and Treatment 1