Southwest Pest and Disease Flashcards

Verticillium wilt is a common vascular disease in Albuquerque's urban trees. Which tree genus is considered highly resistant and a safe planting choice in infested soils?

Answer: Gleditsia (honeylocust)

Gleditsia triacanthos (honeylocust) is among the trees considered highly resistant to Verticillium dahliae and is a suitable choice for infested sites.

A southwestern arborist finds sooty mold coating the leaves and branches of a Chinese elm. The primary cause of sooty mold in this scenario is:

Answer: Honeydew excreted by sap-sucking insects such as aphids or scales

Sooty mold grows on honeydew — the sugary waste excreted by phloem-feeding insects like aphids, scales, and whiteflies — not on the plant tissue itself.

The presence of J-shaped galleries under the bark of a dying ponderosa pine, with frass packed in the gallery, is diagnostic of:

Answer: Mountain pine beetle (Dendroctonus ponderosae)

Mountain pine beetle produces a characteristic J- or S-shaped egg gallery under the bark that is packed tightly with boring dust (frass).

Which disease causes a white, thread-like mycelial fan between the bark and wood at the root collar of oaks and other trees in the Southwest?

Answer: Armillaria root disease (oak root fungus)

Armillaria mellea produces distinctive white mycelial fans (plaques) between bark and sapwood at the root collar, along with black rhizomorphs in soil.

An arborist in the Albuquerque bosque suspects bronze birch borer activity in a river birch. The most diagnostic sign would be:

Answer: Serpentine galleries under bark and D-shaped exit holes in the bark

Bronze birch borer (Agrilus anxius) creates winding serpentine galleries under bark and leaves characteristic D-shaped adult emergence holes.

Mistletoe (Phoradendron sp.) infestations on juniper and other Southwest trees are most accurately classified as:

Answer: A hemiparasitic flowering plant that photosynthesizes but extracts water and minerals from the host

Dwarf mistletoe and leafy mistletoe are hemiparasites — they contain chlorophyll and photosynthesize but rely on the host for water and mineral nutrients.

When scouting for aphid infestations on landscape trees in the Southwest, which biological indicator often signals a heavy infestation indirectly?

Answer: Large numbers of ants tending colonies on shoots and leaves

Ants 'farm' aphids for honeydew and actively protect them from predators, so large ant populations on foliage are a reliable early indicator of aphid colonies.