Southwest Pest and Disease Flashcards

An arborist in Albuquerque is inspecting a group of Piñon pines (Pinus edulis) that are showing signs of stress, including thinning crowns and small, cotton-like masses on the older needles. Some needles appear to have tiny 'chia seeds' attached to them. Which pest is the MOST likely cause of these symptoms?

Answer: Piñon needle scale (Matsucoccus acalyptus)

Piñon needle scale is a common pest of Piñon pines in New Mexico. The females appear as small, black, bean-like sacs ('chia seeds') on the needles, and they produce cottony egg masses. This feeding activity leads to needle drop and thinning crowns, matching the described symptoms perfectly.

A client in the East Mountains is concerned about their Ponderosa and Piñon pines after a prolonged drought. The trees are showing signs of dieback, and small holes are visible on the bark, with fine, sawdust-like frass. What is the most significant threat associated with these symptoms in drought-stressed conifers?

Answer: Bark beetles (Ips spp.)

Drought-stressed conifers are highly susceptible to attack by bark beetles, such as the Ips beetle. These beetles bore into the tree, creating galleries that disrupt the flow of water and nutrients, which is fatal to the tree. They also introduce fungi, like the blue stain fungus, that further harm the tree's vascular system.

Which of the following diseases, caused by the bacterium Erwinia amylovora, primarily affects plants in the Rosaceae family (like apples, pears, and pyracantha) and causes a characteristic 'scorched' appearance on branch tips?

Answer: Fire Blight

Fire Blight is a bacterial disease caused by Erwinia amylovora that affects members of the rose family. It is characterized by the sudden wilting, blackening, and dieback of shoots, making them look as if they have been burned.

When treating a tree for an established infestation of an armored scale insect, such as Piñon needle scale, why is the timing of a contact insecticide application critical for effectiveness?

Answer: Adult armored scales are protected by their waxy covering, but the mobile 'crawler' stage is vulnerable.

Armored scales are protected from contact insecticides by their hard, waxy covering for most of their life cycle. The most vulnerable stage is the newly hatched 'crawler' stage, when the insects are mobile and have not yet formed their protective armor. Targeting this stage is crucial for effective control with contact sprays.

A certified arborist is called to a property in Albuquerque to assess a struggling Honey Locust (Gleditsia triacanthos). The tree shows significant dieback in the upper canopy, D-shaped exit holes on the trunk, and serpentine galleries under the bark. Which pest is the most likely culprit?

Answer: Honeylocust borer (Agrilus difficilis)

The Honeylocust borer is a significant pest of honey locust trees, especially those under stress. The larvae create winding, serpentine galleries under the bark, which girdles branches and leads to canopy dieback. The presence of D-shaped exit holes is a classic sign of an adult flatheaded borer from the genus Agrilus emerging from the tree.

A large, mature cottonwood (Populus deltoides) in an Albuquerque park is oozing a foul-smelling, dark liquid from a crack in the trunk. The area appears water-soaked. This condition, which is common in fast-growing trees and often related to stress, is known as:

Answer: Slime Flux (Bacterial Wetwood)

Slime Flux, also known as Bacterial Wetwood, is a common condition in cottonwoods, elms, and willows. It is caused by bacteria that enter through wounds and ferment the sap, building pressure that forces a dark, foul-smelling liquid out of cracks in the bark.