Did you know: Pest pressure has been on the rise with the increase in environment related stress. Here is a list of the top 10 pests to keep an eye out for:

The Killers (High Threat Level) 

These pests cause irreversible damage and death, often before you realize the plant is infected. 

1. Agave Snout Weevil (Scyphophorus acupunctatus) 

• Targets: Agaves (especially Agave americana and A. weberi). Yuccas are sometimes affected. 

• Why it’s #1: It is widespread and almost always fatal. The weevil enters the base of the plant to lay eggs. The larvae hatch and eat the heart of the agave from the inside out, introducing a rotting bacteria. 

• Symptoms: The plant looks fine until the lower leaves suddenly wrinkle and droop. The center cone may become loose and can be wiggled or pulled right out. By the time you see this, the plant is dead. 

2. Palo Verde Root Borer (Derobrachus hovorei) 

• Targets: Palo Verde, Mesquite, and other desert trees. 

• The Threat: The adult beetles (large, black, 3-4 inches long) are harmless, but their larvae are giant white grubs (up to 5 inches) that live underground for 3–4 years, aggressively chewing through the tree's root system.

• Symptoms: A mature tree generally looks healthy but starts showing slow dieback of branches (stag-heading). In severe cases, the tree loses its structural stability and can fall over in a monsoon storm because it has no roots left to hold it. 

3. Bark Beetles (Ips spp.) 

• Targets: Pines (Aleppo Pine, Mondell Pine, Eldarica Pine). 

• The Threat: These tiny beetles attack pines that are stressed (usually by heat or lack of water). They bore into the bark and lay eggs; the larvae girdle the tree, cutting off nutrient flow. 

• Symptoms: The tree fades from green to light green to straw-yellow very quickly. You may see "pitch tubes" (globules of sap) on the trunk or reddish dust (frass) in the bark crevices. Once the needles turn brown, the tree is dead. 

The Chronic Stressors (Moderate Threat Level) 

These rarely kill established plants but spread disease and ruin aesthetics. 

4. Whiteflies (Bemisia tabaci) 

• Targets: Lantana, Hibiscus, Citrus, Ficus, and Vegetable Gardens. 

• The Threat: They suck sap and excrete "honeydew," which turns into black sooty mold. More importantly, they act as a vector for viral diseases (like leaf curl) that ruin vegetable crops. 

• Symptoms: If you brush the plant, a cloud of tiny white "ash" flies up. Leaves become sticky and black. 

5. Grapeleaf Skeletonizer (Harrisina brillians) 

• Targets: Grapevines, Virginia Creeper, and Thompson Seedless grapes. 

• The Threat: The larvae (yellow caterpillars with blue/black bands) feed side-by-side in a line. They eat the green tissue of the leaf, leaving only the veins (skeleton). 

• Symptoms: Leaves look like lace or skeletons. They can defoliate a vine in days if not caught, exposing the grapes to sunburn. 

6. Aphids (Various species) 

• Targets: Oleanders (Oleander Aphid), Roses, Citrus, Milkweed. 

• The Threat: They suck plant juices, causing new growth to curl and deform. Like whiteflies, they produce honeydew that leads to sooty mold. 

• Symptoms: Clusters of tiny yellow, green, or black bugs on fresh new growth or flower buds. 

7. Cochineal Scale 

• Targets: Prickly Pear (Opuntia).

• The Threat: While often considered "natural," heavy infestations suck the vigor out of prickly pear pads, causing them to turn yellow and drop. 

• Symptoms: White, cottony tufts on the cactus pads. If you squash the white fluff, it bleeds bright red dye (carmine). 

The "Looming" Threat 

Asian Citrus Psyllid: This pest is present in Arizona and is the carrier of Citrus Greening Disease (HLB). While not yet widespread in all backyards, it is the greatest potential threat to the existence of citrus trees in the valley. If you see a tiny insect feeding on citrus leaves at a 45-degree angle, report it immediately.