What Are Agave Snout Weevils?
Agave Snout Weevils are inch-long, dusty black, wingless insects and — as their name suggests — are particularly fond of Agave. Adults are known to lay their eggs between the leaves of Agaves, and the hatching larvae burrow into the plant. Infestation causes Agaves to collapse into a rotting mess during late summer and early fall.
How Do I Know If My Agave Is Infested?
Typically, an Agave Snout Weevil infestation is not discovered until the damage is too severe to save the plant. As the insects feed on the plant, they inject a bacterial infection, causing the leaves begin to wrinkle. The leaves will continue to shrivel over time as the infection moves through the heart of the plant. You might also notice a foul odor as the plant rots. The Agave will eventually collapse, leaving only the central spikes of the plant still standing. By this point, rehabilitating the plant is unlikely.
How Do I Eradicate Them?
Once you’ve recognized that you have an Agave Snout Weevil problem, it’s important that you remove all dead and infected plant parts from your garden. DLC’s Experts recommend inspecting the surrounding soil for adult weevils or larvae. Any remaining adults or larvae must be removed to avoid the infestation of other plants.
The key to eradicating Agave Snout Weevils is proactive prevention. Once the pests have infected your Agave, it’s nearly impossible to reverse the damage. The best thing you can do is prevent future attacks from claiming the lives of other plants. DLC’s Experts suggest applying a pesticide with Imidacloprid as the main ingredient around the base of the plant in early April and again in late May. Imidacloprid is a systemic insecticide so it will work its way from the base through the entire plant and keep Agave Snout Weevils from feeding on it. Pesticides containing Imidacloprid can be found at your local home improvement store or nursery. As with any pesticide, follow the instructions on the label for proper use.
A Wood-boring Beetle
The flatheaded borer is a metallic wood-boring beetle that can do major damage to your trees, even killing young trees. The adult borer lays eggs in crevices or injured areas of trees. The larvae that hatch immediately start to bore tunnels in the wood just under the surface of the bark, which is what they feed on. As the larvae grow they continue to tunnel through the tree, digging deeper and deeper to reach fresh moist wood.
Recognizing an Infestation
The borer beetle is identified by its metallic appearance, but their larvae do the most damage. The larvae’s body has a flat enlargement just behind the head, and are light in color. The tunnels made by the flatheaded borer larvae injure the tree and are filled with finely powdered sawdust. Their digging causes sap to flow and the affected area will appear wet. As these wet areas dry they may crack and expose the borers’ tunnels. The tunnels they create are winding and flattened looking with oval shapes at intersections. When the adult beetle emerges from the bark or wood it leaves a characteristic oval shaped hole.Protecting Your Tree Asset
The best way to protect your trees is to prevent an infestation. By creating a healthy growing environment for your trees, you remove the opportunity for the borer to lay eggs. Proper pruning and care are essential to having and keeping strong, sound trees that can fight infestation.
If you do have an infestation, prune away as much of the infected area as possible and spot treat it by applying insecticide to the surrounding area. Insecticide will only kill the larvae if the chemicals can reach them just below the surface, but it will help to prevent any future invasions. Bayer Tree & Shrub Insect Control is an example of an insecticide that can be purchased at Home Depot to treat a borer infestation.
What are Scale Insects?
If you’re noticing small white bumps or film on your cactus, chances are it’s a scale insect. There are roughly 8,000 known species of scale insects. Though scale insects can be found on many species of plants, they are particularly fond of cacti. The most prevalent species of scale insect found in the desert southwest are those in the Diaspididae family, commonly referred to as the “armored scale.” This nickname is derived from the scale-like protective covering the insects hide under. The most common scale insect found in Arizona is the Cochineal Scale.
Scale insects attach themselves to plant tissue and suck the juices from the cactus. Their attachment is surprisingly strong and when they are removed, they typically leave a scar behind. Though a single scale insect will do very little damage to a mature cactus, they multiply rapidly and could potentially cover the surface of an entire cactus in just a few days. It’s easy to recognize the infestation by the frosty, white appearance of your plants.
How to Treat Scale
The first step in treating a scale infestation is to physically remove the scale insects from your cactus. DLC’s experts recommend simply using a hose with a pressured spray nozzle. A high pressure setting can remove the insects with ease. However, you’ll want to be careful to avoid damaging the cactus. When spraying the cactus, be sure to to get down in the cracks and under the spines to ensure all insects are removed. After removing the insects, remain vigilant of any additional signs of scale insects as they sometimes find their way back to your cactus. To prevent repeated infestations, treat your plant with a systemic insecticide. Systemic means the insecticide is absorbed through the plant’s roots, therefore entering the plant tissue and making it poisonous to any scale insect that dare take a bite. For best results, DLC’s experts recommend applying the insecticide once at the beginning of the growing season.
Until the systemic insecticide has taken effect, you’ll want to continue to monitor your cactus and remove any scale insects. Some products we’ve found available at local home improvement stores labeled for scale insect include:
- Bayer Advanced Tree & Shrub Protect & Feed Dual Action Formula
- Bayer Advanced Insect, Disease & Mite Control
As always, DLC recommends that you follow the directions provided on the insecticide label prior to application.
What is Oleander Blight?
Oleanders are evergreen shrubs capable of living in the harsh desert environment. Oleanders are popular due to their ability to produce vibrant, brightly colored flowers in the summer months. However, they can fall victim to bacterial blight (also known as leaf scorch). The disease often presents as black or brown spots on the leaves. The bacteria is most often spread by rain and high moisture environments. Spray treatments are generally uneffective in removing the disease.
Managing the Disease
There is no known cure for Oleander blight. Pruning out the part of the plant showing symptoms may improve the physical appearance of the Oleander tree or shrub but will not save the plant.
The bacterial disease is limited to the xylem and can be spread from plant to plant by xylem-feeding insects such as the glassy-winged sharpshooter. Because of the year-round abundance of the glassy-winged sharpshooter, insecticides available on
the market are not effective in stopping the spread of the disease. The best management is early removal of plants infected with the Oleander blight bacteria to reduce the chance of it spreading.
Oleander exhibiting signs of leaf scorch
Controlling Oleander Blight
1. Prune branches showing symptoms of Oleander blight with pruning shears. These shears should be cleaned with a diluted bleach solution between cuts to prevent further spread.
2. Water plants directly into the soil beneath the plant. Avoid watering the foliage, as wet leaves and flowers can cause blight to thrive.
3. Fertilize conservatively. Over-fertilizing creates an environment conducive to blight.
4. Remove Oleanders with canker growths on the trunk or that have damage over the majority of the plant. These shrubs are unlikely to recover and could spread the bacteria to other plants.
What Are Skeletonizers?
A Skeletonizer is a caterpillar or moth that devours the upper layer of leaves on various plants. They do not eat the veins, however, leaving just a skeleton of a leaf when they are done feeding.
Where Do They Come From?
The species currently being found across Arizona is an old world Skeletonizer. It’s a new species to our region, and was first discovered in the United States in Southern California just a year ago. This species has now spread throughout Central and Southern Arizona. DLC’s observation is that the Skeletonizers seem to be focused on Tecoma Species such as Orange Jubilee bushes.
How Do I Eradicate Them?
DLC’s experts have been keeping an eye out and it appears the caterpillars have done their damage and are gone for the fall season. We are already seeing signs of promising new growth on affected plants. The Arizona Cooperative Extension recommends not treating the affected plant material and letting the frost kill off the remaining pests.
For incidental treatment, DLC recommends the use of Bacillus Thuringiensis (BT). BT concentrate can be found at your local home improvement store. Check the product’s label for application instructions. You can also follow the Extension’s advice and wait for the frost to help you out.
What Are Whiteflies?
Whiteflies are small winged insects that look more like moths than flies. They have a powdery wax which both protects them and is key to identification. Whiteflies can be found in all parts of the world and thrive year round in the south but go dormant during the winter in northern states. Whiteflies often seem to appear from nowhere. If you’re working in your garden or with your plants and face a sudden wall of flying white bugs, you’ve got whiteflies! As soon as you know you have them, you’ll want to take action as they multiply quickly.
Can They Cause Harm to My Plants?
Whiteflies can damage your plants. They attack the leaves, buds and stems sucking the juice out of them. Without proper pest control, infested plants might turn yellow, experience stunted growth, and ultimately die. Whiteflies can also produce a honeydew that drips onto the plant. This honeydew encourages the growth of a mold that could infect the plant with a virus leading to the plant’s death.
How Can I Treat Them?
Controlling large whitefly infestations can be a challenge because insecticides have been proven to be mostly ineffective. The best way to prevent problems from developing in your garden is by taking proactive steps to eliminate ideal conditions for whiteflies. For plants most commonly affected by whiteflies such as Lantana, DLC experts recommend pruning all blooms by cutting back the first 6 to 8 inches of the stem, then hosing down the plant with water. This washes off any of the honeydew we previously mentioned and gives the plant a better chance of survival.
Other common forms of treatment are:
• Biological control
For a complete list of whitefly management solutions, please visit The University of
California Statewide Integrated Pest Management Program website at: