Agave weevils infest agave crops and landscape plants and are a worldwide problem. Here are the symptoms, treatments, and steps you can take to prevent future infestations.
Agaves are iconic desert plants that are prized for their outstanding good looks. They provide architectural interest all year long and require minimal care. They come in a variety of sizes, forms, and leaf colors.
However, there’s a little bug causing big problems for these desirable landscape plants — agave weevil (Scyphophorus acupunctatus).
When I first learned of agave weevil, I assumed it was a local problem, but these insects are wreaking havoc worldwide and can now be found on 5 continents.
Agave weevil is native to Mexico, where it’s decimated agave crops, especially those grown to make tequila. This invasive pest has proceeded to follow host plants, especially sisal, around the world.
Let’s look at the signs of an infestation, what you can do if your plants are infected, and how to prevent future problems.
Signs of Agave Weevils
The first sign an agave is struggling is that it looks droopy, yellow, and the lower leaves look wrinkly, but the top remains upright. These signs can also indicate that your plant needs watering, so that’s the first step you should take. However, if you water your plant and it doesn’t perk up, suspect agave weevil.
Give your plant a gentle rock — if it’s infected, it will easily move and even break off at the base. The core of an infected plant will be a mass of smelly, black mush. And you’ll probably see white grub-like larvae or small black bugs about half an inch long scattering.
How Agave Weevils Cause Damage
An agave weevil has a sharp snout that punctures a plant and transmits bacteria that eat away at the plant’s core. They then lay their eggs, and the larvae feed on the softened core.
How Do They Find Your Plants?
You might be wondering how agave weevils find your plants. They either hitched a ride with a plant when you brought it home, or it came from nearby plants. They don’t fly, but they do crawl, and it’s believed they can travel blocks to find new host plants.
There’s No Cure – Prevention is Key
Controlling agave weevil is described as “difficult.” Unfortunately, once the rot has set in, the roots have detached from the plant, and nothing can save it.
But there are a few actions you should take if any of your plants get infected to prevent its spread.
First, carefully dig up the plant. Put the plant and surrounding soil on a tarp or into a wheelbarrow or other container to keep any weevils from escaping. Wrap all parts of the plant tightly in a plastic bag and dispose of it.
Keep an eye out for insects on the ground. Sift through the nearby soil to pick out grubs and weevils. Kill them so they don’t infect other plants.
Next, you need to decide if you want to take additional steps to prevent their recurrence.
Pros and Cons of Insecticide Use
If you find agave weevils on a plant, you may be on the fence as to what to do next.
The recommended control is Imidacloprid, a systemic insecticide. It’s absorbed by the plant, making it toxic to boring insects. It’s recommended that you apply in the spring when insects are most active.
Here are some reasons that gardeners may or may not want to use an insecticide to kill and prevent these pests.
Reasons to Using Insecticides
Some gardeners have treasured specimens or valuable collections of agaves that they understandably want to protect, and the right insecticides applied properly do a good job of preventing infestations.
They may also feel obliged to prevent the spread to their neighbors’ plants.
Imidacloprid, a neonicotinoid, is harmful to bees.
So if your agave sends up a flower stalk after treatment,
cut it down promptly before it attracts beneficial insects.
Reasons to Let Nature Take Its Course
There are many reasons plants die and most gardeners accept the occasional loss of a plant in their stride. They view the loss of an agave as no different than losing any other plant. They feel that the chance of harming other creatures, especially important pollinators, is not a good tradeoff.
Agave weevils have evolved to coexist with agaves. They are naturally preyed upon by birds, reptiles, and other animals. Insecticides kill beneficial insects and disrupt a garden’s ecosystem.
Agave weevils often take out old or unhealthy plants that are already near the end of their life cycle. You could even argue that they have a useful purpose since they get the old agave out of the way to make room for the new pups to grow. In this way, they are just part of the circle of life.
Natural and DIY Options
Some gardeners try natural or DIY remedies figuring there’s no harm and they might work. Note that they have not been proven and I can’t attest to their effectiveness.
Some gardeners have used insecticidal soap or neem oil to kill larvae and weevils. Others have tried beneficial nematodes to kill larvae.
For prevention, you can put a ring of diatomaceous earth around plants — it’s believed that weevils can’t survive crossing it. Or you can mulch with earthworm castings which reportedly contain chitinase, an enzyme that destroys insect exoskeletons.
Ways to Prevent Future Infestations
If you bring home a new agave, carefully inspect it for any signs of weevils or larvae. Remove all the dirt from the roots and hose them off.
Consider planting agaves in containers — they’re shallow-rooted and make excellent container plants. It’s unlikely that weevils will venture into a pot. You can also add diatomaceous earth, earthworm castings, or a systemic to your container as added insurance.
Keep your existing agaves healthy. Agave weevils are more likely to attack unhealthy, stressed plants that are over- or under-watered or otherwise stressed or damaged.
Avoid planting the most susceptible species — century plant (Agave Americana and its variegated hybrid) and Weber’s agave (Agave weberii). Other agaves prone to weevil damage include:
- A. angustifolia (Caribbean agave)
- A. attenuata (fox tail agave)
- A. lechuguilla (shindiggers)
- A. nickelsiae (king of the agaves)
- A. palmeri (Palmer’s agave)
- A. parryi (Parry’s agave)
- A. salmiana (giant agave)
- A. schottii (Schott’s century plant)
- A. shawii (coastal agave)
- A. sisalana (sisal)
- A. tequilana (blue agave)
You might assume that agave weevils only infect agaves, but unfortunately, they also infect a handful of other desert landscape plants including:
- desert spoon (Dasylirion longissimum)
- hesperaloe (Hesperaloe parviflora)
- Spanish bayonet (Hesperoyucca whipplei)
- Spanish dagger (Yucca aloifolia)
- Mexican fencepost cactus (Lophocereus marginatus)
- tree yucca (Yucca valida)
Pro Tip!
If you remove an infected agave, replace it with an aloe.
Aloes look similar, have similar care requirements, and are not affected.
The Future of Agave Weevil Treatments
Most of the information I found on agave weevils dated back to the early 2000s. So I did some digging, hoping to find some new treatment and prevention ideas. Here’s what I found.
A 2018 study of potential natural treatments discovered that seed powders and extracts of certain plants reduced the number of larvae and adults. The most successful was a seed extract of the tropical fruit cherimoya (Annona cherimola). Other plant extracts that showed potential included — marigold (Tagetes erecta), garlic (Allium sativum), papaya (Carica papaya), Mexican prickly poppy (Argemone Mexicana), and bastard lime (Trichilia havanensis). Hopefully, natural treatments might become available from these one day.
There is another type of organic control currently under development, a pheromone trap designed to attract adult beetles in search of mates.
Agave farmers in Mexico are currently using wasp traps to attract weevils. This lets farmers detect the presence of weevils before they do serious damage to their crops. Farmers fill the bait with rotten agave core (eewww) or pineapple.
Weevil-resistant agave varieties are being bred, but it could be years before they are widely available to the public.
Other Names for Agave Weevils
I’ve been referring to Scyphophorus acupunctatus as agave weevil, but this insect has many other common names. So if you come across information on any of these, they are discussing the same pest:
- agave snout weevil
- agave snout-nosed weevil
- agave snout-nosed beetle
- agave billbug
- black weevil
- sisal borer
- sisal weevil
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Author Bio
Deane Alban is the creator of Southwest Gardener. She is a science writer with a bachelor’s degree in botany from the University of South Florida. Gardening is her lifelong passion. She’s been gardening in Tucson for 15 years.
Photo Credit
Nanosancho, CC BY-SA 3.0, Wikimedia Commons