Not for the faint of heart

My previous post was about one kind of agave-related affliction: edema caused by sudden changes in temperature and/or light level. This post is about another — one that is far more serious because it’s almost always fatal. I’m talking about the dreaded agave snout weevil.

I wrote about it before: in a neighbor’s garden, and in my own. After my last encounter, back in December, I treated the agaves near the infested plant in my garden with imidacloprid, an insecticide that kills on contact and also works systemically. It was effective because I haven’t had any other problems in that bed. However (isn’t there always a however?), I didn’t go far enough. I should have treated all the agaves inside the front yard fence. Then my beloved Agave ‘Sun Glow’ in the bed next to the front door might still be alive.

I noticed a while ago that ‘Sun Glow’ was leaning forward more than before. I have seen ‘Blue Glow’ (the non-variegated parent of ‘Sun Glow’) do that as the rosette gets heavier and gravity does its thing, so I didn’t think too much about it at first.

However, when I looked at earlier photos (like the one below from March), I realized that something nefarious was up.

March 2025

When I wiggled the rosette, it lifted straight up. That’s when I knew what was going on. My suspicion was confirmed as soon as I flipped the rosette over. The bottom was mush. And wriggling around in that mush were — these creatures:

Watch the video below to get the full effect:

These are agave snout weevil larvae. I didn’t see any adults (i.e. beetles), but if I hadn’t discovered this, there would have been more adults soon. I immediately tossed the carcass of my ‘Sun Glow’ in the yard waste and drenched the area with imidacloprid solution. Then I poured imidacloprid around all the other agaves nearby. Fingers crossed this was enough.

Here’s more information about the agave snout weevil and what you can do for treatment and prevention.

WHAT IT IS

The agave snout weevil (Scyphophorus acupunctatus) is a black beetle, about a half-inch long, with a distinctively long, curved snout (proboscis). In the spring or early summer, a female weevil uses her snout to drill a hole into the base of an agave, right near the soil line. She then lays her eggs inside the soft core of the plant. This action also introduces bacteria that cause the core to rot, creating a hospitable environment for the hatching larvae — the fat white grubs you see in the video above. They begin to feed on the decaying tissue, eventually pupating in the soil beneath the plant.

Agave snout weevils on a neighbor’s Agave americana ‘Mediopicta alba’

While all of this is going on, your agave looks perfectly fine from the outside, but the rot is spreading inside. Finally, after 6 to 12 weeks, your beautiful agave suddenly looks sad and wilted. You might be able to wiggle it, or it might just collapse entirely. By the time you see these symptoms, it’s almost always too late. The internal damage is done.

The snout weevil is so destructive because the damage it causes is hidden until the plant is beyond saving (talk about a Trojan horse!). Since the snout weevil completes its life cycle in less than two months under warm conditions, there can potentially be several generations every year.

TREATMENT AND PREVENTION

Typically, there’s no treatment for the afflicted agave. The only thing you can do is remove it and thoroughly drench the soil with an insecticide to kill the adults and the larvae that might still be there. (If you happen to notice the infestation in its early stages, leave the agave in place and pour the insecticide solution on the plant. This just might save it.)

The most effective insecticide is imidacloprid. It acts both as a contact killer for existing weevils and grubs in the soil and as a systemic for healthy plants that kills future weevils as they chew into the core. In many U.S. states, imidacloprid is still widely available. In California, however, it is only available for purchase by licensed pest control professionals (as of January 1, 2025).

According to this article by Debra Lee Baldwin, the most effective alternative to imidacloprid is to apply two products, acephate and bifenthrin, every 60 days per label instructions. Acephate (sold under the brand name Orthene and others) is a systemic insecticide used for prevention. Bifenthrin (sold under the brand name Talak and others) is an insecticide that kills on contact. In combination, these two products largely do what imidacloprid does, except they need to be applied more frequently. To my knowledge no pre-mixed product containing both ingredients is currently available to home gardeners in the U.S.

VULNERABLE AGAVE SPECIES

While every species of agave is a potential target, some seem to attract snout weevils more than others. #1 is Agave americana and all its cultivars. Several other large agave species are also highly vulnerable, including A. franzosinii, A. ovatifolia, and A. weberi. The common thread among these susceptible species is their substantial size and the presence of broad, fleshy leaves.

Apparently the snout weevil is less attracted to smaller agave species and those with certain leaf characteristics. Agaves with tougher, narrower, or more flexible leaves tend to be less prone to attack. Some of the species reported to be more resistant or less frequently targeted include A. attenuata, A. bracteosa, A. victoriae-reginae, A. nickelsiae, and ‘Sharkskin’ (a hybrid between A. nickelsiae and A. asperrima). The physical attributes of these plants may present a greater challenge for the weevil to penetrate and lay its eggs.

WHAT CAN YOU DO?

Be vigilant. Observe your agaves for any changes, like a leaning rosette or shriveled leaves. If you notice anything suspicious, nudge it to see if it’s still firmly rooted. If so, treat with the insecticides mentioned above. If it wiggles, pull it out and look for adults or larvae.

Beyond that, implore Mayahuel, the goddess of agaves, to keep the critters away from your garden.

© Gerhard Bock, 2025. All rights reserved. To receive all new posts by email, please subscribe here.