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MY LIFE WITH PLANTS: Agavaceae Part 2 – the Aggravation

By: Jim Bishop.

This is a continuation of last month’s article “The Adoration”, Part 1 about growing agaves.

Agaves are great garden plants since most are low water, need little maintenance and can add a strong accent to gardens. However, there are also problems.

The obvious problem with growing agaves is that many of them have sharp leaves. Some pup frequently which means continual maintenance to remove the pups…but you do get free plants to share with others. There is also the problem with removing a very large plant from the garden after it blooms. Agaves are monocarpic and die after blooming.

We had a large 4 foot wide Agave americana variegata part way down the hill planted next to the dry creek bed. One day I noticed that area of the garden looked different, and I realized that the agave was gone. A gopher had eaten the roots away and it rolled down the hill about 30 feet. It was so large, that I left it lay there for several months. Eventually I drug it over to an open spot on the hill and dug a slight depression so it wouldn’t roll further down the hill. It took a few years to regrow roots and start putting on much new growth, but it is now bigger than ever. Like most other plants in our garden, all Agaves are planted in a chicken wire cage to deter gophers. Agaves that send out large pups seem to be most favored by gophers. Some of the ones with wiry roots and stiff leaves as well as the soft leaved varieties have not been attacked by gophers.

Agave rolled down the canyon after roots eaten by a gopher

Last summer and again last month, I noticed these unusual looking black beetles on some Fence Post Cacti, Pachycereus marginatus, in the garden and they had done significant damage to the growing tip. I disposed of the bugs, but a couple of days later saw an article on Facebook about agaves in San Diego being attacked by the Snout-nosed weevil. The bugs in my garden looked exactly likely the ones shown online. Could the same beetle also attack cacti? After doing some research, it turns out the weevil will attach several species of columnar cacti. The weevil uses the snout to cut a hole at the base of the plant and lay eggs. The larva also injects the plant with bacteria that dissolves the tissue of the plant turning the core of the plant into mush. Eventually, the center of the plant falls out. I’ve removed the Fence Post Cacti, and unfortunately, also found damage on a Cereus peruvianus "Monstrosus" cactus and removed it too.

Snout-nosed Agave beetle

I’ve checked many agaves in the garden and haven’t found any signs of the weevil. However, that doesn’t mean they aren’t there. As a preventive, I’ll be treating all of the agaves with a liquid systemic pesticide made for trees. I hate to use any pesticides in the garden unless absolutely necessary, but with over 100 agaves, a weevil infestation could kill most of them in a few years. I’ll also treat all the Yuccas, Beschorneria, Furcraea and other members of the Agavoideae family since many of them are also susceptible to the weevil. From checking articles online about the weevil, it turns out many species of agave seem to not be attacked. Fortunately I have many of these already in the garden.

And in case this article scares you from planting agaves, there are a few things you can do to prevent introducing the weevil into your garden. First of all, plant only pups from other agaves that have had all the soil removed and check for weevil scars at the base before planting. Grow agaves in pots and treat with a systemic pesticide. Plant them in the garden after several months or years and treat again when planting. Look for a list of agaves online that are immune from weevil attacks. Ask the nursery where you purchase the plants if they have ever had problems with the agave weevil in their stock plants.

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