Hi Carol,
I have about a dozen aloe vera plants growing in my yard. Over the last two years they have flowered well and been very prolific. About six months ago I started to notice a strange growth in between the old sections and the new/baby off-shoots. It looks like a fungus or a deformation -- quite large, like a small cauliflower. I can't find any information on it. It's growing rapidly and spreading to all of the plants. Any ideas?
Thanks,
Kathleen

Hello Kathleen,
There are many species of Aloe grown in our Florida landscapes. Most of the aloes are easy-to-grow, clump-forming, succulent plants. Many aloes have thick leaves with spiny edges. The leaves usually emerge in a rosette (from the middle) on a very short stem or on a much compressed stem. One of the attractions for growing aloe in the home landscape, besides the well-known medicinal uses, is the fact that aloe is extremely pest resistant when grown in the right place.

Most aloe species prefer a location that is in full sun and has well drained soil, aloe is very drought resistant. However, whether your aloe is in the right place or not, it sounds like you have something else going on. The description you provide is typical of an infestation of Agrobacterium tumefaciens, the bacteria that causes the disease known as Crown Gall.

The University of Arizona describes Crown Gall as such:
"Crown gall is caused by the soil-borne bacterium, Agrobacterium tumefaciens. This disease is one of the most widely studied of all plant diseases. This gall inducing bacterium enters plants through wounds primarily on lower stems and trunks and roots. Cellular growth is stimulated and galls of varying sizes and shapes are produced in infected plant tissue. Agrobacterium tumefaciens has the largest host range of any bacterial plant pathogen. More than 600 plant species in over 90 plant families are susceptible.

Galls form on stems and roots, especially at the root crown, the area where roots and stem come together. Galls enlarge with host plant growth. Gall formation does not occur in dormant plants. The galls range in size from less than 1/2 inch in diameter to over 8 inches in susceptible, older plants. The size of the galls is influenced by plant species and size and growth rate of the infected plant part. Galls on woody plants are spongy and light colored when young but with age become rough, hard and fissured. Old galls are often sloughed off."

Kathleen, if you could send a picture, I could possibly confirm crown gall, though it has been reported on Aloe, it is by no means a common pest. Whatever the cause, more than likely, physical removal is the only control and that is not easy nor is it likely that you can completely eradicate the pathogen. However, try removing any symptoms of galls by pruning out the galls. You must cut into clean tissue on either side of the gall and sterilize your shears between each cut with a bleach solution.

If the aloe continues to produce galls, it may be best to completely remove the planting and use the sun to sterilize the soil in the area. This process is known as solar soil sterilization or soil solarization, check the BLOG listings for instructions on this process. Once the soil is clean, then you can replant with disease-free plants.

Good luck and Happy Gardening,
Carol