Mayhaws are about as East Texas as I can imagine. It’s a native fruit that produces a wonderful jelly that our friends in the rest of the state just simply do not know about. I’m such a fan of the jelly that I’ve been known to hide the delicious jelly in a back corner of the refrigerator.
The other week, a gentleman that lives off Crippen Road in Huntington was asking what the disease was on his Mayhaws that has left them barren for the past seven years. He too was planning on enjoying the fruit of this tree but they had been afflicted with a disease.
They have a common fungal problem of Mayhaws called “rust”. To be more specific there are two kinds of rust: Quince rust and Cedar Apple rust. Twigs, fruits, leaves and even the thorns of Mayhaws can be infected with this fungal rust. Fungal infection causes the tissue to swell and grow abnormally large.
As the infected site swells the diseased leaves curl and die. Infected fruit appear covered with white, tube-like projections about 2–3 millimeters long. Each white tube splits open lengthwise, revealing orange spores on the fruit surface. Infected tissue typically dies after spore production, resulting in twig dieback.
Rust fungi are fundamentally parasites, and they can only survive on a living plant. The quince rust fungus has a very complicated life cycle and needs to spend part of its life on a juniper or red cedar and part of its life on a plant in the rose family to complete its life cycle.
Some other plants in the rose family (Rosaceae) that are also infected include apples, chokeberry, Mountain ash, Pear, Quince, Serviceberry and, even the landscape favorite, Red Tip Photinia.
During wet or humid weather in midsummer to early fall, spores are released from mayhaws and other susceptible plants in the rose family and are carried by the wind to juniper leaves and green twigs, which may then become infected. In spring of the following year, slightly swollen, spindle-shaped areas called galls form on quince rust-infected juniper twigs and become covered in orange, cushion-like masses of spores.
Galls caused by the cedar apple rust fungus are round with orange spore tendrils poking out of them. Spores produced on the juniper galls are blown to mayhaws and other susceptible hosts in the rose family, where infection may occur during favorable conditions. Galls on junipers are often perennial and produce spores annually for many years, until the branch dies.
Occasionally, the fungus will grow into a year-old branch of mayhaws or rosaceous hosts, and a canker (an area of dead tissue) may form. The fungus can overwinter in cankers and produce spores again the following spring. More typically, the infected tissue on the rosaceous host dies after the first year, resulting in twig dieback.
The potential for rust exists wherever junipers and mayhaws grow near each other. Removing junipers from the area immediately surrounding a mayhaw planting can help reduce disease development. However, the spores of the fungus can travel many miles on air currents, so attempting to remove the juniper host from the environment is not always a reasonable management strategy.
Unfortunately, there are no rust-proof mayhaws. For growers who wish to protect their mayhaw crop, the best fungicides contain the active ingredient myclobutanil.
I’ve known folks to cut down every juniper on their property to reduce the opportunity for the fungus to complete its cycle, but I wonder at the effectiveness as they can be carried on wind for a great distance. A much more judicious approach that would certainly save junipers would be to prune out any infected limbs or to apply the proper fungicides to protect the junipers.
I suppose enough the mayhaw fruit will develop for East Texans to enjoy. But if you are frustrated with poor production, try some the fungicide listed above. And be sure to give me a holler if you ever have more than enough mayhaw jelly.