Fusicoccin

Fusicoccin, or constriction canker, is a fungal disease of almonds and peaches.

You may find this word easier to say than to read at first. It is pronounced FUSE-ih-koksin. Once you say it aloud a few times, it gets easier.

Fusicoccin is a disease that forces plants to open their stomas. Stomas are tiny breathing holes found most often on the underside of leaves, but stems and other tissues can also have stomas. Plants use stomas to create bubbles of high humidity which evaporate, pulling moisture up a plant’s vascular system from the ground. It’s pretty amazing when it works the way it should. When stomas stay open, plants start drying out.

Disease progression

Fusicoccum amygdali fungi are responsible for this disease. These fungi produce chemicals that acidify plant cell walls, causing the stoma to open permanently. They enter plants through blossoms, bud scars, fruit scars, leaf scars, and stipules. Any fresh opening is vulnerable.

Fusicoccin symptoms

The first sign of fusicoccin is wilted leaves and shoots, followed by long, brown cankers on infected buds and nodes. These symptoms usually appear in early summer. They become worse as the disease progresses. You may see constricted areas at the base of infected shoots. Gum may be seen oozing from infected areas, but don’t use that as a diagnostic tool since gumming is a frequent response to several diseases and disorders. Fruit on infected stems tends to shrivel up and fall off the tree, further spreading the disease.

Managing fusicoccin

Research has shown that certain fungicides can control this disease. But many of these products can cause birth defects, cancer, and infertility.

Another option is to fight fire with fire. Or, in this case, fight fungi with fungi. Trichoderma harzianum and Trichoderma viride are antagonistic fungi that work as biofungicides, parasitizing fusicoccin pathogens. Of course, they will also damage your homegrown mushrooms. As gardeners, we must choose our battles. You can buy these biofungicides online or from your local garden center.

To prevent fusicoccin, keep trees healthy by applying biofungicides according to package directions and buying resistant varieties whenever possible. If fusicoccin appears on your peach or almond trees, remove infected branches by cutting several inches below the affected area and throwing those twigs in the garbage. Be sure to sanitize the pruners between each cut to prevent infecting healthy tissue.