Apricot Gummosis

A gooey, clear ooze dripping from your apricot, peach, or nectarine tree may indicate a fungal disease known as gummosis. Or, it might not.

Gummosis on almond tree (jacinta lluch valero) CC BY-SA 2.0

Gumming is a natural protective response used by trees to counteract environmental conditions, such as sunscald, frost damage, improper pruning, planting too deeply, excessive irrigation, and too much fruit production. Mechanical injuries caused by lawnmower collisions, rubbing branches, and outgrown tree supports can also cause gumming, as well as insect infestation by peach tree borers, flathead borers, and other boring insects, and by diseases such as Eutypa dieback, cytospora canker, Fusarium dieback, and bacterial spot.

When mechanical injury or environmental conditions are the cause, it’s usually pretty easy to see. When gumming is caused by insect invasions, you will normally see insects and bits of sawdust caught in the gum. When gumming is in response to disease, you need to read up on the possible diseases to know for sure what your tree has.

Apricot gummosis symptoms

Apricot gummosis starts out looking like blisters on branches and the trunk. As the disease progresses, the tissue around these lesions will begin to die and the tree will produce gum. As fungal spores grow and reproduce, cankers will form.

Apricot gummosis pathogen

Apricot gummosis is caused by Botryosphaeria dothidea fungi. Fungal spores enter through wounds. These fungi are opportunists, causing blueberry stem blight and cankers on a wide variety of plants. Trees suffering from lower limb dieback are commonly infected by this pathogen in their weakened state.

Apricot gummosis prevention and treatment

Apricot gummosis occurs most often in years with a cool, wet spring, followed by high temperatures. There’s nothing you can do about the weather, but there are steps you can take to prevent and treat apricot gummosis.

Since gummosis generally occurs in trees that have been damaged in some way, protecting them from injury in the first place goes a long way toward preventing gummosis. Lawnmowers, weedwackers, careless pruning, borers, limb breakage, and other actions that can poke holes in a tree’s bark should be avoided. Whitewashing trunks and exposed branches can help prevent sunburn damage. Proper feeding and irrigation will keep your trees healthier in general. And always wait until your trees are dry before pruning.

If apricot gummosis is present, all infected wood should be removed, spraying cutting tools with bathroom cleaner between each cut. This helps prevent infecting healthy wood. Cuttings should be removed from the property right away.

Severe infections will require the use of fungicides. Research has shown that fungicides containing benomyl, fenarimol, iprodione, prochloraz, or tebuconazole. According to the study, “The best control was obtained with treatments of prochloraz mc alternated with mancozeb. Applications of bitertanol and fenarimol also significantly reduced the occurrence of cankers.”

As with any time you are using fungicides or other potentially dangerous chemicals, read the label and follow directions exactly.