Citrus foot rot and gummosis

What you see

Amber gum bleeding from cracks in the bark at the base of the trunk, near or just above the graft union. The bark darkens and dies in a vertical patch. The canopy above thins, yellows along the veins and drops fruit.

Conditions

Wet, poorly drained soil against the trunk. Deep planting, soil or mulch piled over the graft union, or a sprinkler that wets the trunk are the standard causes.

Treatment

Pull soil and mulch away from the trunk to expose the crown and let it dry. Cut away dead bark back to clean green tissue and let the wound air-dry. Copper paint on the exposed area. Fix the drainage.

Prevention

Plant high, with the graft union at least 15-20 cm clear of soil. Keep mulch in a ring away from the trunk. Water at the drip line, never at the trunk.

Months: October, November, December, January, February, March

Plants

Orange, Lemon, Tangerine, Lime, Grapefruit

Remedies

Bordeaux mixture (copper)

The thing people get wrong

Nearly every case of citrus foot rot is created at planting, by burying the graft union. Citrus rootstocks are chosen for Phytophthora resistance and the scion above the graft has none - so the moment soil covers that union, you have planted a susceptible stem in wet ground. Look at the base of any struggling citrus: if you cannot see the graft, that is the problem.