QuestionI have a very healthy looking 7 foot calamondin orange tree that is about 10 years old. This tree is indoors from Oct. to April every year. It has thick exudate appearing in about 15 small separate spots on the trunk. Is this gummosis? How can I treat it? I don't have leaf drop or any appearance of disease on leaves. This tree has never flowered or fruited but it is a beautiful tree that I don't want to lose. Thank you in advance.
AnswerHi Karen,
Root Rot Gummosis in citrus is usually caused by soil microbes, Phytophthora parasitica or Phytophthora citrophthora, which both cause dark, oil-like appearing exudates from cracks in the trunks of the trees. These are fungus-like pathogens which reside in the soils, and each has particular environments which allows them to cause disease. One of the major factors is too much water, another is high temperatures (over 80 degrees F.) Obviously, the temperature is probably lower than that in your home.
In heavy infestations of these pathogens, the leaves become yellow and eventually fall from the tree. So, if this is gummosis, it is in its earlier stages. There are copper-based fungicides that can help to control the spread of the pathogen.
If it is Root Rot Gummosis which affects the lower trunk and underground roots by cracking and gumming there is treatment available as follows:
1. Remove soil from around the tree exposing the trunk and upper butress roots.
2. Cut away diseased bark until clean, unaffected bark tissue is exposed. Paint the exposed cuts with a paste made from Bordeau powder. (Bordeau mixture is a copper-based fungicide available from your garden center.)
3. Ensure the trunk remains dry by mounding a ring of soil around the
excavated area. Water will fill up to this dyke watering the tree but
keeping the diseased area dry. When the spread of the disease stops, soil can be returned to the exposed trunk and roots. Keep the soil level below the graft union. Maintain a dry environment by keeping the inner dyke for the life of the tree.
