I always thought that my small citrus trees had a nutrient deficiency because of the yellowish leaves. One has extremely yellow leaves as shown on the picture. Then I thought that some animal has eaten on the bark, but now I believe it is some kind of rot maybe collar rot.
Does it look like collr rot?
What organic remedies are there?
To me it appears to be bacterial or fungal canker on the trees. It definitely does not look like evidence of a critter chewing the bark. The problem with cankers is they may not directly kill a tree, but the open wound in the bark is an invitation to pests like borers to come lay their eggs, then their larvae can really do damage feasting on the healthy tissue under the bark elsewhere on the tree. Neem oil is a good way to deter borers from laying eggs, and the oil can disrupt the lifecycle of the insect if the eggs hatch. Healthy vigorous trees can, with time, heal from canker infections. Those yellow leaves could be the symptom of an iron deficiency or soil pH imbalance resulting in nutrients being less available. My suggestion is a soil analysis from a reputable lab so you have a baseline to start with and know where to go with any pH adjustments or nutrient amendments.
"Study books and observe nature; if they do not agree, throw away the books." ~ William A. Albrecht
Location: cool climate, Blue Mountains, Australia
posted 2 years ago
Thanks! I did not get back very fast. Yes and yes to the soil test. My partner says it's not necessary and we have to build up our soil (fill) so it is patchy. Neem I still have some powder left so I can makie a nice sticky paste and paint it on. Probably I will put some tea tree in too.