CITRUS COLLAR ROT

New Zealand Herald, Volume LXXII, Issue 22214, 14 September 1935, Page 8 (Supplement)

CITRUS COLLAR ROT

PREVENTIVE TREATMENT Tho recent excessively wet conditions have been responsible for many eases of collar rot among citrus, for while the spores of the disease are nearly always present, continued wet conditions are more favourable to their development than when drier weather is experienced. The principal symptoms of collar rot are an exudation of gum just above the bud union. The area around the gummy portion dies and may become hard and dry without any outer evidence of fungoid growth. In the early stages the tree may be saved, but once the stem becomes girdled the tree is doomed and will usually die suddenly. In addition to wet conditions of the soil, the disease is frequently brought about by the collar being buried too deeply, resulting in lack of air around the trunk. Disease germs may also gain nil entrance through wounds or abrasions caused by implements. The sour orange stock is one of the most resistant to this disease. As prevention is better than cure the trees should be examined occasionally for traces of the disease. Treatment consists of cutting away every particle of diseased bark and then painting tho trunk—especially the wound made ■with a mixture of one pound of bluestone, two pounds of unslaked linno and sufficient water to make a thick cream. This should be applied to healthy trees as well if they are growing in positions where thej' are liable to attacks of collar rot. Another disease somewhat similar in its effects is Botrytis gumming or as it is better known, "bark blotch." The disease is characterised by Ipss gumming than in collar rot, but more general infection. Tho outer bark becomes soft in patches from the oufrside inward, and in moist weather is accompanied by cushions of dark grey bodies scattered over the surface of the dead bark. Tho treatment consists of scraping off the outer dead bark, leaving the inner bark wherever alive, and applying the Bordeaux paste as recommended for collar rot.