THE SOIL

Nelson Evening Mail, Volume XLVII, Issue XLVII, 6 November 1912, Page 1

THE SOIL

DISEASE OF LEMONS. AN INTERESTING REPORT. Some specimens of diseased lemons, from trees on JMr. A. Wilkinson's property, in Brook-street, were recently forwarded to the New 'South Wales Department of Agriculture. The specijrens were examined by the Bureau of Microbiology and the report of the Director is published for general information. It. is as follows: . .:' ' At least three different fungi are present on the specimens. One is Septoria Depressa, which causes "Brown Blotch" of lemons,, and a second is very probably Colleaotrichum .Gloeospqridides, which, causes the disease usually known" as "Wither Tip" (not the "Wither, Tip" described by Mc Alpine in his "Fungus Diseases of Citrus Trees"-—;wlhich is a *■ Phoma) in U.S.A., West Indies, South An - .erica; etc. The gloeosporium-like spores are numerous, and identical with this fungus,; and t ne large spot ori : the fruit and the "mummied" fruit are typir cal. The leaves also contain the spores. JThte various effects jprbduced. by . this fungus are so numerous, e.g., -wither tip, leaf spot, fruit spot, canker, antihracnose, that it is sometimes a difficult ircatter to determine with certainly, unless the specimens are very complete. ; There appears to be .much fungus present after two sprajjings of Bordeaux, and the yellowing and falling off of the leaves also suggest some physiological trouble deerahding attention to drainage and (manuring. ■'.'■'•• ~..,. In, the case of lemons i't is found bet-'.' ter to spray with ammoniacal splution.;of copper carlbbnate, as Bordeaux- adheres ' too tenaciously to'the fruit. Bordeaux '■■', can be used in the earlier stages. . To assist in the of "Wither Tip" in the orchard,': and-, to check'its action, the; following facts may W of assistance to you :' '. •'■; The initial-attack is* usually at the '' tip or oh the edge of a leaf. More rarely is a leaf attached at the mid-rib . or some i nterior portion. ''■ ■ All sizes pt trees frocr. seedlings to'the oldest in a grove, are subject to. attack. Budded trees less than a year old are rarely attacked, except in the leaves. Where sucih infections are allowed to remain" on the trees the diseased area extends into the growing twigs and causes the typical wither tip. In such cases the tip dies back for a distance, or the disease may ; go as> far. as the trunk and then stop. .■: A bud below the diseased area then pushes forward, but unless preventive measures are. used, the/, second ■ sprout withers/back like the first. In this\way the disease may prevent the tree from making any growth, and even kill :'t in four or five years. • The "initial attack in older trees is the same as in trees in the nursery row. The fungus grows down' irfto the fruiting twigs. This cuts off ;Vuch of the younger. growth in severe cases, and thus prevents blooming to a large extent. Any agency that lowers .the vitality of the tree, whether fertiliser, nveather, or condition of soil predisposes it to an attack of wither tip; but trees that'are in the most healthy condition possible are also attacked when exposed £o infection. The damage.caused by this disease is. very largely overlooked, from the fact that it occurs upon the smaller twigs and is often attributed to other diseases. PREVENTIVE MEASURES. - ■Much good can .be done (by thorough pruning, especially at frequent intervals: All spurs that have dropped leaves are cut out, and all wood that;has withered. Burn all such material; Spray with Bordeaux, and when the lemon fruit: is well fonrred, use ammonia copper carbonate. Thorough cultivation and fertilisation are very beneficial. Good drainage and- a free circulation of air through the soil , round the roots are essential. A properly cultivated and! well-fertilised tree will "" produce new growth so rapidly and in such quantity, that the amount of wood killed by the fungus as above checked, will be small. ' In choosing fertilisers to aid in warding off these diseases, a large percentage of potash should be used—sulphate of potash has proved very useful with citrus fruits. Sulphate of ammonia is somewhat slower in acting than nitrate of scda, but gives a firmer leaf. Nitrate of soda and nitrogen in organic manures are to.be avoided. ' Acrmonia Copper ,Carbonate is made as follows : Conper carbonate, 6oz; ammonia, about 3pints; water, 50 gallons. , Mix the Copper •Carbonate in a wooden pail with sufficient water to make a thick paste, next add sufficient ammonia to dissolve-the paste, and when all is dissolved, add water to make up to 50 gallons. If Copper Carbonate' cannot be readily obtained, it may be easily <rrade by mixing copper sulphate (bluestone) and" washing soda solutions. >,. Dissolve 51bs of bluestone in water, say two or three gallons, and 61bs washing soda in a separate similar quantity of water. - Pour .the,soda solution into the other and stir. Allow the'sediment formed to settle, and pour off the overlying liquid. Add fresh water and stir up the sediment in it, and again allow to settle. Pour off the over-lving liquid. This washes the copper carbonate (sediment) that, has been, formed.' T-he>sedi- > ■■:■ -merit can then be dried and used in making the spray., .