BLIGHT IN TURNIPS.

Wairarapa Age, Volume XXIX, Issue 8392, 5 April 1907, Page 6

BLIGHT IN TURNIPS.

AGRICULTURAL DEPARTMENT'S SUGGESTIONS.

With regard to the blight which appears to be prevalent in turnip crops around Masterton, the local Agricultural Office is of opinion that the disease is identical with that which affected Swedes in Portobello (Otago) some time ago. The Agricultural Department issued a bulletin on the disease at that time, and it is thought that what is contained in that report will apply to the present cases in Masterton. Examination of the Swedes at Portobello showed that they had been attacked by one of the species of phoma, P. napo-brassica which was first described by Rostrup in 1893 as destructive to turnip-roots in Denmark. The following general account of a diseased root is taken i from the Agricultural Department's | bulletin:—Below the crown and forming a kind of irregular ring round the upper third of the turnip are numerous more or less circular depressed areas of decaying tissue varying considerably in size. Theyl are light-brown and corky, and are generally surrounded by a well-de-fined purple margin. As the disease advances these patches crack and form deep fissureswhich spread deeply into the interior of the turnip, com- , pletely ruining it. Numerous black clots (pyenidia) now appear on the diseased patches; these dots are coneshaped and contain immense numbers of minute spores, which emerge from the apices of the fructifications in small, globular, rose-coloured masses. The spores then soon separate and are disseminated by various agencies, especially wind. Microscopical examination of the dry decayed tissue shows it to be permeated with the hyphaeof the fungus. This pnoma stage of the disease is most likely only part of the full, life-cycle of some other fungus, but whether this is correct has not yet been definitely ascertained. A closely allied species, Phoma betoe, which is very destructive to mangold crops in various parts of the world, is now considered to be a stage in the lifehistory of a fungus which first appears on the mangold-leaves, and is known as Sphoerella tabifica. The turnip-phoma will most likely be found to be connected with some fungus which attacks the leaves and afterwards spreads to the roots, where it has an excellent chance of tiding over the winter months and \ being ready to infect fresh crops the succeeding year. With regard to methods of prevention, it is only possible to recommend those measures known to be efficacious from the experience derived from-the study of similar diseases. There seems no likelihood of being able to check the spread of this fungus in the bulbs themselves once they have become infected, but much may be done in . preventing the disease from spreading from season to season. Great care should be exercised in examining all roots when they are being harvested to ascertain if any show trace of diseases, and all such should at once be burnt. To leave diseased roots in a field is a sure method of spreading the disease. Acting on the knowledge that other species of the same genus pass a part of their, lives on the leaves of the plant they infect, it follows that spraying with a suitable fungicide, such as Bordeaux mixture, might stop this disease from attacking the roots. Crops in which the presence of this j phoma is suspected should be sprayed twice—once when the plants are a few weeks old, and again when they are nearing maturity. The storage ; of the roots from diseased crops should be carefully attended to. A j thoroughly dry and well-ventilated place must be selected, for it is damp, badly ventilated situations that provide the conditions most conducive for the rapid spread of this fungus.