POTATO BLIGHT.

Press, Volume LIV, Issue 16268, 19 July 1918, Page 4

POTATO BLIGHT.

TO THTi EDITOIt OF "THE TRESS "

Sir,—The letter in to-day's issue from Mr Martin, Director of Agricultural -instruction, on potato planum* and potato blight, is interesting, out after all leaves very much information to be' desired. Why will deep plantin" or lieavy moulding up reduce the effects of blight upon the crop? It seems to mo that the only reasonable explanation is that as warmth as weli as moisture is required to develop mo bli -ht, the deeper the potatoes are in the ground the cooler they are. .n my garden this year I noticed that in one plot of potatoes the ends of the rows that were well exposed to the sun were very badly affected, while uhe main part of tho rows that leceived shade from a pear tree and a fence went much less affected. I. notu-c that Mr Martin adopts the theory tlir.t the blight begins at the tops, and goos down to the roots. Mr it. li<. Alexander, Director of Canterbury Agucultural College, informed me some time ago that Irish investigators nau come to the conclusion that_ the bliglit was a climatic disease, and if that ?s so it would naturally attack the tops firot. I am moro inclined to the theory _ that the disease starts the other way aoout; that is, that it develops from the set. Some years ago the Kew Gardens authorities published the results of investigations that had been made ?n re«rard to potato 'blight, and thou* report stated that it was found that the disease developed from the set. lhe organism took two measures to - prolong its life, one by extending down the roots into the new potatoes, and tho other by the mycelium growing ip through the shoots, and if conditions were favourable, throwing off sports when the fungoid organism had reached maturity. It was stated that aie "Towth of the mycelium could be seen microscopically at various stages m the stems. That has always seemed to ma to be a more reasonable theory than the one described by Mr Martin. It goes a good way towards explaining why certain varieties after a time develop blight moro than others, but I admit that it does not explain why the blight should be more or less universal in certain seasons like this year, unless it is that all our potatoesi have the disease in them whether visible i-r n °l have before me a photograph showing the result of an interesting experiment made by a farmer in the Waikato some years ago, when the potato blight fir3t manifested itself in an aggravated form in New Zealand. To my mind it strongly bears out the Kew Gardens theory. The farmer's crop was badly blighted, and he therefore had no olean seed for the next year. Part of his ground he planted with diseased seed, and part he planted with sprouts cut from diseased tubers. The result of the next season's crop was that the diseased sets badlydiseased potatoes, while from the sprouts the potatoes grown were apparently quite healthy. What evidently happened was that the sprouts wejra. taken from the sets before the disease had begun to develop, and the result was a, heal thy plant. The two lots of potatoes,.it may be mentioned, were planted side by 6ide. It has often occurred to me, and I have mentioned it a number of times to potatogrowers, that here is an interesting field for experiment. It might bo possible by planting the sprouts only to produce much more reliable seed, than

we have at present, and perhaps revive somo of the favourite varieties that are now so subject to disease that no one cares to plant them. This is a une that Mr Martin migKt .find it worth while to follow up. and if successful it will be of incalculable benefit to potatogrowers as well as to consumers. — Yours, etc., E HABDCASTLE . July 18th.