SPRAYING POTATOES

Otago Witness, Issue 3384, 22 January 1919, Page 12

SPRAYING POTATOES

! An English farmer —Mr J. Morison, Fishall, Tonbridge—writes an interesting letter to The Times on the subject of potato-spraying. "Twenty years of regular practice," he writes, " nave taught ' me how great the value of spraying is j they have also taught mo what great losses almost certainly follow in a wet year when spraying is neglected or if only carelessly done. It has- been proved over and over again at Government stations and by other. reliable authorities that spraying, even in an ordinary season, can increase the average crop by two tons or thereabouts per acre. That surely is a good enough return for an outlay, for two sprayings of 20s to 25s per acre, not to mention the very valuable addition to the ; food supply. i "Of course, spraying must be carefully ; and intelligently done. I know that some large growers have tried it, and have given it up because they found they had as much blight when they sprayed as when they did not, but there must have been a sufficient cause for their failure.. I suggest that, it . was one of the following:—(1) That the crop had already got the blight spores freely growing, but unnoticed, before spraying began. In such a case spraying would not save the crop. (2) That it was a big haulmed crop, and an insufficient quantity of the solution was put on to moisten the foliage thoroughly. (3) That the solution was too weak. I believe in using more copper than is often advised. (4) That rain had come on too soon after spraying before the solution had time to dry well on. (5) j That a careless operator had driven on ; without looking to his nozzles to see if they were being blocked up, so that parts of the crop were left unsprayed, which would quickly become infected areas. Or a combination of two or three of these causes I might result in disappointment. I. have had failures myself, but I have ' been careful to look for the causes, bo that I might avoid them another time. My worst year was in 1913, when there was every prospect of a big crop, which, indeed, I had. The haulm was plentiful, dark and glossy in colour, showing no ! shortage of nitrogen, though such condition | is highly favourable to disease if once : started. However, I was well prepared, 1 and had sprayed twice thoroughly, two sprayings being, as a rule, sumceint. Ine variety happened to be a very late one, which kept green, on account of the sprayino- till the middle of October, increasing in weight all the time._ Because of following crops I was wanting to dig, but the potatoes were too green, and, instead of a hoped-for frost coming to cut them down, the weather became showery, hot, and then dry, and, to my amazement, blight started, and spread rapidly in the tops. _ The crop was dug, showing a few blights, and clamped. Spores, however, had infected most of it, and 70 per cent, went bad in ; clamp, and it cost as much as the rest ; were worth to sort the bad potatoes out. ! I saw too late that if I had sprayed a I third time at the end of September, when ! the weather conditions became unfavourable, I should have saved the crop. Disasters like mine happened that year to potato crops all over the South of England Since then I have favoured varieties which naturally die down by the end of September, such, for instance, as King Edward and Arran Chief. " I should, perhaps, mention that my spraying has always been done with liquid solutions. Dry spraying with powders is practised, I know, by some careful and thoughtful men; but I cannot see that the results are as good as those from wet

spraying. Also, as to proprietary spraying mixtures, which are very much to the fore, I have nothing to say against them except that I would bid people beware of those which do not completely dissolve in cold water. These cause trouble by clogging the machine and giving a very uneven coating to the plant.. As for the" strength of the solution to be applied, the Burgundy mixture recommended by the authorities consists of 141 b of copper and 17ilb of soda, but my experience is that something stronger is needed in a wet season. I find that 17±lb copper and 221 b soda to. 100 gallons can be absolutely relied on if properly applied, and at the right time, to prevent (not cure) the blight."