POTATO DISEASES

Southland Times, Issue 22210, 30 December 1933, Page 11

POTATO DISEASES

SYMPTOMS AND CONTROL. The potato is subject to a large number of diseases. This is no doubt partly due to the method of propagating the crop. The “tuber,” wrongly called the “seed,” is simply part of the underground stem. Its use for propagative purposes gives rise to no new generation of plants, but is in reality a natural adoption by which the parent plant is preserved from season to season. A tuber carries the weaknesses of its type, and in successive crops tends to multiply and intensify the various diseases to which it is prone. Thus the planting of infected seed is often the essential step in promoting diseases whose harmful effects are only evident on other parts of the plant. One of our worst potato diseases is Late Blight caused by the fungus Phytophthora infestans. This disease is carried oyer from one season to the other in infected tubers. The following symptoms are noticed: The first sign of the disease visible to the naked eye is the appearance on the leaves of dark brown, blackish spots, of irregular size and shape, on the under surface of which a delicate white mould may be seen, especially round the edge of the diseased areas. In wet, muggy weather the whitish mould may grow out from the upper as well as the lower surface of the leaves. If weather conditions are suitable for the growth of fungus the dark coloured patches spread rapidly and the whole of the foliage, and some times the stems become blackened. If dry weather intervenes after a bad attack of “blight” the affected leaves shrivel and fall off, leaving the stems bare. If the weather is wet after the stems have been attacked the tubers soon become affected.

The first signs of the disease on the tubers are discoloured rusty patches just seen through the skin, but seen more clearly when the skin has been scraped away. These diseased tubers frequently rot when stored and generally give off a very distinct and disagreeable smell. The fungus really causes a dry rot, but this is frequently obscured by a bacterial wet rot. The life history of the fungus is interesting. The main part of the fungus lives within the tissues of the leaves and gives origin to very many minute threadlike branches which protrude through the breathing pores or stomata of the leaf. These minute threads end i» small pear-shaped bodies which become detached and are carried by the wind on to a neighbouring healthy plant. If there is plenty of moisture _ present these pear-shaped bodies germinate and give rise to 8 to 10 smaller spores. Each of these small spores can swim about in the moisture on the leaf and each is capable of growing a small branch and penetrating into the tissues of the leaf and again setting up the disease. The period from the time of infection to the production of a new crop of spores may be only a few hours or at the most days, hence the rapidity with which the disease may spread.

These spores frequently get washed down into the soil and this is the main source of infection of the tuber. The main difficulty is that slightly infected tubers are often- overlooked. If seed tubers are boxed the diseased ones either sprout prematurely, do not sprout at all or else produce poor, weakly sprouts. Control Measures. Wherever possible use clean seed and clean ground. The necessity for spraying potatoes has been brought prominently before the farmers of New Zealand. Most of them have learnt their lesson at considerable personal cost, and all admit that it is not safe to attempt to grow the crop now without spraying. The use of sprays such as Bordeaux and Burgandy mixtures should, however, be used as preventions rather than cures. By spraying we prevent or delay the outbreak of the disease, we reduce the virulence of the attack, we obtain increased yields and we have a smaller percentage of diseased tubers. Opinions differ as to the relative value of the two sprays but experimental evidence shows they are both equally efficient as fungicides. Considerable care must be taken in making up both of these mixtures otherwise injury to the foliage will result. Tire method of making Burgandy mixture is as follows: —Four pounds of copper sulphate, 51b of washing soda and 40 gallons of water are used. 1. Dissolve the copper sulphate in a wooden vessel in five gallons of water and make up to 35 gallons. 2. Dissolve in another vessel 51b of washing soda in five gallons of water. When the soda is completely dissolved pour (2) into (1). Use this mixture on the same day.

If smaller quantities are required:— (1) Dissolve lib of copper sulphate in 2J gallons of water in a barrel and then make up to 7 J, gallons. (2) Dissolve in another vessel, in 21 gallons of water, I.llb of washing soda. 3. Add (2) to (1) stirring vigorously. In preparing Bordeaux mixture ,31b of copper sulphate, 41b of quicklime and 50 gallons of water are used. The bluestone should be dissolved in 45 gallons of water in a wooden vessel. Slowly slack the lime by adding only the amount of water the lime can absorb. After the lime is thoroughly slaked make up to five gallons, strain and then mix slowly with the bluestone solution. A serious disadvantage with Bordeaux mixture is that it must be used immediately after preparation as the physical properties of the mixture as a spray deteriorate with extreme rapidity. For small areas Burgundy and Bordeaux mixtures are best applied by means of a knapsack machine which must be fitted with a nozzle that throws a fine misty spray. The person spraying should aim at covering the under surface of the leaves as both sides are liable to infection. It is a mistake to apply too much fluid, and on no account should the plants be washed. Time of spraying depends largely on local conditions. The ideal is to apply about a fortnight before the disease usually makes its appearance. The

condition of the haulm must also be considered it being difficult and sometimes impossible to spray effectively when the haulm is far advanced in growth. Spray preferably in the early morning or evening and not when the hot sun is shining. A second application usually about three weeks after the first is advisable. Remember that it is not too late to spray after the disease first makes its appearance.

PIG RAISING INCREASING THE RETURNS. ESSENTIAL The following radio-lecturette was delivered recently by K. W. Corringe, instructor in swine husbandry:— It is my intention in this article to indicate how dairy farmers, and others interested in pig-raising in the Dominion, may considerably add to their income by the better utilization of the food materials at their command by which they can feed their pigs. It would be very acceptable to the dairy farmer if we could guarantee to him 2d a lb. extra for every pound of butterfat he produces from his dairy, by the proper utilization of his pigs. Yet this does not seem altogether out of reason, because from a survey over many farms in the Manawatu and the data obtained from these, it was revealed that whereas some farms showed similar butterfat production over an equal average and number of cows, the result of the pig-raising activities were very wide and showed marked divergence. It was shown that where one farmer just kept pigs to consume the skim-milk or whey, another farmed his pigs in an up-to-date manner; that is to say, he bred his own pigs and looked after them well. He could, however, have done even better had he known the secret of winter feeding and the proper utilization of his dairy products. The results shown when comparing these farms was very marked; the first type of farmer who kept pigs simply to consume what would otherwise have been wasted did not add materially to his returns, whereas the second type added 2d a lb. to his whole butterfat cheque for the season. It is quite possible that he may have still further added to his returns had he been equipped with the necessary up-to-date knowledge in pig management.

What would this mean to the average dairy farmer if he could obtain even 2d a lb. extra to his butterfat cheques through his pigs? It would mean the salvation of the farm in spite of the low prices that may be ruling for dairy produce in future years. It is advisable that certain factors which are essential to profitable pig-raising he now reviewed and explained. Firstly:—The most essential factor in the future pig-raising of this country is good grazing, that is, of grass and clover. Other heavier forage crops, such as lucerne, rape, green oats, barley, and maize, are very good, but these entail extra cost and labour. The most economical is grass, because every farmer already has this, and it is only a question of devoting a certain acreage of this pasture for pig production. Farmers may argue that they have grass for their pigs, but what does the average pig grazing consist of? One or two small paddocks which eventually cut up in wet weather and the grass gradually disappears, while mud and dust remain, and then the feedingvalue of the paddock is nil. To overcome this disadvantage a number of paddocks are required of an equal area, the paddocks should be large enough to accommodate 20 to 25 pigs, say half-acre sections five chains long and one chain wide. Several of these, according to the number of sows bred, will allow for rotational grazing, and will provide continuous young grass for the whole season. Old grass is of no value for pigs; they leave it alone. The principle involved allows for grazing spelling, top-dressing and harrowing in accordance with that of dairy pasture, without interfering with the general working of the piggery. It must be understood that grazing takes first place in pig management; all other foods become supplementary. It is as well to know that the pig is fully equipped as a grazer and can crop closer than most animals. Therefore, if the pigs are grazing all day, it is only natural that they will not be able to consume large quantities of liquid food in the form of skim milk or whey. It depends on the amount of grazing provided as to what quantities of dairy products are fed. Whereas in the past as much skim-milk or whey as the animal could consume was allowed, under the grazing system only half the quantity of skim-milk and one third the supply of whey are needed. This means that without adding one cow to the dairy, the farmers have an opportunity of increasing their pig stocks, to double or even treble above their previous numbers. It depends entirely on the farmer as to how much land he is prepared to devote to the pig section. In Taranaki, recently after a lecture on this subject, prominent farmers commenced reconstructing their piggeries, and are now deviting up to 10 acres of their high class pastures for further pig production. They realize it is their only chance to recover the ground they have lost through low prices in dairy production, and such prices may prevail for some time to come.

We now come to the second important factor in pig-feeding. Having supplied adequate grass, with its supplement milk food cut down to one half oi- third, the remaining foods, namely, meat-meal and grain or grain-meals, must be supplied. These are the only foods that need be purchased. Meatmeal with its high protein is recognized as the most valuable supplement in pig-feeding. Not only has it extreme value when associated with grass and skim-milk or whey—particularly whey, with its low protein content —but during the winter and early spring months when dairy products are scarce and good grass only medium, it is then associated with other forage crops and roots also ensilage and gives excellent results with a high margin of profit in spite of winter conditions. Grain or grain-meals are not fed _ during the whole of the growing period, but towards the latter portion—about one month before killing—in order to provide a good finish and quality to the carcass. Of course, a little extra weight will be obtained at the same time, but the finish and quality factor is more important than the few extra pounds gained. Both meat meals and grain meals should be fed dry in a divided trough. A design of this particular trough can be obtained from the Department of Agriculture by those wishing to adopt it in their piggery. Now, having the four essential good factors, which are grass, milk, meat meal and grain, maximum results cannot be expected unless comfort is provided by good housing. Inadequate housing of pigs has ruined many a good venture in pig-keeping, therefore it is important that this be given careful attention. It is unfortunate that this reconstruction of the piggery should

come at a most inopportune time, a time when fanners were never so short of cash, and for come to attempt to extend their piggery now is out of the question. They simply cannot imagine it. Some will devote the extra land and just manage to fence it, but to build houses seems impossible. The ordinary portable wooden pig house, measuring Bft by 7ft costs £5 to build, and as the farmer would require a number of these, it would soon amount to a high figure and the present time is inopportune. To relieve him of this anziety of cost, I may mention that excellent shelter houses can be built, 9ft by 7ft, of baled straw, wheat or barley, with iron roof. The construction of such a house can be done in this manner: two sides and back, the front is left open, contain nine bales of straw, placed end to end on the ground. Then build up the two or three bales high. Make the roof to cover to the outside of the bales; then place the roof on top and tie down with wire for drainage to the ffiack. Very simple, is it not? Give careful consideration to the possibilities of the straw house in conjunction with your future operations in pig-raising. LINCOLN COLLEGE ADDRESS BY STAFF. This year Farmer’s Day at Lincoln College attracted a large number of farmers. The visitors expressed themselves as well satisfied with the work that was being done. After a general inspection of the farm and buildings, during which members of the staff gave addresses on particular phases of the work, the visitors were free to go to any part of the farm which interested them most, members of the staff being in attendance to answer questions. The visitors were full of appreciation of this innovation, which allowed each individual more time to discuss his own problems with the experts of the college. On their arrival, the visitors were conducted to the field in which the college Shorthorn dairy herd was depastured. The director, Professor R. E. Alexander, in a short address, used the herd as a demonstration of what could be done in the way of building up an efficient herd by close attention to proper breeding and feeding. _ The cows were all in excellent condition, and gave every indication of the efficiency claimed for them. Three or four generations ago the herd was mainly a beef-producing group, but careful breeding and selection, together with a scientifically-propor-tioned diet designed to allow high production, had turned the herd into a most efficient dairy unit. Professor Alexander maintained that by attention to the same details a farmer could produce practically what he wanted not only from cattle, but also from sheep and pigs. Diseases of Stock. Mr A. Leslie the college veterinarian, spoke in a most entertaining manner of the possiblity of avoiding many of the common stock diseases by proper care and feeding. Experiment at the college had shown that mortality in lambs could be practically eliminated if farmers took the trouble to lamb at the right time. As a general rule, farmers were inclined to lamb too early, before the flush of spring feed came away, and as at this time the ewes were at their lowest constitutional ebb, the earlier lambs did not get a proper start. The mortality among the bigger and older lambs in many flocks was due simply to this fact having been neglected.

The experiments of dipping carried out at the college were referred to by Mr Leslie, who said that present indications pointed to the fact that farmers wasted a great deal of money by dipping at the wrong time. Sheep should be dipped when they were well-wool-led, ..when the fleece would retain enough dip to kill the eggs and pupae of ticks. If dipping were carried through properly there would be no need to dip lambs. However, dipping as it was done now was a fashion which the farmers themselves had always followed, and

which their fathers before them had used, and it was difficult to convince them that they were not getting the best use out of their money. Mr A. H. Flay spoke on the necessity for apportioning the mixture of grasses in a permanent pasture to the needs of the farm. With carefully laid out paddocks it was possible to have green feed for most of the year, and enough dry feed to carry stock profitably. He used as a demonstration a permanent pasture of ryegrass, cocksfoot, and white clover. The ryegrass, which had been good earlier in the season, was past its best, but even after the dryspell the cocksfoot and white clover were producing green leafage. A paddock of red clover next occupied the attention of the visitors, and was outstandingly good, having responded immediately to the rain. For some time this paddock has been carrying 10 sheep to the acre, but as yet it shows very few signs of being fed off. Soil Preparation.

Mr H. P. Donald next stressed the importance of careful cultivation if the best crops were to be got from the soil. Preparation of the seed bed to conserve moisture, to control weeds, and to see that the seeds sown were adequately covered, was a most important item in getting a good crop, no matter of what kind.