POTATO FLIGHT: LECTURE BY PROFESSOR KIRK.

Otago Witness, Issue 2688, 20 September 1905, Page 21

POTATO FLIGHT: LECTURE BY PROFESSOR KIRK.

(Feilding Star.) Doubtless the heavy rain prevented a large number of farmers from being present at Mr Kirk's interesting and instructive lecture. However, it is gratifying to note that there was a fair attendance, which included representatives from all parts of the surrounding districts. , Mr Kirk began by saying that the muca dreaded potato blight (or Phytophthora mfestans) was a disease which had only made dts apearance in New Zealand of late years, and particularly last season. Taking the 26,331 acres of potatoes grown here last year we find that through the blight ■the yield has been reduced on the 'average about two tone per acre. The loss ±o the colonj last season, taking the price at £14 per ton, was £157,986. The cost of spraying potatoes with the Bordeaux mixture is comparatively small only costing 7s per acre. 'Two. forms o£ blight attacked

the potato crops last year, the one known as the early blight and the other as * Irish i or late blight. The early blight we have had for years, but its effect has not been so severe as the late blight. The first .symptoms of the early blight are small circular spots scattered all over the leaves, while the Irish blight is of a triangular form on the edges of the leaves. .« had been asked on various occasions if there were any new varieties of potatoes that were blight-resisting. The speaker answered "No " There was not a potato in th© world that was blight-resisting. The importation of new varieties might help to reduce the blight owing to the old seed being worked jout and weakened. Ihe fun<*us, which is blown from some neighbouring field, first attacks the leaf, where it commences to germinate in plant-hke form, as shown by examination under a microscope. It principally attacks the' plant under the leaf in a small white patch resembling a white mould. It then extends over the leaf and down the stem into the tubes. The fungus produces small eggshaped spores, and in these are contained the mycelium which is carried by the wind through the crop. The speaker had known a whole crop to be infected in 48 houre. In the Old Country it had been known to go through a crop in 12 hours. The man got up in the morning and found his crop smelling where there was hardly a trace the night before. He advised spraying as the only remedy w.hen the crop was 6in high, and again when in flower. Tho proper formula to. use was the Bordeaux mixture, made as follows : —41b of bluestone, 41b of quicklime- to. 40 .gallons .of water. Dissolve the bluestone and quicklime in water and then mix. Slaked lime was practically no use; it is essential that the lime used should be qtiicklime. -A«.a substitute for lime, - use common 'Washing- soda. In order ft> make the same adhere -to the leaves mix with ordinary agricultural treacle. If rain fell within a few hours of spraying it would be necessary to repeat the operation. The nozzle of the spray pump should, if .possible, be a Bordeaux one — that is, on© which is invented to direct the spray under the leaf. Onions are subject to a form of dieease. but the spraying is identical. The potato blight also attacks tomatoes, and the Bordeaux mixture again applies. If the bluesfcone is inferior 61b should be used. What is termed ""Commercial bluestone" is very little use. The w method of testing bluestone is as follows:— Take a small portion and place it in a glass of water, then add some liquid ammonia. Clear light blue clouds will form if the bluestone is pure, but if impure dark clouds will form with sediment in the bottom. When storing potatoes it will be a great assistance to dip them in the solution, but it is of little uee to treat seed previously to sowing. As yet we have no reports of the blight having attacked the crops in Christclmrch. The blight is not worse here than in the Old Country. Wet climates are favourable to the growth of the fungi. A light- breeze j will carry the smut through oats where it { will not carry it through potato crops. Thie i is accounted for by the ears of corn being !in close proximity to each other. In planti ing, the speaker would give preference to i whole seed of a medium size, and could not I recommend cutting. He had received 1 samples of this season's crop from Auckland, and these were infected with blight. He contended that spraying helped the crops, and made them more productive. An illustration of this was given by quoting various returns. 'The speaker then went on to explain the inoculation of nitrogen ' into the soil by cultures. In former years I it was a custom of fanners when clover ; crops failed to cart a load of soil from a 1 field where a good crop was obtained, and distribute this over the land. He did not know why he did this, but next year he had a fairly good crop. In pea crops, and other ped crops, the nitrogen formed in , nodules at the roots of the plants, and this ! being ploughed in resulted in a good grain crop being obtained next year. Nitrogen was a manure of very high commercial value, but by this means a cheap manufacture was set up by Nature. A number of elides were then shown, showing the potato blight at various stages, ana the nodules formed on the roots of pod plants containing stores of nitrogen. Mr Wheeler proposed a hearty vote of thanks to the lecturer, which was seconded by Mr Standen and carried in the usual manner.