POTATO GROWING.

Dominion, Volume 6, Issue 1733, 25 April 1913, Page 8

POTATO GROWING.

BLIGHTS. AND DISEASES DISCUSSED. Although potato-growing is over as for as Uie [)re^ral -season is concerned some remarks by Mr. 11. 11. M'Gowan. of Willowbridge, on (lie subject of blights and diseases of (lie potato nro of interest. At a recent meeting of South Canterbury growers 3lr. M'Gowau remarked that growers in the Douiininn should all now realise the extent of the damage done to the crops by blights, which J. r > to 20 years ago wero unknown. It was easier then to raise 20 tons to the aero than to raise- 10 to 11! tons now, and various diseases and the decreaso in humus were largely responsible for this. In iho order of their occurrence the principal diseases were:— Early blight or stem and leaf curl (Macrosporium solani)—Soon after tho plants, get above ground signs of curling of the leaf may bo noted hero and there in tho crop. £ater these leaves yellow off, and finally the plants prematurely die. This disease may appear at any time during tho growing season. The ends of tho roots too become brown, then black and finally .rotlon. Even- tho tubers that-remain will bo small, and show the rings of disenso through them. Mr. M'Gowan said .ho had seen a. crop in which 50 per cent of the plants wero affected. The only real preventative" was to destroy all affected tubors. Spraying was of littlo.use, as tho disease is .in tho''.tubers and 'works'-up through tho-. Haulms. Potato, griib—This troublo was unusually prevalent in 1901), especially in soino quarters. -On sandy soils the majority of tubers were fiddled with grubs. Tho best preventative measures wero to. nlant fairly deep.and plant early, mould up well and spray with Bordeaux' Mixture, to which had been added-somo Paris green in the proportion of lU>. to 175 to 200 gallons. This poisoned moths that' preceded tho grubs. ~ Late blight (Phytophthora infestans)— This blight attacks tho plants soon after tho flowers have fallen, and spreads rapidly if the weatlier is damp and warm, making tho patch a brown burnt, looking mass in a few days. The only preventative was constant and careful spraying with the i—.i—-10 Bordeaux Mixture for. tho first two sprayings, and adding Jib. .to lib. each of lirao and bluestono for each subsequent spraying. He advised every potato grower to spray, for if the blight was bacl.it would save the crop by 25 to 30 per-., cent, and add two to five tons to the acre in. the nbsenco of blight, by reason of its action in thickening the leaf and lengthening its life. The leaves make-the starch and every week .at the end of the.season added 50 bushels to this acre. • Spraying also increased tho table value. . • ',