POTATO DISEASES.

New Zealand Mail, Issue 1206, 12 April 1895, Page 6

POTATO DISEASES.

THE REPORT OF THE GOVERNMENT BIOLOGIST. Mr T. W. Kirk, Government Biologist, recently paid a visit to Woodville and adjoining districts for the purpose of investigating certain diseases which had seriously affected the potato crops in those places. He has just furnished the Department of Agriculture with an interim giving the -results of his enquiries. The report says that the microscope revealed the existence of two distinct diseases. Mr Kirk examined the fields in parts of Wellington, Hawke's Bay and Taranaki, and found that one of the diseases had caused considerable damage to crops. This, the most serious, Macro-

sporium solani, is a fungus which attacks the foliage. It first appears on the older leaves in the form of small brown or greyish brown spots, which gradually spread, the affected parts becoming curled, hard, and brittle, while the remainder frequently assumes a yellowish colour. In less than a month the whole of the leaves die, and eventually the stems perish. The crop in the north has also suffered from the depredations of the potato moth. The remedy for the Macrosporium, or I rather the preventive against it, and indeed |

against most other potato diseases of fungoid origin, adds Mr Kirk, is Bordeaux mixture, to which, where insects also attack the foliage, a little Paris green should be added as follows: Five pounds of sulphate of copper, 41b fresh lime, 45 gallons of water, 4oz Paris green. The addition of a little treacle is desirable. IThe directions are: Dissolve the bluestone in water, 35 gallons, in a wooden vessel, slack the lime carefully in another vessel, add to it the bluestone solution/and

j stir well till thoroughly mixed ; then add ' sufficient water to bring the whole up to 45 gallons. Stir well and strain out any dirt. Mix the Paris green to the consistency of thin paste, then add it to the mixture. Apply with a proper spray pump; first when the potatoes are between six and nine inches high, and twice later at in • tervals of about 10 days. Repeat later if

necessary. * * * * For small plots of a few acres the knapsack sprayer will j be sufficient; for more extended plantations a larger and more powerful machine will be needed in order to cover the ground as cheaply as possible, * * * It has been proved by extensive experiments in both America and Europe that spraying with »Bordeaux mixture will sot only prevent

or keep down fungus diseases, but will so increase the yield as to more than pay the extra expense incurred. Great care, however, must be taken in mixing and applying the fungicides and insecticides. * * * * The other disease> continues the report, is true potato seabi This attacks the tubers onlyj Considerably reducing the yield and rendering unfit for market many Of those which reach full size. . If potato seed even badly affected with scab be treated as foliowsj the resulting Crop Will be smooth and el<*ah sfeihiiedj—Dissolve in a trough or tub 2oz of corrosive sublimate in a little hot water, then pour this into 12 gallons of cold water and mix thoroughly. The potatoes may be placed in an old basket or bag and immersed in the liquid for 1£ hours; then allowed to dry before planting. The preparation is poisonous.

Mr Kirk is now preparing a leaflet dealing with the above two diseases. Experiments will also be made at the experimental grounds, Momohaki, next season.