Potato Diseases.

Otago Witness, Issue 2667, 26 April 1905, Page 9

Potato Diseases.

■TO THE EDITOR.

Sir, — Dr Griffiths, in his book on " Crops and Diseases and Their Remedies," says that in the leaves of the potato he found lactic acid in small quantities in diseased potato plants. After studying this problem I was in Timaru on March 22, and I consulted Mr Scmmerville, a chemist, as to what effect time would have on the potato disease, tellino him v-hat I had read in Griffith&'s book. He informed mo that either common washing soda, baking soda, or hrae would have the same effect in removing the lactic acid from -the potato, if stored after getting them out of the ground, but he recommended the lime as being the best and the cheapest. He could not give me any idea as to how much I should use, but I brought home a bag of lime to give it a trial. The Journal of the British Board of Agriculture for February in the course of an article on the rotting of potatoes says. — "Heavy losses are often sustained by farmers owing to j>ota,toes rotting when stored through the winter in piles or pits. This roiting is due to the action of the fun^i of the potat disease (Phytophthora infes'tans) and of -winter rot (Nectrea solani). In the ease of the former, spores of the fungus that fall to the ground are washed by rain through the soil, and infect young potatoes, especially those growing near the surface. The mycelium of the fungus also passes down the diseased stems into the young potatoes. If the season is wet and warm, the mycelium present in the potato continues to grow, soon causing brown spots to appear, and ending in the rotting of the tuber. On the other hand, if potatoes that are infected are kept dry, the mycelium in their substance remains stationary until the following spring, when it commences growth and passes along the sprouts, finally appearing in the fruiting condition on the leaves. The fungus of winter rot is undoubtedly very common among potatoes which have rotted in the pits. In the early stages it produces softening and swelling in the tubers, which are later attacked by bacteria, and show wet rot. Experiments, in the prevention of these two diseases were conducted at the Garforth farm belonging to -the Agricultural Department of Leeds University in 1903-4. The effects of dusting with quicklime and slack lime at the rate of 7lb per cwt were tested. One hundredweight and three-quarters of sound potatoes were mixed with 281b of infected potatoes, and then stored in pits for 20 weeks. The experiments showed that in 'piling' either for seed purposes or for consumption in spring, lime may be profitably used to prevent loss. Lime in either of the fornns used,. while it docs not prevent the brown tubers from rotting, yet pi events infection of surrounding tubers and the spread of wefc rot." Of tlie two Inn&s of lima