The Coconino sun., 1917-02-02
HOW 10 TREAT THE
 NEW POTATO DISEASE

A potato disease appearing on cer- tain soils and apparently associated with the lack of potash in the com mercial fertilizers used was prevalent last summer in various sections of the East. According to specialists of the Bureau of Plant industry, United States department of agriculture, the trouble was largely controlled by the use of stable manure. The disease may be expected to appear again with increased severity during the coming season in many potato-growing sec tions, from Maine to Virginia, and probably also further south. It was first noted in scattered fields in 1915. In 1916 it became serious and general over considerable areas. Last year the disease was first observed late in June in Maryland and Virginia, and during the latter part of July in Maine. The affected plants first de- velop downward rolling of the leaf margins, accompanied by peculiar bronzing of the surface, sometimes mistaken for spray injury. Since it occurs on unsprayed as we'll as on sprayed plants, it can not be due to the corrosive action of sprays. The foliage gradually turns brown-not yellow-and the plants ripen premat- urely. Death of the leaves and sud den collapse of the stems at the ground level follow. The yield, of course, is much reduced.
 The disease is found more common ly on fields of early maturing varieti- es, but is not restricted to them. It also appears first on early planted fields.
 What is more striking is the very apparent association of the trouble with certain soil types, at least in Maine, where this relation, as we'll as other features of the trouble, are be- ing investigated by the department experts in cooperation with the Maine Agricultural Experimental Station.
 Soils which originally supported the growth of soft woods, or mixed growth lands," developed the disease condition in its most severe type, while the hardwood ridges showed it least or not at all. The trouble ap- peared first in the swales or lowlands, where the natural drainage was not so good as on the higher ridge land. When the disease appeared at all on the higher ground, it was of a less severe type.
 Specific fungi are frequently found on the stems of the collapsing plants, and some of these most constantly seen belong to the producing groups. Their relation to the trouble is being investigated, but the present indica- tions suggest that they are not the primary cause but have attacked the plants already seriously weakened by other agencies.
 Fertilizer experiments in progress on affected fields demonstrated that the plots receiving potash showed lit tie or no signs of the trouble, even where the other plots were entirely dead. Stable manure also held the disease in almost complete control.
 Investigations of the trouble by the department are incomplete, but the present indications are that it is due to insufficient potash, or, perhaps, in some soils at least, to an excess of nit rates, in the presence of minimum potash supply. Farmers who are un- able to secure potash fertilizer for their potato fields but who have stable manure may insure their crops against attack by it's use. In sections where certain types of soil have been ob- served to suffer from the disease un- der discussion, and it is advisable to plant potatoes on these types next year, it is strongly recommended that potash fertilizers or stable man. ure be applied if either are obtainable.