The Nevada County picayune., 1918-08-22
CONTROL SWEET
 POTATO WILT
Wilt May Be Detected First By Slight
 YelIowiru Of Upper Leaves.
By NJ R. Ensign Pathologist, Exten-
 sion Division. U, of A

blOn DlNlblbn, U. Ol A.
 The loss occasioned by sweet po- tato witt also known as Stem Rot. Blue Stem and Yellow Blight) in Arkansas last year was estimated to be $90,0000O. This tremendous loss is 10 be regretted the more because it might have been largely prevented by following a few simple rules
 Wilt may be detected first by a slight yellowing of the upper, Younger leaves. This is quickly followed by the wilting of part or of the entire plant If the stem of the diseased vine be pinched open 1t will show a blackened center. This blackened area may also extend into the roots Obviously, if these potatoes are used for seed. the sprouts which spring from them are likely to be diseased The diseased seedlings in the hot bed show the same symptoms IS those described above. The blackened : interior of the stem gives the white stem a purplish cast.
 
 II has been shown that the artli. cation of any amount of fertilizer is of no value in the control of the dis. ease. Neither is spraying of any value since the fungus gains entrance through the roots of the plant. For this reason seed selection is an eff fectivs means of control. Disease free seed may be procured in the fall at digging tim while the potatoes are still attached to the vines After the potatoes are dug there is no way of distinguishing the diseased from the healthy roots. Each selected hill should show no blackenine of the vine when split open. Of course a heavy frost prior to digging will make selection difficult as this will also cause a similar discoloration ot the vine The selected seed should be stored in baskets or crates to pre- vent contact with other potatoes.
 In the spring just before bedding, the seed should be treated for five to ten minutes by immersing them in solution made by dissolying one ounce of corrosive sublimate to eight gallons of water. They should then be rinsed in water and dried before bedding.
 Clean Soil Must Be Used.
 After disease once occurs in a soil. the fungus will live over in this soil year after year. This soil should not be used in the bedding of the seed. Soil upon which diseased pota toes are thrown or upon which man ure from animals fed with the dis eased roots (unless previously cooked should in no case be used either fCy the hotbed or for field planting. Hot bed soil once used should be hauled away and the frames and soil around them should be- thoroughly soaked with a solution of formaldehyde made by mixing one pint of formalin tc thirty gallons of water. II is hes' that this treatment be repeated after twenty-four hours,
 The soil for the hotbed should he obtained from some part of the farT where there Is no possibility of IF. being diseased with the wilt fungus Sand from thc wood .ot k good Throw off the upper siX inches aG6 use only lhe -uhsejl. The Wagaa W=ef to haul He deceased gt.ase ua1+s should moi heHe4 fef hfr&.re 'n 9e new soil aal aieaasea fr tt 5 maldgbyde sQ5al.aaz
 A crop rotation pf fhser t1 fgt years should bc pracdca |. far t is known that tbe fungus remains F the soil for several wears,
 Rules to Prevent Disease.
 Sl.p seeding if the proper santa tion k observed in the operation, ia ?. successful way of producing diseased free seed The rules are as follow s quoted from Farmers Bulletin 7l4:
 l. The cuttings should b. mad from healthy vines,
 2. The cuttings should be planted on new ground or on ground on whiHs sweet potatoes have not been grown for al least six years
 B The potatoes produced by the cutting should be picked over and disinfeeted in the spring before bed ding, according to directions already given.
 {. The seed potatoes must be bed ded in a hotbed prepared according to the directions given above.