CONTROL OF BROWN ROT

Nelson Evening Mail, Volume LII, Issue 162, 6 July 1918, Page 2

CONTROL OF BROWN ROT

VALUABLE AMERICAN EXPERIENCE.

LIME-SULPHUR i PROVES EFFECTIVFi.

The control of brown- rol i.s a scrions' matter for growers of fruit in New Zealand, and it is admitted that up to the present experiments' conducted by the Department of Agriculture, as well as .private individuals. have thrown very little light on this difficult problem. Interesting and valuable iiv formation. however, has (states the ■N..Z. Famier) been* received from the United States Department of Agricul- I ture, through,the courtesy of Mr OR.. "W. Rdbne.' of; Auckland, who has received several butlefcins on the subject through the agency of the American Cbnsul-G-ehWral (Mr A. A. "Winslbw). For ■ nearly twenty years brown rot of stone fruit was under investigation, hy the American plant pathologists, a-ndi while much was learned about- the disea.se, its successful control was still unsolved. Th-e principal reason for this was that Bordeaux mixture and other important sprays injured the foliage of the peach and .Japanese plums so seriously that Itheir use was impossible. The" sulphur sprays available for testing, while somewhat more effective against the brown rot of _ the peach, and plum.- were still far too injurious to be recommendf-d. Finally in 1907 M3r W. Mi. Scott, then attached ,to the United States Bureati of Plant Industry, developed the use of the self-boiled lime-sulphur mixture as n spray for this disease and the peach scab fungus?. "Later it was found practicable to Pombine this with the arsenate of lead, and the satisfactory combined insecticide and fungicide spray for the curcnb'o ; and certain other insects- on stone,' I fruits and the brown rot and certain, other fungus diseastes was developed. Of course "im "New Zealand we are not' troubled to any great extent by the attacks of insect pests, on- ©tone fruits, and it is the merit of self-boiled lirne'sulphur as a fungicide that will specially interest New Zealand growers. For the past eight years th-ik? treatment has been canned out- with great success m the commercial peach orchards of the eastern half of the United States, and though not entirely out of the experimenal -stage, the treatment looks very promising. Mr M. B. Waite, the pathologist in charge, concludes, his letter by stating: "I feel that you,can recommend the self-boiled lime-sulphur, with and without arsenate of lead, with every confidence of teniccess against the brown rot, especially on the pearh.

DAMAGE TO THE PEACH. Although the youmg fruits soon after, the petals are shed, may become affected, as a rule no marked outbreak occurs until the fruit is half-grown or larger, and the greatest destruction is wrought at harvest-time. The fruit- crop mav reach maurity in perfect condition, and yet he destroyed before it can be picked. Moreover, the fruit may become affected in transit, or after rtaching the market. Tt is no uncommon experience among peach-growers to have a consignment of peaches leave the orchard in apparently good condition, and- arrive orr the market specked and practi|-allly worthless, owing to the brown-rot- fun>gus. Through handling by pickers ' and packers some fruit in- every package may become contaminated with spores from a few diseased fruits in- the . rchard. Enough moisture usually ae. T «>H>pe | in the case to germinate the spores, _ arid if the refrigeration is poor, the fruit is likelv to go down) in- partial or total decay before reaching the consumer. The fungus also attacks the blossoms,: and extends from these into the i-uit-bea-ring twigs, often girdling them, in a wet spring the fruit crop may thus be matcrialy reduced, although tins form of attack is only <1 :casionally sefions In like manner the fungus may extend from diseased fruits into the Following an outbreak of of "brown-rot on the 'fruit, these tvig infections may become so severe p s to give the trees a blighted appearance.

INFLUENCE OF THE WEATHER. In sections where the brown-rot Is prevalent the. spores are practically omnipresent, and' only,.' favourable conditions for their germination.- and the rapid growth of the fungus are required to start an outbreak of the disease. The most important factor is excessive moisture in the form of ram, which not only favours the production and germination of spores and the o-rowth of the fungus, but renders the fruit sdft and watery, atid . thereiore more susceptible to the disease. iJ.gh temperatures also favour the., disease, although th fungus grows readily m mild summer temperatures. Prolonged cloudy weather, with frequent ktfh* showers, os more dangerous than) a, hardl rain) followed by \cleanng. _ Warm, muggy wealther, when (the fruit is maturing, is often disastrous to the crop. PREPARATION OF LIME-SULPHUR, The standard self-boiled lime : s*ilT>hiir mixture is composed of eight pounds of fresh stone lime and eight pounds of sulphur to 50 gallons! of water. In mild, cases of brown-rot and scab a.'' weaker' mixture .containing six' pounds of each ingredient to 50 gallons of water may be used with satisfactory results. The materials! cost so : little,_ however, that one should not economise in : this direction- where a valuable fruit, crop, is at stake. Any finely-powdered sulphur (flowers, flour, or "commercial ground" sulphur) mav be used in, the preparation of the mixture. In) order ito secure the best action from the lime, the mixture should be prepared in rather large quantities, at least enough for 200 gallons of spray, using 32 pounds of Mine and' 32 Hound's of sulphur. The lime should l be placed \ in a barrel and enough water (about six I gallons) poured on to almost cover ft. As soon as the Ifime begins to slake the sulphur should be added, after running it : through a sieve to break oin the lumps, if any are present. The mixture should be constantly stinTed and. more Water (three or four gallons) added as needed to form at first a thick pj.«te and then gradually a- thin paste. «. The Time will supply enough heat >to boBP the mixture several minutes. As soon as it is Avell slaked water should be add>ed to cool the mixture and prevent further cooking. It is then readv to be sti-ained into the spray tank, diluted, and cpplied. THe stage at which cold water sho.ild be poux'ed on to stop the cooking varies ' with different limes. Some limes are so * sluggish in slaking that it ia diffiicutt to obtain enough heat from them to cook the mixture at all, while other limes become intensely hofc on slaking, and care must be taken not to allow the boiling to proceed too far.

If the mixture is' allowed remain hot for 15 Or 20 mimxtes a.fte r the sOakinfr is completed; the sulphur gradually goes into solution, with the lime to. forni sulphides, which are injurious to peach foliage. It is therefore very important, especially with hot .limej to cool the ,mixture r,unckly by adding a few biickets of water fife soon as the lumps of lime hay© glided down. The intense heat, violent toil-, liig, and constant istilrriiiig restflf; in a uniform mixture of finely-divddedi sulphur; <&iid lime, \tfith only a very email percent-dge of the sulphur in. solution. It should be strained to take onl. coarse particles of liine. hut the ■■•=.wphin' ; should he carefully worked 'through the 1 strainer. * (ToJ>e continued.)