WHEAT BLACK- MOULD.

Marlborough Express, Volume XLVI, Issue 119, 17 May 1912, Page 3

WHEAT BLACK- MOULD.

(By A. H. Cockaviw, in the - Agriculturn 1. Journal.) During wet summers it is not unusual for tho wheat crop to become, quite seriously damaged by a j^-is known as the wheat black-mould tU.t mi'-Mifestß itself by the spotting nr.d blackening of the ea.rs*- The very unfavorable weather that has.been experienced during the past lm-vest has■ accentuated the damage done oy Vrg disease, and a considerable loss ootli iv yield and, quality of the gram is reported. The wheat block-mould i" caused by a- fung;is known as Clad->s-pD'i-ium herbarum. This genus contains many dostructivo pla-nt p;i.-;i-sites, the tomato-rust (Cladpspovinm lulviim) a.nd ven-ucosis, of lemoas (Cliidosparium ele'gans) being .fanu.iar exfi.mples. The whoat-moukl is an extreme.y common fungus, i.nd in normally dry wason.s does but. slight harm, oems then found for the most pa.i-t only '<;n decayed and decaying; vegetation, it is; only when there is an excess -:■) moisture, and when .disoiised' seed . 7-if»i l)oen used, that it attacks and is a.bie to' penetrate into living plant tissues Cereals of'all kinds are liable 10 attack, but wheat and oats are tho crotts chiefly infested and in which tho majority of the damuge is done. By thii Layman it is noticed only when the grain is in ear, but its presence c-in of ton' be detected much ea.r^.cr in the season when the plants-"■an-quite .small. After a comparatively dlry spring followed, by frequent rain* tho wbo.it plants, often assume a ! yellowiiih tint, followed by a shriyoi-

ling and bleaching of the leaves', which become covered with litt'.o blackish tufts, representing one of the v spore^b^aring stages of tlie fungus.- > .-In-certain instances many of the plants ?.re killed1 outright, leaning more or less -circular bare-or. wy thin patches here and there in tho fields. • During, the past season this condition has not been unusual >ti Canterbury, and the cause has ;n many cases» been erroneously attributed to the grass-grub (Odontrta zoalandica.). Again, when the pl'nms are not killed outright they nr-y strugsjle on into«ar, and, not having sufficient vitality to develop tho grain, the st;»lks gradually die :-.na become quite, bleached, thus forming whitish patches that can be offS-'iy seen scattered through the crop. Tne nicvin da.nuige, in New Zealand at *>i\y rate, occurs when the ears aire almost mature. The ears' become spotte:!, ajid sit times almost covered with blackish-olive tufts similar to iho.v developed' on the' leaves. These tu:ts, consist of nisisses of spores tlr-r*.~ germinate almost as soon as they nrc developed, and, provided there isufficient moisture, continue the v/o^k of infection until the whole of the heads become completely coated! avHJj the fungus. The mycelium of Cladosporium m cases of severe attack penetrates rig.lit into ..the wheat grains, and flour ma.cto from them has. frequently a.very aij plenswnt flavor and its value for but ing purposes is greatly impaired. An examination of affected1 .whett shows that brownish patches- aa-e ■'«<.- 'velo.ped on the surface of the graim sometimes forming quite distinct hr>ec. Whon bedly diseased the surface'm-ny even become ciiioked, due to the cc volopment of tho fungus under 'he epiderm.is. Such diseased grain n. many cases quite fails to germinate, and even when it does the. resulting plants are always weakly, and the leaves become spotted with reddiahbrqwn patches earned' by the Clnd 7sporium. - In most seasons Cladosporium her barum is often -frequent. on app»e trees, cfuising- at times quite asevoro defoliation of the trees. When present on apples, the fungus .is often tornWl Dematium puelulans, but Jancezewski has proved experimentally that Ol;'.«:losporium herbarum and" Dematitim peululans are foims of the sutt-c

fungus,

CONTROL

Tho presence of wheat bla-ck-moi.".ld as a paa-asite being almo,st_ entirely dependent on 'weather conditions, xx, is obvious that there can be no e-.sy and effectual methods, of control. Nevertheless, "the . damage caused __ b v Cladosporium might be certainly Jo:~----'senedi by attention to the following methods of restricting its' power c r infection:—*- .

(1) Never on any account sovy sow-i that show:; tlie ; le-ast sign of disease. The use of affected- seed will result m a diseased crop, no. matter wheth-i" dry or wet conditions prevail ait-sr sowing, . , (2) Avoid the growing on the sane land of two grs.-in crops in succession. An uffected crop will leave the soil full of Cladosporium spores, whi<ui will be liable to 'dam?ge any cereal crop that may be resown on-the s:vrr.e area.

(3) The wheat-husks from a disefsed crop are capable of carrying infnq ,£ion. It is ther.-efore . -.\ gdod pracrt'A'e to -burn all husk-s-,- refuse, etc., a:; soon os thresiling is completed.

(4) In cases of very bad attack-r.li the sjtraw should o.lso be destroyed 'i»v burning.