Exit pass for club root

The Tribune (NZ) - - GARDENING - WALLY RICHARDS

Bras­si­cas – cab­bages, broc­coli, cau­li­flower, brus­sels sprouts, radishes, turnips, stocks, wall­flow­ers and other plants be­long­ing to the fam­ily Bras­si­caceae ( Cru­ciferae) – are prone to club root.

The name de­rives from the dam­age the dis­ease does to the roots of its host plants, de­form­ing them into club-like lumps.

Pri­mar­ily as­so­ci­ated with warm, moist, acid soils, the dis­ease spores can rest in the soil with­out any host plants for be­tween 7 to 21 years, which makes it a real prob­lem if any­one is un­for­tu­nate enough to have it in their gar­dens.

As club root is a soil borne dis­ease, be care­ful about in­tro­duc­ing soil from other ar­eas in­clud­ing new top soil, soil on tools or boots, plants from other places grown in soil, in­clud­ing bun­dles of soil-grown plant seedlings.

When young bras­sica plants reach a cer­tain stage, the in­fected roots re­strict the amount of mois­ture or food avail­able to the fo­liage. The leaves then turn yel­low, droop and the plant dies.

There is no chem­i­cal treat­ment I am aware of that will erad­i­cate the dis­ease. The only known way to kill club root in in­fected soil is by us­ing or ap­ply­ing steam – an un­likely op­tion for most peo­ple.

As the dis­ease prefers acid con­di­tions, heav­ily treat­ing the soil with soft gar­den lime will make it dif­fi­cult for the spores to spread to the roots.

I have rec­om­mended us­ing po­tas­sium per­man­ganate (Condy’s crys­tals) as a soil drench to ster­ilise the soil in the plant­ing area. Dis­solve 3⁄ tea­spoon of Condy’s

4 crys­tals into a litre of wa­ter along with three ta­ble­spoons of salt.

Once dis­solved, add an­other 9 litres of wa­ter and ap­ply one litre to each plant­ing hole prior to plant­ing. This ap­pears to ster­ilise the soil, giv­ing seedlings a good chance to es­tab­lish, grow and hope­fully reach ma­tu­rity be­fore the dis­ease chokes off growth.

Plant­ing quick ma­tur­ing crops or plant­ing crops af­ter treat­ing the soil in the early au­tumn can also work as the dis­ease prefers a warm en­vi­ron­ment, not the cold soils of win­ter.

Un­for­tu­nately, Condy’s crys­tals also de­stroys ben­e­fi­cial mi­crobes and fungi. An an­swer could be a prod­uct called Ter­racin which sup­presses soil pathogens and helps in­crease ben­e­fi­cial soil life.

About a month be­fore plant­ing, drench the soil with Ter­racin ac­cord­ing to the la­bel in­struc­tions.

En­sure that the treated area ex­tends a me­tre or more be­yond where the seedlings will be planted.

Lim­ing the area is ad­vis­able, keep­ing the soil moist, but not with chlo­ri­nated wa­ter as it kills ben­e­fi­cial mi­crobes.

Three weeks later ap­ply My­cor­rcin (or Thatch Busta) to in­crease the ben­e­fi­cial mi­crobe pop­u­la­tions.

Plant the seedlings a fur­ther week af­ter this.

The ob­jec­tive is to sur­round the roots with enough ben­e­fi­cial mi­crobes and fungi to re­strict the spread of the dam­ag­ing spores.

Plant­ing bras­si­cas, other than the fast ma­tur­ing bok choy, is not prac­ti­cal un­til af­ter the short­est day, with Au­gust the pre­ferred time for most ar­eas, so there is plenty of time to plan an as­sault on club root.

Prob­lems ring me at 0800 466 464 (Palmer­ston North 357 0606) Email wal­lyjr@gar­de­news.co.nz Web site www.gar­de­news.co.nz

Gar­den­ers want­ing to grow beau­ti­ful heads of broc­coli first need to get on top of club root. Photo: FAIRFAX NZ

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