Peter Cun­dall:

Help­ful ad­vice on how to stem leafcurl

Sunday Tasmanian - Tassie Living - - NEWS - with Peter Cun­dall

Any peach or nec­tarine trees in­fected by leafcurl disease last spring will be in­fected again un­less pre­ven­ta­tive sprays are ap­plied now. It’s ur­gent and fungi­cides must be ap­plied be­fore the tips of the new leaves ap­pear.

The spray to use in­volves cop­per, an ef­fec­tive killer of al­most all par­a­sitic fungi. Right now, leafcurl or­gan­isms are al­ready clus­tered around leaf buds wait­ing for them to open.

This de­struc­tive disease loves mois­ture, es­pe­cially the soft, stick­i­ness of newly-opened leaf buds. As soon as the pro­tec­tive outer skins of leaf buds crack open in about a week, the leafcurl disease at­tacks. It is helped by rain which washes in the deadly or­gan­isms.

Newly-planted peach and nec­tarines are par­tic­u­larly vul­ner­a­ble and many young trees are killed dur­ing the first sea­son be­ing too im­ma­ture to put up much re­sis­tance.

Apart from spray­ing young trees, we

Once leafcurl strikes, no mat­ter how of­ten the trees are sprayed the disease will still con­tinue to dev­as­tate

can pro­vide tem­po­rary pro­tec­tion by stretch­ing clear plas­tic film over the branches to keep rain off. Once leaves have fully opened and are no longer sticky with sap, the rel­a­tively dry sur­faces be­comes re­sis­tant to leafcurl.

Larger trees are too big to be cov­ered so we use sprays that can cling pro­tec­tively around vul­ner­a­ble buds de­spite nor­mal rain­falls. This is why home­made Bordeaux or the much stronger Bur­gundy mixes are so valu­able. The only rea­son why th­ese pre­ven­ta­tive sprays fail to pro­tect is be­cause of poor tim­ing; be­ing ap­plied ei­ther too early or far more com­monly too late.

Once leafcurl disease has struck, no mat­ter how of­ten the trees are sprayed the disease will still con­tinue to dev­as­tate the trees. So get spray­ing this week­end and spray again when blos­som buds swell

and turn pink, al­ways just be­fore leaves ap­pear. If nec­es­sary, cut off about 100mm from the tips of each branch be­cause that’s where the first leaves start to open.

Use two 10 litre buck­ets to make th­ese well-tried fungi­cides. Half-fill one with cold wa­ter and the other with the same amount of warm wa­ter. Dis­solve 100gram of builders’ lime in the cold wa­ter and 100gram of cop­per sul­phate (avail­able at gar­den cen­tres) in the warm wa­ter. Then pour the lime mix into the cop­per mix and stir.

The re­sult is Bordeaux mix­ture, which when freshly made is par­tic­u­larly ef­fec­tive. When ap­ply­ing it to branches – right to tips – keep the con­tents of the bucket ag­i­tated, oth­er­wise it will set­tle and can block spray noz­zles.

Bur­gundy mix is al­most the same ex­cept that in­stead of lime, use wash­ing soda (cheaply avail­able as a foot-bath). This mix is not a noz­zle blocker, which is why I pre­fer to use it, but be­ing much stronger than Bordeaux can cause leaf dam­age.

I also spray quince trees to con­trol fleck, a disease that in­fects the fruit, first cov­er­ing quinces with black scabs be­fore the fi­nally rot be­fore ripen­ing.

Plum and apri­cot trees are also at­tacked by shot-hole, an­other fun­gal disease which causes brown spots to ap­pear on leaves which then open so each leaf is cov­ered with tiny holes.

Spray­ing with ei­ther of th­ese home­made fungi­cides now can give good con­trol.

An­other fun­gal disease which at­tacks lemons and to a lesser ex­tent other cit­rus fruit is cit­rus scab (pic­tured, inset). We see it as black, sunken spots in the skins. The in­fec­tion mainly comes from dis­eased, rot­ting fruit ly­ing be­neath cit­ruses or in­fected fruit still hang­ing. Any branches in con­tact with the soil due to heavy fruit, also trans­mit cit­rus scab.

Skirt prun­ing to cut off all ex­tra-low branches helps, but all fallen or in­fected fruit must be re­moved and taken away – al­though even scabby fruit can still be used for juice.

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