Com­mon cit­rus prob­lems

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Cit­rus grow well in many parts of New Zealand, es­pe­cially in the warmer north­ern re­gions.

Cit­rus are hardy and very for­giv­ing of ne­glect but they can be af­fected by a num­ber of pests and dis­eases. Most prob­lems are rel­a­tively easy to con­trol but the key lies in iden­ti­fy­ing the prob­lem in the first place. Here are some of the most com­mon:

Scales - There are many dif­fer­ent types of scale in­sects that come in a range of shapes and colours, but they’re all char­ac­terised by the pro­tec­tive coat­ing the sap­suck­ing in­sects cre­ate over them­selves. Un­der­neath each coat­ing a pest is busily suck­ing the sugar from the plant. Some­times the ex­cess sugar pro­duced by the scale causes black sooty mould to grow on the leaves. All types of scale on cit­rus can be treated with a spray­ing oil. Af­ter the scale has died, the sooty mould will grad­u­ally flake off.

Aphids - Like scales, aphids are sap-suck­ing pests that clus­ter on the sweet, ten­der grow­ing tips. Small in­fes­ta­tions can be squashed but, if num­bers start to get out of con­trol, it may be nec­es­sary to use a spray­ing oil or Yates Na­ture’s Way In­sect Spray.

Borer - The first ob­vi­ous sign of borer ac­tiv­ity is the saw­dust that ap­pears in branch junc­tions. Closer in­spec­tion will re­veal the hole where the borer has en­tered the branch.

Prune off badly af­fected branches and burn or bin the clip­pings to get rid of the pest. If the prob­lem’s not too se­vere, clear the en­trance to the holes and spray with Yates Na­ture’s Way Pyrethrum.

Ver­ru­co­sis - Pic­tured. This fun­gal dis­ease causes ir­reg­u­lar scabby, wart-like growths to de- velop on the fruit and, oc­ca­sion­ally, on the stems. Al­though the fruit is still us­able, the prob­lem will grad­u­ally get worse if it’s not treated. Af­fected plants can drop large num­bers of im­ma­ture fruit.

Prune off the worst-af­fected stems and spray all over the tree with Cop­per Oxy­chlo­ride or Yates Champ DP. This is most ef­fec­tive if car­ried out when the plant is about mid­way through flow­er­ing. A fol­low up spray is help­ful.

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