Crunch time for pests

Sunday Tasmanian - Tassie Living - - HOME - Peter Cun­dall

THE term codlings was used in me­dieval times to de­scribe small, un­de­vel­oped, plum- sized ap­ples. Most ap­ples will have achieved this size by late spring and that’s when the fi rst signs of at­tack from codling moth grubs be­gin to ap­pear.

Any ne­glected ap­ple trees that car­ried grub- in­fested fruit last sum­mer are cer­tain to be at­tacked again – and even more se­verely un­less con­trol mea­sures are taken.

There’s no point wait­ing for the fi rst ap­ples to be at­tacked, be­cause once grubs have pen­e­trated an ap­ple they re­main com­pletely pro­tected from preda­tors and sprays.

So, in or­der to ob­tain some kind of con­trol, it is es­sen­tial to start now.

The fully fed grubs that emerged from ap­ples last sum­mer found a place to hide over win­ter in co­coons, ei­ther in crevices in the trunk, un­der loose, fl aky bark or even be­tween nearby fence or shed pal­ings.

At the mo­ment many are al­ready emerg­ing and pre­par­ing to change into codling moths. This hap­pens when day­time tem­per­a­tures start to re­main fairly steady at around 21C.

Fe­male moths don’t fl y much, they usu­ally re­main in the same tree, hop­ping and fl ut­ter­ing at the end of a warm, sunny day.

They give off a spe­cial scent to at­tract male codling moths from else­where, while newly formed males fl y off to other vul­ner­a­ble fruit trees.

Af­ter cop­u­la­tion, the fe­males soon be­gin pro­duc­ing shiny, fl at, scale- like eggs which they stick on, or close to, young ap­ples.

Pears, quinces and even wal­nuts are also vul­ner­a­ble to codling grub at­tacks, but to a far lesser ex­tent.

When the time is right, the grubs hatch and move rapidly to pen­e­trate the near­est ap­ple.

Some sim­ply bur­row in from the safe shel­ter of the scale cover, while oth­ers crawl to a with­ered ca­lyx at the base of an ap­ple and en­ter from there.

If you don’t start con­trol mea­sures now, large num­bers of fruit will be show­ing signs of dam­age, even as early as Christ­mas.

By the end of Fe­bru­ary or early March, all the dam­age has been done and most grubs will have found a place to shel­ter through win­ter, ready to start the cy­cle again next spring.

Ap­ply­ing band traps, loose pieces of hes­sian or cor­ru­gated card­board around the trunks of ap­ple trees is a great help. They go on now.

How­ever, keep in mind that they can­not pro­tect this year’s ap­ple crop.

Th­ese bands sim­ply pro­vide dry, pro­tected places for the grubs to hide af­ter they have eaten their way through the fruit.

This is why th­ese bands con­tain­ing the fi rst wave of skulk­ing grubs must be re­moved and de­stroyed in late De­cem­ber and im­me­di­ately re­placed with new ones. Th­ese are re­moved and de­stroyed in March.

This is one way of re­duc­ing grub pop­u­la­tions so less dam­age hap­pens the fol­low­ing year.

The big­gest blun­der is to leave trap bands on dur­ing win­ter, be­cause most are full of codling moth co­coons.

For more im­me­di­ate con­trol, fe­male scent ( pheromone) traps are very ef­fec­tive.

They look like lit­tle toy houses and are hung from trees.

The scent given off lures in­com­ing male moths to a sticky sur­face, where they die.

Un­fer­tilised fe­male moths don’t lay eggs and have a short, bar­ren life.

One trap for ev­ery three trees seems to do the trick.

The traps also clearly in­di­cate when moths are most ac­tive.

It also helps if the lower trunks of ap­ple trees are given a brisk scrub­bing with a stiff wire brush.

This re­moves fl ak­ing bark and ei­ther kills or ex­poses em­bed­ded co­coons, which can be killed with a nail.

As fruit be­gins to de­velop in late Novem­ber, I in­spect them ev­ery few days. It’s an easy task to pick off at­tacked ap­ples and place them in a bucket. This also re­moves feed­ing grubs. All fallen ap­ples must also be col­lected and, by plac­ing them in a sealed plas­tic bag and leav­ing it out in the sun, all grubs are de­stroyed.

This timely ap­ple re­moval is also an­other method of thin­ning the fruit, be­cause trees al­ways pro­duce too much.

Used in con­junc­tion with pheromone and band traps, this has proved very ef­fec­tive at con­trol­ling codling moth dam­age.

And all with­out the use of poi­sonous sprays, so the ap­ples are safe to eat.

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