WHY IT’S TIME TO SET A CUN­NING TRAP

This is the month some lit­tle nas­ties that want to ruin your sum­mer fruit get to work, so it’s time to set a cun­ning trap or three.

NZ Lifestyle Block - - Contents - WORDS SH­ERYN CLOTH­IER

Irun my or­chard as closely aligned with na­ture as pos­si­ble. That means I use very, very few sprays (even or­ganic ones) as I be­lieve in al­low­ing the nat­u­ral bal­ance to as­sert it­self. If my fruit aren’t all per­fect, so be it, as long as there are enough.

This prac­tice works well in the­ory. The prob­lem is fruit trees aren’t in New Zealand’s nat­u­ral bal­ance. They are rel­a­tive new­com­ers to our ecosys­tem and all their pests and dis­eases that have come in with them are rel­a­tive newbies too. This means they may not have nat­u­ral preda­tors here.

Codling moth ( Cy­dia pomonella) is one such pest. It in­fests all pipfruit (ap­ples, pears, quince, crabap­ples, nashi) and wal­nuts. The cater­pil­lar feeds for three weeks in­side the fruit. Signs are an in­fected core and ac­cess hole ringed with brown frass (residue from chew­ing or ex­cre­ment).

There are sev­eral or­ganic meth­ods to con­trol codling num­bers in your or­chard. Un­for­tu­nately, some com­monly-known ones are not par­tic­u­larly ef­fec­tive and all the meth­ods tar­get dif­fer­ent stages of the life cy­cle so it is im­por­tant to be do­ing the right one at the right time of year.

Win­ter

Dur­ing win­ter the pu­pae spin a silken co­coon in a crevice or un­der bark and await tem­per­a­tures of 15°C.

STRAT­EGY: re­move and de­stroy pu­pae

Clean up all fallen fruit and lit­ter from un­der the trees. You don’t want any hid­den habi­tats they can over­win­ter in.

Hav­ing chick­ens run­ning un­der the trees may seem a so­lu­tion, but cara­bid bee­tles and disease will kill any codling on the ground. Those who have trees both in and out­side their chicken pen say there is no dif­fer­ence in the codling lev­els.

One rem­edy is to wrap the tree trunk in cor­ru­gated card­board. The the­ory is that the cater­pil­lar will find it an at­trac­tive hidey hole and spin their co­coon in there. You can then re­move and burn it be­fore they hatch in spring.

The prob­lem is there are lots of places fur­ther up the branches they can choose to hi­ber­nate and there can be sev­eral generations a year.

To be most ef­fec­tive, place the card­board as high up the trunk as pos­si­ble (but be­low any fruit), grease or make a sticky band be­low the card­board to stop them pass­ing on by, and re­move and burn fre­quently from early sum­mer to af­ter har­vest. Even then, you will only get a pro­por­tion of the codling co­coons.

Spring

This is the start of their ac­tive life cy­cle. Once the blos­soms start show­ing a pink colour, the pupa de­vel­ops the fea­tures of an adult moth and emerges late in spring (about petal fall). Adults will con­tinue to emerge for sev­eral weeks and are most ac­tive on warm evenings.

They will mate and the fe­male will sin­gu­larly lay tiny eggs (about 1mm long) on or near de­vel­op­ing fruit. These eggs take 8-14 days to hatch into tiny lar­vae which then crawl in­side the fruit. This pe­riod is the most ef­fec­tive time to at­tack.

STRAT­EGY 1: dis­rupt mat­ing with pheromone traps

Pheromone traps are com­monly avail­able at gar­den cen­tres or hard­ware stores. They have a lure, a sticky trap base and a tri­an­gu­lar cover to hang in the tree. These use the fe­male mat­ing scent to at­tract males.

To use them as a form of con­trol is like putting a pub on the cor­ner and hop­ing it will stop teenage preg­nan­cies. Males can mate many times and a mated fe­male can lay as many as 200 eggs. You would have to trap ev­ery male as a vir­gin to be ef­fec­tive.

How­ever the traps are a use­ful way to mon­i­tor when the moths are ac­tive (so you can spray). They are only ef­fec­tive if the sticky base is sticky and dust can quickly coat them. Fold them in half and then re-open to re­store the sticky ten­drils and ex­tend their ef­fec­tive­ness.

Pheromone dis­rup­tors

Or­ganic pheromone mat­ing dis­pensers are a twist tie that you slip over a branch at the be­gin­ning of the sea­son. When ap­plied at 100 to the hectare, they re­lease the fe­male scent to such a de­gree it con­fuses the male and pre­vents mat­ing. Moth num­bers should fall in the sticky base trap if they are work­ing ef­fec­tively.

How­ever, these are not easy to source, and al­though well re­garded, I tried

them for two years run­ning with lit­tle no­tice­able ef­fect. How­ever, I had three closely-planted ap­ple trees that are badly in­fected, and these are ap­par­ently more ef­fec­tive when used with low den­sity of codling spread over a wide area/larger or­chard.

STRAT­EGY 2: trap adult moths

See method un­der sum­mer strate­gies.

STRAT­EGY 3: kill the eggs

Neem oil, con­queror oil or any oil spray will smother and kill the eggs. To be ef­fec­tive, this must be re­peated at eight day in­ter­vals un­til your traps show the adults have stopped fly­ing and lay­ing, and full cover of the eggs must be achieved – spray un­der and over.

I pre­sume the oils will also kill ev­ery other liv­ing be­ing on your tree while you are at it so this is not a strat­egy I prac­tice.

STRAT­EGY 4: kill the emerg­ing lar­vae be­fore it en­ters the fruit

This needs to be done at ap­prox­i­mately 80% petal fall, and needs to be re­peated for suc­cess.

You can use any spray at this stage that is ef­fec­tive against cater­pil­lars. Be aware that or­ganic pyrethrum sprays and home­made gar­lic sprays will also af­fect ben­e­fi­cial in­sects, in­clud­ing your pol­li­nat­ing bees.

There are two or­ganic sprays which are more spe­cific, avail­able at gar­den cen­tres. You can get a sa­chet of Ki­wicare’s or­ganic cater­pil­lar bio­con­trol. It does not list the codling as a tar­get (it is aimed at white but­ter­fly, leaf rollers, looper and other cater­pil­lars) but the Bacil­lus thuringien­sis (BT) it con­tains is also very ef­fec­tive against the codling cater­pil­lar.

The other is avail­able through hor­ti­cul­tural sup­ply stores and is branded as Madex-3. This con­tains the Cy­dia pomonella gran­ulises virus which is spe­cific to the codling moth. It comes in 100ml to mix in 2000 litres to do a hectare and costs around $125 so is only eco­nom­i­cal for those with larger or­chards, or you could band to­gether with friends to pur­chase a bot­tle.

Spray 10 days af­ter the mon­i­tor­ing traps start trap­ping moths, and again ev­ery 10 days un­til 10 days af­ter the traps are no longer catch­ing any­thing. In my cli­mate, this equals 2-3 times at 10-day in­ter­vals from ap­prox­i­mately 80% petal fall.

Once the cater­pil­lar is in­side the fruit it is pro­tected from sprays.

Sum­mer

The cater­pil­lar will spend about three weeks gorg­ing it­self on the flesh of your ap­ple, be­fore emerg­ing to seek a hidey hole to make its co­coon (see Win­ter). North of Auck­land, they com­monly hatch a sec­ond gen­er­a­tion about Novem­ber and the­o­ret­i­cally they can have more generations in one year depend­ing on the tem­per­a­tures. Fur­ther south, the records show it to be more a sin­gle long stretch of ac­tiv­ity.

Use traps to mon­i­tor and spray lar­vae 10 days af­ter peak pe­ri­ods, and/or to catch adult moths.

STRAT­EGY: trap adult moths

Moth traps can be used to sig­nif­i­cantly re­duce num­bers. While these have proven some­what suc­cess­ful for me in the past, they were not ef­fec­tive enough in them­selves for ad­e­quate con­trol and there is no way to en­sure you catch the fe­male be­fore she has laid her eggs.

How­ever, gar­den­ers I know have found them to be very ef­fec­tive, al­most to­tally erad­i­cat­ing codling within three years, and they swear by them. I found all these op­tions equally ef­fec­tive.

You need to put them out by mid­blos­som and main­tain them un­til af­ter har­vest in March to catch as many moths as pos­si­ble. You can note the fluc­tu­a­tions in num­bers and use these as in­di­ca­tor traps (spray for lar­vae 10 days af­ter peak pe­ri­ods) as well. You will need to clean and re­plen­ish them fre­quently.

Light traps

Moths are at­tracted to light. Any light or so­lar light seems to work, al­though LED blue/white lights are said to be bet­ter than yel­low-hued lights.

A con­tainer of wa­ter with a lit­tle cook­ing oil float­ing on top un­der the light will catch the moths. I have seen ev­ery­thing from corded lights un­der

a Chi­nese-hat lamp­shade over a shal­low dish, to cheap so­lar lights with their lens as the con­tainer.

Milk bot­tle traps

Cut an open­ing in the side of the milk bot­tle and fill with ei­ther of the fol­low­ing recipes – both work. Check af­ter rain and clean out and re­place as needed.

Recipe 1

Mix 1 litre of warm wa­ter with 100g sugar (white or brown), 1 tsp Mar­mite, ½ tbsp cloudy am­mo­nia and ½ tbsp vanilla and place in milk bot­tles with an open­ing cut in the side.

Recipe 2

Put 1 tbsp of vine­gar and 1 tbsp of trea­cle or mo­lasses in a milk bot­tle with an open­ing cut in the side and half fill with warm wa­ter.

Not what I want to eat.

Card­board wraps are lim­ited in their ef­fec­tive­ness.

A so­phis­ti­cated light trap us­ing a light un­der a lamp shade, over a dish of wa­ter.

Once the cater­pil­lar is in­side the fruit, it is pro­tected from any spray you use.

Photo: Peggy Gregg

A sweet mix in an old milk bot­tle.

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