Time to scale back pests

Sunday Tasmanian - Tassie Living - - HOME - Peter Cun­dall

PLANTS most at risk from pests and dis­eases dur­ing Oc­to­ber are now pro­duc­ing soft, juicy vul­ner­a­ble shoots. Cit­rus trees now com­ing into new growth are a per­fect ex­am­ple.

In Tas­ma­nia, th­ese plants can cop the lot dur­ing spring. Chilly, sat­u­rated soils have an ad­di­tional weak­en­ing ef­fect.

Here are some of the most com­mon cit­rus prob­lems now hap­pen­ing:

Un­thrifty le­mon and other cit­rus trees have leaves and fruit cov­ered with an un­sightly, black, sooty mould.

This is a typ­i­cal in­di­ca­tion of in­fes­ta­tion by scale in­sects.

Turn over a leaf and you’ll see them, some over­lap­ping and gen­er­ally clus­tered along midribs and young branches. Scale pests feed on sap and mul­ti­ply rapidly. The sooty mould is noth­ing more than their drop­pings go­ing mouldy.

The an­swer is to spray over and un­der the leaves three times at weekly in­ter­vals. Use white oil or pest oil di­luted with 40 parts of wa­ter.

Home­made white oil emul­sion costs only a few cents and suf­fo­cates th­ese pests. Sim­ply mix one cup­ful of cheap cook­ing oil with half a cup of wa­ter in a blender. Add a tea­spoon­ful of wash­ing up de­ter­gent.

The re­sult­ing creamy “may­on­naise” is di­luted with 40 parts of wa­ter and sprayed over and un­der all scale- in­fested fo­liage. Does the trick per­fectly at vir­tu­ally no cost. The sooty mould is grad­u­ally washed off by rain.

The re­main­ing home­made white oil con­cen­trate can be stored in a jar in a safe place.

Another prob­lem is when young, soft cit­rus shoots are cov­ered with masses of black in­sects.

Th­ese are black cit­rus aphids which mass to­gether, suck­ing sap from new growth. If not con­trolled they can se­ri­ously weaken cit­rus trees.

Spray th­ese aphids with pyrethrum mixed, strictly ac­cord­ing to in­struc­tions on con­tain­ers.

This is an in­stant, con­tact killer of aphids and many other pests, but safe for us. Al­ways buy it by the con­tainer so only wa­ter needs to be added. This is much more eco­nomic than us­ing ex­pen­sive pres­sure packs.

Some­times lemons be­come grotesquely de­formed, fail to ma­ture prop­erly and con­tain vir­tu­ally no juice. This is be­cause of tiny cit­rus bud mites. They at­tack flower buds to cause dis­torted flow­ers which form ab­nor­mal fruit.

This prob­lem looks bad but few fruit are af­fected so no spray­ing is needed.

Right now many cit­rus fruit, es­pe­cially lemons are turn­ing mouldy and be­gin to rot, even while still hang­ing.

This is a com­mon prob­lem which tends to oc­cur when cit­rus tree canopies are badly con­gested.

Th­ese trees need an oc­ca­sional prun­ing to al­low good air cir­cu­la­tion. Some­times, spines scratch fruit skins al­low­ing mould or­gan­isms to gain ac­cess and flour­ish. “Lis­bon” lemons are vul­ner­a­ble be­cause the trees are thorny.

Prune a con­gested tree to open it up for al­low bet­ter air move­ment. That job is best car­ried out in spring or early sum­mer.

All small branches are cut off so only main limbs are left and even the tips of th­ese are snipped off. If the de­nuded tree is heav­ily wa­tered, fresh clean growth will ap­pear in weeks. Al­ways rake up and re­move all de­bris. Some­times new leaves of grape­fruit trees are heav­ily wrin­kled and twisted.

It is com­mon dis­or­der with grape­fruit known as Crin­kle Leaf. As leaves age and de­velop, all wrin­kling dis­ap­pears. In short, stop wor­ry­ing and do noth­ing.

Oc­ca­sion­ally lemons or or­anges de­velop dead, grey patches on skins, al­ways in late win­ter and spring.

Per­fectly nor­mal in Tas­ma­nia be­cause it is noth­ing more than frost dam­age. Some­times, af­ter a cold, frosty win­ter, some outer leaves ap­pear burnt.

Just cut off all dam­aged fruit. If frosts still re­main a dan­ger, leave the dead fo­liage un­touched un­til early sum­mer as a pro­tec­tive shield against fur­ther dam­age.

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