Time to scale back pests
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.