![]() ![]() Distinct patterns of yellowing can indicate a lack of one or more trace elements. These nutrients, which include iron, zinc, manganese and magnesium, are needed in small quantities to help the tree grow, flower and produce fruit. Sometimes, however, citrus lack trace elements. Yellowing leaves in winter are often related to cold soil conditions that inhibit the uptake of nutrients. This is fixed with a twice-yearly feed of complete citrus food (feed in August and February). When they are lacking general nutrients such as nitrogen, they are likely to develop yellow leaves, which is especially obvious in new growth. Scale on fruit can be wiped away before the fruit is eaten.Ĭitrus trees need lots of nutrients, especially from spring to early autumn when they are in active growth. Scale can be an indication of stress so provide extra water and fertiliser and apply horticultural spray oil to affected areas. The scale is a small, soft-bodied insect that is protected by a waxy cover. They can be spotted clinging along stems, on the back or front of leaves or encrusted on the skin of fruit. Several scale insects attack citrus trees. Holes (the size of a small pin prick) in the gall indicate that the wasp has hatched and gone, so pruning at this stage won’t control the pest. To control gall wasp, cut off the affected branches before the larvae hatch (usually in late winter) and dispose of the cut piece in a bag in the rubbish bin. Gall wasp damage isn’t as damaging as it once was, as a predatory insect that acts as a biological control agent is controlling it. The wasp lays eggs under the bark and the branch develops an ugly lump in response. Swellings and lumps on branches are signs of gall wasp attack. Left: extensive citrus gall wasp damage right: a white wax scale infestation. Some options include Eco-Lure Fruit Fly Traps and eco-naturalure. To prevent attack use organic baits and attractants near the crop to lure fruit fly away from the fruit. The entire life cycle from egg to newly-minted adult can take just four weeks, which is why the pest spreads so rapidly. Maggots flip and wriggle themselves out of the fruit and into the ground under the fruit tree where they pupate and emerge as adults. Telltale signs of their presence include stings on the fruit skin, signs of brown rot and fruit drop. ![]() These small, creamy-white, writhing larvae hatch and feed in soft fruit. Rather than looking for flies, concentrate on looking for larvae or maggots in fruit or rot. The adults are large but elusive flies that are difficult to spot. Thin-skinned lemons and mandarins may be attacked by fruit fly (usually Queensland fruit fly in eastern Australia). Although it looks unsightly, this is one problem that shouldn’t affect the overall tree health. To remove damage, simply prune away tip growth and place it in a bag in the rubbish bin. If signs are visible, treat with Success Ultra. Spray with horticultural oil as new growth appears to stop the adult insect laying eggs on the leaves and starting the life cycle. New leaf growth becomes distorted, twisted and marked with silver lines as the larvae of this pest burrow under the surface of the leaf. Left: citrus leaf miner larvae causing visible foliage damage right: a fruit fly poised to cause untold destruction. Also note that adults can fly from tree to tree. ![]() Note: Always wear eye protection when dealing with stinkbugs, as adults emit a caustic spray when disturbed which can cause serious eye damage. They can be squashed ‘en masse’ using something flexible such as an old thong, or picked off the tree and destroyed by dropping them into a bucket of soapy water. On hot days these pests will congregate on shaded trunks of citrus trees. During late spring and summer, destroy adult bugs. In early spring, treat with Yates Nature's Way Citrus & Ornamental Spray. At this time they're vulnerable to horticultural oils like PestOil and Eco Oil, which can smother and kill them. The problem actually starts in winter, when these insects are in a juvenile stage. They feed on developing fruit, leaving it dry inside when it matures. ![]() Before treating, check that the aphids are not already being brought under control by ladybirds and their larvae that feed on aphids.Īdult bronze-coloured stinkbugs and also smaller green stinkbugs are found on citrus trees in late spring and summer. Squash gently (don’t damage growth), hose them off ensuring you comply with any water restrictions in your area, or apply an organic pesticide registered against aphids, such as Yates Citrus Spray. These tiny insects cluster on new growth, especially in spring. Left: ladybeetles feeding on an infestation of black aphids right: a bronze orange bug, also known as a stinkbug. ![]()
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