How to plant and grow citrus
PESTS THAT CAN AFFECT CITRUS
Plant Information - Citrus (764 KB)
Always follow directions on the chemical packaging precisely. Remember to pay particular attention to the time from when you spray until when you can safely eat the fruit.
INSECTS ON CITRUS
APHIDSThese may attack new growth. ECO-OIL, MAVRICK, CONFIDOR, MALATHON or PYRETHRUM should control these.
BORERSMay cause die back of limbs that are badly affected. Severely damaged limbs should be completely removed. Pour MALATHON or CONFIDOR concentrate into the holes to kill the insect and spray STERIPRUNE over the damaged bark to stop wood-rotting fungus disease.
BRONZE ORANGE BUG (STINK BUGS)These insects suck the sap from new shoots. Control the problem with MALATHON or CONFIDOR as recommended.
CATERPILLARSSeveral types of these pests attack citrus. Spray with MAVRIK, SUCCESS, DIPEL or BUG GUN as recommended. Any one of these products will control this pest.
FRUIT FLYThese puncture the fruit causing it to discolour and become infected with larvae (maggots). Spray with NATRASOAP or CONFIDOR watching timing of spray to final harvest of fruit.
GALL WASPThe wasps lay their eggs in the new spring growth and burrow through the stem, causing swelling and galling. They can be controlled by pruning the affected shoots and burning them. This must be done before the eggs hatch (mid August). THIS IS A DECLARED PEST AND MUST BE CONTROLLED.
SCALEVarious types of scale affect citrus trees. WHITE OIL, PESTOIL or SCALE GUN should get rid of these. Bad infestations may need spraying every two weeks apart until cleared.
SNAILSThese may eat the rind and the flesh. They are mainly a problem during wet springs and autumns. Sprinkle SNAIL PELLETS around tree, but careful attention when applied if animals are an issue.
DISEASES ON CITRUS
BLACK SPOTThis fungus causes slightly sunken brown or black spots on the fruit. Common on Valencia oranges grown in humid coastal areas. Spray with TRIFORINE, MANCOZEB, LIQUID COPPER or FUNGUS FIGHTER, ROSE SPRAY or FUNGUS GUN
COLLAR ROTThe bark splits and becomes soggy near the base and gum may be exuded (this is caused by a fungus). Clean away the damaged bark and spray with ANTI-ROT. Seal the wound with a dressing such as STERIPRUNE.
MELANOSEThis fungus disease causes a brown stain or clusters of tiny brown spots on the fruit, leaves and stem. It may accompany die back of twigs.
SOOTY MOULDThis is a symptom of scale or aphid attack. It grows on the honeydew excreted by these pests. Spraying with COPPER OXYCHLORIDE or FUNGUS FIGHTER will kill this problem but the pests causing it must also be controlled. ECO-OIL, WHITE OIL or PEST OIL may be useful.
MINERAL DEFICIENCIES AFFECTING CITRUS
There are various mineral deficiencies that affect citrus occasionally. The most common are:
IRONYellowing mainly of new growth with the veins standing out in green. This is caused by liming too heavily or alkaline soil. Spray and water plant with IRON CHELATES at the recommended rate.
MAGNESIUMThis causes yellowing mainly of the mature leaves starting as a blotch and spreading to a characteristic inverted V shape at the leaf tip and may cause leaves to fall prematurely. Branches carrying the most fruit are usually the most affected. Water the soil around the base of the tree. Mix 2 tablespoons of MAGNESIUM SULPHATE (EPSOM SALTS) with 10 litres of water and soak 8 litres of this into the soil. Spray the tree with remaining 2 litres. It may take several months to correct this problem but the new growth should be green.
NITROGENLack of sufficient quantities of this will cause an overall pale or yellowish foliage colour and poor, stunted growth. See under FERTILISING.
LACK OF FRUITThis is often of concern and can be caused by a number of things. When new plants are planted in the ground a flush of growth usually occurs and it may take several years for the tree to mature enough to fruit again. Wheeny grapefruit tend to fruit every second year and mandarins may produce such dense growth they fail to fruit. This is particularly so for Thorny mandarins. In this case prune back to the second or third strong shoot from the fruit cluster or where the fruit has been. Other causes for lack of fruit can be heavy soil, root bound when planted, not enough fertiliser or water, or too much nitrogen or fertiliser.
FRUIT DROPDropping of some very small fruit is natural particularly when the trees have set a very large crop. If the fruit is ten cent piece size or larger this can be cause by insufficient moisture particularly in mid-summer in hot dry conditions or an acute lack of nutrients. Washington Navel oranges are especially prone to fruit drop which can be over feeding which damages the fine roots that take in moisture.
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