AZALEA PROBLEMS - AND HOW TO TREAT THEM

AZALEAS: DISEASES

PETAL BLIGHT

SYMPTOMS: Small pin spots on flowers. Flowers have collapsed. Flowers have a greasy or slimy feel.

CAUSE: The fungus Ovulinia azaleae which is spread by wind and water splash. The first sign of the disease is circular pin prick spots on the petals (showing brown on white flowers and pale on dark flowers). The spots quickly enlarge and become irregular, and eventually the flower collapses. Affected parts have a slimy feel which is more obvious as the spots become larger.

TREATMENT: Spray with the fungicide MANCOZEB PLUS, as soon as the buds start to show colour, then every 10-14 days while flowering. Remove any affected flowers from the plants and destroy.

LEAF GALL

SYMPTOMS:Thick fleshy leaves

CAUSE: Leaf Gall - caused by the fungus Exobasidium vaccinii - is more likely to occur in humid, shady conditions on new growth. In humid conditions the galls will have a whitish bloom of fungal spores which then spread to other plants. Only affects new leaf buds and sometimes flower buds.

TREATMENT: Carefully prune affected parts and destroy. Sterilise secateurs after each cut.

PHYTOPHTHORA (ROOT ROT)

SYMPTOMS: Branches dying back from tips. Plant dies suddenly in hot weather. Plant not thriving instead of putting on new growth during warmer months.

CAUSE: Phytophthora is a fungus which infects the root hairs and starts rotting the fine roots. It usually occurs when the soil is too wet.

TREATMENT: Remove and destroy the affected plant. Before replanting, apply FONGARID® as directed, to the soil in the affected area and around plants close by. If a plant is only partly affected, it may be saved by applying FONGARID® as above. In any case, avoid overwatering and improve drainage where possible.

WITCHES BROOM

SYMPTOMS: A mass of tight, brush like growth different to the rest of the plant.

CAUSE: This is commonly known as witches broom, and is believed to be caused by a virus-like organism called microplasma, which is introduced to the plant by Leaf Hoppers.

TREATMENT: If the effect is not severe and results in a mild dwarfing of the affected part it can be ignored, otherwise it should be removed. Secateurs should be sterilised after each cut.

POWDERY MILDEW

SYMPTOMS: White powdery growth on leaves.

CAUSE: Powdery mildew, which develops in cloudy overcast weather conditions, more rapidly in warmer temperatures, particularly in shaded areas.

TREATMENT: Spray with MANCOZEB PLUS.

LACEBUG

AZALEAS: INSECTS

AZALEA LACE BUG

SYMPTOMS: Silvery leaves, mottled leaves.

CAUSE: Azalea Lace Bug. These insects are about 4mm long with lacy wings, and feed on the back of the leaves, depositing their droppings (sticky black spots) as they feed. Damage will first occur on new seasons foliage as the weather warms up in Spring. The damage will be minor at first (usually only one or two pin pricks on the surface) but if not treated will increase rapidly.

TREATMENT: Spray with CONFIDOR®, or a systemic insecticide such as ROGOR® or FOLIMAT®, making sure the underside of the foliage is sprayed. Check your azaleas for minor marking on new seasons foliage regularly during Spring and begin a spray program when damage is first noticed.

Repeat in 7-10 days and again as necessary through Summer. NOTE: Once the leaves are damaged it cannot be reversed. Damaged foliage will drop of in its own accord in time.

TWO SPOTTED MITE

SYMPTOMS: New growth is curling under and has a slight brownish tinge. Older leaves curved under and may be an odd shape. Fine webbing in the area.

CAUSE: Two spotted mite. Formerly called Red Spider Mite, they congregate on the underside of the leaves. Mites are very small and just visible to the naked eye, but can be easily detected with a magnifying glass.

TREATMENT: Spray with ROGOR® or FOLIMAT®, or a specific miticide, KELTHANE®. Follow up with a second spray to ensure that nymphs are also controlled. Do not spray too often with the same chemical as mites will develop an immunity.

AZALEA LEAF MINER

SYMPTOMS: Angular brown patches along the midrib of the leaf. Tips of petals folded over.

CAUSE: This is caused by a caterpillar called Azalea Leafminer. The adult moth lays its eggs singly along the leaf midrib. The caterpillars feed between the leaf layers causing a small dead patch, they move to the tip, folding it over and feeding in the fold.

TREATMENT: If only a few, remove the affected leaves and kill the larvae. Otherwise spray with FOLIMAT®.

GREENHOUSE THRIPS

SYMPTOMS: Silvering of upper leaf surface. Small insect about 1.5mm long on the underside of leaf.

CAUSE: Greenhouse Thrips. These insects feed on the underside of the leaves, causing a silvering of the upper surface and leaving a dark deposit on the leaves. Mainly occuring in moist, shady conditions.

TREATMENT: Spray with CONFIDOR®, ROGOR® or FOLIMAT®, making sure you spray the underside of the leaves.

BLACK VINE WEEVIL

SYMPTOMS: Leaf edges have been chewed. Bark has been chewed from the base of the stems. Plant has suddenly wilted and died.

CAUSE: Black Vine Weevil. The adult weevil chews the leaf edges at night and hides in the foliage during the day. Eggs are layed in the soil around the base of the plant. The larvae chew on the bark of roots and lower stem of the azalea, often resulting in the stem being ringbarked.

TREATMENT: Apply BAYTHROID ® to the soil in summer to control the larvae and spray the foliage with BAYTHROID ® to control the adult weevils, making sure to spray all surfaces.

AZALEA WHITEFLY

SYMPTOMS: Surface of leaves mottled yellow. Small white insects on underside of leaves. Insects fly off when disturbed.

CAUSE: Azalea Whitefly. The insects suck sap from the underside of the leaves and can leave a deposit of honeydew in which sooty mould can grow.

TREATMENT: Spray with FOLIMAT® or ROGOR®, making sure the underside of the leaves is sprayed. Once the supply of honeydew has been stopped, any sooty mould will disappear.

AZALEAS:ENVIRONMENTAL

NO FLOWERS OR BUDS

SYMPTOMS: Plant produces few or no flowers

CAUSE: 1. Late pruning 2. Plant has been dry during the bud formation stage

TREATMENT: 1. Don't prune after late January - early February. Azaleas will still produce new growth in temperatures too low to form flower buds. 2. Ensure proper watering. Azaleas like the soil to be moist, not excessively dry or wet. Mulching will help.

CHLOROSIS

SYMPTOMS: All or many of the leaves have turned yellow, but the veins are green.

CAUSE: This is called Chlorosis, and can be caused by the soil being too acid or too alkaline.

TREATMENT: Azaleas like an acid soil with a pH from 4.5 to 5.5, certainly no higher than 6.0. Do a pH test on your soil, and if it is lower than 4.5 or higher them 6.0, take the following action.

1. pH lower than 4.5 - dust the soil with dolomite and water in well. Test pH again in a couple of weeks before applying again.

2. pH higher than 6.0 - apply PHOSTROGEN® Acid Plant Food and Tonic or YATES ACITONE as directed on the pack, until the problem is corrected. Do not use in conjuction with any other nitrogenous fertilizer.

BUD FAILURE

TREATMENT: OSMOCOTE® PLUS for Azaleas, Camellias and Rhododendrons

PESTICIDES AND HOW TO USE THEM

1. Read label and instructions carefully before using. Use only for applications listed on the label/instructions.

2. Pesticides should only be used at the rates shown on the label/instructions and should not be mixed with other chemicals unless compatible.

3. Use separate spray equipment for herbicides. Any herbicide residue can damage plants you are spraying with another pesticide.

4. Wear protective clothing where possible: long sleeved shirt, trousers, gumboots, safety glasses, face mask, long rubberised gloves. Change your clothes and wash after you have finished spraying.

5. Avoid spraying in hot sunny weather. Spray early morning or late afternoon. Also do not spray in windy conditions.

6. Handle pesticides with care. They should be stored in a secure area away from children, foodstuffs, and fertilizers. Dispose of empty containers properly.