Identify Diseases

We have listed the main disease problems on plants our customers ask us about.

1. Black Spot – Is a fungal disease and roses are badly affected. It thrives in warm, humid, moist conditions. It starts with black spots on the leaves then they turn yellow and fall off, it weakens the plant and if its not treated and becomes really bad may kill the plant. Keep the plants healthy, remove any debris from under plant, mulch well, water in the mornings around base of plant and not foliage, roses need at least 6-8 hours of sun every day, make sure there is good air circulation around plant, feed every 6-8 weeks in the growing season to make plants stronger and more resistant to disease. When the black spore lands on the leaf it germinates and multiplies then can spread to other parts of the plant or blow over to another plant close by. It can infect in one day then after 5 days there will be visible signs of damage. Remove damaged leaves and dispose of in the rubbish bin, feed with Potash to encourage new flowering and spray with a Fungacide.
2. Blight – If a healthy tomato suddenly develops brown or black splotches all over their stems and foliage especially in warm wet weather fungal disease Blight is generally to blame. Yellow circles then spread to rot the whole leaf and in a severe attack the foliage may end up a rotting mess in a few days. Give good ventilation and don’t splash water on foliage. Copper sprays or fungicide can slow down the spread but late blight at the end of summer is usually a death knell. Don’t compost, remove plant and don’t plant tomatoes again in the same spot next time
3. Blossom end Rot – Is a serious disease usually associated with vegetables especially tomatoes. Peppers, Eggplant. Melons and Squash can also be affected. Its caused by a calcium deficiency in the soil and erratic watering. Other things which aid the attack is sometimes excessive moisture fluctuations, excessive nitrogen fertiliser which causes rapid growth, and drought stress. Tomatoes planted in cold heavy soils often have poorly developed root systems which weakens the plant also. Cultivation too near to vulnerable roots which need to take up minerals and water could start the cycle of disease too. It looks like a discoloured watersoaked, dark sunken decay of  half of the fruit at the blossom end (opposite to the stem) of many fruit especially the first fruit of the season or just as fruit is ripening and can be very damaging. Fungicides and Pesticides don’t really help so infected fruit should be disposed of.
4. Conifer Canker – Is a serious disease of Conifers, it enters the conifers by some defect in the tree like borer holes, wounds in the bark, fine cracks in the bark, or pruning wounds. The fungus interferes with the sap system eventually causing death of the branch or main trunk above the wound. Older trees are more prone but any tree if it is stressed by drought or poor nutrients will be at risk. When the branches become infected the fungus ringbarks the limb so the foliage yellows and dies from the tips back. Gold varieties usually lose colour and become brown. It commonly starts at the top of the tree. Branches die rapidly almost overnight and death may occur. You can often see resin bleeding on the stem and purple red discolouring on the bark. Disease can spread in the wind, insects or birds, overhead irrigation or rain, or from pruning tools. Infected branches may be pruned off and you can try spraying any insects. Badly affected plants should be destroyed. There are not alot of fungicides currently available for its control. You could try applying a copper based fungicide before it takes hold or try a phosphoric acid, usually injected. If you can find a product called Phospho-jet (its a systemic fungicide) that might be worth trying also.
5. Die-back – Is a soil borne mould that produces an infection called root rot or die-back. It causes the gradual dying of a plants shoots starting at the tips, its found all over the world and there is really no cure at present. It attacks many species with Banskias and Grevilleas susceptible.This soil fungus like organism invades the roots of plants starving it of nutrients and water. It spreads in soil or plant material and can move through areas by vehicles, peoples shoes, bush-walkers, and feral animals like pigs and climatic conditions. There is an environmentally safe spray that can be injected into the tree which has been tried, careful garden hygiene and using clean equipment, keep pots of the ground with good drainage. Potting mix can get contaminated if transplanting so use fresh mix.
6. Dollar Spot – Dollar spot is a serious lawn disease which can kill grass down to the roots. It can infect many different varieties of lawn. It results in silvery grey spots appearing in the lawn which then brown off. Spots can be from 1-6 inches round. Its caused by a fungus. Its not active in Winter but as soon as the weather warms it grows and thrives. It thrives in lawns that aren’t watered properly, by a lack of nitrogen, lots of thatch in the lawn which prevents water pentrating the soil, and mowing lawn too short in dry periods. Try to water lawn in the morning so its dries before night when fungus thrives. Fungicides are available to treat the disease and you may need to reseed damaged areas.
7. Frizzle top – Is a fungal condition in Palms when a new frond emerges stunted often yellowed with a shredded look rather than as a firm long green leaf. It results from a lack of manganese in the soil and palm tissues. It also affects drought stressed plants. Manganese deficiency is common in sandy soils rich in lime. Apply Manganese Sulphate mixed in water to the foliage and soil and an application of the fungicide Mancozeb at the start of Summer can help. It can take months or years to correct. If frizzletop is too severe fertilising will not work before palm weakens, new leaves appear weak, scorched, withered and reduced in size.
8. Leaf Curl – Peaches and nectarines need to be sprayed with a copper based fungicide as a preventative for the fungal disease leaf curl. It occasionally affects apricots and spraying apples, pears and quinces also helps control black spot. Infected leaves become thickened, curled and deformed, then the leaf changes colour to a lighter green with red or purple tinges. The leaf eventually turns brown, withers and drops prematurely. Infected fruit is rare but they can develop blister like areas that are raised. Young trees are most susceptible but all can be affected. The best time to spray is when the buds have started to swell but are not yet open. Spray when the tree is dry and when rain is not forecast for at least 24 hours.
9. Powdery mildew – Summer rain and humidity is when powdery mildew is most common. It looks like a white grey mould on the leaves and stems and though it does not kill plants it weakens them and leaves can fall prematurely. It is a fungal disease spread by spores and carried in winds and splashing waters. Spores can survive long periods on weeds and plant debris. It starts in patches then spreads . Have good circulation around plants, prune or thin out if crowded. Don’t water plants from above. Remove and destroy all infected plants from garden. Spray with a fungicide.
10. Rust – Is a fungal disease causing leaves to yellow and fall prematurely. You can see little powdery yellow rusty or bright orange pustules on the underside of affected leaves. Excessive moisture and cool weather promote rust which is a fast growing fungi that travels through the air until it settles and can contribute to the decline of the plant by stunting its growth and branches dying. If only a few plants are affected prune those off. The spores are carried by the wind and can travel for miles. It thrives on damp foliage so water plants in the late morning so they dry off during the day. Geraniums, snapdragons, roses, gerberas, beans, and sometimes trees are prone to rust invasions. Spray with a fungicide
11. Sooty mould – Are fungi which cover plant leaves, stems, and twigs in a black sticky substance. It usually occurs secondary to an infestation of either ants, aphids, scale, mealy bugs or whiteflies. Treat the insects and the mould should dry up and infected leaves will fall off or mould may wash off. If the leaf surface is covered completely in mould it blocks the light essential for growth. You can wash off mould with soap and water or treat with a Fungicide.
12. Tomato borer – These fruit boring insects are abundant in the growing season and are difficult to manage as they have burrowed inside as protection from insecticides and predators. They cause significant damage and render the infected fruit unusable. They are the larvae of moths and tunnel into the tomato crown to complete their growth inside the tomato. The inside gets filled with fluid and droppings and it quickly decays then rots with a fungus appearing. Try and inspect tomatoes regularly looking for small eggs and larvae, unfortunately adult moths are mostly nocturnal and are most active in laying eggs at dusk. They attack tomatoes just after fruit begins to set and grow but before they ripen so are usually found when the tomato is green. The holes can be the size of a pea head. Remove any infected fruit and destroy. Cover plants with a fine netting may help. Plant Dill and Parsley nearby and after harvesting work soil over well to destroy any pupae left in the ground.