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Rose clinic
Symptoms, diagnosis and treatment for all your rose problems.
Aphids
Symptoms: Tiny green 1mm long insects gathering in numbers on new foliage and buds. Leaves can become distorted and damaged. Aphids excrete honeydew that often results in the presence of sooty mould.
Diagnosis: Aphids are sap-suckers that love the new growth and tender young buds of roses. They cause stems to wilt and can transmit virus from one plant to another.
Treatment: Remove them with a gloved hand, or use a pyrethrum-based spray. Persistent infestations may require the use of stronger sprays such as Confidor or Mavrik. Use strictly in accordance with directions and follow safety precautions.
Thrips
Symptoms: A white mottled appearance on leaves, browning of petals and flower drop
Diagnosis: These tiny thread-like insects suck the sap from leaves and flowers, often spreading plant viruses. If left unchecked, plant tissue becomes damaged and deformed.
Treatment: Thrip lay eggs in unopened buds making them difficult to control. They blow in on westerly winds and infest mostly light-coloured roses, then pass on to other areas. Pest presence is often short lived, but may be devastating if in high numbers. Apply Confidor at first sign of thrip to reduce pest symptoms.
Scale
Symptoms: White-crusted stems, often accompanied by sooty mould.
Diagnosis: Scale are small, sap-sucking insects with a hard cap which is difficult to remove. Scale found on roses includes cottony cushion scale, red scale and rose scale.
Treatment: Eco-oil kills all stages of scale insects by suffocation. Yates Lime Sulphur is also a useful tool in reducing the population of scale; spray bare stems after winter pruning. Best treatment is prevention – scale is commonly found on weak roses. Keep plants healthy and prune away damaged and diseased stems.
Two-spotted mite
Symptoms: Tiny insects, almost invisible to the naked eye. Silver webbing on leaves can occur if pest numbers are high.
Diagnosis: Often referred to as red spider mite due to females changing to a orange to red colour over cooler months. Mites usually have two distinct dark spots on their back. Pests can be difficult to overcome once in high numbers. They prefer hot and dry conditions.
Treatment: Insecticidal potassium soap sprays such as Natrasoap work by blocking the breathing pores and dissolving the scale’s outer covering, causing dehydration. These treatments will not harm beneficial insects and have a very low toxicity to people and pets.
Fungal disease:
Black spot
Symptoms: Rounded black spots with fringed edges. Damage can often cause leaf drop and poor health.
Diagnosis: The fungus can be persistent, especially in humid growing conditions and in plants of poor health.
Powdery mildew
Symptoms: White powdery growth on leaves, buds and stems. Can appear as spotted markings that will eventually cover plant surfaces if left unchecked.
Diagnosis: This fungus will usually appear during warm dry days that are followed by cool, damp nights. It spreads quickly and is common among roses.
Treatment: apply a fungicide once a fortnight. Spray applications should begin when the first leaves appear in spring, and continue through summer and autumn. Recommended products are Rose Shield and Eco Rose. Spray till the plant is dripping with the mixture.
Cane or stem canker
Symptoms: Canes become discoloured, turning dark drown. They will often appear sunken and withered.
Diagnosis: Fungi will cause stems to rot back, leaves become wilted and die. Spores can be observed on effected parts of the plant.
Treatment: Cut back diseased canes or stems well below the affected area. Spray Yates Liquid Copper to control cane and stem canker.
Autumn
Spray: every week with Yates Rose Shield plus Eco-Guard, alternate every week with Eco-Oil plus Eco-Rose
Winter
Spray: Yates Lime Sulphur is useful in reducing the population of insects, disease, fungal spores and insect eggs, disinfecting the rose, giving it a fresh start for the coming spring season. This must be done onto bare stems, not on leaves, so is a job for just after the winter prune.
Spring
Spray: every second week spray with Yates Rose Shield plus Eco-Guard, alternate every second week with Eco-Oil plus Eco-Rose. |
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