RESOLVE HEALTH ISSUES IN ROSES
Roses are prone to a number of pests and diseases, so it’s important to get in early with the right controls to keep your plants in top condition.
POWDERY MILDEW This disease causes powdery patches on rose leaves, stems and buds.
BLACK SPOT A fungal disease that causes ragged-edged black spots on the leaves, followed by leaf yellowing and leaf drop. It looks ugly, and weakens the plant.
APHIDS
This is the main insect that attacks roses, feeding on soft, new growth. Numbers increase exponentially when conditions suit them, and shoots become smothered in aphids. These pests weaken plants by sucking their sap, and carry diseases from one rose to another.
THRIPS
These tiny sap-sucking insects spoil light-coloured blooms, especially in spring. The edges of petals look as if they’ve been burnt. Thrips are particularly hard to control when they shelter in full double blooms.
Control
Follow the tips (below) for controlling black spot
Change the variety, as some roses are more vulnerable
Control
Keep foliage dry as the fungus infects plants when leaves remain damp overnight
Grow roses in full sun with lots of space around them
Fertilise regularly, especially with a product high in potash
Control
Squash aphids by hand, which is easy as they tend to cluster together on new growth
Prune off badly affected tip pieces, wrap in plastic, and bin
Grow a mix of flowering plants in your garden to attract natural aphid predators such as wasps and hoverflies
Control
Put foil under plants to reflect the light – thrips don’t like glare Apply insecticidal soap spray Hang sticky yellow traps made from plastic coated with petroleum jelly, or cut sticky yellow tape into small sections
Strengthen your plants by giving them regular doses of liquid seaweed, following the instructions on the label
Spray plants with a rose fungicide or make up a spray based on bicarbonate of soda
Pick up any infected leaves that are lying on the ground, and dispose of them in the bin, not in the compost
Spray with a pyrethrum insecticide, but avoid doing this if ladybirds are around as they love eating aphids. Juvenile ladybirds, which look nothing like the adults as they have narrow, spiny, segmented bodies, devour even more of the pests than their parents
Plant some decoy flowers nearby, such as alyssum (Lobularia maritima) to attract pests away from the roses
Wait until the weather changes, when the problem will naturally reduce