If you have noticed deformed growth, silvering or discoloured patches on leaves that look almost burnt and damage to the flowers on your roses, the most likely culprit is Chilli Thrip.

Adult and larval stages of thrip feed on flowers and foliage causing extensive damage. As well as attacking roses, they also feed on citrus and their hybrids, a range of fruit and vegetables plus other host plants common in Perth gardens. They are active during spring, summer and autumn and thrive in warm humid conditions.

They are very hard to spot as the adult is only 1-2mm long.  To confirm the presence of thrip, cut some of the damaged foliage and shake it over a piece of white paper. If you see  tiny insects coloured pale or translucent to black, and specks of black dung, then you have thrip.

Controlling this pest takes monitoring and persistence. The life cycle lasts several weeks, and repeated treatments will be required to control chilli thrip. There may be infestations in nearby host plants or in neighbouring gardens.

Steps for Control

• Prune off any affected foliage and flowers.
• Dispose of cuttings in a plastic bag in general waste. Do not put into compost or green waste disposal.
• Thrip love to hide in shady dry places, so a blast of the hose on the underside of leaves can help to dislodge them.
• Insecticidal soaps such as Nature’s Way Vegie and Herb Spray or Natrasoap can be used to control this pest. Horticultural oils, such as Neem Oil, registered for other thrip can also be effective.
• Products that contain imidacloprid, spinetoram or pyrethrum are recommended insecticides.
• Thoroughly spray plants including the underside of leaves and the ground under affected plants to try and control the different stages of the insect.
• It is important to monitor the pest and do repeat applications to break the life cycle of the thrip.

More information on Chilli Thrip is available at https://www.agric.wa.gov.au/horticulture/chilli-thrips-roses

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This is intended as general information only. Please ask one of our qualified horticulturists for more specific advice for your situation.