Rosemary leaf beetle

Symptoms

Feeding on Rosemary, Thyme and Sage, the Rosemary Leaf Beetle also attacks lavender.

Spot them

The rosemary beetle is an 8mm long metallic green beetle with purple stripes. The grubs are greyish white with five darker longitudinal lines; fully grown larvae are 5-8mm long. The 2mm long sausage-shaped eggs are laid on the underside of the leaves.

Rosemary beetle adults remain inactive on their host plants during the summer months (June to August). In late August and September the beetles resume feeding, mate and begin to lay eggs, which they continue to do on warm winter days until spring. The eggs hatch within two weeks and the larvae feed for approximately three weeks before entering the soil to pupate. The pupal stage lasts for a further two to three weeks before adults emerge.