Rocket: Pests & Diseases
Rocket is a quick, peppery salad crop that can be sown repeatedly from spring to early autumn. It grows best in moist, fertile soil and light shade during warm weather, which keeps leaves tender for longer. Its rapid growth makes it ideal for containers, gaps between crops and small allotment beds.
Common pests
Flea beetle is rocket's main pest, making numerous tiny shot-holes in leaves, especially during warm, dry weather. Slugs can strip seedlings and leave ragged holes in low foliage after rain. Cabbage white caterpillars and other brassica caterpillars may chew leaves, while pigeons can peck or pull at young plants. Aphids and whitefly are occasional visitors, particularly on crowded crops or plants allowed to stand too long in warm conditions.
Common diseases
Downy mildew causes yellowish angular patches on upper leaf surfaces, with greyish mould below in cool, humid weather. Damping-off can kill dense seedlings in cold, wet compost or soil. Grey mould may affect crowded leaves that remain damp. Club root is possible where rocket follows other brassicas in infected soil, producing swollen roots and wilting. Bolting is not a disease, but heat, drought and long days quickly make leaves hot and coarse.
Prevention
Use a long rotation away from cabbage-family crops where club root is known, and avoid planting into badly infected ground. Sow thinly and little and often, thinning seedlings for airflow. Keep soil evenly moist and mulch lightly in dry weather. Fine fleece or insect mesh from sowing is the most dependable way to exclude flea beetles and caterpillars. Remove old leaves and finished plants promptly, and avoid overhead watering late in the day.
Non-chemical control
Keep fleece or fine mesh securely over crops until harvest to prevent flea beetle, caterpillars and birds reaching leaves. Hand-pick caterpillars and slugs, especially at dusk or after rain, and remove eggs from leaf undersides. Use slug barriers around seedlings and encourage ground beetles, birds and frogs. Pull up plants badly affected by downy mildew or club root. Water and shade crops during heat to slow bolting and reduce flea beetle damage.
What to look for
Check seedlings daily in warm, dry weather for fresh shot-holes from flea beetle. After rain, inspect soil and lower leaves for slugs. Look beneath leaves weekly for caterpillar eggs and young larvae. In cool, humid periods, watch for yellow angular patches and grey mould. Check older plants for rising flower stems.
Tips
Sow every two to three weeks for a steady supply, harvesting young outer leaves before they become strongly peppery. A shaded container close to the kitchen is especially useful in summer. Watering consistently is the simplest way to delay bolting.
Rocket pests & diseases: frequently asked questions
What are the common pests of rocket?
Flea beetle is rocket's main pest, making numerous tiny shot-holes in leaves, especially during warm, dry weather.
What diseases affect rocket?
Downy mildew causes yellowish angular patches on upper leaf surfaces, with greyish mould below in cool, humid weather.
How do I prevent pests and diseases on rocket?
Use a long rotation away from cabbage-family crops where club root is known, and avoid planting into badly infected ground.
General guidance for UK home gardens, focused on prevention and non-chemical control. The RHS or a local garden centre can help with tricky cases. Page updated 19 Sep 2026.