Is your salad rocket full of holes? The fightback starts here
Flea beetles: A healthy seedling that grows quickly in good soil will outgrow their munching. Photograph: Jacqui Dracup/Garden World Images

April soils are perfectly suited to growing salad rocket – warmed and wet, they will have rocket germinating as its name suggests. Merely scatter the seeds across compost or soil and wait a few days: success is guaranteed. Unfortunately, the flea beetle is also primed for this moment and will munch your new crop into lace doilies. After that, it will move on to any other brassicas you are growing.

You have several options: wait to sow until early autumn, when the flea beetle has stopped laying. Or sow now and cover your rocket immediately after sowing with enviromesh or fleece so that the beetles can't get in.

If flea beetles do appear, keep the soil damp around young seedlings, because these pests do best in warm, dry weather. Also, make sure your plants aren't overcrowded, which makes it easier to hop from one food source to the next. Intercropping with plants not from the brassica family will slow their progress, too.

Several kinds of flea beetle are responsible. These small insects are 2-3mm long, with metallic black, green or blue coats, some with a broad yellow stripe running the length of the wing case. They have enlarged back legs that allow them to leap about (hence their moniker).

You can use this to your advantage. If you paint a piece of paper with honey (leaving the bottom inch clean so it doesn't stick to the plants) and then drag it over the leaves, the beetles will try to jump from danger – or in this case on to your sticky trap. It is not entirely effective, as many leap in other directions, but it will keep someone small amused for a while. Once you're bored, you can compost the whole thing.

The beetles mostly do very little harm to healthy seedlings. They and their root-eating larvae like to eat tender young growth. They will move on to other brassicas, such as turnips and swedes, but a healthy seedling that grows quickly in good soil will outgrow the munching.

You can encourage a number of natural predators to keep this pest in check, including two that parasitise it: microscopic braconid wasps and tachinid flies, which look like small houseflies. In both cases, the larval stage feeds on the flea beetle, while the adults feed on nectar and pollen; some species are even important pollinators.

If you want these good guys around, plant some flowers between your crops: umbels such as caraway, herb fennel, coriander and Ammi majus, and simple open flowers such as California poppies and pot marigolds, as well as yarrows. Nature will do the hard work for you.

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