Bagrada bug

look for pale, whitish or yellowish star-shaped scorch marks stippled across the leaves of young plants, where the bugs have sucked out the sap. Heavily fed patches look wilted and scorched, as if burnt by the sun.

on seedlings the bug kills the growing tip (the heart of the plant), so it makes no head at all ("blind"), or throws out several small useless heads instead of one. In hot weather a whole seedbed can be stunted or destroyed within days.

a small shield-shaped stink bug about the size of a grain of rice (5–7 mm), shiny black with bright orange and white spots and stripes — which is why it is called the painted bug. You often see them in pairs, joined tail-to-tail, out on the plants in the heat of the day, and crushing one gives off a bad stink.

smaller, wingless and bright red-orange, often in clusters on the seedlings or down at the plant base. They look like tiny round red beads and do just as much damage as the adults.

with the ladybird, which is a friend that eats aphids and is round and dome-shaped — bagrada is flatter, shield-shaped, and swarms seedlings leaving star-spots. Aphids are tiny and soft and leave sticky, curled leaves (not star-spots), while flea beetles chew small round holes rather than pale star marks.

watch most closely from the seedbed stage through the first 3–4 weeks after transplanting — the young, tender stage when a single bug can kill the growing tip. Step up your scouting during hot, dry spells, when the bug breeds fastest.

, when the bugs come out to feed and mate in the open on the plants. Walk a big "W" across the field so you cover the middle and all four corners, not just the edge nearest the path.

Make about 10 stops, and at each stop check 10 plants. Look at the heart (growing tip), the undersides of the leaves, and the stem base and soil right around each plant.

— search under soil clods, in cracks in the soil, and under any mulch or trash at the plant base. That is also where the females lay their eggs in the soil, out of sight.

, or fresh star-spots on 1 in every 10 young plants. The trigger is deliberately this low — seedlings are killed so easily that you cannot wait for the numbers to build.

before planting, pull and destroy volunteer brassicas and cruciferous weeds — wild mustard, wild radish, rape regrowth — that feed the bug, and clear old crop residues and soil clods where it shelters and lays eggs. Don't plant right next to a just-harvested cabbage field, and rotate your brassicas onto fresh ground away from last season's.

cover seedbeds and young transplants with fine insect netting through the tender weeks so the bugs simply can't reach them. Set out strong, vigorous seedlings that grow away fast, and where you can, avoid transplanting in the peak of the hot, dry season, when the bug is at its worst.

in the cool of early morning, when the bugs are slow, pick them off or tap them into a tin of soapy water, and check the plant base and under clods for the red young. On a small seedbed, done daily, this alone can save the crop.

a neem-based (botanical) spray partly controls the young bugs if you start early and repeat every few days — it is gentle and breaks down fast, so one spray is never enough. Aim it at the undersides of the leaves and the plant base, where the bugs shelter.

if bugs are still on the seedlings past threshold, spot-spray just the affected bed or young plants with a pyrethroid, directing it at the plant base and soil where they hide. Cover your skin, eyes, nose and mouth; spray in the cool of the day with the wind at your back; keep it away from food, water, children and bees; wash well afterwards; and respect the pre-harvest interval — the number of days you must wait between spraying and eating or selling the crop. Rotate to a different chemical group each time so the bug does not build resistance (stop being killed by the spray).

widen your clean-up to the weeds and volunteers around the field, make sure you are hitting the plant base early, while the bugs are still small, and switch to a different chemical group next time. If a seedbed is already ruined — plants blind or many-headed — those seedlings will never form proper heads, so don't waste labour transplanting them: pull and destroy them, clean up the bed, and re-sow into a fresh, netted bed away from the infested ground, ideally after the hot-dry peak has passed.