Cocoons on Brassicas

If you come across a cluster of small, yellow cocoons on leaves of Brassica vegetables – don’t spray them or feed them to the chooks. They do not belong to garden pests. (See photos below.)
These cocoons are, in fact, the pupation stage of a very small, black wasp. This wasp belongs to the Braconidae family. Braconids are parasitic wasps and very beneficial insects to have in your garden.
The female adult wasps, which are barely 5 mm long, lay their eggs in caterpillars of the Cabbage White Butterfly, which feeds on the leaves of stressed broccoli, Brussels sprouts, cabbage, cauliflower, horseradish, kale, radish, rocket, swedes and turnips.
The wasp larvae then feed on the caterpillars from the inside until they are ready to pupate. (Sounds gruesome, doesn’t it.)
They each then spin a small cocoon on the remains of the caterpillar, and hatch out two or three weeks later to repeat the cycle.
Adult wasps feed on nectar from flowers. It is worthwhile growing some nectar-producing plants to encourage these useful pest predators.
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