Illustration © nic-nic 2017
February 2018 — Cabbage whitefly
A little sucker of sap, the cabbage whitefly is a common resident on the underside of brassicas in allotments everywhere. It is their excrement, honeydew, that causes mild mould problems.
This warm winter, with brassicas now mature and tasty, it is happily multiplying. Every time you harvest a Brussels sprout or clear the leaves away from spring purple sprouting broccoli, white snows of them billow out and fall in heaps. A real invasion. But whitefly don’t usually cause problems with your harvest—unless the infestation is severe they tend to avoid new growth and the parts of the brassica we eat. And so long as they have not already bitten into the flesh, a good wash will erase them from your leaves in the kitchen.
Advice says that you should keep your brassica beds clean and tidy and for the most part, learn to live with a moderate number of whitefly. If things escalate, as they have this winter, you can resort to using non-chemical soap sprays and organic controls in an attempt to curb the population. But as brassica leaves are waxy and thick, sprays and chemical solutions do not necessarily prove effective. And even organic pesticides should only be used on the lower leaves and as minimally as possible.
Cabbage whitefly (up to 1.5mm long)
Image credit: CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=39889