Pest or guest of the month
This monthly selection offers a description of some of Warriston's beasty and 'beastly' inhabitants and advice on how to live with them organically. Find more in our Pest or Guest archive
September 2019—Cabbage whitefly
AB, east side
Pick a brassica leaf now and you'll likely find yourself caught in a choking cloud of tiny white-winged insects, thousands of them disturbed from a laid back life style on the underside of the host plant's leaves. An all year round resident, the larvae/nymphs have spent the summer increasing in number and are now ready as adult colonies to cosy into our crops over winter.
The little angels are a particular nuisance on kale and purple sprouting broccoli, the large leaves of which are less tightly bound than a head of cabbage. While the adults multiply, the nymphs cling on, both generations sucking sap and secreting a sticky honeydew which harbours sooty moulds and makes leaves less than desirable for dinner.
What to do?
The cabbage whitefly is not easy to shift. It travels easily from plot to plot spreading quite happily across the whole site. It is also very resistant to any chemical treatment so those tempted to spray should be put off doing so — the chances of removing them permanently are non existent and none of us want toxic produce for the table).
The best way forward is to tolerate the little mites. And let the ladybirds and lacewings munch away.
And by way of prevention: keep your brassica bed clear of dead material and space plants out well. Pick kale leaves regularly for harvest— and in particular take off leaves/take out whole plants that seem to be harbouring whole metropolises or that have become mouldy and compost. Leaves with minor infestations can be washed thoroughly in the kitchen and eaten without worry.
Note that the cabbage whitefly is not the same creature as the greenhouse whitefly.
For more detail on the above, and how a hoover can help!, check out Alys Fowler's tips: www.theguardian.com/lifeandstyle/2011/dec/02/alys-fowler-whitefly-brassicas
Cabbage whitefly (up to 1.5mm long)
Image credit: CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=39889Small white caterpillar