Deterring leek pests
Leeks make a great winter vegetable, standing proud on your plot for months, to give you a delicate onion flavour long after you’ve harvested garlic, bulb onions and chives. But a couple of pests, new to our gardens this century, can spoil your harvest if you let them. Both leek moth and allium leaf mining fly produce larvae that feed within leek plants, leaving damage that makes the vegetable susceptible to secondary rots.
These pests aren’t active in January; the moth caterpillars have pupated in white cocoons on the leaves, turned into moths and are overwintering in sheltered spots, and the fly maggots have turned into brown pupae in the stems. Meanwhile, the holes made in your leeks will have allowed rot to gain entry and caused more damage.
This year you will need to cover your leeks with fine mesh netting to keep out the adult moths or flies and do this right from the start, as soon as you plant them out. Crop rotation is essential too, as both pests may be resting in the soil after an infestation, ready to invade the next crop!