Allium leaf miner at large!
This big problem for veg growers takes some tackling to eradicate
Gardening, and especially growing your own fruit and veg, can be challenging at times. If it’s not the pigeons pecking at your brassicas during winter, it’s mice munching at autumnsown peas. If that wasn’t enough, we’re constantly getting new pests and diseases to challenge our vegetable-growing skills.
Earlier in the year I told you how I’d been suffering from onion white rot, but now I’ve got more problems with alliums – allium leaf miner on my leeks. This small, grey-brown fly can also affect onion, chives, shallots and garlic. Being a relative newcomer to the UK, first detected in 2002, many gardeners don’t know what to look out for when the problem starts. Damage is done by the fly’s small, juvenile maggots, which lets in secondary infections and the alliums begin to rot.
The fly has two life cycles during the year, one from March to June and the second September to November, with the later period normally being the one that causes bigger problems.
I first noticed an issue with my leeks in June, with what first looked like the start of rust – yet it didn’t spread. It was just lines of holes on the leaves; these are caused by the fly feeding on the sap from the leeks, which were starting to look a little sad for themselves. When I pulled a few to see what was going on, I noticed the shaft of the leek was a little soft.
I removed a few layers of the leek to discover brown maggot larvae hiding inside the shaft, with evidence of rot setting in. Sadly, at this stage there isn’t really much you can do to save the crop apart from lifting all the leeks and chopping out the unaffected parts to use straight away (or blanch and freeze for later use).
What’s even more maddening is that there’s no treatment to stop allium leaf miner. All we can do is net alliums with extra-fine insect netting and rotate our crops every year, making sure not to plant any other allium in the same bed year after year. Don’t forget to check your leeks this weekend and burn any affected ones, or dispose of them in the household rubbish to try to reduce the problem next year.