The Leek Moth, AKA Garlic Moth, attacks members of the onion (allium) family. There are lots of really good technical articles online that teach about history and life cycle, so I won’t try to repeat that information. Here is one such site from the Ontario Government http://www.omafra.gov.on.ca/english/crops/facts/08-009.htm.
I write to add my experiences and information gathered so that others may hopefully benefit, learn, and in return share information to help us control this newly invading species.
I first encountered this moth about four years ago. Since it was the new kid on the block, it sort of snuck into my patch by night (literally – more on that later) and destroyed about twenty-five percent of the garlic crop. The bulbs were turned to mush. I was really disgusted and disappointed. Until that fateful season, I thought garlic was the perfect crop; easy to grow, health-giving, and free of pests and diseases. It was now officially open season on Leek moths. I needed to find a control. Turns out there are several organic-friendly defences for public enemy number one.
My first control, and still my “go to” friend, is a ten percent solution (one part raw ammonia to ten parts water) of common household ammonia, available in the cleaning aisle of most grocery and hardware stores. Use great caution, and even more common sense, when handling this stuff. It is caustic and smells really strong – it will clean your sinuses out like you never wanted them to be cleaned out. It’s chemical formula is NH3; one molecule of nitrogen and three molecules of hydrogen. Besides being a wonderful cleaner and disinfectant (according to my wife), it is also used in the manufacture of nitrogen fertilizer… and explosives! This I knew from my former life in the mining industry. One, it was obviously a good and safe explosive; and two, that it was a fertilizer… the miners used to “borrow” it by the lunch pail full for their lawns and gardens… until the company started inoculating it with fuel oil to make it pack better in the drill holes. It may not qualify as a totally organic substance, I just don’t know that much chemistry, but at least it isn’t like dumping arsenic on your soil. At the first sign of trouble, I spray all the allium crops, and continue to do so about every five days. These pests stay around all summer, going through several generations, and then have the nerve to stay the winter, and show up for lunch again next spring. I have never rinsed the ammonia off of anything, and I have never seen any damage from it… except for dead bugs. They don’t develop antibodies to this stuff!
One of the concerns I initially had was the effect of ammonia on the soil ecology. It probably does kill microbes etc right where I soak the soil against the garlic or leek root, but the stuff is really volatile, so won’t hang around to spread throughout the garden.
I’ve also discovered that ammonia has a ph of about 12, very alkaline, so that is actually a plus, at least in my neck of the woods.
As I said, this is my “go to” ally in my war on bad bugs. One of the really good points about ammonia is that it is very selective. Most everything I’ve sprayed it on died – almost instantly! Earwigs, slugs, slug eggs, tent caterpillars, asparagus worms… but since I don’t spray the bees, no harm done there.
Bacillus Thuringensis, AKA BT, is a very safe bacterial control that I have used on cabbage loopers etc., and because this current enemy is exactly the same critter, only on a smaller scale, it works here too. But it is slower. The larvae eat the stuff and then get a wicked belly ache – serves ‘em right – then take about four days to enter bug heaven. Personally, I like to see ‘em dead – NOW!
Row covers can also work, but you have to be pretty diligent about the seal. I have some Agribon 15 that I purchased from William Dam Seeds www.damseeds.ca, the lightest weight they carry, that I use for frost protection over low hoops, and it works really well for that purpose. Since the moths are nocturnal, you need to have the cover on by dusk… or else. You can remove it by day for cultivating, but not necessary for watering or to allow light in. The material passes water and light just fine.
Crop rotation is another tool we have at our disposal. Since rotation is a good practice anyway, we might as well use it here too.
Well, the leeks are up and doing fine under the lights downstairs, and so far no moths. Here’s hoping for a great allium harvest. If I’m diligent in my defences, it will be. At the end of the season, I predict the score this way…
Lively Dirt 1 – Leek Moth 0