In early October, I needed an onion. They were still on the curing rack so I went to the garage to grab one. I’d been using up the Ailsa Craigs first since they don’t keep very long – only 2-3 months – but I decided to go for a Copra this time.
Seems ok on the outside, other than a tiny bit of frass
(I always seem to have some damage, so that doesn't usually set off any alarm bells)
Inside: Nothing but air
A quick once over of the onions on the rack revealed the problem:
Not just a bit of frass...a LOT of frass
Seeing some damage this year was not in itself unusual - that happens every year. What was unusual was the extent of the damage and how many onions were affected. Many were a total loss - this is what the above onion looked like inside (Warning! If you're squeamish, scroll down quickly!):
The "yuck" factor doesn't get much higher than this
So how did I come to realize that leek moths were to blame? From their webbed cocoons:
Webbed cocoons - the tell-tale sigh of leek moths
Knowing I'm dealing with leek moths rather than onion maggots doesn't change my main method of control, which is covering the beds with netting. But it's always good to know what you are dealing with as each insect/disease, no matter how similar it is to others, has it's nuances. For example, onion fly causes the most damage early in the season while leek moth does the most damage in July/August. I harvest my onions in mid-August which is likely why I only notice the damage a few weeks later when the larva tunnel out of the onion and form their cocoons.
So here I was with a rack full of onions that had to be dealt with asap. First things first - I went through all of the onions and set aside those that were a total loss. These went into the burn pile since leek moth can overwinter on plant debris.
As I mentioned, the Copras were the most heavily hit - out of 73 onions, 46 were tossed. The rest were at least partially salvageable so those were trimmed, sliced and frozen, as were all the other onions that had moderate damage.
Moderately damaged onions were trimmed,
sliced and frozen in a zip lock bag
After dealing with all of the more heavily damaged onions, this is what we were left with:
Ailsa Craig & Red Wing onions; Camelot, Ambition & Golden shallots
Top, clockwise from top left:
Golden shallots, Red Wing, Jaune Paille de Vertus, Rossa di Milano
The numbers for this years harvest look like this:
Note: The damage on the Copras that were not tossed was still pretty significant
and required a lot of trimming, so I reduced the harvest #'s accordingly.
The good news? I'll have to be a bit stingy when using onions but I'll be ok until next year. At least the average size of the Red Wing improved. The Copra's also seemed to improve in size but the numbers may be misleading as so many of the bulbs were discarded.
This past season, I increased the amendments that I added to the allium beds but they were still rather small compared to those I've grown in the past. The average size of the onions back in 2014 (excluding the freakishly large Ailsa Craigs), ranged from 110-119 grams (3.9-4.2 oz) which, to me, is the perfect size - not too large, not too small.
Plan for Next Year
There are a few things that can be done to help minimize or eliminate leek moth damage to allium crops. Crop rotation - a practice I have always followed - is obviously a must. What I have not done in the past is destroy onion/garlic debris - it has always gone in the compost. While leek moth continues to be an issue in the garden, all the debris will now be burned. I'm hoping this makes at least a small dent in the leek moth population.
In future, vigilance in keeping the allium beds covered will be key. I'm actually in the process of replacing my finicky netting with cages which are sturdier and more reliable, especially in a windy area such as ours. I'm hoping to have those in place for all the allium crops next season.
I'm going to hold the course when it comes to both the quantity and varieties grown. Had the onions been a good size and leek moth not been an issue, I would have had more than enough onions to last until next season.
Although leek moth may contribute somewhat to the small size of the onions, I don't believe that they are the primary cause. I suspect it's more of a cultural issue...as in an issue with how I'm growing them, not the fact that I'm Canadian ;). I'll be saving my thoughts on that for a future post, however, as it affects other veg as well.