Trouble with Asparagus, Part 1

Asparagus is super easy to grow for the home gardener. Once the crowns are established, keep your bed weeded, give it lots of compost in the fall, and mulch it well for the winter. By mid-spring, you’ll be rewarded with a bountiful harvest!

But while very hardy, asparagus can be vulnerable to pests. In my garden, I just discovered a very destructive one. The good news is, the remedy can be simple! 

Read on for more about raising asparagus…

Ten days ago, my asparagus crop looked terrible. And it seemed to look worse with each passing day.

The first spears of the season are normally very robust. Starting around the first of May, the smooth asparagus tips are vigorously pushing out of the soil, greenish white and purple-pink around the edges, the spears a healthy dull green.

Not this year. The tips were curled over, and looked like they’d been chewed on, exposing the tiny buds that should turn into ferns. The stalks seemed to have tiny bites taken out of them. And whole spears were turning yellow and shriveling. 

Slugs?

Slugs are the usual culprit at our place when it comes to damaged asparagus. Only there were two problems with my slug theory: first, this month has been so dry I’ve seen exactly one slug in the yard instead of hundreds. And second, slug damage will affect individual spears, one at a time.

Slugs eating spears here and there doesn’t affect the vigor of new tips emerging. And at the beginning of a normal harvesting season, sometimes I’ll be picking 20 spears each day. And more on hot days.

What was odd about this May’s crop was that the entire crop seemed slowed down. There would be maybe seven or eight spears of harvestable size each day, all of them damaged.

It didn’t look like slugs, but I sprinkled some suitable-for-organic-gardens iron sulfate around the bed anyway, like a moat.

The next day, I was in the bed for more discouraging harvesting, when I saw two black and red spotted bugs about 1/8 of an inch long, parked on a small leaf next to a spear.

I’d read about pests that attack asparagus, but didn’t pay much attention. I’d never had a problem all our years raising asparagus. But now, I had to do something; my formerly vigorous crop was shriveling right before my eyes!

As soon as I was inside, I Googled asparagus beetles.

The first prompt was “Asparagus beetles in home gardens.” I clicked on it, and pulled up the University of Minnesota Extension site. I was raised in Minnesota, so this was my lucky link...

Photo: University of Minnesota Extension

Well, BINGO. The U of M Extension photo showed beetles that looked exactly like the pair I’d just seen.

On the site I discovered pretty much everything a home gardener would need to know about asparagus beetles. I’d already seen the beetles can wreak a lot of havoc. But I learned the damaged spears won’t develop properly into the fern stage, when the crown is rebuilding over the summer and fall months. As a result, your crowns can be permanently damaged.

Still, an organic remedy for an asparagus beetle infestation is simple...I'll be back next week for more about how to manage this pest!

Until then, have a wonderful week, and I hope you get to spend lots of time in your garden!

~Susan