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Are These Beetles Devouring Your Asparagus?

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You Can Control Asparagus Beetles Naturally With These Simple Methods.

I had never heard of asparagus beetles until this year, when we planted our first asparagus bed. I heard they weren’t all that common, and figured they probably wouldn’t bother our new bed, since we had never grown asparagus before.

I was wrong!

Our beautiful new asparagus plants are now covered with little bugs and gross, slimy little gray larvae. Mother Earth News to the rescue!

Check out this article for some tips on controlling these destructive little bugs – without harming other, more beneficial bugs that may be in your asparagus patch:

What Are Asparagus Beetles?

C. duodecimpunctata
Spotted asparagus beetle (C. duodecimpunctata). (Photo credit: Wikipedia)

The common asparagus beetle (Crioceris asparagi) is the most prevalent asparagus pest that damages young asparagus spears. Overwintering as an adult, this slender, elongated beetle bears four white or yellowish spots on its wings, is reddish underneath and on the wing edges, and has a dark-red thorax. It is 1/4 to 1/3 inch long.The spotted asparagus beetle (Crioceris duodecimpunctata) is also quite colorful. In the western United States, the spotted asparagus beetle is bright pumpkin orange with tiny black dots on its wings. (For more on the less common spotted beetle, see the full article here.)

Asparagus Beetle Damage

In early spring, just as asparagus spears are breaking the surface, adult asparagus beetles emerge after overwintering in plant debris. They begin feeding on the earliest spears, causing them to crook like a shepherd’s crook. Soon after mating, the females lay tiny, dark, elongated eggs on the little spears and new foliage, which stick out at right angles. Adults dine on the main spears, while the grayish-green, soft-bodied larvae feed on spears and foliage. Indentations caused by the feeding are brown in color and will decrease the vigor and size of affected spears. Severe feeding reduces the vigor of the asparagus plants.

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Asparagus Beetle Reproduction

Soon after emerging in spring, asparagus beetles lay eggs on emerging spears, which hatch in three to eight days. The small soft-bodied, grayish grubs feed on the tender new growth in spring. Later in summer, eggs and larvae can be found feeding on asparagus foliage. When the grubs mature after about two weeks of feeding, they drop to the ground and pupate inside an earthen cell for seven to 10 days before emerging as adults. In most climates, there are two generations each year, but in warm climates there may be as many as five generations of this asparagus pest.

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Natural Enemies of Asparagus Beetles

Birds often eat asparagus beetles and larvae, which appear during nesting season when birds need more protein. Lady beetles eat young larvae, but the most effective predator is small black Eulophid wasp (Tetrastichus asparagi),which eats asparagus beetle eggs early in the season, and lays its eggs in asparagus beetle eggs in summer.

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Organic Asparagus Beetle Control

When dealing with the asparagus beetle, organic control methods can be quite effective. One key is to remove plant debris from the patch in fall and compost it in an active compost pile. Larvae and adults can be removed by hand. When handpicking, place a pail of water on the ground, and many beetles will drop into it when knocked from the plants. Beneficial wasps will parasitize beetle eggs. Chickens also do a good job of gathering asparagus beetles when allowed to forage in the patch in late summer. In severe situations, you can get good organic control of asparagus beetles by spraying plants with neem early in the season, when populations are modest. Do not use neem or any other pesticide if small black or green wasps are present in your asparagus patch.

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Find more tips for controlling asparagus beetles naturally at Mother Earth News.
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