Q&A

DEAR NEW FARM:

I busted my butt three years ago digging 14-inch (deep and wide) trenches in my rocky Pennsylvania soil, picking out all the rocks, and mixing in compost so that my family could enjoy a bounty of fresh asparagus in the spring.

This year the crop is lackluster and many of the spears appear out of the ground twisted and tattered with shiny black eggs on them. What is it and what can a do about it, organically speaking?

Asparagus distressed in Pennsylvania

 

DEAR DISTRESSED:

Put down the spear and step away from the bed. We asked our research agronomist Dave Wilson. Here’s what Dave had to say:

It's the Asparagus Beetle (Crioceris aspragi, aka C. duodecimpunctata). The female beetles lay rows of their dark brown or shiny black eggs on end; the eggs are glued to the stems and young spears. Both the adults and larvae chew holes in the green spears, causing a brown blemish. Later the beetles attack the stems and strip the leaves from the fronds leaving the branches bare. The eggs are probably from the first generation, and there can be up to five generations of beetles per year.

The eggs hatch in three to eight days. The larvae hatch out and crawl up the plants and feed for up to two weeks, then they crawl back down to burrow into the soil just below the surface and there they pupate. They emerge from the soil as adults in about 10 days to go out, have some fun with their mates, and lay eggs on stems and foliage to repeat the cycle over again.

Luckily, these beetles typically attack only asparagus.

Some suggested management practices:

  • A clean garden is the best prevention. Eliminate any places the beetle can hide, and till the soil to rouse them from hibernation.
  • Grow tomatoes with your asparagus. Asparagus beetles do not like tomato plants, and asparagus plants kill the nematodes that often attack tomatoes. Intersperse the plants so that they protect each other. Yeah, biodiversity!
  • Cheesecloth netting can protect tender young asparagus. In early spring, cover asparagus spears with floating row covers of Remay until the end of harvest.
  • Birds, chickens, and ducks love to eat the asparagus beetle, and ladybugs and the chalchid wasp feed on the larvae. Cut the asparagus shoots every 2 or 3 days, before the beetle eggs can hatch, and wash off the eggs.
  • Dust asparagus with bone meal or rock phosphate. Surround (kaolin clay) might work as well.
  • The spotted asparagus beetle cannot fly in the morning and can be handpicked. Handpick the beetles and larvae especially in early spring when this has the greatest impact on reducing the second generation of beetles.
  • Where the beetles are numerous, spray pyrethrins. (PyGanic) pyrethrum - a botanical insecticide derived from chrysanthemums. (Conventional chemical control includes Carbaryl, Rotenone or Malithion).

    For future consideration, it is recommended to remove plant debris in winter to prevent adults from over wintering.

 

DEAR NEW FARM AND DAVE:

Come to think of it, we didn’t do a very good job of cleaning up our plant debris after last season, and we mulched the crowns fairly heavily with straw. We took your advice and planted this year’s tomato crop right in front of the asparagus beds.

Less distressed

 

DEAR LESS:

Some thoughts about companion planting for your asparagus: It’s reported that petunias repel asparagus beetles, leafhoppers, certain aphids and tomato worms. Also, the leaves can be used to make a tea to use as a bug spray. So you may want to consider planting some petunias in among your asparagus plants.

One problem with this in our climate is that in order to get early effect against the first generation of asparagus beetle, the petunias would have to be planted early enough in the spring, which in our area may leave them vulnerable to frost damage. So to employ this as a control, the petunias would have to be covered when there is a chance of frost. This can be done easy enough on a small scale but not on a large scale. If you used the Remay as cover for the young asparagus plants then that Remay cover could second as a frost barrier for the petunias, giving you both a physical barrier toward the asparagus beetles with the Remay and a phyto-chemical repellant toward the asparagus beetle with the petunias. In a southern, more-temperate climate, there would not be the danger of frost so the petunias would not need the cover.

Many plants have natural substances in their roots, flowers, leaves etc., that can alternately repel and/or attract insects, depending on your needs. The theory behind the practice of companion planting is that the repellent action of the companion plants will impart some degree of protection to other plants. Most plants considered as companion plants are herbs or other plants that have volatile odors. In Africa, some cropping systems use this concept. In certain areas they call it the "push-pull" method, where certain companion plants are planted with the food crops. These companion plants act to "push" or repel certain insect pests away. At the same time, other plants are planted to the outside of the field away from the cash crops to attract or "pull" the insects toward them. I don't think this practice can be depended on as a stand alone practice that will give total control of an insect pest, but in a "systems" approach it can be used along with the other methods mentioned earlier to cumulatively contribute a certain degree of efficacy.

The scale of application also needs to be considered. This interplanting may be more applicable and practical to gardeners and small-scale CSAs and farm patches but perhaps not on a large scale because of the scope of labor needed. In a small garden and/or CSA setting, the herbs and flowers can have a "dual" purpose; one to be used for their properties as a companion plant, and two to fetch some income for their intrinsic value as an herb or a cut flower or plant.

Good luck,
Dave (and NF)

 

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