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
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
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
Luckily, these beetles typically attack
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.
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
Dave (and NF)
us with comments, suggestions and questions.