Interest in planting
no-till into cover crops without the use of herbicide continues
to grow. It seems farmers from every corner of the globe are
realizing that the best way to build soil and manage weeds
is through cover crops. Check out the article Choosing
cover crops for no-till organic soybeans for more information.
Or click
here to download plans and build your own no-till cover
crop roller.
This year our farm grew some of the best cover crops I’ve
ever seen. We had thick stands of hairy vetch that measured
8,000 pounds of dry matter biomass per acre, more than enough
to supply the nitrogen requirements for our corn crop and
suppress early weed germination. The rye we no-tilled soybeans
into wasn’t as good, but still the beans look great.
Then ………. Well, then came lots of rain.
The moist green mat of rolled hairy vetch became a haven for
cutworms, which decimated the first planting. Sometimes it
seems just as we move forward several steps, we move backwards
one step. While most of our rolled/no-tilled corn fields worked
out great, I had one 3-acre field that was completely eaten
by cutworms. The little *#*##@@. At first I wasn’t sure
what was happening, but a little exploration in the soil early
in the morning turned up lots and lots of the critters.
I replanted the field and while the stand looks fine, I lost
some of the early weed control afforded by the mulch. The
replanting operation also disturbed the mulch, allowing more
weeds the opportunity to emerge. The passage of time gives
the weeds a head start, as well.
The cutworms seemed to like the cool, moist conditions under
the layer of plant matter left by the cover crop roller. It
gave them a great place to hide, and the corn was the perfect
food source. As I was replanting the field, I could see the
moths lifting off the soil as the pupated cutworms matured
and left the field. The replanted corn was virtually untouched.
So, it seems timing of the planting operation will be critical
to the system's success.
I’m sure the weather had a lot to do with the population
explosion of the worms. This isn’t a problem we’ve
had in the past. But then we don’t always get these
weather patterns. Several other growers in the area who were
no-tilling also had cutworm damage. Of course now the question
is: How can we design a management strategy to deal with this
pest in the future? A quick look at the ATTRA web site shows
the following practices and control measures as possible methods
to attack this problem.
Biological controls
Cutworm larvae have a number of natural enemies. Predators
include several species of ground beetles. Parasitoids include
tachinid flies and braconid wasps. Cutworms may also be attacked
by fungi, bacteria and nematodes. Understanding the biology
of beneficial organisms is imperative in order to use them
effectively as pest-control agents. For example, insect parasitic
nematodes like Steinerema carpocapsae or insect-infecting
fungi like Beauveria bassiana require adequate humidity
to be effective. Other predators include spiders, minute pirate
bugs, damsel bugs and lacewing larvae. Birds also prey on
cutworms, so do not assume the birds in the field are causing
the seedling damage. As with other pests discussed, farmscaping
is a recommended means of increasing the numbers of beneficial
predators and parasites that help to keep cutworms under control.
An ATTRA publication that is a good starting point for biointensive
IPM is Biointensive
Integrated Pest Management.
Alternative pesticides and applications
Scout for the presence of cutworm larvae early in the season,
and after destruction of adjacent habitats. Cutworms are best
scouted at night, when they are most active, using a flashlight.
Look for cut-off or damaged seedlings and dig around the base
of the plant to locate the larvae.
Bait formulations, sometimes using bran or applying rolled
oats with molasses containing Bacillus thuringiensis
var. kurstaki, have been known to effectively control
cutworm species when applied to the soil. Sprayed formulations
may have variable results with cutworms, as the worms may
not ingest enough of the toxin for it to be effective. Nightime
spraying of Bacillus thuringiensis has shown to be
more effective.
Research on the parasitic nematode species, Steinernematidae
carpocapsae, has shown it to be a very successful control
agent for cutworms, but make sure the soil is sufficiently
moist to support nematode populations
Click
here for the full ATTRA entry on cutworms.
Other recommendations
Other literature indicates that diatomaceous earth has some
effect on the pesky critters as well. While we haven’t
identified the practices we’ll try next year, we do
know we’ll be looking at the economics and efficacy
of each of these measures to determine what option has the
best chance of success. We’ll also be re-evaluating
our planting time, which is strongly linked to the flowering
time of the cover crop.
Many of the control measures listed above just aren’t
practical for this particular system, since they rely on clean
culture and the removal of the very material we are trying
to grow—namely the cover crop itself. Nature always
has a way of throwing new challenges in our path. Solving
one problem by changing parts of a complex living situation
can open new challenges.
But hey, the soybeans no-tilled into rye had no ill effects
from insects. Most of the corn was untouched by the cutworms
and the replanted corn is going strong.
There’s always a positive note. Let me know if you’ve
had similar experiences. Talk to you soon ……
From One Farm to Another
Jeff
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