Managing Cover Crops Profitably - Valley Crops Home

• Subterranean Clover (Trifolium
subterraneum)—A self-reseeding annual
legume, fall-planted subterranean clover carries
the same risks as crimson clover with soilborne
diseases and nematodes. It suppresses
weeds more effectively in the deep South,
however, because of its thick and low growth
habit. Subclover supports a high level of
beneficial insects.
• Cahaba White Vetch (V. sativa X V.
cordata)—This cool-season annual legume is a
hybrid vetch that increases soilborne diseases
yet suppresses root-knot nematodes. It
supports beneficial insects, yet attracts very
high numbers of the tarnished plant bug, a
serious pest.
• Buckwheat (Fagopyrum esculentum)—
A summer annual non-legume, buckwheat is
very effective in suppressing weeds when
planted thickly. It also supports high densities
of beneficial insects. It is suitable for sequential
planting around non-crop areas to provide
food and habitat for beneficial insects. It is
very attractive to honeybees.
A well-planned crop rotation maximizes
benefits and compensates for the risks of
cover crops and cash crops. Planting rye in a
no-till system substantially reduces root-knot
nematodes, soil-borne diseases and broadleaf
weeds. By using clovers and vetches in your
fields and adding beneficial habitat in noncultivated
areas, you can increase populations
of beneficial insects that help to keep insects
pests under control. Mixed plantings of a small
grains and legumes combine benefits of both
while reducing their shortcomings.
As pesticides of all types (fungicides,
herbicides, nematicides and insecticides) are
reduced, the field environment becomes
increasingly resilient in keeping pest outbreaks
in check. Plantings to further increase
beneficial habitat in non-cultivated areas can
help maintain pollinating insects and pest
predators, but should be monitored to avoid
build-ups of potential pests. Researchers are
only beginning to understand how to manage
these “insectary plantings.”
Editor’s Note: Each cover crop listed here,
except for cahaba vetch, is included in the
charts (pp. 48 and following) and is fully
described in its respective section. Check the
Table of Contents (p. 6) for location.
—Sharad C. Phatak
Nematode Management
Nematodes are minute roundworms that interact
directly and indirectly with plants. Some species
feed on roots and weaker plants, and also introduce
disease through feeding wounds. Most
nematodes are not plant parasites,but feed on and
interact with many soil-borne microorganisms,
including fungi, bacteria and protozoa. Damage
from plant-parasitic nematodes results in a breakdown
of plant tissue, such as lesions or yellow
foliage; retarded growth of cells, seen as stunted
growth or shoots; or excessive growth such as
root galls, swollen root tips or unnatural root
branching.
If the community of nematodes contains
diverse species, no single species will dominate.
This coexistence would be the case in the undisturbed
field or woodland described above.
In conventional crop systems, pest nematodes
have abundant food and little environmental resistance.
This can lead to rapid expansion of plant
parasitic species, plant disease and yield loss.
Cropping systems that increase biological diversity
over time usually prevent the onset of
nematode problems. Reasons may include a
dynamic soil ecological balance and improved,
healthier soil structure with higher organic
matter. In Michigan, some potato growers report
that two years of alfalfa to limit nematodes
between potato crops is sustainable for them
because of improvements to potato production
and lower pest control costs (20).
MANAGING PESTS WITH COVER CROPS 31