Cover Crops Lure Beneficial
Insects, Improve Bottom Line in Cotton
SARE-funded researchers in Georgia seeking
new ways to raise healthy cotton—traditionally
one of the most pest-plagued, thus one of
the most chemically treated commodities—focused
on attracting insects that prey on damaging
pests. A group of scientists from USDA’s
Agricultural Research Service, the University
of Georgia, and Fort Valley State University
planted a variety of flowering cover crops
amid cotton rows to test whether their blooms
would bring earworm- and budworm-killing
predators to minimize the need for insecticides.
Working on seven mid- and southern Georgia
cotton farms, the team eliminated one insecticide
application by planting legume cover crop
mixes that brought predators like the pirate
bug, big-eyed bug, and fire ants to prey
on damaging worms. Using conservation tillage
to plant cotton amid the cover crops also
improved yields—on average, 2,300 pounds
of seed cotton compared to 1,700 pounds on
control plots. (Seed cotton weight includes
lint and seed before cleaning.)
Growing a mix of balansa clover, crimson
clover, and hairy vetch prolonged cover crop
flowering from early March through late April
and had the added benefit of out-competing
weeds. “With this range of blooming,
we’re able to start building the beneficial
populations early in the season,” said
Harry Schomberg, an ARS ecologist and project
leader. “Reducing one application of
insecticides could be pretty substantial
on a larger scale like 100 acres.”
Glynn Tillman, an ARS entomologist who collaborated
on the project, found that predator bugs
moved from the cover crops into the cotton
early in the season, providing more worm
control. Moreover, the conservation tillage
and cover crop residue resulted in more beneficial
soil organisms that likely contributed to
better cotton yields.
To demonstrate their results, the team went
beyond holding field days. Tillman introduced
the promising system of cotton, cover crops,
and conservation tillage to hundreds of thousands
attending the Sun Belt Ag Expo in Moultrie,
GA. “It was well received,” Tillman
said, adding that she fielded many questions
from growers, some calling later for more
information on adopting cover crops into
integrated pest management systems for cotton.
Schomberg cautions that the system requires
careful management. In the fall, they seeded
alternating strips of cereal rye and legume
cover crops. In the spring, they killed the
15-inch-wide strips of rye with an herbicide
and followed by planting cotton in the same
rows, using conservation tillage. “Spacing
is key,” he said. “You have to
think about and tinker with your planting
equipment.” Killing cover crops, he
added, is easier than killing a diverse population
of winter weeds.
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