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Superintendent
David Davis
21262 Genoa Road
Linneus, MO 64653
Phone: 660 895-5121
FAX: 660 895=5122
Email:
DavisDK@missouri.edu
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October - Dec., 2007
Forage Systems Update
Vol 16, No. 4
Field Notes from Valerie Tate
One of the first big tasks I was involved with after starting work at FSRC
in 2001, was to seed alfalfa for an alfalfa integrated pest management project.
After six years of harvesting, counting plants, fertilizing and field scouting,
the project has concluded. Dr. Jerry Nelson initiated this project to
address the use of alfalfa with glandular hair (tiny hairs on the leaves
and stems) as a means of resisting potato leaf hopper feeding, as well as,
the level of potassium fertilizer and its effect on potato leafhopper
populations.
Two alfalfa cultivars were established, one with glandular hair and one
without, in four replications. Potassium fertilizer treatments were applied:
one treatment received no potassium for the duration of the experiment,
one received 125 pounds annually, in a split application, half in the spring
following the first harvest, and half in the fall following the last
harvest, and one treatment received 250 pounds of potassium annually,
in a similar split application. Finally, plots were divided into potato
leafhopper control methods. One third of the area was treated with
insecticide 7 and 21 days post harvest following the first harvest through
early August. One third of the area was never treated for potato
leafhopper and the final third of the area was treated only when the
potato leafhoppers reached economic threshold levels. All of the plots
were scouted weekly following the first harvest through early August.
The 2007 growing season was stressful for alfalfa. The warm weather in
April caused the alfalfa to break dormancy and begin growing earlier than
normal. It looked as though we were going to have a bumper alfalfa crop.
When the stems had about six inches of new growth, the hard freeze in
early April froze back all of that material, resulting in extreme stress
to the alfalfa plants. We experienced a reduced first harvest yield in
May due the April freeze and slow recovery of alfalfa following that
freeze. The weakened plants left many bare areas in the stand and weeds
invaded. Barnyard grass and pigweed ran rampant in the open canopy of
the aging stand. And once again the second harvest yield in late June was
lower as a result of the weed competition. The weeds were treated with
herbicides, but the third harvest was reduced by drought conditions in late
June and July. The final harvest, taken in September, was once again lower
than expected, a result of a stressful year on an aged alfalfa stand.
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