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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

October - Dec., 2007
Forage Systems Update
Vol 16, No. 4

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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