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| Ohio alfalfa hay endures summer stress, disease |
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Hay yields were only about half of what we would expect in the first cutting because the plants essentially needed to start over after the April freeze. The regrowth has been very slow because we have been so dry and the plants have used their root reserves to come back after the cold. If you took your first cut on about May 25, it would probably be best to wait until July 5 to harvest the second cutting. We would recommend you allow at least 35 days after the first cutting before you take a second cut; let the alfalfa go until it is full bloom.
Alfalfa is infested with potato leafhopper every year in Butler County, Ohio. Treatment usually just depends on how many are present and how quickly the hay is growing. As you might expect, the leafhopper are going to be a problem this year on many fields.
Damage has been done by the time you see the characteristic triangle shape yellow/purple color at the tip of the leaf. You have lost more than enough yield potential to pay for treatment when the signs show up; treat before. We would normally treat when you catch more leafhoppers, per ten sweeps, than plant height. So if the alfalfa is six inches tall and in ten sweeps you catch seven leafhoppers, you should treat.
This year we are suggesting you lower that threshold by a third. If the plant is six inches tall and you catch five, treat. If the plant is 12 inches tall and in ten sweeps you catch eight, rescue the crop. For potato leafhopper-resistant varieties of alfalfa, the economic threshold is three times as many leafhoppers.
There are a number of good products you can use. Be sure to watch the harvest restrictions. You sure don’t want to use a product that has a thirty-day harvest restriction if the hay is 12 inches tall. The latest recommendations are in Control of Insect Pests of Field Crops, Bulletin 545. Go on line at http://ohioline.osu.edu/b545 for a copy. |
| 7/5/2007 |
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