Iowa State University Extension and Outreach

East-Central and Southeast Iowa Crop Information


April 22, 2004

Much of the following is quoted from Jim Fawcett, my counterpart to the west.

Oats Yield Best if Seeded By April 15

We are past the best time to seed oats, so any left to do should be done ASAP.  Oats are a cool season crop and yield best when planted in late March to April 15 so that flowering occurs before the hot part of the summer. Grain yields drop about 10-15% per week after April 15 in the central part of the state. Seeding rate should be about 30 seeds per square foot, which is about 2-3 bu/A. Best results are obtained with a drill. See Small Grain Production for Iowa-Spring (Pm-1497) at

Much of the oats seeding will be done as a companion crop for alfalfa and other small seeded forages. The seeding rate should be cut some to reduce competition with the forage. One to 2 bu/A of oats is commonly seeded with alfalfa.

Forage Seeding

Forages may also be seeded by April 15, but mid-April to late-April is a better seeding time for forages since they require soil temperatures similar to corn and soybean for germination. Soil temperature information around the state can be found at:

It is best to have forages seeded by late-April because as we get later into the spring, the soil surface tends to dry out more rapidly with the warmer temperatures, making successful establishment of forages more difficult. Seeding depth and seed-soil contact are critical for the establishment of alfalfa, smooth bromegrass, and other small-seeded forages. They should be seeded no deeper than 0.25-0.5 inches deep. Seed-soil contact can be improved by following the seeding with a cultipacker or harrow.

Alfalfa Weevil

It is also time to start scouting hay fields for alfalfa weevils in areas along and south Highway 30 and very soon north of Highway 30.  Alfalfa weevils begin to hatch at 300 Growing Degree days (GDD) Base 48 and quit feeding at 900 GDD Base 48. Because south facing slopes are somewhat warmer than average, they should be scouted beginning at 200 (south of I-80) - 250 (north of I-80) GDD Base 48.

Following are GDD Base 48 accumulations as of the end of the respective day.


April 15        240.5           202.5           210.5           149
April 16        261.5           221.5           232.5           166.5
April 17        285             241             252             181
April 18        310             265.5           276             199.5
April 19        323.5           276             287.5           209.5
April 20        335.5           282.5           297             214.5
April 21        343             288             302             219

For details on managing this insect, see pages 22-23 of the April 19, 2004 Integrated Crop Management Newsletter Also, watch for updated information on the development of this and other insects during 2004.

Stalk Borers Begin to Hatch

Stalk borers are beginning to hatch along Highway 34 (Burlington - Mount Pleasant area), and the hatch will move north.  In areas of fields with high grassy weed or giant ragweed pressure in 2003, spraying an insecticide just prior to egg hatch is one strategy to consider if corn will be planted this year.  Stalk borers begin to hatch at 575 Growing degree days base 41 and hatch is complete at 750 GDD Base 41.

Following are GDD Base 41 accumulations as of the end of the respective day.


April 15        438             349.5           374.5           282
April 16        466             374             403.5           306
April 17        496.5           400.5           430             327.5
April 18        528.5           432             461             353
April 19        549             447             477.5           366.5
April 20        568             457             491.5           375
April 21        582             466             500             383

For more details on managing this pest, see


If you have any questions, please feel free to contact the Iowa State University Extension Office.

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Last Update: April 22, 2004
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