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East-Central and Southeast Iowa Crop Information

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5/10/2012

CROP UPDATE

 

CORN

 

Time to Scout for Black Cutworms

 

            With the unusual weather the spring, it may be harder to predict when cutworms will start becoming an issue because some early moth flights may have been missed and the frost in April may have taken care of some of the early cutworms. Some cutting has already been reported in the southern third of the state, and an early moth flight may mean cutting could be occurring now in central Iowa. Cutworms are a sporadic problem and not likely to be an issue in most fields, but fields should be scouted so they can be treated if needed. A general rule of thumb is to treat if you find 2-3% of the plants cut and the worms are less than 3/4 inch long. With the high corn prices I’d lean towards the 2% figure. For more information see http://www.extension.iastate.edu/CropNews/2012/0425sissonjessehodgson.htm.

 


Spraying Fields with Emerged Corn

Many corn fields were planted April 25 - 27, 2012 did not receive intended soil applied herbicides before the corn began to emerge. In some cases, it was also the intention to apply 100+ units of liquid nitrogen fertilizer with the herbicide. And now emerged weeds are there too. So now what? UAN alone at up to 90 lb/A can be applied to corn up to about V4 (about 8 Inches) without much risk, although some burning will occur. However, most herbicides should NOT be included with the UAN or severe injury can occur. This may mean having to change the planned herbicide and/or nitrogen program. Bob Hartzler and John Sawyer address these issues in the article at http://www.extension.iastate.edu/CropNews/2012/0508hartzler.htm.

 

Stalk Borers on the Move

 

According to Growing Degree Day accumulations, base 41, stalk borers are starting to move from grassy areas into nearby corn fields along and south of Highway 34 (Burlington – Mount Pleasant – Fairfield area) and will soon start to move from grass into nearby corn fields north of Highway 34. Information on scouting and management can be found at the ICM News article at http://www.extension.iastate.edu/CropNews/2012/0508hodgsonsisson.htm. Local Growing Degree Day accumulations are shown at http://www.extension.iastate.edu/Pages/eccrops/stalkborer.html.

 

You can get an early “heads up” of the size of potential movement of stalk borers into corn by examining the grass for dead heads; the vast majority of dead heads will have been killed by stalk borers who are outgrowing the grass plant and moving into nearby corn. The more dead heads you find, the more stalk borers may be poised to move into corn.

 


SOYBEANS

 

What Population to Plant?

 

Thirty or forty years ago it may have made sense to plant soybeans at 150-200,000 seeds per acre. Part of the reason to shoot for high populations was to try to improve weed control. Soybean seed was also a lot less expensive, especially when bin-run beans were used. Today with the higher price of seed and better weed control tools, it makes less sense to overplant by 50-100%. Numerous studies have shown no advantage to populations of greater than 100,000 plants per acre. In a study at Crawfordsville last year we had harvest populations down to 35,000 plants per acre yielding as well as 120,000 plants per acre. I’m certainly not going to recommend a population of 35,000 for soybeans, but it does show the tremendous ability of soybeans to make up for reduced stands. A fact sheet with more information on soybean populations is available at http://extension.agron.iastate.edu/soybean/documents/OptimumPlantPop_000.pdf.

 

 

Bean Leaf Beetles are Back

 

          We haven’t seen much of a problem with bean leaf beetles for several years now, but with the mild temperatures this winter, we may have to contend with them again. Some early planted soybeans at the Crawfordsville Research Farm that are emerged have attracted a large number of beetles. Fortunately young soybeans can tolerate a lot of leaf loss without much of an effect on the final yield, but if stands are being reduced and/or about 2 beetles per plant are found on seedling (VE-V1) soybeans, an insecticide seed treatment may pay off. Seed treatments are also effective on bean leaf beetles. The beetles can do a lot more damage during pod fill in August.

 

 

 

 


FOR YOUR CALENDAR

 

SOUTHEAST IOWA RESEARCH and DEMONSTRATION FARM, Crawfordsville

SPRING FIELD DAY and 25th Anniversary Celebration (afternoon) &

SPECIAL SESSION FOR CCAs (morning)

JUNE 21, 2012

Details are posted at http://www.extension.iastate.edu/Pages/eccrops/meetserc.html.

 

NORTHEAST IOWA RESEARCH and DEMONSTRATION FARM, Nashua

SPRING FIELD DAY

JUNE 28, 2012, 1 – 4:30 p.m.

Details are posted at http://www.extension.iastate.edu/Pages/eccrops/meetnerf.html.

 

TECHNIQUES TO AVOID SPRAY DRIFT

July 17, 2012, Field Extension Education Laboratory (FEEL) near Boone, IA

Two half-day sessions (morning session repeated in the afternoon) (no cost to participants) will be conducted, focusing on:

- Nozzle selection/use with demonstration on spray table

- Balancing efficacy and drift

- Environmental factors, adjuvants and limitations, field demonstration, etc.

More information and registration will soon be available at http://www.aep.iastate.edu/.

 

 

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

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Last Update: May 10, 2012
Contact: Jim Fawcett fawcett@iastate.edu


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