Degree Days - A Warm Start to Summer

June 24, 2009

By Rich Pope, Department of Plant Pathology

Iowa weather took a turn to the warmer in mid June. Although uneven corn stands are still easy to find, particularly in corn following corn, the warm days have allowed plants to green up and make up in development.

accumulated degree days in Iowa since May 1 2009

Last week I wrote that the cold-limited crops only put in a 4- to 5-day week; this week produced some overtime. The average degree-day accumulations for the week of June 14-21 netted nearly one extra normal June day of  performance.

A few early planted southwestern Iowa soybeans fields have just begun to flower, marking growth stage R1.  On that note, producers in Iowa should begin monitoring fields for soybean aphid.  The first Iowa sitings of aphids were about three weeks ago near Decorah; numerous reports of small populations have been noted in central Iowa.  None of these reports are near the treatment threshold  - 250 aphids per plant and the population increasing - but monitoring important nonetheless.

Rich Pope is a program specialist with responsibilities with Integrated Pest Management. Pope can be contacted by email at or by calling (515)294-5899.

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