Integrated Crop Management News

Links to these articles are strongly encouraged. Articles may be republished without further permission if published as written and if credit is given to the author, Integrated Crop Management News, and Iowa State University Extension and Outreach. If articles are used in any other manner, permission from the author is required.

Producers and Applicators Legally Responsible to Heed Preharvest Intervals for Treated Soybean

August 30, 2008
Table of insecticides labed for use in Iowa soybeans and days to harvest after application

By Marlin E. Rice, Department of Entomology

Based on reports from my Extension agronomist colleagues, hundreds of thousands of soybean acres were sprayed with insecticides during July and August for control of soybean aphids and bean leaf beetles. All insecticides listed in Table 1 have at least a 21-day preharvest interval, and several have moderate intervals of 30 days or very long preharvest intervals of 60 days. The preharvest interval is the minimum number of days a farmer must wait before harvesting a treated crop.

Factors Needed to Maximize Corn Yield Potential in 2008

August 30, 2008
Table of predicted corn yields for different regions of Iowa

By Roger Elmore and Lori Abendroth, Department of Agronomy

The start of the 2008 growing season was extremely difficult for planting and crop establishment, however, environmental conditions since have been fairly good. What type of yields should we expect from this turbulent season? What will it take to obtain high yields from this point in the growing season forward? And, the other side of that question – what don’t we want to see happen?

Soybean Top Dieback Shows Up in Iowa Again

August 25, 2008
Close view of top dieback

By XB Yang, Plant Pathology Department, John Saywer, Agronomy Department
Extension field agronomists report the occurrence of soybean top dieback in northeastern Iowa soybean fields this week. Soybean top dieback symptoms have shown up occasionally since it was first reported by Jim Fawcett and Jerry Long in Cedar County a few years ago. Last year it was also found in eastern and central Iowa.

Pre-harvest Restrictions for Fungicides

August 24, 2008
Table of corn/soybean foliar fungicides and their preharvest intervals

By Daren Mueller, Department of Plant Pathology
With the buzz of airplanes still being heard out in the countryside and September within sight, this is just a quick reminder to growers about the pre-harvest intervals (PHI) for fungicides applied to corn and soybean. Last month in Kansas, some wheat was embargoed when fungicide levels were questioned until tests could be completed to determine residue levels.

Changes in Retail Fertilizer Market Impact Producers

August 22, 2008

By Roger Ginder, Department of Economics
Major change in retail fertilizer markets over the past three years include price volatility and price increases. But, in addition to the unprecedented price volatility, basic changes in the trade practices at the manufacturing, wholesaling, and retail levels in the fertilizer value chain are affecting producers.

Plan for 2009 Crop Year by Managing Flooded Soils

August 11, 2008

By Mahdi Al-Kaisi, and Stephen Barnhart, Department of Agronomy
Approximately 1.2 million acres of Iowa farm land affected by flooding early this year have not been planted to any crop. There are potential economic and soil environmental consequences of leaving these soils unattended. The long-term damage to soil and water quality in areas of significant flooding need to be considered when planning for next season’s crop.

Reviewing Decision Thresholds for Pest Insect Control

July 30, 2008
Image of soybean aphids on a bean leaf

By Jon Tollefson, Matt O’Neal, and Marlin Rice, Department of Entomology


Three tools need to be understood in order to make decisions regarding the control of insects found on crops: damage boundary, economic injury level, and the economic threshold. The existing values for these three variables are now being questioned with the increase value of Iowa’s row crops and the cost of controlling the pests. This article reviews the use of these tools in regards to soybean aphid control.


Preventative vs. Curative Fungicides

July 29, 2008

By Daren Mueller and Alison Robertson, Department of Plant Pathology

We have received several questions about selection of fungicides, especially with regards to deciding between “curative” and “preventative” fungicides. People want to know if they should be applying a strobilurin fungicide, triazole fungicide, or a premix of both. 

Is that Common or Southern Rust Showing up in Iowa Fields?

July 22, 2008
Image of lesions characteristic of common rust

By Alison Robertson, Department of Plant Pathology


Is that common or southern rust showing up in Iowa fields?  Chances are it is common rust. It has probably been too cool and wet so far this growing season to see southern rust. Symptoms of the two rusts are very similar but there are subtle differences.


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