Keep An Eye On Corn And Soybean Fields In July

Keep An Eye On Corn And Soybean Fields In July

ISU Extension agronomist reminds you to keep on top of problems, continue to scout crops during 2014 growing season.

Welcome to monsoon season in Iowa…or so it seems with the heavy rainstorms Iowa has received the past few weeks. "Of course, it can all change in a matter of days and hot, dry weather could dominate July and August," notes Iowa State University Extension field agronomist Clarke McGrath. "The good news is that our subsoil is pretty well completely recharged in most of the state; subsoil moisture reserves are now greatly improved compared to earlier this year. Only three months ago, 82% of Iowa was in some form of drought, according to the national Drought Monitor website."

WATCH FOR SPRAY DRIFT: There is an increased risk of corn and soybean foliar diseases developing due to all the rain so far this growing season. Also, be careful spraying pesticides during this time of year; avoid drift problems onto nearby non-target fields, yards and gardens.

The bad news is that there are also fields that have been flooded from all the recent heavy rains. "Some of these acres are lost for the year," says McGrath. "Significant soil erosion has occurred as well. Let's hope for periodic rainfall through the rest of the growing season for those who need it—in liquid rather than ice. Our hail plots (where we are studying replant vs leaving marginal stands) are telling us that while damaged plants are resilient, sustained wet weather is a recipe for disease. These hailed-upon fields could use some drier weather as well."

Its pesticide drift season, be careful as you spray
In addition to visiting farmers' hail-damaged fields and some flooded fields this week, and answering questions and providing information to farmers to help them with replant decisions at this late date, McGrath has also been answering "the usual questions" he gets at this time of the year—the last week or so of June.

That is, questions about weeds, disease and other scouting issues and wrapping up the first round of soybean spraying.  Drift and contamination calls are now coming in at a higher rate, he says. "There are many ways to handle pesticide drift issues and attempt to work them out amicably," adds McGrath. "The key to the process is opening up dialogue and cooperation among all parties involved as soon as possible after discovery of suspected drift symptoms or injury on nearby crops or gardens or whatever."


If needed, the Iowa Department of Agriculture and Land Stewardship has pesticide investigators that can be brought in to look at the situation. "We get a lot of questions about who to call at IDALS and what they can and cannot do in these cases," says McGrath. "Now we have a concise resource we can share with clients. IDALS has recently printed copies of their new pesticide investigation and enforcement brochure. You can make copies of the attached flier."

Scouting tips to keep on top of problems in your fields
Turning to another timely topic, McGrath reminds farmers to keep scouting their fields and watching for problems. "The first thing you need to do is know your fields," he says.

Know your fields. Before you go into the field to do any crop scouting, there are several key pieces of knowledge you should be aware of in order to get the most out of your time inspecting fields, he points out.

1. Know the history of your fields and consider the impact of details such as herbicides applied the previous year.

2. Know the characteristics of a healthy crop, and then look for signs of crop damage such as thinning, stunting, early dying, discoloration or damaged stems or leaves. Each disease and insect will cause specific damage to a crop, so it is also important to be familiar with the symptoms of a wide variety of infestations and diseases, including pests and their life cycles.

3. Analyze the weather, crop stage, weed development and pest biology so scouting occurs at the right time.

4. When scouting for pests, be aware that different sampling methods are appropriate for different pests. Keep track of the facts. Record keeping is perhaps the most important step in crop scouting. Records should include: field location; how the samples were collected; data collected at each site; plant counts; row spacing; stage of crop development; and crop damage, if it is present. Use clear language so you can benefit from the report year after year.


In the past, record-keeping was done by notebook or scouting forms, but new technology is making this easier. Smartphone apps are continually evolving, and a multitude of agricultural apps are available as tools for crop scouting. Farm Progress recently introduced an app to help identify weeds, which allows you to search by month, location, crop and weed type.1 Other crop scouting apps, such as Trimble's "Connect Farm" app, allows farmers to map field boundaries and input scouting information. 

Drones or UAVs can also be used as a scouting tool to take aerial photos of crops. They can be helpful in identifying areas of crop stress as well as weeds or pest infestations.

Know your weed problems. McGrath says he's getting a lot of questions this summer about weeds becoming resistant to herbicides. "Considering that resistant weeds are an increasing problem but also considering that they have been around for decades, this is an even better reason to keep good scouting records," he says. "More recent developments such as glyphosate-resistant giant ragweed, marestail and waterhemp have changed the game. This is where good scouting of fields and accurate record keeping can help raise our batting average. If a patch of weeds is consistently resisting herbicides, it might be time to try a different approach to managing them."

Always a good investment. Thorough crop scouting has many benefits, McGrath notes. Some of those key benefits: improved weed, insect and disease control, an understanding of opportunities for improved equipment performance, and the development of accurate records of each fields' history. When these benefits come together with good management, improved yields are the result.

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