soybean field
LESSONS LEARNED: Review the 2018 growing season for each field and make informed decisions for 2019 on variety selection, seed treatments and weed control.

Looking back and forward

The challenges of 2018 can help with 2019 planning.

With 2019 around the corner and the 2018 crop season having been a bumpy ride at best, it’s tempting to keep our eyes locked on the road ahead.

As many customers and clients have taught me over the years, focusing on what’s in front takes priority, but the rearview mirror has a purpose, too. So, let’s look back at a few of the challenges we saw this year and see if the experience helps going forward. We’ll focus on soybeans but some of the concepts work across our other crops, too.

Cool, wet springs new norm?
It seems like we fight our way through cold and wet planting seasons more often than not lately, and 2018 didn’t do anything to change that impression. With planting dates shifting earlier over time, it makes sense that cool, wet weather may be a more consistent challenge.

Another impression I took away from 2018 was that variety placement and the right seed treatments can make a big difference during stand establishment and beyond. Is the difference enough? Do the economics of seed treatments work with these bean prices? Let’s look at the fungicide aspect first.

If you are planting in the early part of the window (if soil conditions are suitable, during the last week of April for the southern two-thirds of Iowa and the first week of May for the northern third of the state), you should strongly consider using seed treatments.

Cold soils slow root development, making the stand more susceptible to root-rotting pathogens. And if there is a history of seedling diseases from phytophthora, pythium, rhizoctonia or fusarium, fungicide seed treatment is recommended.

When we move on to the other types of seed treatment, the discussion gets deeper, so we’ll hit those in upcoming months.

How fast does SCN develop?
The warmer, drier weather that finally came in May was great for our moods and our crops. Turns out it was good for something else: soybean cyst nematode. It typically takes 35 to 42 days (or more) after planting for the first adult SCN females of the growing season to develop and appear on roots.

This past June, ISU’s own SCN expert, Greg Tylka, wrote an article about an interesting (and not in a good way) observation related to the improved growing conditions at the time: “Soybean plants from two fields in central Iowa were brought to Iowa State University on June 5, and numerous adult SCN females were observed on the roots. The soybeans were planted on May 10.”

June is usually pretty wild with all the scouting and spraying going on — my excuse for not really catching what that meant. Tylka also wrote, “The appearance of SCN females on soybean roots just 26 days after planting is as early as I have seen.” That got my full attention; he’s been studying SCN in Iowa since 1990. “As early as I have seen” carries a lot of implications: none good.

A few more key points from Tylka’s recent articles might help guide your SCN management plans:

 SCN tends to do best in warm, dry growing conditions, so the great May weather factored heavily in SCN females developing on plants from those two fields in 26 days, rather than the more typical 35 or more.

 Finding white, adult SCN females on roots indicates the first generation is being completed — way ahead of schedule if the two central Iowa fields are any indication. SCN continues to reproduce in successive generations throughout the growing season into the fall. With the warm and dry weather that much of Iowa had for a good chunk of the summer, more generations of SCN may have been produced in the 2018 growing season than in seasons with cooler temperatures.

 Each SCN female produces 250 or more eggs. When numerous generations occur in a single growing season, SCN population densities (numbers) can “blow up” to disastrous proportions in a single year.

 The beans from those two fields were two different SCN-resistant soybean varieties. It’s not uncommon to find a few SCN on the roots of SCN-resistant soybean varieties, but Tylka said it was “troubling to see so many SCN females on the roots of resistant soybean varieties so early in the season.”

What can we do going forward? Glad you asked. Rather than try to pack an abbreviated answer into this article, check out the recommendations from ISU,  Soybean Research & Information Initiative and The SCN Coalition

Gall what?
Text-messaging can be useful, with the added fun of auto-correct derailing things once in a while. In western Iowa, an unexpected new pest started showing up in early summer. No experience or training over the years as an agronomist, firefighter or EMT prepared me to help a couple of friends who texted about having “gallstones” or “gallbladders” in their soybean field borders, but I gave it a shot anyway.

We traded wisecracks about their needing new reading glasses to type and my sketchy medical advice, and then decided the topic was the soybean gall midge. For that topic, I had no advice, just questions.

Hats off to the region’s farmers and agronomists for the great scouting work they did last summer. Information they shared was critical to ISU and industry entomologists, as they began working on the soybean gall midge.

Note the phrase “began working.” This insect blindsided 66 counties in Iowa, Nebraska, Minnesota and South Dakota this year. University and industry experts are working on it, but to get any sort of reliable research data, it could be a couple of years.

ISU entomologist Erin Hodgson is taking the lead for us on gall midge and will be sharing the latest information at Crop Advantage Series meetings across Iowa throughout January. In addition to those, she and her team will keep us up to date through ISU blogs, newsletters and Twitter, which you can find through her ISU webpage

Field research may take some time, but stay tuned to the meetings and other resources above as new information is coming in quickly. Experts from the U.S. and Japan just identified the adult stage of this pest a few weeks ago.

For now, control recommendations just can’t be made on a pest that is this new with so little known about it. While the natural reaction to having dealt with something like this last season is to fight back next season, nobody knows how to prepare us for it yet.

Outside of legitimate researchers looking for help with replicated trials, if someone approaches you with the “answer” to knock out the soybean gall midge, you know the drill. Hodgson has a few things to share this winter, but as of now, it sure doesn’t look like any insecticide recommendations are in the cards.

Speaking of legitimate researchers, ISU and the Iowa Soybean Association are considering some different field trials. If you are interested in participating in the research, reaching out to ISA or Hodgson is a great place to start.

Have a great holiday season!

McGrath is the on-farm research and Extension coordinator for the Iowa Soybean Research Center at ISU. Contact him at [email protected].

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