Scouting for soy (or corn) in the summer heat and humidity isn’t high on everyone’s list of fun activities, but it’s still worth it. There is always a long list of things to watch out for, like weed breakouts, pests, and disease outbreaks. Abnormally dry weather, as much of the condition suffers, can bring additional challenges to pests that warrant increased vigilance – for example, spider mites and grasshoppers.

In addition to good pest management against the challenges mentioned above, testing for beans can offer a few additional benefits. Farmers and agronomists who spend a lot of time in the field – and these are the people who have taught me more about Scouting than any course or book – often look beyond the bugs, weeds and trees. diseases.

Examine the progress and performance of different genetics, observe the performance of planters, check terraces and streams for repairs or weed problems, and assess soil problems like soil compaction or erosion are also part of a long list of what many follow on screening trips.

Pack a shovel

While we’re outside sweating and looking at the bean fields, we might as well dig a little deeper – literally, because that’s where we can (OK, probably) find our biggest challenge. And what is this challenge, the most damaging soybean pathogen in Iowa and across the United States? You probably guessed it already; Soybean public enemy No. 1 is the soybean cyst nematode.

As Iowa State University SCN expert Greg Tylka pointed out in his recent ICM (Integrated Crop Management) News article: “Gaining ground in the battle against SCN starts with knowing the situation. of SNA in every field where soybeans are grown, and we can begin the quest for knowledge by checking soybean roots now. ”His article is full of good information and can be viewed on the Integrated Crop Management website. ‘ISU.

Fields infested with SCN may appear healthy above the ground, but adult female SCNs will be present on the roots of infected plants. To check for the presence of SCN on soybean roots, dig rather than pulling the roots out of the soil and gently shake the soil from the roots. If the soil does not fall easily from the roots, break up large clods of soil and crumble the soil from the roots by hand. Adult SCN females mainly form on newer soybean roots. So be careful not to remove the smaller, younger soybean roots while removing the soil from the root ball. Adult females are round, white objects visible to the naked eye, and are much smaller and lighter in color than the nitrogen-fixing nodules that form on soybean roots.

While we may have good intentions of treating the NCS with post-harvest soil sampling, experience tells us that the window is small at this time of year and the task may disappear from the radar given all other fall tasks to be completed. If we think about it now and work on a plan with our local agronomists by harvest, there’s a good chance it will, especially if digging reveals evidence of SCN.

I’m planting SCN resistant beans, so why bother digging?

A point well taken, since we have managed to manage SCN for many years by growing SCN resistant soybeans in rotation with maize. But for over 30 years we have relied almost exclusively on SCN resistance genes from the same breeding line, named PI 88788. You probably have a good idea of ​​what happened after using the same tool on a pest. for so long. The SCN Coalition says, “Take the test and know your numbers” because managing SCN involves more than just planting a variety resistant to SCN. You need to know your numbers, and here’s why:

• Almost all varieties resistant to SCN have the same source of resistance: the aforementioned PI 88788.

• SCN populations adapt and breed on PI 88788 – they become resistant to resistance.

• As the reproduction of SCN increases, the yield decreases.

So even in fields using genetics resistant to SCN, we should test and know our numbers regularly, to paraphrase the SCN Coalition. Before harvest, sit down with your local agronomist to set up rounds of nematode sampling based on adult SCN females invariably found in many fields during excavations, coupled with new active management recommendations from the SCN Coalition .

Of all the mid-season and end-of-season soybean management topics that we have covered in Soybean Source columns over the past few seasons, the SNA summer root digs and fall sampling have been of great importance. good chance of being the most important. Good luck, and don’t forget the sunscreen, bug spray, something cold to drink… and your shovel.

McGrath is an extension field agronomist at Iowa State University and on-farm research and extension coordinator for the ISU Iowa Soybean Research Center.