Lately we’ve seen a few soybean diseases show up within our growing region. It’s important to be able to differentiate between diseases that may show similar symptoms out in the field, such as brown stem rot (BSR), sudden death syndrome (SDS) and charcoal rot. While a disease like frogeye leaf spot may be easily distinguishable, it may be harder to verify what these other diseases are without taking a closer look into the plant.
SDS and BSR are similar looking when they start to show symptoms on the leaves, but when you break the stem of the plant, BSR will have a brown inner pith, compared to a more normal, healthy looking stem on SDS. You may also find blue growths on the roots of an SDS affected plant. Charcoal rot has more of a yellowing leaf symptom than interveinal chlorosis and typically shows up when the plant is stressed from heat and drought. Charcoal rot also creates small dark spores in and around the stem of the plant.
Crop rotation, choosing varieties with tolerance, average-to-later planting dates can all help to minimize issues with these diseases later in the season. Seed treatments will not help with BSR or charcoal rot, but ILEVO can help with SDS susceptible areas.
It is necessary to have a game plan if you have had a history of seeing any of these diseases present on your acres. Thinking ahead with variety selection, crop rotation, as well as other management techniques can help you maximize yield through susceptible fields.
- Jonathan Williams, Southern Region Product Agronomist
While walking in corn fields this past week I noticed the corn aphid population has dramatically increased. A few weeks ago it was hard to find any corn aphids, but now they are making walking corn very uncomfortable. This particular corn field was in West Central Iowa and was treated with fungicide and insecticide two weeks prior.
Corn aphids are becoming a common pest for corn growers and have the potential to develop into massive populations. Aphids can be found throughout the corn-growing season, but post-pollination corn aphids are a relatively new issue. It’s important to understand the damage aphids can cause to determine if management is necessary.
Here are a few facts you should know about corn aphids:
Aphids feed on the sap from the plant phloem and excrete sugar-rich honeydew that covers the plant, which can interrupt both plant growth and pollination. Aphids colonize deep within the whorl. Excessive feeding within the whorl before tassel emergence leads to incomplete kernel development or barren ears.
Aphids are problematic during tasseling and can colonize corn later in the summer, threatening yield potential. Drought-stressed corn plants also can be sensitive to aphid feeding.
Beneficial insects, such as ladybugs, can help control aphids.
In extreme cases, aphids are associated with dying leaves or, rarely, the death of entire plants. Sooty molds can colonize these sugary leaf surfaces, further reducing leaf photosynthesis.
Aphids can, and often do, leave corn as it begins to mature to dough stage. If subsequent rainfall washes off the sooty mold, honeydew and cast skins, the only evidence of the infestation may be small discolored areas on the leaf sheath and shanks.
Spot damage: Heavily infested plants are discolored and stunted with wilted, curled or yellowed leaves and sometimes shriveled ears.
Scout: Start scouting three weeks before tasseling. Check five locations within the field and 20 plants at each location. Examine the ear, leaves and stalk.
Control before tassel emergence: Protect yield by controlling aphids two to three weeks before tassels emerge. Treat plants if 50 percent are infested with colonies of over 75 aphids per plant.
Manage late-season: Treat if more that 50 percent of the tassels are covered with aphids and their honeydew, before pollination is halfway complete.
Historically, little attention has been paid to the late-milk stage bird-cherry oat populations.
Aphid infestation can lead to significant yield loss in corn.
Aphids can populate quickly and cause extensive damage.
Post-pollination aphids rarely cause significant yield loss.
Scout and treat fields before tasseling to prevent costly damage.
-Eric Solberg, Eastern Region Product Agronomist
Now that it’s August, a good percentage of the corn has tasseled, and it’s time to be scouting for foliar disease in your corn fields.
There are two main foliar diseases in the Western Corn Belt:
Gray Leaf Spot (GLS). This is the most common disease we see in the area. GLS survives in infested residues from previous corn crops. We see it almost every year at varying levels depending on hybrid tolerance and weather. Learn more about GLS here.
Southern Rust. This is another disease we are seeing in the Western Corn Belt. Southern rust has made its way through Oklahoma and Kansas and has now been confirmed in Southern Nebraska. Southern rust thrives in warm, humid environments, so irrigated corn country in Nebraska is a perfect home. Learn more about southern rust here.
Foliar diseases can cause significant damage to corn yields, but with a little scouting and a fungicide application, you can protect your corn crop.
-Craig Langemeier, Western Product Agronomist
, gray leaf spot
, southern rust
foliar diseases, gray leaf spot, Southern Rust
With the rough start to our region’s growing season, we need to start thinking about keeping our fields strong and healthy all the way to harvest. With favorable weather this growing season we still have the potential to grow a high yielding crop, despite being planted late. Below are fungicide efficacy ratings for several products out on the market, as well as a link to the UNL plant disease website. If you have any questions regarding disease problems in your fields, contact your Hoegemeyer product agronomist for help determining the best plan of action.
- Jonathan Williams, Southern Region Product Agronomist
Within the Hoegemeyer footprint we have corn at many different stages of growth depending on when producers could get into the field. In our southern regions, we have corn well over our knees. As we move into Nebraska there is corn anywhere from knee high to emerging. As we move into northern Iowa and southern South Dakota there are a lot of planters rolling as I type this since mother nature is finally cooperating.
Something we have been noticing in corn that is further along is Rapid Growth Syndrome. Certain genetics seem to be more prone to this and we will see some “repeat offenders” that seem to have this issue every year. The corn always comes out of it, but if you see corn with twisted whorls this article gives you a good background on why this happens.
As always if you have any questions feel free to call your Hoegemeyer DSM or agronomist.
-Craig Langemeier, Western Region Product Agronomist