Cooler and wet conditions in the Western Corn Belt have delayed harvest and slowed grain drying, leading to increased ear rot diseases and grain molds. Some producers and consultants also are observing rotted cobs, which can be related to several ear rot diseases.
What you should know:
Scout for ear molds beginning at late-dent stage by pulling husks back and examining each ear for rot or mold.
To identify a disease, consider conditions in which the crop was planted, field history, husk type and environmental conditions at tasseling, silking and pollination.
If you can’t identify the ear mold, send the entire ear to your Hoegemeyer agronomist or university agriculture extension for evaluation.
Learn more here with this Hoegemeyer agronomy profile on ear molds.
-Eric Solberg, Eastern Product Agronomist
In Hoegemeyer’s footprint, we started out 2019 with a cold finish to winter and a late start to planting season due to all the flooding and excess moisture. Most areas of Nebraska received more rainfall than needed during the growing season leaving just a few dry areas. Most of the state caught rain in the last week and they are calling for more later this week, resulting in an increased chance for below average stalk quality for harvest.
There are two main culprits I have seen this growing season including Fusarium verticilliodes and Anthracnose stalk rot and top dieback. Fusarium is most commonly seen when we have dry conditions early and normal precipitation later in the growing season. Symptoms are a white color on the stem around the node, decayed pith tissue inside the stem while the vascular bundles stay intact, and a pink to salmon color inside the stem. The second pathogen I have seen above average incidence of is Anthracnose.
The pathogen that causes Anthracnose infects in two ways. The first is anthracnose top dieback, and this form typically doesn’t have a major impact on yield. Anthracnose stalk rot on the other hand can cause significant yield loss. Symptoms of this phase include black discoloration under the leaf sheath on the stems and a brown discoloration at the nodes. This will lead to lodging later in harvest.
So how do I know which fields are affected? First check both the stalk strength and anthracnose ratings in your Hoegemeyer seed guide. Checking all fields would be best, but if time is of concern start with fields that have lower ratings in the seed guide.
To test stalk strength this time of year we can do a simple push test.
Stand next to a corn plant and put your arm from your hand to your elbow parallel to the plant.
Simple extend your arm out and see if the plant breaks off below the ear or is the plant able to continue standing.
This should be done in five different areas of the field, 20 plants at a time. If you have 10 to 15 plants that break you may want to harvest that field first.
If you have any questions, feel free to contact your local Hoegemeyer agronomist or dealer.
-Craig Langemeier, Western 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