The Effect Aphids Can Have on Corn Yield

August 26, 2019

     

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.

Management Tips:

  • 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. 

Summary:

  • 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


Categories: aphids, Corn     Comments: 0     Tags: aphids    

Two Foliar Diseases to Start Scouting

August 5, 2019

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:

  1. 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.
  2. 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


Categories: corn, gray leaf spot, southern rust     Comments: 0     Tags: foliar diseases, gray leaf spot, Southern Rust    

Advanced Planning for Disease Control

July 10, 2019

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.

Resources:

https://www.extension.purdue.edu/extmedia/BP/BP-160-W.pdf

https://cropwatch.unl.edu/plantdisease/corn

- Jonathan Williams, Southern Region Product Agronomist


Categories: corn, Disease     Comments: 0     Tags: Goss's Wilt Corn Disease    

Twisted Whorls in Corn

June 19, 2019

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


Categories: corn growth     Comments: 0    

Corn Growth & Development

May 29, 2019

This year has been another season of extreme weather from very little planted in the north and good planting conditions in the south to storms and possible replant in the middle of the Hoegemeyer footprint. Because of all these weather events and planting timings it is important to be able to stage your corn growth. Staging the corn growth enables you to understand when the optimal time is to apply fertilizers, spray post applied chemicals, spray fungicide and to scout for certain insects.

Corn growth stages are defined into two stages, first comes the vegetative stages (V) and reproductive stages (R). The vegetative stages are divided into substages V1, V2, V3, etc. identifying the number of leaf collars. The reproductive stages are divided into substages R1, R2, R3, etc. identifying ear development.

Staging A Corn Seedling

Each leaf stage is defined according to the uppermost leaf whose leaf collar is visible. The first part of the collar that is visible is the back, which appears as a discolored line between the leaf blade and leaf sheath. The characteristically oval-shaped first leaf is a reference point for counting upward to the top visible leaf collar.

Emergence & Stand Establishment

  • VE Stage – This is emergence and takes place approximately 100-120 GDU’s or 4-5 days. The seed will need to take up approximately 30% moisture to begin germination.
  • V1 Stage – The first leaf to become visible will have a rounded tip and all other leaves after that will be pointed. The leaf will come out approximately 3-4 days after VE.
  • V2 Stage – Will take place approximately 200 GDU’s or 7-10 days after VE.
  • V3-V6 Stages – Will take place approximately 475 GDU’s or about 21 days after VE. This marks the end of the seed being the main source of food for the plant and the beginning of photosynthesis and the nodal root for food. The number of kernel rows are being determined.  Growing point is starting to come out of the ground.
  • V7-V9 Stages – Will take place approximately 610 GDU’s. This is a good stage to do any foliar treatments because it is the beginning of rapid growth and nutrient uptake.

Rapid Growth & Dry Matter Accumulation 

  • V10-V13 Stages – The plant has entered its fast growth stage. New leaves or V stages will happen every 2-3 days. Water and nutrient demand is great during this period. As growth works it way to V13 the ear will determine how long the kernel rows will be and complete the determination of ear size. In general, earlier season hybrids will move through these stages in less time.  We will be a good 6 weeks after emergence.
  • V14-V(n) – This is the final stages of the vegetative growth of the corn plant. Depending on growing conditions and the location of the field in the corn belt will determine the number of leaves on the plant.  In general, most plants will be around 16-22 leaves.  At V15 there is only 12-15 days until the reproductive stages begin. Root growth is ramped up to support the taller plant with an ear.  Roots could reach 5-8 feet deep at this point.

Pollination

  • VT Stage – This is when the tassel is completely visible. The tassel will appear 2-3 days prior to silk emerging R1. Pollen shed normally occurs during the late morning or early evening. This is when most fungicides are recommended to be applied.
  • R1 Stage – Silks will appear, and pollination will begin. This process normally takes 2 -3 days. There is rapid uptake of nitrogen and phosphorus.

Grain Fill

  • R2 Stage – Blister looking kernel is forming on the cob and will continue to grow through R6. The cob is in its full size.
  • R3 Stage – Milk occurs about 18-22 days after R1. Corn kernels will start to yellow and the kernel growth will occur from cell expansion and starch accumulation.
  • R4 Stage – Dough is when the kernels start to thicken and accumulated 50% of their dry weight.
  • R5 Stage – Dent the kernel is around 55% moisture. This is where livestock producers will watch for the milk line to move from the top of the kernel to the tip for silage cutting.
  • R6 Stage – Physiological maturity has been achieved about 55-65 days after R1. The tip of the kernel will appear black and is called black layer. The kernel moisture at this point is 30-35% and dry down for grain harvest will start.

Corn development stages is an important part of managing your crop throughout the year. Today you need to know when it is safe to spray your post herbicides and to understand when the plant needs the most fertility. As you can see above the ear determines the number of kernels two different times during its growth, V6 and V12. Understanding your corn fields and hybrids give you a much better chance of managing corn development for a greater chance of higher yields.

-Stuart Carlson, Northern Region Product Agronomist


Categories: corn growth     Comments: 0     Tags: 2019 Planting, Corn Development    

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