Stress Emergence in Corn

April 21, 2020

Impact of Cold Stress on Stand Establishment

The optimal temperature for corn emergence is in the range of 80° to 90° Fahrenheit. Emergence is greatly reduced at lower temperatures and is effectively halted around 50° to 55° Fahrenheit or below. Since soil temperatures in the early season are almost never optimal, emerging seeds will experience a degree of stress. The degree of stress, and potential damage from stress is determined mostly by soil and water temperatures during imbibition and seedling emergence.

For successful emergence to occur, all parts of the shoot (roots, mesocotyl, coleoptile and leaf within) must work in a coordinated way to push the coleoptile above the soil surface and allow the first leaf to unfurl. Damage to any one of these structures will likely result in loss of the seedling and its yield potential.

The Critical First Hours

When the dry seed imbibes cold water (typically 50° F or below), imbibitional chilling injury may result. The degree of damage ranges from seed death to abnormalities such as corkscrews or fused coleoptiles.

The potential for cold-water damage generally decreases as the seedlings emerge. It also decreases if the initial imbibition takes place at temperatures above 50° F. This may help explain observations where early-planted corn, which was followed by favorable weather, emerged better than corn planted later and followed by a cold spell.

Damage to the emerging root usually has less severe consequences on seedling survival. This is because the primary root, which is the first structure to emerge, plays a relatively minor role in seedling establishment compared to the lateral and nodal roots. Seedling establishment can usually progress normally if the lateral and nodal roots are intact. Any damage to the roots, however, will likely reduce vigor and increase the potential for disease and insect injury.

Seedling Disease and Stress Emergence

Stress emergence is an agronomic trait intended to reflect genetic variability for tolerance to abiotic stress in the early season. It is not a rating for disease resistance. Early-season stress can promote seedling disease if certain conditions are met, including inoculum presence and prolonged cool, wet conditions. Injury to emerging seedlings will also promote seedling disease. Injury can be caused by chilling, such as imbibitional damage, or by feeding of insects such as seedcorn maggots, white grubs and wireworms.

In environments with heavy inoculum pressure, disease progression is often in a race with seedling growth. Conditions that promote rapid soil warming will generally favor seedling growth and reduce disease incidence. On the other hand, extended cool, wet conditions will generally favor disease progression. 

Many soil pathogens, including some Pythium species, are most active at temperatures in the 40s and 50s (F). Low temperatures such as these can injure emerging seedlings and facilitate infection. Low temperatures also retard stand establishment and increase the window of vulnerability to infection. Seed treatment fungicides generally provide good efficacy against target organisms for 10 to 14 days after planting. However, protection will be diminished if emergence and stand establishment are delayed beyond this period.

Summary

Successful stand establishment requires understanding and managing risks. Early-season damage is difficult to diagnose since most of it occurs before the crop emerges. The best management strategy is to understand the conditions and environmental factors that can cause stand reduction and to minimize exposure to these adverse environments.

Deciding when to plant is probably the factor with the largest single impact on stand establishment. The risk of damage to emergence is greatest if the crop is planted into very cold soil or if planting is followed by severe cold weather. Often, planting date is dictated by workload and field conditions. If a cold spell is expected after planting, it is advisable to plant fields with better drainage and less residue first. Choosing hybrids with strong stress emergence helps reduce genetic vulnerability to stress, and planting seeds with a premium seed treatment helps provide critical protection in stressful environments where seeds are vulnerable to attack.

-Stuart Carlson, Northern Region Product Agronomist

Sources

  • Corteva 2020

Categories: corn     Comments: 0    

Controlling Volunteer Corn This Planting Season

March 10, 2020

Volunteer corn with herbicide resistance traits can be difficult to control after a strong wind or hail event causes ears to drop on the ground. Some areas can till these fields after fall harvest and irrigate to promote corn germination during the fall. This may not be an option for your management system due to either late harvests or your climate is too cold. There is still corn on the soil surface and the upcoming planting season is rapidly approaching - don’t panic. There are still ways to control volunteer corn in the upcoming planting season. If you still have corn on the soil surface this spring, try to avoid tillage, as this could promote germination of the volunteer corn.

The best chemical control option for volunteer corn in soybeans are grass herbicides. Grass herbicides are the ones with group 1 on the label. This group of herbicides usually need an adjuvant to help increase foliar uptake of the herbicide. Always consult the herbicide label for approved adjuvants. In hot and dry application conditions some speckling can be observed on soybean leaves due to the adjuvant burning the leaf and is not actually due to herbicide injury. A couple examples of commonly used grass herbicides on soybeans include both Select Max (clethodim) and DuPont Assure II (quizalofop). Before deciding which herbicide to spray, double check compatibility with your current soybean herbicide program.

Going forward, farmers will have a new tool to help control volunteer corn in corn. The Enlist Corn trait comes with tolerance to 2,4-D choline, glyphosate, and FOP herbicides (such as DuPont Assure II herbicide). Assure II, normally kills corn, but it can be used in Enlist Corn to control non-Enlist volunteer corn.  In the future Hoegemeyer will offer an increasing selection of Enlist Corn product options, stacked with key insect and herbicide tolerant traits.

  • It is encouraged to apply Enlist One and Assure II separately because of antagonism causing reduced control on grasses
  • If a split application is not possible, apply Enlist One and a higher rate of Assure II with an approved adjuvant (Assure II rate is 5-12 oz/acre and Enlist One application rate is 1.5-2.0 pints/acre)
  • Use an approved adjuvant when tank mixing according to www.EnlistTankMix.com and the Assure II label
  • Assure II has an application timing window of V2-V6 in Enlist corn
  • Enlist One application timing for corn is before V8
  • Always double check Enlist One and Assure II labels for application timings and susceptible crops before application          

*Always consult Enlist One label for proper application timings, instructions and nozzle selection.

If you don’t have Enlist corn and still want to control volunteer corn this upcoming season, you can use Select Max to control any emerged volunteer corn before planting. Select Max has a label for situations like this where it is applied at a rate of 6oz/ac and a minimum of 6 days is required before planting/replanting corn. Do not utilize Assure II in this manner since the plant back restrictions for corn without the Enlist trait is 120 days. For any questions about how to handle volunteer corn for this season corn or soybean crop contact your regional Hoegemeyer agronomist or DSM.

-Teal Mills, Southern Product Agronomist

‚ÄčSources


Categories: corn, Enlist Corn     Comments: 0    

Managing Corn Rootworms

February 19, 2020

The state of Iowa is one of the best corn producing states in the Unites States. With the potential for increased corn acres across the state and increased corn after corn acres managing corn rootworms is a major concern. Three species of rootworm found in Iowa include the northern corn rootworm (NCR), southern corn rootworm (SCR), and western corn rootworm (WCR). 

SCR (left), WCR (middle), NRC (right)

Southern corn rootworms typically don’t cause economic injury to corn in Iowa. Northern and western corn rootworms are the most common rootworm pest that cause economic damage to our corn crop. Over the past 5-10 years northern and western corn rootworms have adapted where they lay their eggs. They have started to lay their eggs in fields adjacent to corn fields where the crop is not corn. Northern corn rootworms have one generation per year, but some NCR populations survive as eggs in the soil for multiple years, this is called extended diapause. Extended diapause is usually found in the Western part of Iowa, however has been found elsewhere as well. Where extended diapause occurs, first year corn can show economic impact where left untreated. When a western corn rootworm lays its eggs in fields containing other crops it is called the “soybean variant”. Typical corn-soybean rotation has been a great tool to control corn rootworms in the past. Rootworms have adapted by extended diapause in northern corn rootworm and the rootworm variant in western corn rootworms. 

Once corn rootworm eggs hatch the larvae feed on corn roots and can potentially cause severe economic loss. For every node of roots pruned by larvae, expect a 15% yield loss on average (Tinsley et al. 2013). Monitoring fields in-season will assist you in identifying the problem and help improve your management strategy.

Management Tips: Bt traits have been the best tool we have to help us control corn rootworms. Using multiple types of Bt proteins in combination to control the same pest has been very successful. Where heavy rootworm populations exist, resistance has been observed to certain Bt proteins. Identifying where these populations are present and implementing a management plan is crucial. 

The use of insecticides in furrow to control corn rootworms is a very successful way to assist in controlling rootworms. When using insecticides, make sure you rotate the mode of action used from year to year to ensure you don’t develop a resistant population to the product being used.

Where resistant populations are present, the best control is to use a combination of stacked Bt traits combined with in-furrow insecticide. This practice gives three or more modes of control to control the corn rootworms and a very low chance of resistance developing.

Scouting corn fields in early July for corn rootworm adults in high pressure fields is recommended.  Where adult corn rootworm beetles are present we can predict where the eggs will be laid, and the larvae will be present next growing season.  If the planned rotation is corn on corn for that field, an insecticide application with the proper timing will dramatically reduce the corn rootworm population that lays eggs and the potential economic impact for next year.

Corn rootworm is the number one economic pest effecting corn production in the Midwest.  In some regions, the northern corn and western corn rootworms have adapted to traditional crop rotation management practices. Adjusting management practices, scouting fields and identifying extended diapause (NCR) and soybean variant (WCR) history can reduce future damage.

Corn rootworms continue to adapt and change their habits.  Having a game plan before the season starts of using multiple control methods to control this pest is key to be good stewards and protecting the methods we must use to control this pest across the corn belt is paramount. 

Product Options: Hoegemeyer has a full line-up of Qrome traited corn products. Hoegemeyer brand Qrome products are the most optimized balance of insect protection and agronomic performance in our corn product portfolio. These products are fully equipped with a triple stack of defensive traits and dual modes of action to defend against above and below ground pests, and offer an integrated refuge solution. Qrome products include a unique moleculat stack of the proven Bt proteins from Hercules I and Herculex RW traits. This new technology is the key to unlocking higher yield potential on your acres.

-Eric Solberg, Eastern Product Agronomist

Sources

  • Erin Hodgson, ISU associate professor, Adult corn rootworm identification 2015
  • Eric Hodgson, ISU associate professor, Corn Rootworm Management update Aug. 2015
  • Managing corn rootworm diapause, Corteva 2019

Categories: corn, rootworm     Comments: 0     Tags: rootworm    

Identify and Manage Corn Ear Molds

October 21, 2019

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


Categories: corn, ear mold     Comments: 0    

Late Season Stalk Rots in 2019

September 24, 2019

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. 

  1. Stand next to a corn plant and put your arm from your hand to your elbow parallel to the plant.
  2. Simple extend your arm out and see if the plant breaks off below the ear or is the plant able to continue standing.
  3. 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


Categories: corn, stalk rot     Comments: 0    

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