Corn | | Latham Hi-Tech Seeds

Latham Hi‑Tech Seeds

Stalk Lodging

Credit: The Ohio State University

Stalk lodging can lead to reduced yield and grain quality. Lodging refers to the breakage of the stalk below the ear and is often connected with stalk rots, soil-borne pathogens and other environmental stressors that occur after pollination.

Causes of Stalk Lodging

Carbohydrate demand during grain fill is the primary driver of stalk lodging. When carbohydrate reserves in corn leaves are depleted during ear development, the plant will begin sourcing the macronutrient from stalks and roots. Environmental stresses can feed into this cycle. For example, warm weather and high temperatures increase plant growth which can lead to high demand for carbohydrates.

While energy demand during grain fill is the primary cause of lodging, fungal pathogens can reduce stalk vigor. Stalk rot pathogens can also weaken stalks and are another major cause of lodging. Generally, if more than 10 to 15% of stalks exhibit rotting, stalk lodging is likely to be a significant problem.

As it relates to weather, high winds and heavy rainfall can also cause stalks to become physiologically weak and eventually lodge. Injuries from hail or frost damage, or insect feeding that creates lesions on leaves, can reduce the amount of energy created by plants. This leads to a higher use of stalk carbohydrate reserves.

Nutrient deficiencies are also a major cause of stalk lodging. Excess nitrogen and low levels of potassium have been associated with reduced stalk quality. Maintaining sufficient potassium levels in corn is especially important as it is the building block for leaf and stalk tissue.

Scouting and Treatment Options

When scouting for stalk lodging, choose ten consecutive plants across ten different areas of the field. Check for signs of lodging by pinching the stalk at the first or second internode above the ground, or by pushing the plant over 8 to 12 inches at ear level. If the plant fails to stay standing upon exerting force, it is considered lodged.

Adjust your harvest plan to harvest lodged corn first before lodging becomes more widespread. Selecting the right corn hybrid for your farm can mitigate issues with insect feeding that would otherwise reduce stalk quality. The level of resistance to stalk lodging among hybrids is highly variant and some have genetically stronger stalks than others. Be sure to consult with your local Latham representative to determine the best management strategy for stalk lodging.

Latham Seeds Precision Agronomy Advisors

April 1, 2019

Agronomics, Corn, Crop, Season, Summer
Latham Hi‑Tech Seeds

Physoderma Stalk Rot

There are a variety of stalk rots that infect corn, causing extensive damage to crops and losses in yield. Common factors make corn susceptible to stalk rot including warm and wet weather, stress after pollination, fertility issues, stalk boring insects, and the presence of other foliar diseases. There are key signs, symptoms and differences that distinguish the different types of stalk rot.

Credit: Crop Protection Network

Scouting for Signs and Symptoms

Physoderma stalk rot is caused by the pathogen Physoderma maydis, the same fungus responsible for causing Physoderma brown spot. The fungal disease seems to be showing up in more and more corn fields each year, but typically shows up on random plants and and has minimal impact on yield. Like most stalk rot diseases, warm and wet weather favor the development of Physoderma stalk rot.

Physoderma stalk rot infects corn between the V4 and V9 stages. The disease is not associated with any foliar signs, so it is important to inspect plants closely at the base. Dark brown or black lesions will appear at the base of the stalk, and rotting of the pith will be observed upon splitting the stalk open. Overtime, blackening of the pith will move to higher nodes. Sporangia can also be found on the outside of nodes and within the rotted pith tissue.

Scout for symptoms of Physoderma stalk rot across five areas of the field. Stalks will make a distint “pop” and snap at one of the first 3 nodes above the soil line. If more than 10 to 15% of plants exhibit stalk rot, the field should be harvested early.

Management Strategies

With this being a newer disease we are still learning differences in hybrid tolerances to both stalk and foliar phases of this disease.

As a majority of stalk rots overwinter, one to two-year rotation away from corn and controlling corn residue are key for preventing the return of the disease. Fungicides may also be applied to prevent Physoderma leaf blight , but these studies are in early phases as well given the novel nature of this diesease

Latham Seeds Precision Agronomy Advisors

April 1, 2019

Agronomics, Corn, Crop, Disease, Fall, Season, Summer
Latham Hi‑Tech Seeds

Corn Aphids

Credit: Purdue University

Corn aphids have the ability to negatively impact yield end of year. Proper identification and management can protect your crop.

Identification

Corn aphids have a blue-green to gray appearance and are 1/16 inch in length. Aphids extract sap from corn plants and excrete honeydew. The honeydew creates sooty-looking mold that can interfere with pollination.

As opposed to laying eggs, female aphids reproduce by giving birth to nymphs. The insects can build large colonies comprised of more than one species such as bird-cherry oat aphids. Aphids are most often wingless, but when the size of their colonies begin to grow, some can form wings to migrate to other corn plants. Corn leaf aphids cannot overwinter and usually migrate to southern states ahead of the cold months.

Scouting and Implications

Aphids will begin to appear in corn around mid-June and early July. Mature aphids can be found near the tassels, silks and the base of the corn stalk. The insects predominately live in the whorls where they are protected from outside elements. Infected corn plants may exhibit stunting or wilting and curling of the leaves

When scouting for aphids, select 20 non-consecutive plants from five different areas of the field. Unroll the whorl to count the number of insects present. The general treatment threshold advised by Iowa State University is when 50% of corn plants have more than 100 aphids per plant.

Overall, aphid infestations have been found to reduce grain quality and decrease kernel size. A study from Penn State University finds that 30-40% of aphid-infested corn stalks will become barren or earless. Drought stress can also worsen the impacts of aphid feeding and should be included when considering a treatment plan.

Treatment Options

The best time to begin manage aphid-infested corn is two to three weeks prior to tasseling. Corn plants with aphid colonies above the ear are more susceptible to yield loss than plants with aphids found below the ear.

Since aphids mainly colonize inside corn whorls, spraying insecticides is not the most effective solution. Insecticide application is most effective when aphids are found on the outermost areas of leaves. If corn plants that have reached the hard dent stage, applying insecticides will not pay.

Fungi and other beneficial insects including lacewings and lady beetles can reduce aphid populations. Look for signs of bloating or discoloration in aphids – this could be evidence of fungi at work. If over 20% of aphids appear to be parasitized, consider holding off on a management plan. Be sure to talk with your local Latham representative to develop an effective treatment strategy for managing aphids.

Latham Seeds Precision Agronomy Advisors

April 1, 2019

Agronomics, Corn, Crop, Insects, Season, Summer
Latham Hi‑Tech Seeds

Japanese Beetle in Corn and Soybeans

Credit: Purdue University

Japanese beetles cause damage to corn by interfering with pollination and lead to defoliation in soybeans. Their distinct metallic-green heads and bronze wings make them distinguishable from other look-alike beetles. The insect undergoes one life cycle per year with adults reaching 5/16 inches in length.

Eggs are laid during July and August and overwinter until temperatures rise in the spring. For both corn and soybeans, adults migrate from grass and begin feeding in late May or early June. The peak emergence for Japanese beetles occurs 4 to 5 weeks after feeding begins.

Japanese beetles tend to feed in concentrated areas and in groups. After the female burrows into the soil, she will lay 1 to 4 eggs at a time for several weeks. Adult grubs feed on turf grass in late summer and early spring before emerging to feed on crops.

Corn

In corn, Japanese beetles can feed on silks and interfere with pollination. Though leaf feeding in corn is possible, a majority of the economic impacts are attributed to silk feeding. Plants should be treated if there are three or more beetles per ear.

Research from the University of Tennessee found that repeated clipping of silks did not always lead to yield loss. More importantly, the environment has a stronger influence on the damage Japanese beetles can cause. Higher yield loss in infested corn plants that were under drought stress as opposed to plants that were not.

Soybeans

In soybeans, the beetle strictly feeds on the soft tissue bordering leaf veins, leaving them skeletonized. Soybeans growing in sandy soils are even more susceptible to defoliation from Japanese beetles. Though yield loss from Japanese beetles has not been quantified, figures from North Dakota State University (see table) point to the general yield impacts from defoliation.

Research from the University of Nebraska advises treatment when damage reaches 30% defoliation before bloom or 20% defoliation during flowering. As long as beetles appear to be actively feeding, insecticide application is advised.

Other Considerations

Japanese beetles are easily confused with other species of beetles, including masked chafers and May or June beetles. Be sure to consult with your local Latham representative to confirm suspected Japanese beetle infestations and determine the right treatment plan.

__________

Photo Credit: Purdue University

Latham Seeds Precision Agronomy Advisors

April 1, 2019

Agronomics, Corn, Crop, Insects, Season, Soybeans, Summer
Latham Hi‑Tech Seeds

Anthracnose Stalk Rot
Credit: Crop Protection Network

There are a variety of stalk rots that infect corn, causing extensive damage to crops and losses in yield. Common factors make corn susceptible to stalk rot including warm and wet weather, stress after pollination, fertility issues, stalk boring insects, and the presence of other foliar diseases. There are key signs, symptoms and differences that distinguish the different types of stalk rot.

Anthracnose stalk rot is the most common type of stalk rot and is caused by the fungus Colletotrichum graminicola. The fungus is favored by wet, warm weather and overwinters in corn residue. Signs of the disease will be observed four to six weeks following pollination.

Scouting for Signs and Symptoms

The disease undergoes three phases with distinct signs and symptoms:
- In the first phase, foliar lesions will appear in the early part of the growing season. The leaf blight will begin on the lowest leaves, and will reach the upper leaves by late season.
- During the second phase, top-dieback will appear in the middle part of the season after tasseling, killing the parts of the plant located above the ear.
- In the third phase, shiny black lesions will appear on outside surface of stalks. Look for setae, or bristles that cover the surface of the stalk. A hand lens can be used to look for the bristle-like texture and black dots in the center of lesions.
Stalks will exhibit fragility and appear to be brittle when handled. Different from other forms of stalk rot, anthracnose stalk rot will cause plants to lodge at the upper portion of the stalk. Pinching or bending at the nodes can be used to test for stalk lodging.

Stalk rot can lead to death just before maturity and reduce yield. In addition, plants defoliated from hail damage and those that are nitrogen deficient are at an increased risk for being infected from the stalk rot.

Management Strategies

Planting hybrids with resistance to stalk rots is a helpful defense against these diseases.
Latham Seeds Precision Agronomy Advisors

April 1, 2019

Agronomics, Corn, Crop, Disease, Fall, Season, Summer
Latham Hi‑Tech Seeds

Rust Diseases in Corn

Southern Rust. Credit: Crop Protection Network

Common Rust and Southern Rust infect corn in the late summer. The diseases generate raised spores known as “pustules” on the surface of leaves, leading to reduced yield and poor grain quality.

Common rust (Puccinia sorghi) and southern rust (Puccinia polysora) fungi are unable to overwinter in the Midwest and require a host plant to remain alive. The spores created by rust diseases are transported by wind to the Midwest from Southern states.

Temperatures ranging from 61–77° fuel the growth of rust diseases. Cool and humid temperatures, especially when exhibited overnight, can further drive the development of the fungi.

As long as the weather conditions are right for rust diseases, the cycle of spore development will continue. The return of hot and dry weather can prevent further development of the fungus and kill off the spores.

Implications

Rust can reduce yield and decrease grain quality. Foliar damage from rust diseases can interfere with water transpirationand reduce photosynthetic leaf area.

Nutrients designated to support plant growth are rerouted in response to the damage incurred by leaves. Damage from rust diseases deplete carbohydrate reserves in corn leaves. As a result, the plant will begin sourcing the nutrients from stalks and roots, leading to reduced yield and stalk rot.

Common Rust. Credit: Crop Protection Network

Scouting for Rust Diseases

While common rust has less of an impact on yield, southern rust has been found to reduce yield by 25 bu/acre in corn with no fungicide application. The fungi can begin to infect plants under favorable conditions in as little as six hours.

Southern rust signs are evident on the upper leaf surface and are round, as opposed to elongated in plants infected with common rust. The pustules will be orange compared to the darker color of common rust. Overtime, southern rust pustules will become brown or black.

Common rust pustules are found on the upper and lower leaf surface and are oblong. Common rust pustules will be brick red in appearance and can coalesce to kill parts of leaves. In order to determine the difference between common and southern rust pustules, use a magnifying lens to inspect the leaf surface.

Management

Planting early is one of the best ways to reduce corn’s vulnerability to rust diseases. Corn planted late in the season is most susceptible to experiencing yield loss and grain damage. Many hybrids are also equipped with resistance to rust diseases, though the extent to which they are protected from the fungus can vary.

When pustules are observed on 50% of scouted plants, it is advised to begin implementing a treatment plan. Fungicides can also be used to treat corn infected with common and southern rust. Be sure to consult with your local Latham representative to determine the best management options for rust diseases.

Latham Seeds Precision Agronomy Advisors

April 1, 2019

Agronomics, Corn, Crop, Disease, Fall, Season, Summer
Latham Hi‑Tech Seeds

Western Bean Cutworm

Credit: Iowa State University

The Western Bean Cutworm can dramatically reduce end-of-season corn profit. The Western Bean Cutworm does not cut stalks but feeds on ears, posing as a threat to grain quality and corn yield. The cutworm moths are gray to brown with a wing span of 1 ½ inches. As a late summer insect, moths first emerge in early July and only one generation is produced each year.

Female moths lay eggs in whorls just ahead of the pollination stage and will lay an average of 50 eggs at a time. Eggs develop over the course of 5 to 7 days. Eggs will first be white, then become tan as they develop and will turn purple once they are close to hatching.

Only a small percentage of eggs typically survive, but larvae that reach full maturity can cause measurable damage to corn.

Scouting and Implications

Pheromone traps can be used to identify Western Bean Cutworm in fields. When multiple moths are caught at a high frequency, scouting for symptoms should take place. When scouting, focus on fields that are close to shedding pollen and examine 20 consecutive plants in 5 different locations.

Credit: Purdue University

Western Bean Cutworms feed on leaf tissue and silks as they approach the ear where most of the damage is incurred. The Western Bean Cutworm can be confused with other species of cutworm. The dark brown stripes behind their head that appear during the third instar distinguishes them from other cutworms.

The most mature larvae will feed on fully developed ears and can sometimes burrow into the sides of the ear. When scouting, it is important to pull back the husks to fully determine if the cutworms are present.

After feeding on the ears, the larvae will drop to the soil and burrow deep underground where they overwinter. It is common for many larvae to feed on one ear at once, increasing the severity of feeding damage. Ears with multiple larvae can exhibit up to 50-60% in kernel loss.

An average of one larva per plant has resulted in yield loss of 4 bu/acre in Iowa and Nebraska. Aside from yield loss, damaged kernels are prone to mold growth which reduces overall grain quality.

Managing Western Bean Cutworm

Managing Western Bean Cutworm should take place close to hatching, just before pollination. Once larvae hatch and move underneath tight leaves surrounding the ear, they become difficult to exterminate. Applying a foliar insecticide is recommended when 5-8% of plants have egg masses or young larvae present but not before at least 90% of plants have emerged tassels.

SmartStax, Viptera, and eventually we will have Duracade traited hybrids that provide aboveground protection against Western Bean Cutworm. Though Western Bean Cutworm overwinters, there is no evidence that tillage is an effective way to combat infestation. Be sure to consult with your local Latham representative to design the most effective treatment plan.

Latham Seeds Precision Agronomy Advisors

April 1, 2019

Agronomics, Corn, Crop, Insects, Season, Summer
Latham Hi‑Tech Seeds

Fall Frost Damage in Corn and Soybeans

Frost damage occurs in corn and soybeans when plants are exposed to freezing or below-freezing temperatures. Damage can occur to the plants above and below the soil when temperatures range from 28 to 32°F and colder. Corn and soybean plants exposed to air temperatures below 28°F are often lethal and prevent plants from undergoing full recovery from injuries. The key in assessing frost damage is waiting five days to allow for any potential growth recovery or rehabilitation to occur.

Credit: Michigan State University

Fall Frost in Soybeans

Once soybeans begin maturity and already have developed pods, they are most often immune from frost injury. Soybeans placed in narrow rows can have more protection from freezing air temperatures in being covered by leaf canopies. Pods growing on the lower portion of the plant are less vulnerable to frost damage than those on the top part of the canopy. Injured soybeans exhibit elongated pods that shrink to smaller than normal sizes upon drying. Most yield loss occurs during the full seed maturity stage.

Soybeans damaged by frost should be dried at a temperature no higher than 130°F and may have lower oil content. Both frost damaged corn and soybeans may also have delayed dry down.

Credit: University of Minnesota

Fall Frost in Corn

Frost-damaged corn can exhibit softened kernels prone to breakage and should be dried at temperatures below 160°F and be stored at a moisture level no higher than 14%. The storage life for frost-damaged corn will be cut in half and damaged corn should be handled separately from uninjured corn.

Latham Seeds Precision Agronomy Advisors

April 1, 2019

Agronomics, Corn, Crop, Fall, Frost, Season, Soybeans, Weather
Latham Hi‑Tech Seeds

Nitrogen Deficiency in Corn

Photo credit: University of Minnesota Extension

Nitrogen is an essential nutrient and its depletion can lead to severe yield loss. Nitrogen deficiency can be difficult to spot as different hybrids exhibit different symptoms. Most corn plants deficient in nitrogen will exhibit pale-yellowish leaves with a spindled appearance.

Nitrogen is a mobile nutrient and moves to the newest leaves first, leaving the oldest leaves more susceptible to deficiency. By moving from the oldest to youngest leaves, signs of yellowing will often form a “V” pattern on the plant leaf.

Causes of Nitrogen Deficiency

Cold or saturated soils are the primary causes of nitrogen deficiency in corn. Periods of heavy rainfall increase nitrogen leaching, depleting saturated soils of the vital nutrient. Aside from soil leaching, nitrogen can be lost through denitrification – where the nutrient is converted to a gas form and lost in the atmosphere.

When soil conditions are dry, sandy or poorly fertilized, early-applied nitrogen fails to be absorbed by plants. Insect diseases that injure root systems can further prevent proper absorption of nitrogen and lead to deficiency.

Other unavoidable circumstances happen later in the growing season when the increase in plant height and density can block sunlight absorption and reduce photosynthesis. This leads corn to use nutrient reserves within the plant, which will weaken stalks.

Implications

60% of the nitrogen needed to support corn growth is built-up between V4 and pollination, making this an important time to monitor for deficiency. Scouting for nitrogen deficiency should also take place after episodes of heavy rainfall.

While having negative implications on yield potential and crop quality, nitrogen deficiency can also contribute to other corn disorders including tip-dieback and kernel abortion. Plants that are nitrogen deficient will cannibalize their stalks to compensate for the nutrient loss. This makes stalks more vulnerable to lodging and pinching.

Management Options

Tissue sampling can provide insight into how severe deficiency is. When testing for nitrogen deficiency in corn, gather samples from different areas of the field to compare nitrogen levels in deficient corn with healthy plants.

Nitrogen deficient corn should be harvested early in order to prevent additional yield loss from stalk lodging. When planning for next year’s crop, avoid planting hybrids with a history of poor nitrogen uptake. Some hybrids also demand a higher level of nitrogen during grain fill than others, so it is important to consider when planning for the next crop.

Be sure to consult with your local Latham representative to determine the best plan for managing nitrogen deficiency in corn.

Latham Seeds Precision Agronomy Advisors

April 1, 2019

Agronomics, Corn, Crop, Fertility, Growth Stages
Latham Hi‑Tech Seeds

Anthracnose Leaf Blight

Photo Credit: University of Minnesota

Colletotrichum graminicola is a fungal pathogen that causes anthracnose leaf blight. Anthracnose leaf blight is a foliar disease that appears in the early and late stages of growth in corn plants. The fungus survives in infected corn residue that remains in the field over the winter. The disease creates elongated lesions with a dried, brown appearance across the length of the leaf blade and is bordered by a darker reddish-brown color.

In the earliest part of the season, leaf blight will impact the lower leaves of the plant and expand toward the top of the plant by late season. The upper part of the plant will begin to exhibit early senescence while the lowest part of the corn plant will remain green and healthy.  This is a characteristic of the Top Dieback part of this disease.

Disease Causes

Anthracnose leaf blight develops predominately from the infected residue left behind in the field. No-till, reduced till and corn on corn rotations can increase the likelihood of the disease to emerge. Though no-till and reduced-till methods are critical for preventing erosion and other corn disorders, it can lead to the accumulation of corn debris that is conducive for housing the fungal pathogen.

The fungus thrives in a warm and wet environment. Moisture from rainfall will often create black specks that appear across the lesions. Wind can also act as a transportation method for the fungus as spores can travel by air or water.

Implications and Treatment

The disease will infect at the seedling stage, causing foliar damage, and end at the growing season, causing stalk rot. Although anthracnose leaf blight has the potential to occur later in the growing season, early signs of the infection do not guarantee that it will resurface closer to harvest. Iowa State University researchers state that because of the early-season nature of the leaf blight, impacts on yield are rarely demonstrated. The late season stalk rot phase of the disease tends to be more detrimental on yield and harvestability.

Crop rotation and the use of resistant hybrids are the best ways to combat leaf blight. Fungicides can keep anthracnose leaf blight in control, but it likely will not be effective for combatting the stalk rot phase. Further, corn hybrids that provide resistance against the earliest stages of leaf blight are not often effective for preventing the onset of late-season stalk rot.

If tillage is used, methods that bury infected corn residue can prevent leaf blight from emerging again during the next season. Crop rotation has also been deemed as an effective way to prevent the continued onset of anthracnose leaf blight. For corn that has perpetually been impacted by leaf blight, two-year rotations away from corn are also advised.

Latham Seeds Precision Agronomy Advisors

April 1, 2019

Agronomics, Corn, Crop, Disease