Field Observations Thru August 25

Corn

Growth & Development

Last week I highlighted the R3 (milk) growth stage.  R4 is the next stage, occurring approximately 26 days after silking.

R4 – Dough

  • This stage is about 26 days after silking.

 

  • The kernel has thickened to a pasty (doughy) consistency from the earlier milky state (starch has continued to accumulate and kernel moisture content has decreased).
  • The embryo of the seed is growing while the kernels are just beginning to dry at the top (dent).
  • Kernels have accumulated 50 percent of their dry weight and have about 70 percent moisture.
  • Unfavorable environmental conditions or nutrient deficiencies still can result in unfilled kernels and “chaffy” ears.

Scouting

Disease pressure throughout the county continues to be very low. Continue to scout for:

Chaffy Ears

  • Foliar diseases
  • Weed escapes (especially Palmer and Waterhemp)
  • Head smut
  • European corn borer
  • Barren stalks, poor pollination
  • Nutrient deficiencies

 

Soybeans

Growth & Development

Soybeans are continuing to mature.  Recent rains will help with seed fill.  Last week I highlighted the R5 (Beginning Seed) growth stage.  R6 is the next stage, occurring approximately 10 days after R4.

R6 – Full Seed

R6 Full seed

Pod containing a green seed that fills the pod cavity at one of the four uppermost nodes on the main stem with a fully developed leaf

 

  • Beans of many sizes can be found on the plant
  • Total plant pod weight is maximized
  • Large amounts of nitrogen are still being accumulated from the soil and remobilized to the seed
  • Root growth is complete between R6 and R7.

Scouting

As you continue to scout your bean fields, look for

  • Foliar diseases – Sudden Death Syndrome, White Mold, and Frogeye Leaf Spot.
  • Insect feeding – Grasshoppers.
  • Weed escapes (especially Palmer and Waterhemp).

Click here for tips on identifying pigweed, palmer and waterhemp.

County Rainfall Update

Weed of the week – Cocklebur

Every year it seems as if we have one weed that that hasn’t really been a problem for a while suddenly pop up everywhere.  This year Cocklebur wins the 2023 award for Comeback Weed of the Year!

Family:  Asteraceae (Composite family)

Life cycle:  Annual

Description: Erect plant reaching heights of 6 to 7 ft.  Stems are rough with dark spots.  Leaves are rough, triangular in shape with wavy or toothed margins and long petioles.  Inconspicuous flowers produce egg-shaped burs with two beaks at end. Seedling has long, fleshy cotyledons.

Seedlings:  The stem below the cotyledons (hypocotyl) is purple at the base and often green in the upper portion. Cotyledons are linear to oblong in outline, waxy, smooth, fleshy, thick, approximately 3/4 to1 3/4 inches long and usually no more than 1/2 inch wide. The first true leaves are opposite, while all subsequent leaves are alternate.

Roots:  Taproot

Stem: Mature stems are green, 1-4 ft. tall, highly branched, hairy, and flecked with maroon to black spots.  Ridges are present on the stem.  Upright hairs cause leaves to feel abrasive and gritty.

Leaves:  The first true leaves are opposite, all subsequent leaves are alternate. Leaves are triangular to ovate in outline, have stiff hairs, and are approximately 2 to 6 inches long. Leave are irregularly lobed with leaf margins that have relatively inconspicuous teeth. Leaves occur on long petioles and also have three prominent veins on the upper surface of the leaf that arise from the same point.

Flower/Seedhead:  Inconspicuous, greenish in color, arising from the area between the leaf petioles and the stems (axillary flowers) and at the ends of the erect stems (terminal flowers).

Special Identifying Characteristics:  The relatively large, linear to oblong waxy cotyledons helps to distinguish this weed in the early stages of development.  Additionally, the long-petioled triangular leaves, stems with maroon to black stem lesions, and the distinctive prickly cocklebur fruit are all features that help in the identification of this weed.In the early stages of development, this weed might be confused with Giant Ragweed (Ambrosia trifida), however the cotyledons of common cocklebur are much longer and more linear than those of giant ragweed. Spiny Cocklebur (Xanthium spinosum) is a closely related and similar species, however, unlike common cocklebur, this weed has very distinctive 3-parted spines that arise at the base of each leaf.

If you have a dog, you will now if you have cocklebur! 

Red Crown Rot of Soybean

Figure 1. Foliar Symptoms

Red crown rot (RCR) is a soybean disease caused by the soilborne fungus Calonectria ilicicola that is spreading to parts of the Midwest. There have been no confirmed reports of RCR in Ohio, but it has been detected in Kentucky and Illinois.  RCR can be easily confused with other soybean diseases that cause similar foliar symptoms.

RCR can be misidentified as sudden death syndrome (SDS) or brown stem rot (BSR) as all three diseases can cause yellowing between the leaf veins or interveinal leaf chlorosis (Figure 1.)

Figure 2. Stem discoloration

Proper diagnosis will require digging up the plant, scraping the soil off, and inspecting for red discoloration on the outer stem (Figure 2). Also look for small, brick red perithecia (fungal sexual structure) on the lower stem or root crown area. These perithecia will be smaller than the tip of a pencil and more likely to be observed following wet weather.

In general, concentrate scouting efforts for RCR in low-lying, saturated areas of the field between the R3 (beginning pod) and R5 (beginning seed) growth stages. Keep an eye out for scattered patches of plants dying off early.

If you have questionable areas in your beans and suspect RCR or sudden death let me know.  I can collect plant samples and send them to our lab for diagnosis.

Field Observations Thru August 18

Corn

Growth & Development

Corn development continues to vary throughout the county.  Last week I highlighted the R2 (Blister) growth stage.  R3 is the next stage, occurring approximately 20 days after silking.

R3 – Milk Stage

  • Occurs approximately 18‐20 days after silking.

  • The  kernel is colored yellow with the inside containing ‘milky’ white fluid.
  • Kernel moisture  content is approximately 80%
  • Starch is beginning to accumulate in the kernel.
  • Stress is not as severe at R3 as at R1; however, yield reduction can occur due to a reduction in the number of kernels that ultimately develop and to the final size and weight of the kernels.
  • Very little root growth occurs after R3.

Scouting

Disease pressure throughout the county continues to be very low.  At this stage of growth, with little to no disease pressure, and new crop corn under $5 can we justify at least $25 per acre for a fungicide application?

Read more on disease scouting here.

Soybeans

Growth & Development

Like corn, soybean development continues to vary throughout the county.  Beans are looking much better than they were a few weeks ago. Last week I highlighted the R4 (Full Pod) growth stage.  R5 (Beginning Seed) is the next stage, occurring approximately 10 days after R4.

  • Seed is 1/8 inches long in the pod at one of the four uppermost nodes on the main stem with a fully developed leaf .

  • Rapid seed filling begins, while root growth slows.
  • Dry weight and nutrients begin redistributing through the plant to the developing seed.
  • 50% defoliation can decrease yield by 15-17%.
  • Symptoms of many diseases, including white mold and SDS begin to show up at this growth stage.
  • This is a good growth stage to determine the severity of disease.
  • Treating most diseases with fungicides is not recommended at this time.

Scouting

All of the bean fields that I have seen this week look very similar to this one.  I am seeing very little (if any) disease pressure.  Current and projected weather conditions may change  this.  As you continue to scout your bean fields, look for Sudden Death Syndrome, White Mold, and Frogeye Leaf Spot.

Weeds

It’s that time of year when weeds are beginning to show their ugly heads above the soybean canopy in many fields.  During your scouting, if you find Palmer Amaranth or Waterhemp you should do whatever you can to prevent these devastating weeds from going to seed, including removing the entire plant from the field.

Click here for tips on identifying pigweed, palmer and waterhemp.

County Rainfall Update

Is it Pigweed or Palmer? – Hope it’s not Waterhemp!

It’s that time of year when weeds are beginning to show their ugly heads above the soybean canopy in many fields.  During your scouting, if you find Palmer Amaranth or Waterhemp you should do whatever you can to prevent these devastating weeds from going to seed, including removing the entire plant from the field.

Each of the last 3 weeks I have included a post highlighting the different characteristics of Pigweed, Palmer Amaranth and Waterhemp.  These posts also included a step by step video to help with the identification process for these weeds.

Depending upon the growth stage, identifying these weeds in the field can be challenging. If a seedhead is present, most weeds are easier to identify, including pigweed, palmer and waterhemp. If you have seen a mature palmer seadhaed you will never forget it!  (see pictures above)

When trying to differentiate between these weeds I look for the following 3 plant characteristics:

1.Hair

Pigweed has hair the others do not.  Rub the stem and leaves checking for a “rough” texture.  Palmer and waterhemp will be smooth.

 

2. Leaves

Long Lanceolate Leaves

Waterhemp has long, slender leaves (lanceolate). While pigweed and palmer are more oval in shape.  Pigweed is wider in the middle and palmer is wider near the base of the leaf (this is usually hard do differentiate in the field).

 

 

3. Petiole

The petiole is the part of the plant that connects the leaf to the stem.  The petiole on palmer plant is as long or longer than the leaf.  Pigweed and waterhemp have much shorter petioles (often less than 1/2 the length of the leaf).

These weeds are here, they best way to prevent the spread is by preventing them from developing a seedhead.  One mature female plant  can produce up to 1,000,000 seeds.

 

Weed Identification Videos

 

If you  are still not sure about the identification, do not hesitate to call 740-397-0401) or send (barker.41@osu.edu) me a picture!!!

Scout for Soybean Diseases

Source: Horacio Lopez-Nicora

Now is the time to scout for mid-season soybean diseases. Though, disease levels across Ohio are low to moderate, current weather conditions are turning things around, and more fields are developing disease symptoms.

Sudden Death Syndrome (SDS)
We are finding fields in Ohio affected by sudden death syndrome (SDS). These symptoms are showing up earlier than normal. SDS is caused by the fungal pathogen Fusarium virguliforme. This species is the most prevalent in the region, however, other Fusarium species can cause SDS. SDS above-ground symptoms can be confused with those produced by a different fungus (Cadophora gregata) that causes brown stem rot (BSR). To distinguish SDS from BSR, symptomatic plants should be dug out and stem cut open longitudinally. SDS-infected plants have white, healthy-looking pith, while BSR-infected plants present brown discoloration of the pith. Moreover, fields with severe SDS symptoms can also have high levels of soybean cyst nematode (SCN).

If you are seeing SDS symptoms, we encourage you to submit a sample to the Soybean Pathology and Nematology Laboratory in the Department of Plant Pathology at The Ohio State University in Columbus (read more HERE). We will confirm if it is SDS or BSR; additionally, if it is SDS, we want to determine what Fusarium species is the causal agent. To submit samples, dig out three to five symptomatic plants (including roots), placed them in a plastic bag, complete the SDS submission form, and submit them to our lab. Do not hesitate to contact your extension educator or us if you have any questions.

White Mold, and Phytophthora Root and Stem Rot
Weather conditions are favorable for development of white mold, a fungal disease caused by Sclerotinia sclerotiorum. To scout for this disease, we recommend walking soybean fields and looking in-between rows. A white fluffy mass of fungal mycelia will be observed in infected plants (Fig. 4). Black round sclerotia will be present amidst the white mycelia. Visit here for more information about scouting for white mold of soybean.

We continue to receive samples with plants affected by Phytophthora root and stem rot. Commonly, these samples come from fields with poor drainage. Phytophthora root and stem rot can sometimes be confused with stem canker and white moldYou are welcome to submit samples to the Soybean Pathology and Nematology Lab for diagnosis. Visit here for more information about scouting for Phytophthora root and stem rot in soybean.

Frogeye Leaf Spot
We are finding frogeye leaf spot in our fungicide trials in northern and southern Ohio. Frogeye leaf spot is caused by a fungal pathogen (Cercospora sojina) which can reduce yield if plants are severely affected between R3 to R5 soybean growth stages. This year, symptoms in Ohio are visible at R2/R3 growth stage. We encourage growers to submit samples with frogeye leaf spot lesions to our lab. The fungus can develop resistance to fungicide, and we want to determine if these populations are present in Ohio. Best way to submit frogeye leaf spot samples to our lab is by placing symptomatic leaves in a plastic Ziploc bag and mail it to our lab as soon as possible. Keep samples in cool conditions and avoid exposure to sunlight and heat. Visit here for more information on frogeye leaf spot.

We can help diagnose soybean diseases with you!
You are welcome to submit your samples to the address below. Contact us if you have any questions. Send your samples to:

Soybean Pathology and Nematology Lab
Attn: Horacio Lopez-Nicora, Ph.D.
110 Kottman Hall
2021 Coffey Rd.
Columbus, Ohio 43210
lopez-nicora.1@osu.edu

Sudden Death Syndrome of Soybean in Ohio

Source: Horacio Lopez-Nicora

We are finding fields in Ohio affected by sudden death syndrome (SDS). These symptoms are showing up earlier than normal. SDS is caused by the fungal pathogen Fusarium virguliforme. This species is the most prevalent in the region, however, other Fusarium species can cause SDS.

With support and funding from Ohio Soybean Council, we will process soybean plants with SDS symptoms from fields in Ohio to: 1) Determine the species and genetic diversity of Fusarium associated with SDS in Ohio, and 2) Determine the fungicide sensitivity of isolates in the culture collection. To successfully achieve these goals, we need your help.

If you are seeing SDS symptoms, we encourage you to submit a sample to the Soybean Pathology and Nematology Laboratory in the Department of Plant Pathology at The Ohio State University in Columbus (read more HERE). If it is SDS, we want to determine what Fusarium species is the causal agent. To submit samples, dig out three to five symptomatic plants (including roots), placed them in a plastic bag, complete the SDS submission form, and submit them to our lab. Do not hesitate to contact your extension educator or us if you have any questions. Read more about SDS and other mid-season diseases of soybean HERE.

Mail your samples to:

OSU Soybean Pathology and Nematology Lab 
Attn: Horacio Lopez-Nicora, Ph.D.
110 Kottman Hall
2021 Coffey Rd.
Columbus, Ohio 43210
lopez-nicora.1@osu.edu

Read more about SDS here

Field Observations Thru August 11

Corn

Growth & Development

Corn development continues to vary throughout the county.  Last week I highlighted the R1 (Silking) growth stage.  R2 is the next stage, occurring approximately 10 days after silking.

R2 – Blister

  • Occurs about 10‐12 days after silking.
  • The kernel is visible  and resembles a blister

  • Clear fluid fills the kernel
  • The embryo is barely visible
  • Approximately 85% moisture content.
  • If severe stress occurs now or during R3, kernels can be aborted from the tip downward.
  • Kernel abortion will occur until the plant has a sufficient supply of carbohydrates for the  remaining kernels.

Scouting

Disease pressure throughout the county is very low.  SO … Do I spray or not?  This is literally the same decision that we had to make with our wheat crop this year.  Read more on disease scouting here.

Soybeans

Growth & Development

Like corn, soybean development continues to vary throughout the county.  Beans are looking much better than they were a few weeks ago. Last week I highlighted the R3 (Beginning Pod) growth stage.  R4 (Full Pod) is the next stage, occurring approximately 10 days after R3.

R4 – Full Pod

  • A 3/4 inch pod at one of the four uppermost nodes on the main stem
  • Rapid pod growth & beginning seed development
  • From R4 to middle R5 critical period for soybean yield potential
  • Flowering is complete
  • Pod abortion occurs naturally and allows the soybean plant to adapt to current environmental conditions.
  • Pod number and seed size affect yield more than seeds per pod.

Scouting

All of the bean fields that I have seen this week look very similar to this one.  I am seeing very little (if any) disease pressure.  Current and projected weather conditions may change  this.  As you continue to scout your bean fields, look for Sudden Death Syndrome, White Mold, and Frogeye Leaf Spot.  More information on scouting for these problems next week.

County Rainfall Update

Corn Water Requirements

Soybean Water Requirements

Sudden Death Syndrome (SDS)

Sudden death syndrome (SDS) of soybean can be found in fields around the Midwest but still has limited distribution in Ohio. Yield losses associated with SDS in Ohio have been highly variable depending on the timing and severity of the initial infection, subsequent weather conditions, timing of defoliation, and the level of soybean cyst nematode (SCN) infestation in the field.

Symptoms and Signs – Foliar:

The first observed SDS symptoms are often early leaf symptoms, including yellow spots between leaf veins, known as interveinal chlorosis.

 

These lesions may expand and turn brown as the spots expand between veins, which is called interveinal necrosis. Leaf veins remain green. As the disease progresses, leaves die and prematurely fall from the plant, while petioles remain attached to the stem. Pods and seeds may be aborted.

Foliar symptoms of SDS can resemble those of many other diseases. These symptoms can occur in fields with high levels of inoculum as early as the vegetative stage, but most often occur near the middle pod-fill stages (R3-R4).

Symptoms and Signs – Roots & Stems:

Infected plants can have discolored and decaying roots even if there are no noticeable foliar symptoms of SDS. The woody tissue in the taproot can be brown to dark gray, while the upper portion of stem pith remains white.

Disease Cycle:

The fungus that causes SDS survives the winter in crop residue and soil. Early in the season, the fungus infects soybean roots, sometimes within a few days of seed germination. Infection is favored by cool, wet soil conditions. The SDS fungus produces toxins that plants transport through their water-conducting vessels (xylem) up to the leaves, which results in foliar symptoms. Typically, these symptoms occur after flowering, but they have been observed during early soybean growth stages on highly susceptible varieties or when conditions are favorable.

Conditions that Favor Disease: Cool, wet field conditions shortly after planting favor early root infections and disease establishment. Frequent or heavy rains midseason can favor early symptoms.  Hot and/or dry conditions in the spring or summer can halt SDS development.

The presence of soybean cyst nematode (SCN) in the same field where SDS is found can increase the severity of SDS symptoms. Therefore, fields with SDS should be tested for the presence of SCN. Research has linked the presence of SCN with higher levels of SDS and increased yield loss. However, SDS can occur independently of SCN, and vice versa. Some crop production practices may also increase the risk of disease development. Fields with poor soil nutrients, low pH, poor drainage, or moderate to severe soil compaction are at higher risk of SDS.

Yield Loss and Impact: Yield losses due to SDS can be highly variable and depend on several factors, including the environment, the timing of symptom development, the susceptibility of a soybean variety to the disease, and the levels of SCN present in the field. SDS can weaken plants and cause premature defoliation — infected plants also may produce fewer and smaller seeds.

Yield losses can be substantial in years when susceptible soybean varieties are planted in cool, wet fields with a history of SDS and SCN. If symptoms develop later in the season, or weather is not conducive for disease development, yield losses can be minimal. Losses are rarely fieldwide since the disease often occurs in patches.  If foliar symptoms appear at or after growth stage R6, yield loss may be minimal.

Management: SDS management strategies include planting soybean varieties with SDS resistance, managing SCN, using effective fungicide seed treatments, improving soil drainage in fields with recurring SDS, rotating crops, avoiding or reducing soil compaction, and maintaining proper pH and fertility levels.

Weed of the week – Palmer Amaranth

Palmer Amaranth

FamilyPigweed, Amaranthaceae.

Life cycle: Summer annual.

Description: An erect summer annual that may reach 6 1/2 feet in height. Palmer amaranth closely resembles many other pigweed species,

Seedlings:  Stems below the cotyledons (hypocotyls) are without hairs (glabrous), and are often red in color. Cotyledons are narrow and green to reddish in color on the upper surface. Lower surfaces of cotyledons have a reddish tint. First true leaves are alternate, ovate in shape, and are slightly notched at the tip of the leaf blade

Roots: Taproot that is often, but not always, reddish in color

Stem: One central stem occurs from which several lateral branches arise. Stems are without hairs and can appear glossy.

 

 

Leaves: Alternate, without hairs (glabrous), and lance-shaped or egg-shaped in outline. Leaves are 2 to 8 inches long and 1/2 to 2 1/2 inches wide with prominent white veins on the undersurface. Leaves occur on relatively long petioles.

Flower/Seedhead: Small, green, inconspicuous flowers are produced in dense, compact, terminal panicles that are from 1/2 to 1 1/2 feet long. Smaller lateral flowers also occur between the stem and the leaf petioles (leaf axils).  Male and female flowers occur on separate plants. Each terminal panicle contains many densely packed branched spikes that have bracts that are 3 to 6 mm long; can produce 500 thousand to 1 million seeds per plant.

Similar Plants: Loosely resembles many other pigweed species. Palmer’s petioles are as long or longer than the actual leaf. This plant is hairless and has elongated seed heads. Leaves are typically more diamond shaped than other pigweed species, and occasionally has one hair at the tip of the leaf.

The Problem is……..Palmer amaranth is one of the most difficult weeds to control in agricultural crops.  It developed a major glyphosate resistance problem in the southern US from 2006-2010, and has been spreading in the midwestern US since, causing crop loss and increases in weed management costs. Characteristics that make it a successful annual weed include: rapid growth rate; wide window of emergence (early May through late summer); prolific seed production (upwards of 500,000 seeds/plant); tendency to develop herbicide resistance; and tolerance to many post-emergence herbicides when more than 3 inches tall.