Check your corn now for stalk strength

As harvest approaches, its time to check our corn plants for stalk integrity.  Time spent tin the field now, may pay huge dividends later this fall.  As stalk tissue becomes compromised below the main ear the stalk may become brittle or weak and be prone to lodging.

There are a number of plant pathogens that can cause stalk rot including, Anthracnose, Bacteria, Charcoal, Diplodia, Fusarium, Gibberella, and Pythium. Some of these stalk rots have very characteristic symptoms that can help identify the specific problem, while others may require laboratory diagnosis (Table 1).  The Purdue Extension Publication Corn Diseases: Stalk Rot has good images to help identify the major stalk rot diseases. (https://www.extension.purdue.edu/extmedia/BP/BP-89-W.pdf ).

Check field by using the Push or Pinch Test by evaluating 20 plants in at least five random areas in a field.

  • Pinch Test – grab the stalk somewhere between the lowest two internodes and pinch between your fingers to see if the stalk is strong enough to handle the force – if the stalk collapses, it fails.
  • Push Test – push the stalk to a 30-degree angle – if it pops back up when released, it passes the test, if not it fails.

Threshold: 10% or more of the stalks fail then consider field for early harvesting to avoid risk for lodging.

What can you do in the future – management options will depend on the specific disease (see table 1). Production practices that promote good plant health including balanced fertilization, appropriate plant populations, and good water management can reduce stresses that might predispose corn to stalk rot. In addition, these key management tools can help mitigate future stalk rot issues.

  1. Properly diagnosis the stalk rot pathogen.
  2. Select hybrids with resistance if available.
  3. Crop Rotation – rotating to non-host crop will help reduce stalk rot potential in a field. Note that Charcoal rot and Gibberella stalk rot can infect other rotational crops.
  4. Tillage – burying infected crop residue will encourage more rapid desiccation and help reduces risk of overwintering in crop residue.
  5. Good soil drainage and reduced compaction.
  6. Foliar Fungicides – applying foliar fungicides can help protect crop from foliar diseases that could predispose plant to stalk rot when present, but devoid of foliar disease pressure fungicides applications have not consistently been found to help reduce stalk rot.

Field Observations Thru September 8

Corn

Growth & Development

Most of the corn that I have seen this week is in either the R4 (Dough) or the R5 growth stage.

R5 – Dent

  • The second to last stage of corn development.
  • R5 (dent) occurs approximately 31‐33 days after silking.
  • Kernels are dented in at the top with the “milk line” separating the liquid and
    solid (starch) portions.
  • Within R5, kernels are often staged according to the progression of the milk line; i.e. ¼, ½, and ¾.
  • At the beginning of R5, kernels have 60% moisture content.
  • Stresses will reduce kernel weight at this time.

Scouting

I have heard a wide range for projected corn yields this year.  The Yield Component Method is the most widely used procedure for estimating corn yield.  While  you are out checking potential corn yields, also keep an eye out for:

  • Ear rots.
  • Stalk rots.
  • Anthracnose top dieback.
  • Stalk lodging.
  • Abnormal ear fill which identifies periods of stress.
  • Weed escapes (especially palmer & waterhemp).

Soybeans

Growth & Development

Soybeans are continuing to mature.  Last week I highlighted the R6 growth stage  the next stage is R7 the last growth stage prior to maturity.

R7 – Begining Maturity

  • One mature-colored pod anywhere on the main stem.
  • Yellow pods are moving toward maturity.
  • Tan, brown or tawny pods (depending on variety) signal physiological maturity.
  • Seeds at the R7 growth stage are at approximately 60% moisture.

Scouting

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

Estimating soybean yields

It is much more difficult to accurately predict soybean yield.  The process to estimate soybean yields can be found here.

County Rainfall Update

Field Observations Thru September 1

They are here!  Palmer Amaranth and Waterhemp are prevalent in MANY Knox County fields.  One female plant can produce 1,000,000 seeds.  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.

Continue to remain vigilant!  

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

Corn

Growth & Development

Most of the corn that I have seen this week is in either the R3 (Milk) or the R4 (Dough) growth stage.  Some of our early maturing hybrids have reached the R5 dent stage.

Scouting

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

  • Foliar diseases – Gray Leafspot, Tar Spot, Northern Corn Leaf Blight.
  • Weed escapes (especially Palmer and Waterhemp).

Soybeans

Growth & Development

Most of the corn that I have seen this week is in the R6 (Full Seed) growth stage.  Some of the early maturity beans are entering the R7 (Beginning Maturity) stage soon.

Scouting

Disease pressure throughout the county continues to be very low.  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).

County Rainfall Update

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

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

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