Disease

Field Observations Thru May 26

Alfalfa

Most of our first cutting is complete.  If you have not mowed yet continue to monitor for alfalfa weevil.  As regrowth starts begin to monitor for potato leafhopper.

Corn

What a difference a week makes.  Most of our corn is now planted and about 50% has emerged.

 

Soil Crusting

Soil crusting is still an issue.  Continue to scout for emergence problems.  A few fields saw a return of the rotary hoe to help break the crust and aid in crop emergence.

Beans

Like corn, bean planting is coming to an end.  Soil crusting is also an issue in many of our bean fields. Continue to scout these fields for emergence problems.  Read more here.

Slugs

Slug damage was a problem early in a few fields.  The forecasted warm and dry weather should help to eliminate this problem.

 

Wheat

Scout for disease and insects:

Cereal Leaf Beetle Scouting Information

Powdery Mildew Scouting information

Head Scab Scouting Information

Most of our wheat is nearing a time when a decision must be made.  All of the wheat fields that I have looked at are showing no signs of disease pressure.  Here are some factors to consider

  1. No existing disease pressure
  2. The head scab forecast system is showing a very low chance of scab
  3. Fungicide cost can range from $12 – $18/acre plus application charges
  4. New crop wheat price is hovering around $6.20/bushel
  5. The 6 – 10 day precipitation outlook is for below normal rainfall and mild temperatures.

READ MORE HERE

To Spray Or Not To Spray?

Head Scab Forecasting System Click here to enlarge

Most of our wheat is nearing a time when a decision must be made –

To spray or not to spray?!  

Fungicide costs can range from $12 to $18 per acre plus application cost.  Today’s new crop wheat is hovering around $6.20 per bushel.

All of the wheat fields that I have looked at are showing no signs of disease pressure.  The head scab forecast system is showing a very low chance of scab and the 6 – 10 day precipitation outlook is for below normal rainfall and mild temperatures.  These factors are not conducive to disease development.

Below are additional thoughts from Dr. Pierce Paul and Dr. Kelley Tillman from this week’s C.O.R.N. Newsletter.

Fungicide and Insecticide at Flowering: Is This Really Warranted?

The wheat crop is flowering or will soon begin to flower in southern and central Ohio. Flowering will continue in the northern half of the state over the next two weeks. This is the growth stage as which the crop is most susceptible to infection by Fusarium graminearum, the fungus that causes head scab. Consequently, questions are being asked about applying a fungicide at flowering to control head scab, and at the same time, mixing in an insecticide to control cereal leaf beetle. According to the scab forecasting system (https://www.wheatscab.psu.edu/), the risk for head scab development has been low across the state over the past week. This is likely due, at least in part, to the cool, relatively dry conditions we have experienced across most of the state. The extended forecast suggests that dry (rain-free) conditions will persist over the next week or so.

Warm and consistently wet or humid conditions are required for head scab to develop. In fact, humid/wet conditions are also necessary for the development of most of the other economically important diseases of wheat such as Septoria, Stagonospora, and rust. When conditions are as consistently dry as they have been over the last few weeks, fungicides are not warranted. However, do continue to monitor the weather, and if it begins to rain, use the scab forecasting system to determine if the risk for scab is increasing as the crop continues to flower in the northern half of the state.

We specifically do not recommend tank-mixing an insecticide with a fungicide application if the insect populations do not legitimately warrant it.  Not only will it kill pollinators, but it also can eliminate the beneficial parasitic insects that attack cereal leaf beetle.  Insecticide is warranted for cereal leaf beetle control if there are 3 larvae per stem up to the boot stage, followed by a threshold of 1 larva per stem or flag leaf at boot stage and thereafter.  As the wheat begins to mature and grain fill has progressed, the need for spraying diminishes as it will not provide a return on investment.

Field Observations Thru May 19

Throughout the growing season I will post information on different pests or issues I am seeing in our fields in Knox County.

We are making a lot of planting progress this week.  Maybe not the most ideal conditions, but, we are getting seeds in the ground!  Below are a some to observations to keep an eye on.

Alfalfa

Not many changes this week, continue to scout fields for Alfalfa Weevil.

Click here for Alfalfa Weevil Scouting Guide

 

 

Corn

Soil Crusting

When heavy rains occur after planting, soil crusting can become a concern, inducing a shallow hard layer on the soil surface that forms due to rapid drying (e.g., warm days and wind).  This can affect seedling emergence.  Click here for more information.

Planting Depth

Occasionally check and verify planting depth.  When we get in a hurry sometimes we let a few things slide.  Improper planting depth can haunt you later in the season.

Plant Stand

Most of our early planted corn has emerged.

Now is a good time to take a few stand counts to evaluate your plant stand.  For 30 inch rows, measure 17′ 5″ and count the number of plants.  Multiply the number of plants you count by 1,000 to determine your plant stand.  Click here for more information.  Plant Stand Table

Click here to read the following post from OSU Agronomists Osler Ortez, Laura Lindsey, Alexander Lindsey

Soybeans

Same story as corn.  Check for emergence issues, planting depth and stand counts for early planted beans.  Check back next week for more detailed information on these issues.

Wheat

Continue to scout wheat, especially if you are considering a fungicide application.  More information can be found in this post.

Soybean Diseases are Showing up in Ohio

by: Horacio Lopez-Nicora, Stephanie Karhoff, OSU Extension

In early August we recommended to start scouting fields for soybean diseases. At that time (two weeks ago), disease incidence across Ohio was very low to moderate. Conducive environmental conditions, however, are turning things around and more fields are developing disease symptoms.

Sudden Death Syndrome (SDS)
We are finding fields in Ohio severely affected by sudden death syndrome (SDS) [Fig.1 and Fig. 2]. 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). Visit here for more information on SDS.

Figure 1. Soybean field in south Ohio severely affected by sudden death syndrome (SDS) with premature defoliation in the R5/R6 growth stage (A); symptoms begin with interveinal yellowing (chlorosis) of leaf (B); eventually leaf tissue dies and becomes brown but veins remain green (C). The fungus infects the root and produces toxins that are responsible for the above-ground symptoms.

If you have SDS, 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 (see address below). 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, and submit them to our lab. Do not hesitate to contact your extension educator or us if you have any questions.

Bacterial Blight, White Mold, and Phytophthora Root and Stem Rot

Continue reading →

More on Tar Spot: Mid to Late R-Stage Fungicide Application

Most of the corn across the state of Ohio is now between the late-R1 (silking) and late-R3 (milk) growth stages, with a few late-planted fields at late vegetative stages. Concerns about tar spot, but more likely, a sense of security provided by relatively high grain prices have led to several fields being sprayed with a fungicide at or shortly after R1 and questions being asked about spraying additional fields that are now at mid reproductive stages (between late-R2 [kernel blister] and R3 [milk]) of development. Concerns about tar spot are understandable, given how widespread the disease was last year (2021) and the level of damage it is capable of causing. However, the basic approach for tar spot management in Ohio should be no different from the approach commonly recommended for managing other, more common foliar, fungal diseases such as gray leaf spot. You have to scout fields, monitor the weather, and if needed, apply the fungicide when it is most likely to be effective, without violating label restrictions.

So far this season, of the more than 15 samples examined (actual leaves or images) and 40+ field scouted at 15-day intervals, only three were positive for tar spot. This is considerably lower than what we saw at a similar time and growth stage in 2021. Does this mean that your R2-R3 corn is no longer at risk for tar spot? In places where the disease is endemic (hot spots where lots of spores may be readily available), a susceptible hybrid is planted, and weather conditions are favorable (moderate temperatures and wet and humid), tar spot may still develop and spread quickly after R3. However, under conditions less favorable for tar spot development (cool and dry) where spores need to blow in from outside, the crop is at lower risk for tar spot, even if symptoms begin to develop at R3. So, the short answer is, if you planted a susceptible hybrid no-till or minimum-till in a corn field that had tar spot last year, and weather conditions become highly favorable over the next few weeks, your crop could still be at risk.

Continue reading →

Tar Spot Of Corn: What To Know And New Research

by: Dan Quinn and Darcy Telenko, Purdue University

Due to its relatively recent U.S. discovery and its ability to cause significant production and economic losses, tar spot is often a topic of angst and anxiety amongst corn farmers and agronomists in Indiana. For example, a severely infected field can reach yield losses upwards of 60 bushels per acre! Yield losses are often a result of reduced photosynthetic capacity (green leaf area) of the corn plant during grain fill resulting in poor grain fill, kernel abortion, and reduced kernel weight. In addition, severe infection can reduce corn stalk integrity and cause significant lodging later in the season. Tar spot was first confirmed in northwest Indiana in 2015 and the first significant yield-reducing event of the disease was observed in 2018. Similarly, severe outbreaks and large areas of infection of this disease were observed in Indiana in 2021. Tar spot is caused by the fungus known as Phyllachora maydis and can be identified by small, raised black and circular spots present on corn leaves, stalks, and husks (Figure 1). These black and circular spots are known as fungal fruiting structures called stromata, each of which can produce thousands of spores. Overall, tar spot infection and severity can vary based on environmental conditions, the total amount of the pathogen present in the field, and corn hybrid chosen.

What Conditions Cause Tar Spot? Continue reading →

Xyway Corn Fungicide Trial

Knox County Xyway Trials

Taking stand counts at our Xyway plot – Great looking field of corn!

 

 

A Special Thanks to Ed & Vicki Piar!!

 

The goal of this study is to determine corn’s response to an at-plant soil application of flutriafol (Xyway™) fungicide. Information from this trial will be used to improve corn disease management recommendations for growers throughout the state.