2023 Wisconsin Fungicide Test and Disease Management Summary Now Available!

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Brian Mueller, Researcher II, UW-Madison, Plant Pathology

Damon Smith, Professor and Extension Specialist, UW-Madison, Plant Pathology

Each year the Wisconsin Field Crops Pathology Program conducts a wide array of fungicide and disease management tests on alfalfa, corn, soybeans, and wheat. These tests help inform researchers, practitioners, and farmers about the efficacy of certain fungicide products on specific diseases and how to pair them with other disease management strategies. We hope you find this report useful in making decisions for the 2024 field season.

The 2023 Wisconsin Field Crops Fungicide Test and Disease Management Summary is available by clicking here. These tests are by no means an exhaustive evaluation of all products available, but can be used to understand the general performance of a particular fungicide in a particular environment. Keep in mind that the best data to make an informed decision, come from multiple years and environments. To find fungicide performance data from Wisconsin in other years, visit the Wisconsin Fungicide Test Summaries page. You can also consult publication A3646 – Pest Management in Wisconsin Field Crops to find information on products labeled for specific crops and efficacy ratings for particular products. Additional efficacy ratings for some fungicide products for corn foliar fungicides, soybean foliar and seed-applied fungicides, and wheat foliar fungicides can be found on the Crop Protection Network website.

Mention of specific products in these publications are for your convenience and do not represent an endorsement or criticism. Remember that this is by no means a complete test of all products available.  You are responsible for using pesticides according to the manufacturers current label. Some products listed in the reports referenced above may not actually have an approved Wisconsin pesticide label. Be sure to check with your local extension office or agricultural chemical supplier to be sure the product you would like to use has an approved label.  Follow all label instructions when using any pesticide. Remember the label is the law!

Wisconsin Field Crops Disease Update, August 9, 2023

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Damon Smith, Extension Field Crops Pathologist, Department of Plant Pathology, University of Wisconsin-Madison

Figure 1. A Screen shot of a map developed in the Field Prophet app showing risk for tar spot development in Wisconsin as of August 9, 2023.

Well, it was going to happen sometime soon, tar spot has been confirmed in two counties in Wisconsin. You can track tar spot confirmations in realtime HERE. Both Lafayette and Rock counties were confirmed to have low levels of tar spot in several fields this week. The good news is that these finds are a month behind the initial confirmations in the state for the last two seasons. What does this mean? Well, it means that the tar spot impact on grain yield will likely not be has significant as it has been over the last couple of seasons. Exceptions to this statement will include late-planted corn where the current growth stages are around VT (tasseling) and susceptible silage hybrids. You should scout and track these situations carefully. Be prepared to chop silage early if tar spot really starts to move. You will want to watch moisture carefully in these situations.

The current risk for tar spot development remains moderate to high across much of the state (Fig. 1). Cooler weather and dewy evenings and mornings are keeping the risk elevated. Fungicide applications for much of the corn in the state should have happened already. Remember the optimal time to apply fungicides to control tar spot (and most other foliar corn diseases) is between the VT (tasseling) and R3 (milk) growth stages. Spraying fungicide after R3 has not yielded much of a return on investment. If you find tar spot, please don’t hesitate to send a high-quality photo to damon.smith@wisc.edu. We don’t disclose exact locations, but do like to track the county-level tar spot information. If you would like to learn more about tar spot and managing it, see my previous post HERE.

Figure 2. Sporecaster predictions for selected non-irrigated locations in Wisconsin for August 9, 2023.

In other news, white mold risk ranges from low in the southern portion of the state to moderate and high in the mid and upper portions of the state, respectively (Fig. 2). Most soybeans are probably headed toward the R4 or R5 growth stage. This means fungicide applications will no longer yield positive returns on investment. If soybeans were planted late and they are still in the R1 to R3 growth stages and you are in a moderate to high risk area, a fungicide should be applied at this time. If you would like to learn more about white mold management, see my previous post HERE. We have observed active white mold on susceptible varieties under irrigation already this season. I am anticipating pockets of white mold in the state, especially in our typical areas of concern in the central and northeastern quadrants.

As always, make sure you are out and scouting to be prepared for what is coming ahead!

Wisconsin Field Crops Disease Update, July 27, 2023

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Damon Smith, Extension Field Crops Pathologist, Department of Plant Pathology, University of Wisconsin-Madison

Shawn Conley, Extension Soybean and Small Grains Agronomist, Department of Plant and Agroecosystem Sciences, University of Wisconsin-Madison

Rains continue to fall around Wisconsin. While we still have a moderate drought in much of the state, some of that drought is being alleviated. However, with these timely rains, come disease concerns. Here are our thoughts on what is happening.

Phytophthora Root and Stem Rot of Soybean

Figure 1. Stem rot symptoms of Phythophthora rot and stem rot on soybeans.

It has been a couple of years since we have seen a significant epidemic of Phytophthora root and stem rot (PRSR) of soybean. However, since it has started raining, we have got a good look at how susceptible many of our soybean varieties are here in Wisconsin. PRSR is primarily cause by the fungal-like organism, Phytophthora sojae. PRSR is usually worse in fields that are no-till and/or are slow to drain. The PRSR pathogen likes to survive in old soybean residue and can also persist as a long-term survival structure in the soil itself. The organisms that causes PRSR becomes active if the soil temperatures are over 60 F and the soil becomes saturated. We had those conditions occur back in early to mid-July. Once the soil dried out a bit and a bit of environmental stress kicked in, we can readily observe the damage the organism caused in early July. Primarily what we are seeing right now is the stem rot phase (Fig. 1), with the symptoms including wilting of the plant and a distinct purple-brown lesion extending from the soil surface upward. If plants are pulled from the ground, you will also see poor root systems which is where the organisms typically first infects and causes damage.

At this point in the season, there is nothing that can be done.  DO NOT spray foliar fungicides for this problem. This will not be effective. You will want to check on the variety with the symptoms and consult the tech sheet to see what type of “Phytophthora gene” may have been included in the variety. These genes are called Rps genes and provide race-level resistance. The population of the PRSR pathogen can be a single race or mixed races in the field. The last time a survey of Phytophthora races was done in Wisconsin, it was noted that the Rps 1-k resistance gene should be effective on about 99% of the acres in the state. However, that survey was done over 15 years ago. Due to heavy use of the Rps 1-k resistance gene, we believe that the population in the state has shifted. We are seeing that resistance readily overcome. Unfortunately, most of the varieties currently grown in the state have this resistance. A recent check of the soybean variety trials 2022 show that out of 265 varieties tested 25% had no PRSR resistance gene, 2% had Rps 1-a, 29% Rps 1-c, 26% Rps 1-k, 9% Rps 3-a, and 9% had multi-genes. We are actively working with the Wisconsin Soybean Marketing Board to understand what the current population looks like. However, it is too early to tell what the races are primarily in our fields. Moving forward. perhaps choosing Rps 3-a or mixed gene varieties could help, but that is a shot in the dark for now.

Other things you can do for PRSR are to open up the rotation between soybean crops, and improve drainage in fields that are typically saturated for long periods of time. Like I said above, adjusting variety choice can help too. Seed treatment fungicides can also be used. However remember that the seed treatment is only going to be effective for the first 30 days or so after planting. After that we have to rely on varietal resistance to manage this problem. If you would like to find efficacy data on the seed treatments you can find that HERE.

We are looking for samples of PRSR from around Wisconsin. So feel free to reach out (damon.smith@wisc.edu) and we can coordinate getting samples sent to us. This will help with our survey efforts and eventual varietal recommendations.

Tar Spot Update

Figure 2. A Screen shot of a map developed in the Field Prophet app showing risk for tar spot development in Wisconsin as of July 27, 2023.

You can find the most recent updates on tar spot confirmations across the U.S. here: https://corn.ipmpipe.org/tarspot/.  Tarspotter is also showing mostly moderate to high risk across the state of Wisconsin (Fig. 2). This means you should be actively scouting for tar spot at this time. The risk is likely that you will find it across much of the state. If the corn growth stage is between VT/R1 and R3, then you might go ahead and consider a fungicide application. Our research has shown that one well-timed application of fungicide somewhere between VT/R1 – R3 will control tar spot enough for a yield response even in a heavy-pressure year. You can learn more about managing tar spot by clicking here. If you think you found tar spot I would appreciate if you would let us know. We can enter the county level data into the Corn IPMPipe Map and contribute to the cause.

White Mold Update

Figure 3. Sporecaster predictions for selected non-irrigated locations in Wisconsin for July 27, 2023.

The risk for white mold according to Sporecaster is a bit more spotty, compared to tar spot. Mostly the northern tier of the state is at high risk while central and southern Wisconsin varies from moderate to low (Fig. 3). If you are in a low-risk area and you are at R3 or beyond, you might not have much to worry about for this year when it comes to white mold. However, if you are in a moderate-risk zone, watch this situation carefully. If you are at R3 and the crop has good canopy, you might consider one late R3 application. If you are in a high-risk zone, the crop has canopied, and your soybean crop is in the bloom period, it is time to think about a fungicide application. The recent rains have made the risk in these areas generally stay high or increase. These will be the areas I would expect to find white mold 1-3 weeks from now. If you would like to learn more about white mold management, check out my previous article HERE.

As always, get out and look the crop. Scout, scout, scout!

Wisconsin Field Crops Disease Update, July 12, 2023

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Damon Smith, Extension Field Crops Pathologist, Department of Plant Pathology, University of Wisconsin-Madison

Here is southern Wisconsin we are finally getting some rains. These rains are appreciated and timely for the crops out there, but also timely for some important pathogens of wheat, corn, and soybeans. Let’s talk about where we are at with disease risk this week.

What’s up with Wheat?

Let’s talk first about wheat first. Folks have started harvesting the crop and bailing straw and I have been getting photos of sooty mold on heads. You can find out more about sooty molds on wheat by clicking here. Essentially sooty mold is caused by a number of opportunistic fungi that can come in and cause mostly aesthetic problems on wheat heads that might have matured early, died early, or had other stress. These fungi do not need to be controlled. However, you should harvest affected wheat as soon as possible. Occasionally if wheat with sooty mold is left in the field for a long time, these fungi can eventually find their way in to the kernel and cause a problem called black point which can lead to quality problems. Get out and get that crop in as fast as you can!

Should I be Spraying for Tar Spot?

Figure 1. A Screen shot of a map developed in the Field Prophet app showing risk for tar spot development in Wisconsin as of July 12, 2023.

The short answer is not yet! Be patient. Yes, there have been many recent confirmations of the disease across the Midwest. You can find the most recent updates on tar spot confirmations here: https://corn.ipmpipe.org/tarspot/.  Tarspotter is also showing mostly high risk across the state (Fig. 1). This means you should get out and scout! Remember, the best time to spray fungicide for tar spot is between the VT and R3 growth stages. We are not quite there yet and need to be patient to maximize the performance of our fungicides. You can learn more about managing tar spot by clicking here. If you think you found tar spot I would appreciate if you would let us know. We can enter the county level data into the Corn IPMPipe Map and contribute to the cause.  Again, be patient and get out there and scout and get your steps in!

What to Do About Soybean White Mold?

Figure 2. Sporecaster predictions for selected non-irrigated locations in Wisconsin for July 12, 2023.

Yeah, it’s bean dry, yeah soybeans are slow to canopy. If you didn’t plant soybeans in narrow rows, you need to be patient and let soybeans get to full canopy. If this happens before the R3 growth stage, then check Sporecaster and see what the risk is. As of today, risk is low to moderate in south and south-central Wisconsin, Southwest Wisconsin, while in east and northeast Wisconsin risk is high if soybeans are flowering and canopy is nearly closed (Fig. 2). Again, I know it has been dry, but we are getting some timely rains that are impacting risk and resulting in the increase in risk. I do think that we can be patient and wait to the R3 growth stage to make the fungicide application decision. Our data suggest that this is the best time to spray for white mold in Wisconsin in recent years. If you would like to learn more about white mold management, check out my previous article HERE.

What Should I do About Tar Spot of Corn in 2023?

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Damon Smith, Extension Field Crops Pathologist, Department of Plant Pathology, University of Wisconsin-Madison

Brian Mueller, Researcher II, Department of Plant Pathology, University of Wisconsin-Madison

Roger Schmidt, Nutrient and Pest Management Program, University of Wisconsin-Madison

It didn’t take long this year to find tar spot in the Midwest. Over the last several weeks we have seen confirmed positives for tar spot in parts of Iowa, Missouri, Kansas, and Nebraska (Fig. 1). This is earlier than last year despite. With that said, the severity is extremely low and does not necessitate spraying fungicide at the moment! So what should you do?

Figure 1. Map of U.S. counties where tar spot has been confirmed in the 2023 season, as of July 5, 2023. Map source: https://corn.ipmpipe.org/tarspot/.

What should I do?

My advice is to get prepared and make sure you have the tools in place to deal with this problem. As I said the last few seasons, tar spot is here to stay and we need to simply be prepared and ready to fight the disease. The first line of defense is to know if you have had tar spot before. This will tell you if there is resident inoculum sources present that can initiate epidemics. If you have seen tar spot on your farm before, then assume the pathogen is present and in close proximity to corn (the host). Remember the disease triangle? The last component of the triangle is the weather. If there has been conducive weather then the triangle has been met and risk is high for finding tar spots. So how do you know if the weather is conducive? Well, there is an app for that!

Tarspotter and Field Prophet are both Smartphone applications that can help you determine if the weather has been conducive to put your corn crop at high risk of tar spot development. Figure 2 shows a map of Wisconsin from the Field Prophet version of the tool that is showing that weather has been highly conducive for the development of tar spots. The app DOES NOT tell you if the pathogen is present. We are working on this part of the triangle to improve our predictions, but you need to determine if the pathogen is present in your field. This tool just tells you if the weather has been conducive.

Figure 2. A Screen shot of a map developed in the Field Prophet app showing risk for tar spot development in Wisconsin as of July 5, 2023.

So what weather is conducive for tar spot development? You are probably asking yourself this as we are in an epic drought, yet the forecasted risk of tar spot is high across the state. Well conducive weather for the pathogen it is different that the weather needed to grow corn. Yes, precipitation is helpful, but more importantly, we need intermittent wet/dry cycles to give us intermittent leaf wetness. Specifically leaf wetness at night. What gives leaf wetness this time of year other than rain? That would be high dew points and humidity. These variables are included in the models that run in Tarspotter and Field Prophet. We also include temperature which is an influential variable too. These variables are measured over the last 14 days and 30 days and included in each daily run of the tool. We use the GPS on the smartphone to pull down cloud-based weather for a precise location. Thus, these results are site-specific. I also like to the use the Field Prophet version of the models as this version provides a 7-day trend line on how weather has been progressing and also allows for a true 7-day forecast. These additional tools can better help with the decision-making process. If you would like to learn more about the “nuts and bolts” that run behind the smartphone apps, you can find our research publication HERE.

My corn is at V10, should I spray Fungicide?

My short answer is no! The disease is just getting started. If you find it in Wisconsin right now, it will be at low severity and is low in the canopy on leaves that are not going to contribute to yield. My advice is to use your prior knowledge of where tar spot occurred and the Tarspotter tool to help guide your scouting efforts. Get out into the fields and know what you are dealing with. Figure 3 shows various severity levels on a corn leaf. We don’t start to see yield loss until we reach about 10% severity on the ear leaves or above. Thus, you have time! Target fields planted to known susceptible hybrids. Get yourself prepared and use those lower leaves to monitor severity and tar spot progress. Be ready to protect (put fungicide on) those leaves that contribute to yield (ear leaf and above), later on especially if the weather becomes increasingly conducive (think wet/dry cycles!) and/or your scouting indicates severity is increasing.

When should I spray fungicide? What should I use?

Figure 3. Tar spot severity diagram indicating various levels of tar spot on corn leaves. Yield loss isn’t typically detectable in the field until severity reaches 10% or more on the ear leaf or leaves above this leaf.

Our recent work has shown that if you get the product right, you can generally control tar spot to the point to preserve your yield potential, with one well timed spray. So what is that timing of the single application? That would be between the VT (tasseling) and R3 (milk) growth stages. We determined this using a series of trials where we did single applications of fungicide for individual growth stages. Figure 4 shows the results of two trials from 2020 where the window of opportunity to reduce the severity of tar spot with a single application is between VT and R3. Yes, the two-spray program (V8+VT) did also control tar spot, but all the work was done by the VT application, not the V8-timed spray! Thus, if you chose to spray your 2023 crop at this point in the season, you stand a good chance of having to come back with a second application later in the season.

Also notice in figure 4 that Tarspotter was tested in 2020 and did not perform very well. This was an early iteration of the tool and we have since improved its performance. So please don’t judge the tool based on this figure. If you would like to see how Tarspotter performed in advising fungicide applications last season, check out this article based on the 2021 field season.

Now the questions is what fungicide should you choose? The short answer is that you have lots of options. You can learn more about fungicides and fungicide performance by CLICKING HERE. You can also check out the efficacy of various fungicides based on a collective of University research by viewing the “Fungicide Efficacy for Control of Corn Diseases” on the Crop Protection Network website. In addition, Dr. Darcy Telenko at Purdue University led an effort to publish data from a multi-state coordinated fungicide trial where we tested various fungicides during the 2021 epidemic.

Figure 4. Tar spot intensity after spraying fungicide once at each corn growth stage during the 2020 field season.

 

Figures 5 shows the tar spot severity, while figure 6 the corn yield, from those trials where a single application of each of the products was made at the VT growth stage. Clearly you have lots of options when it comes to products that can control tar spot. That is good news! Yes, some products do a bit better in preserving yield over others, but all fungicides tested in 2021 resulted in numerically higher yields than not-treating. Remember that 2021 was a banner year for tar spot. These results might not be as clear in a year where tar spot is not as intense.

Figure 5. Tar spot severity from multi-state trials where corn was treated with foliar fungicides at the VT corn growth stage, or not treated. Source: Telenko et al., 2022 – https://apsjournals.apsnet.org/doi/10.1094/PHP-02-22-0012-BR.

Figure 6. Corn yield from multi-state trials where corn was treated with foliar fungicides at the VT corn growth stage, or not treated. Source: Telenko et al., 2022 – https://apsjournals.apsnet.org/doi/10.1094/PHP-02-22-0012-BR.

The Conclusion

DON’T PANIC! This is just a call to be ready. Download the apps and know what the weather is doing. Use your prior knowledge and scouting in key locations to track tar spot. Get your management plan in place. Have your fungicide of choice available. Communicate with your custom applicator. Be ready to spray between the VT and R3 growth stages if you plan to use just one fungicide application and you are seeing tar spot increase. If you spray between the V8 and VT growth stages, be ready to monitor the smartphone apps and do more scouting as you might have to pull the trigger again later in the season. Get out and SCOUT, SCOUT, SCOUT!

Other Resources

2022 Wisconsin Fungicide Test and Disease Management Summary Now Available!

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Brian Mueller, Researcher II, UW-Madison, Plant Pathology

Damon Smith, Associate Professor and Extension Specialist, UW-Madison, Plant Pathology

Each year the Wisconsin Field Crops Pathology Program conducts a wide array of fungicide and disease management tests on alfalfa, corn, soybeans, and wheat. These tests help inform researchers, practitioners, and farmers about the efficacy of certain fungicide products on specific diseases and how to pair them with other disease management strategies. We hope you find this report useful in making decisions for the 2023 field season.

The 2022 Wisconsin Field Crops Fungicide Test and Disease Management Summary is available by clicking here. These tests are by no means an exhaustive evaluation of all products available, but can be used to understand the general performance of a particular fungicide in a particular environment. Keep in mind that the best data to make an informed decision, come from multiple years and environments. To find fungicide performance data from Wisconsin in other years, visit the Wisconsin Fungicide Test Summaries page. You can also consult publication A3646 – Pest Management in Wisconsin Field Crops to find information on products labeled for specific crops and efficacy ratings for particular products. Additional efficacy ratings for some fungicide products for corn foliar fungicides, soybean foliar and seed-applied fungicides, and wheat foliar fungicides can be found on the Crop Protection Network website.

Mention of specific products in these publications are for your convenience and do not represent an endorsement or criticism. Remember that this is by no means a complete test of all products available.  You are responsible for using pesticides according to the manufacturers current label. Some products listed in the reports referenced above may not actually have an approved Wisconsin pesticide label. Be sure to check with your local extension office or agricultural chemical supplier to be sure the product you would like to use has an approved label.  Follow all label instructions when using any pesticide. Remember the label is the law!

Are My Fungicides Messing with the Good (Microbes) Guys?

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The following blog post was written as a part of a graduate level class assignment at the University of Wisconsin-Madison. Of course much more work needs to be done in this area, but there is some interesting “food for thought” and should be considered the next time you might want to spray a fungicide.    ~Damon Smith, Professor and Extension Specialist

 

Kelly Debbink, master’s student, Department of Plant Pathology, University of Wisconsin-Madison

Have you ever wondered if fungicides can negatively impact soil microbes? Since their job is to kill fungi, it seems logical that they may have this effect on the fungi in the soil, right? This thought process is exactly what led me into reading a few too many published studies related to the topic.

Background

Let me start with a bit of what we know about soil microbes (mainly fungi and bacteria). Some microbes form symbiotic relationships with plants, through which they can colonize the root system (rhizosphere), the above ground plant surfaces (phyllosphere), and even internal tissues (endosphere). These microbes can help plants access nutrients and water, fight off diseases caused by other pathogenic microbes, and deal with stressful environments. Many other types of microbes may not form direct relationships with plants, but still live in the soil and provide services, like breaking down nutrients.

To carry out many of these useful activities, microorganisms produce diverse groups of enzymes. They are proteins that work to facilitate different processes and are necessary in many services related to soil health, including decomposing organic matter, nutrient cycling, and degrading hazardous compounds. Enzyme amounts are sensitive to environmental factors like pH and soil organic matter as well as management practices like crop type, chemical use, and fertilizer use. Any alteration of the soil microbial community will lead to changes in enzyme production, so they are commonly used as a soil health indicator. Lower enzyme levels are generally tied to less fertile soil and less productive crops.

So, if microbes are responsible for all these services, could we be causing them harm and hindering some of these services when we apply fungicides?

In my search I was specifically hoping to find field research instead of lab research, so I could find information that was a closer proximation to real life conditions. I will admit that most studies I found on this topic were performed in the lab by removing soil from an agricultural region, dosing it with fungicides, and running soil health tests on it. I did find a few field studies in which treated and non-treated plots were compared in normal cropping systems. These studies were all a bit different in their approaches to measuring changes, and they tested many different fungicides with different modes of action, so I would not compare these studies side-by-side to each other, but I will share some general trends that appeared in their results.

Soil Microbes

To start, there do appear to be shifts in some of the fungal and bacterial communities related to fungicide treatments. In a study that looked at seed coatings (fungicides & insecticides), these did not appear to decrease the richness (total # of microbe species) but did shift the abundance of different groups of microbes. In another study, the number of culturable bacteria and fungi were decreased, which at least suggested a decrease in richness of the subset of microbes that are culturable on lab media. Other lab experiments showed declines or shifts in the fungal community, but differing results on the bacterial community (they may decline as well or may increase). In some conditions, bacteria may be able to thrive once they have decreased competition from fungi. In one field trial, the label application rate and 2x the label rate led to short-term declines in measures of viable microbes. These declines all recovered by harvest. Additionally, this study tested 10x the label rate, but in this treatment, microbes remained low through harvest.

Soil Enzymes

Shifts in soil enzymes related to microbial activity and nutrient cycling were observed in multiple field trials. The general trend appears to be that at lower fungicide application levels, like label rate and twice the label rate, these enzymes may shift up and down, but often return near normal levels by harvest time. In contrast, the study that applied 10x the label rate observed declines in most enzymes that did not recover by harvest. This suggests that improper overuse or accumulation of fungicides may be detrimental to soil functions like nutrient cycling.

Conclusion

Overall, there are many environmental conditions that play a role in soil fungal and bacterial populations and enzyme activity. Many management decisions can have an impact on these, like crop rotation, tillage, and fertilizer use. Chemical use, like fungicides and other types of pesticides, likely also play a role in at least short-term shifts in soil microbes and enzyme activity. Obviously, the main goal of these fungicides is to control disease, and they are certainly a useful and necessary tool to protect crop yields and minimize disease. However, these studies do help remind us that there can be negative soil health effects to their overuse, in addition to the increased risk of pesticide resistance. It’s a good reminder that fungicides are only one tool in the toolbox, and other management decisions like choosing resistant varieties can help us control disease with fewer necessary fungicide applications.

 

References:

Background

Turner TR, James EK, Poole PS. The plant microbiome. Genome Biol. 2013 Jun 25;14(6):209. doi: 10.1186/gb-2013-14-6-209. PMID: 23805896; PMCID: PMC3706808.

Chettri, D., Sharma, B., Verma, A. K., & Verma, A. K. (2021). Significance of Microbial Enzyme Activities in Agriculture. Microbiological Activity for Soil and Plant Health Management, 351–373. https://doi.org/10.1007/978-981-16-2922-8_15

Field Trials

Hou, K., Lu, C., Shi, B., Xiao, Z., Wang, X., Zhang, J., Cheng, C., Ma, J., Du, Z., Li, B., & Zhu, L. (2022). Evaluation of agricultural soil health after applying pyraclostrobin in wheat/maize rotation field based on the response of soil microbes. Agriculture, Ecosystems & Environment, 340, 108186. https://doi.org/10.1016/j.agee.2022.108186

Saha, A., Pipariya, A., & Bhaduri, D. (2016). Enzymatic activities and microbial biomass in peanut field soil as affected by the foliar application of tebuconazole. Environmental Earth Sciences, 75(7). https://doi.org/10.1007/s12665-015-5116-x

‌ Nettles, R., Watkins, J., Ricks, K., Boyer, M., Licht, M., Atwood, L. W., Peoples, M., Smith, R. G., Mortensen, D. A., & Koide, R. T. (2016). Influence of pesticide seed treatments on rhizosphere fungal and bacterial communities and leaf fungal endophyte communities in maize and soybean. Applied Soil Ecology, 102, 61–69. https://doi.org/10.1016/j.apsoil.2016.02.008

‌Lab Experiments

Han, L., Xu, M., Kong, X., Liu, X., Wang, Q., Chen, G., Xu, K., & Nie, J. (2022). Deciphering the diversity, composition, function, and network complexity of the soil microbial community after repeated exposure to a fungicide boscalid. Environmental Pollution, 312, 120060. https://doi.org/10.1016/j.envpol.2022.120060

‌ Cycoń, M., Piotrowska-Seget, Z., & Kozdrój, J. (2010). Responses of indigenous microorganisms to a fungicidal mixture of mancozeb and dimethomorph added to sandy soils. International Biodeterioration & Biodegradation, 64(4), 316–323. https://doi.org/10.1016/j.ibiod.2010.03.006

 

2022 Badger Crops and Soils Update Meetings

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The annual UW Agronomy, Pest Management and Soil, Water, and Nutrient Management meetings are moving to a new format this year and will be offered as a single day-long program. Two in-person sessions as well as a virtual option will be offered. In-person sessions in Green Bay and La Crosse will follow the same agenda. The virtual option will follow a similar but abbreviated agenda.

This year’s program will be focused on the theme of “Achieving a Positive Return on Investment in an Era of High Input Costs (a.k.a Small steps, Big change).” The meetings will present the latest information on agronomic, pest, and nutrient management research coming out of UW with a lens to on-farm application.

For details and to register for the event, please CLICK HERE or scan the QR code in the attached flyer. We are looking forward to seeing you and kicking off a busy winter meeting season!

Wisconsin Corn and Soybean Disease Update and Forecast – July 21, 2022

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Damon Smith, Extension Field Crops Pathologist, Department of Plant Pathology, University of Wisconsin-Madison

Roger Schmidt, Nutrient and Pest Management Program, University of Wisconsin-Madison

Rain, and the return of more humid weather, has meant that risk of tar spot of corn and white mold of soybean has increased over the past week. Now is the time to think about your in-season management plan for both of these diseases. Let’s dig in a bit on what the risk looks like for each disease.

Tar Spot of Corn

This week we added Fond du Lac County to the tar spot map (Fig. 1). We also continue to see tar spot slowly increasing in plots and production fields on the Arlington research station. Looking back at our records from last season, we are tracking almost identically with what happened last year. I know folks think it is dry, but the tar spot fungus doesn’t care. It might move slow in these conditions, but the elevated humidity provides adequate leaf wetness for the disease to slowly progress. Should it start raining more regularly I expect the disease to pick up speed.

Corn is rapidly approaching (if not already at) the optimal window of opportunity (VT-R3) for spraying fungicide to control tar spot. Given the high risk for tar spot across much of the state (Fig. 2), now is the time to call in that fungicide application if you are planning on it. Given the possible constraints on locating a custom applicator, getting the order in earlier than later may ensure application of fungicide by the R3 corn growth stage. Get out and scout, scout, scout!

Figure 2. Tar Spot Risk for Wisconsin on July 21, 2022

White Mold of Soybean

White mold risk has increased from reasonably low last week, to mostly moderate across the state, this week (Fig. 3). Risk trends are also increasing, indicating that weather is continuing to become more favorable for white mold development. As we approach the R3 soybean growth stage, it will be important to make a decision on fungicide application, especially if you haven’t already applied a fungicide. If rain moves in over the next 7-10 days, expect risk to continue to increase. In irrigated fields we have been able to find apothecia (the mushroom-like structure that produces spores that infect soybean). This corroborates the increased risk we are seeing even in non-irrigated fields.

Figure 3. White mold risk in Wisconsin for July 21, 2022.

The Field Prophet Tool

For those who like all of their disease prediction tools in one place you might check out the Field Prophet version of the Tarspotter and Sporecaster apps. This tool consolidates all of our disease prediction tools into one convenient tool. The app also allows for true 7-day forecasting and will display 7-day trends to better inform your disease management decisions. Field Prophet, Inc is a startup company supported by UW-Madison and uses science-based information and the same models as Tarspotter and Sporecaster to deliver informative tools for agriculture clientele. You can also download and use Field Prophet for free for the next 6 months! You might find this tool as a handy alternative to Tarspotter and Sporecaster.

 

 

Wisconsin Corn and Soybean Disease Update and Forecast – July 14, 2022

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Damon Smith, Extension Field Crops Pathologist, Department of Plant Pathology, University of Wisconsin-Madison

Roger Schmidt, Nutrient and Pest Management Program, University of Wisconsin-Madison

Weather over the last week has been generally drier with milder temperatures in most of Wisconsin. Isolated storms have occurred and periods of leaf wetness have prevailed. So what does that mean for important plant diseases of corn and soybeans? Let’s break that down.

Tar Spot of Corn

As noted last week we found tar spot in Columbia county Wisconsin, which was the first report for 2022. This week we add Dane County to the list (Fig. 1). Tarspotter risk has remained high for much of the state over the last week due to milder temperatures and periods of leaf wetting events. It is important to note that conditions favorable for tar spot development are different than those for white mold in soybean. For white mold rain, more sustained wetting events, and cooler temperatures are required (see below). As of today (July 14, 2022) tar spot risk remains high or elevated for most of the state (Fig. 2). Over the next week the forecast is putting us a bit drier and hotter. Thus, the tar spot risk could continue to decline. However, remember that tar spot will continue to show up due to favorable weather 2 or more weeks back. The tar spot pathogen has a long incubation period (time from infection to tar spot appearance). Thus, you shouldn’t be surprised in finding tar spot at low levels over the next week. So should you spray fungicide now? If you can, wait until at least the VT (tasseling growth stage). The evidence is strong that the optimum window to spray fungicide to control tar spot is between the VT and R3 (milk) growth stages. Spraying before VT might leave corn plants vulnerable to a late-season tar spot increase. Thus, if you spray before VT, you might need to come back with a second application of fungicide closer to the R3 growth stage. For guidance on when/if to spray fungicide to manage tar spot, see my previous article.

Figure 2. Tar spot risk for Wisconsin on July 14, 2022.

White Mold of Soybean

White mold risk remains generally low and is dropping for most of the state of Wisconsin (Fig. 3). This is not surprising as temperatures have remained moderate with drier conditions. Based on the current risk and the 7-day forecast, fungicide applications can be held back. Folks should pay attention to the weather and Sporecaster risk as the crop moves into full bloom and early pod development. In recent years we have seen white mold risk increase during the late bloom time necessitating a fungicide application around the R3 growth stage. I would expect this same scenario to set up in 2022 in at least a portion of Wisconsin. Folks should monitor this situation carefully as we move ahead over the next 2 weeks. For more information on white mold and making the fungicide spray decision, see this previous article.

Figure 3. White mold risk for Wisconsin for July 14, 2022.

The Field Prophet Tool

For those who like all of their disease prediction tools in one place you might check out the Field Prophet version of the Tarspotter and Sporecaster apps. This tool consolidates all of our disease prediction tools into one convenient tool. The app also allows for true 7-day forecasting and will display 7-day trends to better inform your disease management decisions. Field Prophet, Inc is a startup company supported by UW-Madison and uses science-based information and the same models as Tarspotter and Sporecaster to deliver informative tools for agriculture clientele. You can also download and use Field Prophet for free for the next 6 months! You might find this tool as a handy alternative to Tarspotter and Sporecaster.