Month: June 2019

Fusarium Head Blight (Scab) of Wheat: Things to Consider When Harvesting

BY: DARCY TELENKO (Purdue University Extension)

Wheat harvest has begun in Southern Indiana. Fusarium head blight (FHB) or scab is one of the most important diseases of wheat and most challenging to prevent. In addition, FHB infection can cause the production of a mycotoxin called deoxynivalenol (DON or vomitoxin). The environmental conditions have been extremely conducive to FHB development and it is not surprising that I have started to receive reports about issues with FHB and DON contamination. Our research sites in both West Lafayette and Vincennes have high levels of FHB develop in our non-treated susceptible variety checks and initial DON testing was at 7 ppm.

Fusarium head blight management is difficult and requires an integrated approach. This includes selection of varieties with moderate resistance and timely fungicide application at flowering. We are now past implementing either of these management options, but these are important to remember for next year. In addition, it will be important to assess your fields this season to determine if you have FHB. FHB can cause direct yield loss creating seeds that are shriveled and have a rough, sunken appearance to complete head loss (which I have already seen in multiple fields around the state). FHB infection can also reduce seed quality and feeding value of the grain due to the risk of mycotoxin (DON/vomitoxin) production in infected seed.

The question now is “I have scab in my field what do I need do?” Here’s a short list.

  1. Document the issues in each field, so you have records for making decisions on future disease management. FHB is easy to see when the head is still green – it will be much more difficult to rate as the heads reach maturity. See images of FHB in the head both at green and more mature stages. You might be able to see the pink salmon sporulation and/or purple-black fruiting bodies on mature heads (Figure 1).  In addition, it is good to note during the season what management tools were attempted – spray date and growth stage of crop, was there variability in the growth stages, weather conditions after fungicide applications. These all can play a role in effective disease management.
    Figure 1. Wheat spikes showing bleached florets affected by scab. Salmon to pink sporulation may be visible and can help confirm once the spikes have reached maturity (pink arrows). Dark purplish-black fruiting bodies can also occur mature wheat heads (black arrows),

    Figure 1. Wheat spikes showing bleached florets affected by scab. Salmon to pink sporulation may be visible and can help confirm once the spikes have reached maturity (pink arrows). Dark purplish-black fruiting bodies can also occur mature wheat heads (black arrows).

  2. Harvest fields with lowest disease first; adjust combine settings to blow out the smaller, shriveled kernels and chaff; and separate loads from healthy and disease fields. Mycotoxin contamination is usually the highest in the more heavily disease kernels and if they can be removed that would help reduced mycotoxin level.
  3. Test for DON levels in both kernel and straw before feeding to livestock. Scabby kernels do not always indicate high DON and vice versa. It is important to test and know what your DON numbers are in your grain, even if you don’t see a high level of disease. Straw can also contain DON. DO NOT use straw for bedding or feed from fields with high level of scab.
  4. Understand your elevators inspection and dockage procedures (each one can have a different practice). Levels of DON greater than 2 ppm may lead to price discounts.
  5. It is not recommended to store grain from field with high levels of scab – accumulation of DON and other mycotoxins can continue in stored grain. Suspect grain, if stored, should be dried to 5% moisture as soon as possible after harvest and kept separate from the good quality grain.
  6. Planting seed from fields that had moderate to heavy scab is not advisable. The infected seed will have low germination and poor vigor resulting in a thin stand. If going to use this seed, it should be cleaned thoroughly to remove the scabby seeds, and a fungicide seed treatment would be advised to protect germination and reduce seedling blight.

 

The next question “Why was is it so bad? I followed the guidelines applied my fungicide at flowering but we still have poor control.”

Here’s a few of my observations:

  1. Highly favorable environmental conditions for Fusarium head blight (FHB)/scab occurred all spring.
  2. Many wheat varieties have moderate resistance that help can reduce the risk of sever disease, and fungicides can help suppress the development, but this may only provide about 50% suppression. Therefore, even with the best management programs in place the extremely favorable conditions for FHB have led to high levels of infection this season.
  3. There was extremely variable growth in individual fields this year – plants ranged from boot to full flower when trying to make a decision on fungicide timing. In addition, fungicides may only provide partial suppression of FHB and timing is a significant issue for obtaining moderate levels of control.
  4. Frequent rains not only complicated planting, but any and every other trip across the field. Rain events closely following fungicide application may have diluted or washed off applications further reducing expected efficacy.

Additional references:

US Wheat and Barley Scab Initiative https://scabusa.org/

Cowger, C., and Arellano, C. 2013. Fusarium graminearum infection and deoxynivalenol concentrations during development of wheat spikes. Phytopathology 103:460-471. https://apsjournals.apsnet.org/doi/pdf/10.1094/PHYTO-03-12-0054-R

De Wolf, E. 2019. Fusarium head blight. https://www.bookstore.ksre.ksu.edu/pubs/MF3458.pdf

Salgado, J. D., Wallhead, M., Madden, L. V., and Paul, P. A. 2011. Grain harvesting strategies to minimize grain quality losses due to Fusarium head blight in wheat. Plant Dis. 95:1448-1457. https://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-04-11-0309

Wise, K. et al. 2015. Diseases of Wheat: Fusarium Head Blight (Head Scab) https://www.extension.purdue.edu/extmedia/BP/BP-33-W.pdf

Prevent Plant, Cover Crops, and More

Last night I was in attendance as a panel of experts talked us through a lot of the issues we are facing in agriculture this spring/summer.  The event was put on by OSU Extension and Ohio No-Till Council and held at the McIntosh Center on the campus of Ohio Northern University.  We’re also thankful that the Ohio Country Journal was on hand to record the panel and you can watch the video at their website, ocj.com. I’m going to try and summarize some of the issues, but if you have specific questions please get in contact with the extension office by calling 419-879-9108.

  1. If you have livestock and are running low on forages now, or anticipate a need before this winter what are your options? You can plant a forage crop on prevented plant acres and harvest it after September 1st under the new RMA/crop insurance guidelines. In this scenario corn is eligible to planted and chopped for silage.  However, you need to check with your crop insurance adjuster on what exactly is allowable so that you do not jeopardize your prevent plant payment. A common recommendation seems to be to plant the corn in 20″ rows or narrower and increase planted populations to 40,000 seeds per acre or higher.  Again, check with your agent/adjuster to make sure you are in compliance.  Other popular forage options are sorghum/sudan grass and oats.  If you are interested in either of these crops please try to get your seed ordered as soon as possible as supply will get tight.
  2. What can I do with treated soybean seed that is not returnable to the dealer? By far, the best option is to plant them, even as just a cover crop.  There are concerns about the insecticide used and what is the maximum rate that they can be planted at.  We would prefer rates of no more than 300,000 seeds per acre. This seed also needs to be covered so that it isn’t creating a harmful impact to wildlife or pollinators.  If you plan on broadcasting the treated seed you will need to incorporate it with either a disk or vertical tillage tool.  We do not recommend trying to carry seed over for planting in 2020.  The 2018 crop had some issues with poor germination scores already and those scores will only get worse even if the seed is stored under ideal conditions (less than 50 degrees and 50% humidity).
  3. What are my options on trying to kill some of these larger weeds that have grown up in preventive plant fields? Mowing them down would be the cheapest option, but most time consuming.  It will also scatter the weed seed and prolong your problem.  Tillage is an option, but it will probably take several passes to get everything killed.  There are lots of herbicide options available, but we need to be cautious on what the plant back intervals are for each herbicide used.  Most of the fields will have at least one species of weeds that is resistant to glyphosate so we need to be using higher rates and tank mix partners.  We also need to be aware of sensitive crops or gardens that might be impacted by drifts or temperature inversions if we are using Dicamba or 2,4-D products.  Mowing first will not make the weeds easier to kill with a herbicide later.
  4.  Are there any cost sharing opportunities for planting cover crops from soil and water districts or USDA – NRCS? The NRCS today has announced that they have $4 million available to producers that plant a cover crop.  Details are still coming out as far as payment amounts and eligibility requirements.  As more information becomes available it will be shared with producers.
  5. How has the excessive rain impacted my soil health? The rains have diminished our soil structure no matter what management practices are in place on your farm.  No air has been incorporated into the soil and this is greatly impacting the natural soil biology. We need to start the recovery process this summer on those acres.  Do not let them sit fallow until next spring.  Get your soils tested and then use this opportunity to apply lime and gypsum if needed.  This might also be an opportunity to apply manure on fields with low phosphorous levels.

I also want to take this opportunity to thank the Lima and Allen County community for the warm welcome I’ve received over the last couple of weeks.  I’m really excited to meet more of you in the ag community here.  I’m currently looking for some volunteers that would let me come out to their farm and pull samples for some research OSU is doing on soybean cyst nematodes. We need to stay ahead of this pathogen so we can continue to develop resistant varieties.  If you are interested please contact me via email at schroeder.307@osu.edu or by calling the extension office at 419-879-9108.

Wet Weather and Soybean Stands

By:  Laura Lindsey and Alexander Lindsey, Ohio State University

Saturated soils after soybean planting can cause uneven emergence and stand reductions of varying extent depending on the stage of the soybean plant and other environmental factors including temperature and duration of saturated conditions. Additionally, increased disease incidence may further reduce plant stand.Flooded soybean field

Saturated Soil Prior to Germination: While soil moisture is necessary for germination, soybean seeds will not germinate when soils are saturated because oxygen is limiting.

Saturated Soil during Germination: Saturated soils during soybean germination may cause uneven emergence. In a laboratory study, soybean germination was reduced by ~15% after only one hour of flood conditions (Wuebker et al., 2001). After 48 hours of flood conditions, soybean germination was reduced 33-70% depending on when imbibition (seed taking up water) began relative to the flooding conditions. Practically, for Ohio, this means if soybean seeds were further along in the germination process when flooding occurred, the seeds will be more susceptible to flooding stress.

Saturated Soil during Vegetative Stage: Warmer temperatures will cause soybean plants to die faster. At temperatures, 80 degrees and greater, submerged soybean plants will likely due in 24 to 48 hours. However, cool, cloudy days (…and we’ve had plenty this year) and clear nights increase the survival potential of a flooded soybean crop. Flooded plants may also exhibit poor nodulation, resulting in yellow, stunted plants.

Evaluate Stand: To quickly estimate stand, count the number of plants in 69’8” of the row for 7.5-inch row spacing, 34’10” for 15-inch row spacing, or 17’5” of the row for 30-inch row spacing. These counts represent 1/1000th of an acre (i.e., 120 plants in 7.5-inch row spacing = 120,000 plants/acre).

Keep in mind, the effect of plant population on yield is very small over the normal range of seeding rates. For soybeans planted in May, final populations of 100,000 to 120,000 plants/acre are generally adequate for maximum economic return. For example, in our seeding rate trials in Clark County, 100% yield (77 bu./acre) was achieved with a final plant stand of 125,000 plants/acre. However, a 95% yield (73 bu./acre) was achieved with only 77,000 plants/acre. (This trial was planted the second half of May in 15-inch row width.)

Source:

Wuebker, E.F., R.E. Mullen, and K. Koehler. 2001. Flooding and temperature effects on soybean germination. Crop Sci. 41:1857-1861.

Welcome to the Allen County Ag and Natural Resources Blog!

Welcome to the Allen County Ag and Natural Resources Blog! My name is Clint Schroeder, and I am the Agriculture and Natural Resources Extension Educator for Allen County. You can find out more about me and my background if you click the About tab on the home page. This blog will feature recent articles about agronomy, livestock production, home gardening, farm management, and current topics affecting Allen County and the surrounding area. If you have any questions, please do not hesitate to call me at 419-879-9108 or e-mail at schroeder.307@osu.edu.