C.O.R.N. Newsletter: 2025-14
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May Chill Ahead
Climate Summary
May weather often brings much warmer temperatures and the first hints of that summer humidity from time to time, and this past week was no exception. In fact, Ohio has added about 200 growing degree day heating units over the last two weeks, helping those crops that have been planted emerge from the ground. However, the weather pattern so far in May has limited the average suitable fieldwork days across the Buckeye State to just 1-3 days per week. With systems moving in every couple of days, the ground has remained fairly saturated despite warmer temperatures. Precipitation for the last seven days varied considerably across Ohio (Figure 1). Many counties in the east and far southwest only saw 0.25-0.5 inch, while pockets of 2-4 inches occurred in places near Findlay and Zaneville. Severe weather was prevalent as well, with reports of baseball sized hail (2.5 inches in diameter) in Highland County. For the latest up-to-date conditions, seasonal outlooks, and monthly climate summaries, please visit the State Climate Office of Ohio.
Figure 1: Total precipitation (inches) over the last seven days, ending at 2 pm EDT Monday May 19, 2025. Figure courtesty of the Ohio River Forecast Center in Wilmington, Ohio.
Weather Forecast
Although we started the week off with another beautiful Monday, our next weather maker will make its presense known for much of the upcoming week. Periods of showers and a few storms are likely for Tuesday through Thursday. Temperatures will fall as well, with mostly 60s for highs on Tuesday, followed by 50s on Wednesday and Thursday. These temperatures will be about 15 degrees below average for this time of year. Much of Ohio will see 0.5-1 inch of rain over the next seven days, but locally heavier amounts are possible where thunderstorms occur. A few lingering showers are possible on Friday, with drier and warmer temperatures expected for the weekend. The National Weather Service is currently forecasting 0.5-1 inch of rain for the bulk of Ohio, with 1-2” possible in northeast and southwest Ohio (Figure 2).
Figure 2). Precipitation forecast from the National Weather Service for 8pm May 19 - 26, 2025.
The 8-14 day outlook from the Climate Prediction Center and the 16-Day Rainfall Outlook from NOAA/NWS/Ohio River Forecast Center show strong probabilities toward of cooler than normal temperatures with near normal precipitation (Figure 3). Climate averages include a high-temperature range of 74-78°F, a low-temperature range of 52-57°F, and weekly total precipitation of 0.90-1.15 inches.
Figure 3) Climate Prediction Center 6-10 Day Outlook valid for May 27 – June 2, 2025, for left) temperatures and right) precipitation. Colors represent the probability of below, normal, or above normal conditions.
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Head Scab Risk Update
Thanks to recent rainfall, head scab risk remains moderate-to-high in central and southern Ohio, for wheat flowering today and later this week, while the remainder of the state is at medium-risk for infection (Figure 1). These risk estimates were generated by The Fusarium Risk Tool available at https://www.wheatscab.psu.edu/. This tool uses temperature, rainfall, and relative humidity to estimate the risk of infection by Fusarium graminearum that causes Fusarium head blight or head scab in wheat. The fungus also produces the mycotoxin deoxynivalenol (DON) or vomitoxin. Keep in mind, the estimate shown in the map is applicable to fields flowering today if a susceptible variety is planted. You should check the tool periodically as more fields begin to flower to see if the risk changes.
Figure 1. Fusarium Risk Assessment Tool Ohio map generated on May 19, 2025. Red = high risk, Orange = medium risk, and Yellow = low risk for Fusarium head blight.
Fungicide applications to reduce head scab development and DON contamination should be made at early flowering (Feekes 10.5.1) when yellow anthers are seen at the center of the wheat spike (Figure 2). (Wheat flowering stage video: https://www.youtube.com/watch?v=pEJrX6UqF_E&list=PLYlh_BdeqniJ8oD8TnyGhQHRd96ptV0Yt&index=5) However, applications delayed 4 days after initial flowering can still suppress head scab and DON. Be sure to select a triazole-based fungicide and follow all product label instructions.
Figure 2. Wheat head flowering.
Fungicides with a ‘good’ efficacy rating based on multi-state fungicide trials, include Proline 480 SC, Prosaro 421 SC, Sphaerex, Miravis Ace SE, and Prosaro Pro SC. Access the complete wheat fungicide efficacy chart provided by the Crop Protection Network at https://cropprotectionnetwork.org/publications/fungicide-efficacy-for-control-of-wheat-diseases.
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Scouting for Soybean Seedling Diseases in Ohio
Persistent cool and wet weather across Ohio has created ideal conditions for soybean seedling diseases. As we move through the early stages of the growing season, it’s critical to scout fields for symptoms and signs of seedling blights and root rots that can compromise stand establishment and yield potential.
What to Look For
Soybean seedling diseases are often difficult to diagnose in the field because symptoms can overlap with abiotic stress or insect injury. However, early identification is key to managing these issues effectively. Here are some common culprits to watch for:
- Pythium seedling blight: Look for water-soaked, mushy seedlings with poorly developed roots. This disease thrives in cool, saturated soils.
- Phytophthora root rot: Symptoms include mushy stems and stunted or wilted seedlings. Unlike Pythium, Phytophthora prefers warmer soils but still benefits from wet conditions.
- Fusarium root rot: Characterized by light to dark brown lesions on roots and a reduced root system.
- Rhizoctonia seedling blight: Look for dry, sunken, reddish-brown lesions on the hypocotyl.
For accurate diagnosis, collect about 10 symptomatic seedlings from different areas of the field, keeping the roots intact. Gently remove excess soil, wrap roots in damp paper towels, place in a sealed plastic bag, and ship promptly to a diagnostic lab. For guidance on where to send samples, see our previous article on diagnostic submission here.
Seed Treatments: Not a Silver Bullet
Even with seed treatments, seedling diseases can still occur. The Crop Protection Network (CPN) publication Seed Treatments: Questions that Emerge When Plants Don’t outlines several reasons why treatments may fail:
- The wrong active ingredient for the pathogen present.
- Suboptimal application rates.
- Environmental conditions overwhelming the protection.
- Misdiagnosis of the actual cause of poor emergence.
Choosing the right fungicide seed treatment is essential. For example, metalaxyl and mefenoxam are effective against Pythium and Phytophthora, but not against Fusarium or Rhizoctonia. Refer to the updated 2025 Fungicide Efficacy Table for guidance on active ingredient performance.
Scouting Resources
The Crop Protection Network offers excellent resources to support your scouting efforts:
- Scouting for Soybean Seedling Diseases
- Overview of Soybean Seedling Diseases
- Fungicide Efficacy for Control of Soybean Seedling Diseases (2025)
Help Us Improve Disease Management – Take the Survey
We’re collaborating with the Crop Protection Network (CPN) to better understand how seedling diseases are impacting soybean production across the region. Our goal is to support professionals in making informed decisions on soybean disease management.
To help us improve the effectiveness and value of the information we provide, we invite you to participate in the 2025 Soybean Seedling and Stem Disease Survey. Your input is very valuable to us.
- Participation is voluntary.
- You may skip any question or exit the survey at any time.
- The survey is anonymous—no names, IP addresses, email addresses, or any other identifiable information will be collected.
- You must be 18 years of age or older to participate.
Please take a few minutes to complete this short survey:
Take the CPN Soybean Seedling Disease Survey
Your input will help shape future research and extension efforts.
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Battle for the Belt: Season 3, Episode 8: Wet Weather and Nitrogen Loss
Season 3, Episode 8 of Battle for the Belt is now available: https://www.youtube.com/watch?v=3H-eyJkPUNI
In Episode 8, we are with Dr. Manbir Rakkar, Ohio State Extension Fertility and Nutrient Management Specialist, discussing management of nitrogen under saturated soil conditions.
What are the implications of excess or surplus water in planting and nitrogen losses?
Water is essential for crop growth and high yields; however, too much has the potential to cause several problems. With wet conditions, fieldwork can be delayed, and planting in saturated soil greatly increases the risk of soil compaction. If already planted, standing water can disrupt the germination processes and even suffocate the roots of the crop. Important to note is the effect that excess water has on nitrogen losses. Management of nitrogen is especially difficult in flooded or waterlogged conditions. Nitrogen is a highly important macronutrient, but in these environments, nitrogen losses from the soil are accelerated, causing developmental issues or yellowing in corn (Figure 1).
Figure 1. Yellowed corn at the Northwest location on May 13th. Photo credit: Taylor Dill
What are the main nitrogen forms in the soil?
here are two main forms of nitrogen in the soil: organic nitrogen and inorganic nitrogen. Organic nitrogen is found in soil organic matter. In general, 1% of organic matter holds about 2,000 lbs. of nitrogen per acre, but only about 20 lbs./acre are available for plants to utilize during the growing season. Inorganic nitrogen is in the form of ammonium (NH4+) and nitrate (NO3-), and these are more readily available to plants. We get these forms either through mineralization of organic matter or from fertilizers like urea or UAN.
What are the main nitrogen loss pathways?
There are several pathways for the loss of nitrogen, dependent on field conditions. Volatilization occurs in hot and dry conditions. This is especially the case with broadcasted urea. A common occurrence with heavy rainfall is runoff and erosion. Nitrogen applied to the surface can be washed away. In well-drained, coarse-textured soils, leaching may occur, causing the nitrogen to flow out of the root zone of the plant. Denitrification takes place in fine-textured soils and is the conversion of nitrate into gases. These escape into the atmosphere. The process worsens with higher soil temperatures and longer periods of saturation.
What options are out there to mitigate nitrogen losses?
The key to managing nitrogen losses is by following the four R’s of nutrient stewardship:
- Right Time: Synchronization of the nitrogen supply and the crop demand. Split applications may reduce losses and better align with crop uptake. This can include the addition of a fraction of nitrogen pre-planting, or at planting, followed by an application of the remaining nitrogen at V4-V6, when the plant requires it the most.
- Right Placement: Nitrogen should be placed where the crop can access it and where less losses are expected. One of the best methods for placement is sidedressing in a 2-by-2, or two inches to the side of the row, and two inches below the soil surface. Broadcast nitrogen applications are an option as well, but often more susceptible to losses.
- Right Source: Fertilizer types should be selected based on what is suitable for your field’s conditions. Nitrogen inhibitors may be a necessary addition if your field is susceptible to nitrogen losses. Some forms of N are at higher risk of losses than others.
- Right Rate: Applications should be neither too much nor too little. The rate is often based on crop needs, soil tests, and decision tools such as the Corn Nitrogen Rate Calculator are available.
What are some tools and resources for aiding in nitrogen management?
- Tri-State Fertilizer Recommendations: A regional guide to nutrient management practices. https://agcrops.osu.edu/FertilityResources/tri-state_info
- Corn Nitrogen Rate Calculator (CNRC): Helps to determine economic optimum nitrogen rates. https://www.cornnratecalc.org/
- Ohio State C.O.R.N Newsletter: Timely updates on general crop management, including nutrients and weather. https://agcrops.osu.edu/newsletter/corn-newsletter
- Extension educators and specialists: Reach out for localized advice and support.
Field & Crop Progress Updates
All three locations successfully added another planting date this past week! A stretch of consecutive dry days allowed soils to dry down enough, providing suitable conditions for planting before some additional rain moved in. Wooster and Northwest locations planted the third planting date on Monday, May 12th. Western was also able to plant on May 12th, getting the second planting date in the ground. Table 1 summarizes field conditions in those three sites at the most recent date of planting.
Table 1. Planting date soil and air temperature conditions for the first day of planting at the Northwest Agricultural Research Station in Wood County, the Wooster Campus in Wayne County, and the Western Agricultural Research Station in Clark County. The soil and air temperature data were retrieved from https://weather.cfaes.osu.edu/; reported as average temperatures.
Location
Soil Temp
Air Temp
Date
Northwest Agricultural Research Station, Wood County
62°F
60°F
5/12
Wooster Campus, Wayne County
64°F
63°F
5/12
Western Agricultural Research Station, Clark County
62°F
63°F
5/12
Soybeans from earlier planting dates range from VC to V1 across locations, with Western being slightly ahead despite being planted three weeks behind the others (Table 2). Corn stages range from V2 in planting date two to V3 in planting date one, with western again being slightly ahead of the other locations, as represented in figures 2 and 3.
Figure 2. Corn planting date one progress comparison between locations. Photo credits: Maria Kessler and Taylor Dill
Figure 3. Soybean planting date one progress comparison between locations. Photo credits: Maria Kessler
Table 2. Precipitation, soil temperature, average air temperature, cumulative GDDs, and stage at the Western Agricultural Research Station, the Northwest Agricultural Research Station, and Wooster Campus. Weather data retrieved from: https://weather.cfaes.osu.edu/.
Location
Precipitation
(Inches)
(May 12 - May 18)
2-inch soil temperature
(May 12 - May 18)Air Temperature
(May 12 - May 18)
Planting date
GDDs
(Cumulative)
Corn
Growth
StageSoybean Growth
StageWestern,
Clark County
0.81
Min: 63°F
Max: 70°F
Mean: 67°F
Min: 64°F
Max: 74°F
Mean: 68°F
April 18
383
V3
V1
Wooster,
Wayne County
0.79
Min: 63°F
Max: 70°F
Mean: 66°F
Min: 62°F
Max: 74°F
Mean: 66°F
March 27
April 18
368
308
V2
V2
VC
VC
Northwest,
Wood County1.16
Min: 60°F
Max: 71°F
Mean: 65°F
Min: 62°F
Max: 77°F
Mean: 68°F
March 27
April 16/17
375
326
V2
V2
VC
VC
If you would like to learn more, check out our research updates through C.O.R.N. article updates and YouTube Videos this growing season! You can find the full video playlist of Battle for the Belt on the Ohio State Agronomy YouTube channel.
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Crop Progress Update and Replanting Decisions in Corn and Soybeans
As of May 18, 2025, USDA’s crop progress report estimated 34% of corn acres planted in Ohio, and 22% of corn emerged. Corn planting progress was behind the 5-year average (48%), but corn emergence was slightly ahead (20%). On the same report, 40% of soybean acres were planted and 24% of soybeans emerged. Soybean planting and emergence progress were ahead of the 5-year average (39% planting, 14% emerged).
Weather, pests, and diseases can affect seedling vigor, plant growth, stand establishment, plant population, and crop yield. This year’s early planting dates have been affected by a combination of cold air and soil temperatures, precipitation, and recent storm events (including hail) in some parts of the state, which may lead to reduced stands. Some stress factors can include imbibitional chilling, soil crusting, standing water, frost, slugs, and disease.
If reduced stands are a concern, a potential option to consider is to replant fields. However, replanting does not always translate into better yields. Here is a list of aspects to look at if you consider replanting:
Step 1. Wait… Plant stands should be assessed after ‘stable’ and ‘better’ conditions are achieved to allow the chance for seeds to germinate/emerge (e.g., warmer temperatures, better soil conditions). Often, hasty decisions are not the best.
- For corn, past work has shown that 50% emergence can be expected following the accumulation of 100-150 soil GDDs (base of 50°F) from the time of planting. This can be achieved in about 5-7 days under adequate temperatures and soil conditions.
- For soybean, assess the stand at the VC growth stage. Visual stand assessment at the VE growth stage often underestimates the total number of plants that will emerge.
Step 2. Estimate the number of plants per acre from several areas within the field by conducting stand counts. Field variability exists, and collecting stand counts from several representative areas is important (Figure 1).
Figure 1. In-field plant emergence variability in corn. Left and right plants with more growth and development relative to the plant in the center. Source: Osler Ortez.
- For corn, after estimating the number of plants per acre, for reference, you can use Table 1 to locate the expected yield of the plant stand depending on the planting date. Then, locate the expected replant yield by reading across from the expected replanting date to the stand that would be replanted. The difference between these numbers is the percentage yield change (increase or decrease) expected from a replanting decision.
Table 1. Replant Chart Developed Under High-Yielding Conditions (adapted from the University of Illinois - Nafziger, 1995-1996).
Plants per acre at harvest
Planting Date
10,000
15,000
20,000
25,000
30,000
35,000
% of optimum yield
April 10
62
76
83
92
94
93
April 20
67
81
91
97
99
97
April 30
68
82
92
98
100
98
May 9
65
79
89
95
97
96
May 19
59
73
84
89
91
89
May 29
49
62
73
79
81
79
- For soybean, if the plant population is relatively uniform, replant is recommended if the stand is less than 50,000 plants per acre. If the plant population is non-uniform, farmers may want to consider replanting at <75,000 plants per acre. Although the stand will look poor, soybean plants can compensate for low plant populations by increasing the number of branches (Figure 2). In our research, going from 100,000 to 50,000 plants per acre resulted in only a 9 to 14% reduction in yield.
Figure 2. Soybean plants seeded at 100,000, 140,000, and 180,000 plants per acre. Source: Will Hamman.
Step 3. Check the weather forecast. How soon can you get back to the field to replant?
- For corn, early planting dates with lower stands can still produce good yields. From past research, a stand of 20,000-25,000 plants per acre planted on April 20 can still yield 91-97% of the optimum yield. Corn yield loss resulting from delayed planting can be about 1.75 bushels per acre per day.
- For soybean, the date of planting has more effect on soybean grain yield than any other production practice. Yield loss resulting from delayed planting can range from 0.25 to 1.0 bushel per acre per day.
Replanting at later dates, past the recommended window (late April or early May), may result in lower yields compared to having lower plant populations planted earlier in the year. Seed cost and labor should be considered. When low plant populations exist, a common question is whether to replant fields or not.
Another factor is crop insurance. For those who carry Multi-Peril Crop Insurance (MPCI) in the form of Revenue Protection (RP) or Yield Protection (YP), we encourage you to discuss replant provisions with your agent if plant population is a concern. Per crop insurance policies, the insured must file a replant claim and speak to an adjuster before taking any replant action. The standard 2025 replant coverage per acre for corn is 8 bushels x $4.70 (Projected Price) = $37.60/acre. On the other hand, the standard 2025 replant coverage per acre for soybeans is 3 bushels x $10.54 (Projected Price) = $31.62/acre. Additionally, a minimum of 20 acres or 20% of the acres per unit must qualify for replant before the standard policy provides coverage. If feasible, utilizing crop insurance is one of the many tools to manage/mitigate risk in farming operations.
Replant recommendations for corn and soybean are an active area of research. In 2025, we started a new project aimed at revising replant decisions for corn and soybean. The project is funded by USDA-NIFA-AFRI under the Critical Agriculture Research and Extension (CARE) program, with the main goal of identifying soybean and corn replant thresholds based on plant populations and planting dates for three distinct growing regions in Ohio. Stay tuned for more updates and results on the new project.
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Lep Monitoring Network – Black Cutworm and True Armyworm Update # 4
We are in our fourth week of monitoring for black cutworm (BCW) and true armyworm (AMW) across Ohio. We had some warm days over the past week and our moth numbers are still high in a number of counties, with the majority of high numbers in the northwest part of the state. Read below for more specific information.
Black cutworm
A number of counties are still reporting high trap numbers for BCW. Over the past week our team has monitored 52 traps in 21 counties. Our overall statewide average was down this past week to 7.9 (it was 11.0 last week), and with the upcoming cold weather, it will likely continue to decrease. We recommend monitoring fields until plants reach the v6 growth stage, especially in counties that have had averages of 7 moths or more per week. This week those counties include Allen, Hardin, Henry, Lucas, Madison, Muskingum, Van Wert and Wood (Figure 1).
For more information on how to scout BCW please visit: https://aginsects.osu.edu/sites/aginsects/files/imce/ENT_35_14 BCW.pdf
Black cutworm moth map
Week 3: May 12th to May 18th, 2025
Figure 1. Average black cutworm (BCW) moths captured from May 12th to May 18th. The bold number on the left indicates the average moth count for the week, followed by the standard number on the right which indicates the total traps set up in that county.
True Armyworm
We also monitored 50 traps in 21 counties for AMW moths (Figure 2). We are still seeing AMW, but it seems to be in fewer counties across Ohio compared to BCW. Our overall statewide average stayed consistent this week at 3.8 moths (slightly higher than last weeks average of 3.2). Similar to last week, only 3 counties reported an average of 7 moths or more and those counties include Henry, Van Wert and Wood (the same counties as last week).
True Armyworm moth map
Week 3: May 12th to May 18th, 2025
Figure 2. Average true armyworm (AMW) moths captured from May 12th to May 18th. The bold number indicates the average moth count for the week, and the standard number in parentheses is the total number of traps set in that county.
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Alfalfa Weevil Update
Alfalfa weevils are currently mainly in their larger larval stages or beginning the process of pupation, transitioning to their adult forms. The growing degree days (GDD) took a leap from last week, putting much of the state above the window for peak damage of 325 to 575 GDDs (accumulation from a base of 48°F starting January 1st). As of writing this (Jan. 1 – May 19), heat units range from 842 in southcentral Ohio to 521 in northeast Ohio.
Figure 1. Map of accumulated growing degree days (base 48°F sine calculation method) for January 1 – May 19, 2025 at CFAES Ag Weather stations across the state (https://weather.cfaes.osu.edu//) and additional NOAA stations around Ohio (Midwestern Regional Climate Center (https://www.mrcc.purdue.edu))
Our county educators continued the state-wide scouting effort, and overall we saw a drop in the number of average larvae per stem throughout each county, with many counties seeing zero larvae do to treatment efforts. The following table shows the average state of alfalfa fields scouted in each county. Be sure to scout your field to gauge your situation specifically.
Table 1: County alfalfa weevil scouting reports for May 13 – May 19
County
Alfalfa Height (inches)
Larvae Count per Stem
Allen
16-24
0
Defiance
19-30
0.9
Mercer
22-33
1.2
Perry
18-27
1.3
Ross
14-30
0.5
A key topic to note is to watch for populations that may be presenting resistance to insecticide treatments, namely, pyrethroids. There have been confirmed cases of pyrethroid-resistant alfalfa weevil populations in the western US, but Penn State put out an article last week, where they have been getting reports of such resistance in the eastern part of Pennsylvania (Read that article here: Alfalfa Weevils in Eastern PA May Be Resistant to Pyrethroid Insecticides). Those cases of resistance are not confirmed, but it is a good reminder to scout fields that have been sprayed to ensure an effective treatment. It is also recommended to rotate the insecticide used, and the OSU and MSU “Field Crops Insect Pest Management Guide” is a great resource and can be found here: https://aginsects.osu.edu/extension-publications/msuosu-ipm-guide.
A final note, we are to the point in the season where the most economical choice for many of the affected fields is to harvest. Be sure to scout for alfalfa weevil the week following harvest to ensure the population doesn’t persist and impact the second cutting. If still looking to make an insecticide application, make sure to take into account the harvest restrictions associated with the application
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Pastures for Profit will be offered in-person this June in Logan Co
Pastures for Profit is a collaborative program between Ohio State, Ohio Forage and Grassland Council, Ohio Department of Agriculture, and Soil and Water Conservation Districts. Curriculum for Pastures for Profits has been evolving since the 1990s, and it includes topics such as grazing management, plant physiology, fencing & water infrastructure, economics, and more. Participants in 2025 PFP programs will receive a new manual that includes revised goal setting worksheets, new soil management information, and other changes.
If you are interested in participating in an in-person Pastures for Profit series, join us in Logan County on June 10th and 12th at 5:30 pm. Presentations on Tuesday night will cover goal setting, growth habits of perennial forages, soil fertility, and other topics, and speakers will be present from ODA, OSU, and NRCS. Thursday night will take place on-farm, and participants will get experience with fencing tools, pasture evaluation, plant identification, and other topics.
Dinner is provided, and registration information is available here: https://www.eventbrite.com/e/logan-county-pastures-for-profit-grazing-course-tickets-1306810227569?aff=ebdssbdestsearch
Crop Observation and Recommendation Network
C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.
Contributors
Disclaimer
The information presented here, along with any trade names used, is supplied with the understanding that no discrimination is intended and no endorsement is made by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.
CFAES provides research and related educational programs to clientele on a nondiscriminatory basis. For an accessible format of this publication, visit cfaes.osu.edu/accessibility.