Cucurbit Downy Mildew – One Day Update

Cucumber downy mildew, Hardin County OH. Photo by Francesca Rotondo.

Just after posting yesterday, July 30 I received a confirmed report of downy mildew in cucumbers in Hardin County. See that post for recommendations.

Cucurbit downy mildew outbreaks in Ohio counties. Red color indicates reports less than 7 days ago.


Cucurbit Downy Mildew Outbreaks Increasing

Cucurbit downy mildew outbreak map.

We have three new reports of downy mildew on cucumbers this week, all from home or community gardens in Coshocton, Muskingum and Geauga counties. Thanks to OSU Extension educators David Marrison and Clifton Martin for the finds in Coshocton and Muskingum counties. The Geauga County outbreak was reported by one of our Ohio Master Gardener Volunteers participating in a multi-state Citizen Science project to monitor and report cucurbit downy mildew (thanks Annie!). Numerous reports in other states show that downy mildew is on the move (see map), mostly still in cucumbers and melons. In Ohio the cucumber/melon outbreaks have been in the northern and central counties, likely caused by the downy mildew “pathotype” that circulates in the Great Lakes region and infects only cucumbers and melons. However, last week downy mildew was reported on squash and pumpkins in Central Kentucky and on squash in Western New York. The downy mildew “pathotype” that infects squash and other cucurbits moves up into the Midwest from the deep South, so Ohio growers, especially in the southern counties, should step up scouting of all cucurbits and apply protectant fungicides such as chlorothalanil products. When downy mildew is confirmed nearby and conditions are conducive (cool, rainy, humid, overcast), more effective fungicides should be applied.

Spray Program Recommendations for Ohio Cucurbit Growers

  1. Northern and Central Ohio cucumber and melon growers: add effective fungicides shown in green in the table to the spray program now. Tank mix with a protectant fungicide such as chlorothalanil (Bravo, Equus, etc.), alternate fungicides with different modes of action (FRAC codes) and follow the label restrictions and requirements. Shorten the application interval to 7 days under favorable weather for downy mildew.
  2. Southern and Central Ohio cucurbit growers (all types): apply a protectant fungicide on a 7-10 day schedule now.

If favorable conditions for downy mildew persist and downy mildew is present in your area, add effective fungicides shown in green in Table 3 to the spray program. Tank mix with a protectant fungicide, alternate fungicides with different modes of action (FRAC codes) and follow the label restrictions and requirements. Shorten the application interval to 7 days under favorable weather for downy mildew.

  1. Forum, Presidio, Quadris, Zampro and Revus are not recommended. Curzate may be moderately effective in some locations.
  2. Follow this blog, Twitter @OhioVeggieDoc or the Cucurbit Downy Mildew IPM PIPE for downy mildew reports.

Click to enlarge.

Pumpkin Field Day – August 26

Pumpkin flower.

It’s been approximately 730.5 days (but who’s counting) since the last in person pumpkin field day was held at the Western Ag Research Station (7721 S. Charleston Pike, South Charleston, 45368), so be sure to mark your calendar for Aug. 26!

The field day will start promptly at 5:30PM and end at 7:30PM. After a brief wagon ride out to the research and demonstration area, both new and experienced growers will hear at least four talks:
-How climate and weather impact Ohio vegetable crops (Dr. Aaron Wilson, Extension/Byrd Polar Center);
-Weed management and Reflex herbicide trial results (Tony Dobbels, Horticulture & Crop Science);
-Jim Jasinski (Extension) will give a brief update on the powdery mildew fungicide trial and germ plasm hybrid trial.
-We also have a visiting scientist from Purdue University, Dr. Dan Egel (Plant Pathology) who will cover general disease management or other hot disease topics at that time.

To attend the event you need to pre-register by August 24:

Even though the field day will be held outside we will still be following University Covid protocols which call for social distancing and possibly masks, so please come prepared. We will not be able to serve refreshments as we have done in the past so please bring your favorite beverage or water.

For more information on the event please see the attached flyer or contact Jim Jasinski (937-772-6014 or

Pumpkin field day flyer

Wayne County IPM Notes from July 19 – 23

Vegetable Crops

Powdery mildew found on a cucurbit plant in a Wayne County field.

The Vegetable Pathology Lab at OARDC has confirmed several more cases of downy mildew, on both cucumbers and cantaloupe. It is important to take steps to either protect your crop or stop the spread of any ongoing infections. Powdery mildew is also spreading rapidly through the area. Although some heavy rains may have slowed its spread, favorable conditions have led to some fields rapidly becoming infected.

Flea beetles feeding on young green cabbage plants.

Bacterial diseases continue to spread in pepper and tomato plantings. Pay close attention to these crops in particular, and make sure that you are taking the necessary precautions so as to not spread bacterial diseases. Bacteria can be spread from plant to plant via clothing, equipment, or animals. More from APS

Flea beetles are feeding heavily on recently planted cole crops, which left uncontrolled can cause stunted and underperforming plants. Another insect we have seen quite a few of is the squash vine borer. Although these are not typically going to harm large numbers of plants, they can still be a nuisance, especially in smaller plantings.

Small Fruit and Orchards

 This week we found our first incidence of scab in apples. While this was only an isolated find on a few leaves, it is a good reminder to take some time to scout your apple trees and look for any signs of scab. Oriental fruit moth numbers were significantly above threshold again this week. Japanese beetles were also

Severe damage from Japanese beetles feeding on the foliage of apple trees.

still feeding heavily in many of the fruit crops we scout. Spotted wing drosophila are still being found in all of our traps, and for anyone with small fruit in the area, it is recommended that you treat for SWD.

Optimizing Vegetable Fertilizer Programs

Recent farm visits, questions from growers, and observations of research plots have me thinking about nitrogen and other fertilizer programs for vegetable crops grown in open fields and high tunnels for fresh and processing markets. What are optimal ranges for each production situation, which factors influence optimal rates most significantly, and what steps can growers and others take to identify optimal rates for each farm and planting?

Ranges currently recognized as optimal are published in numerous guides, handbooks, and other resources. The Midwest Vegetable Production Guide for Commercial Growers, Southeast Vegetable Production Handbook, Mid-Atlantic Commercial Vegetable Production Recommendations, New England Vegetable Management Guide, and references available from Cornell (e.g., and other universities are helpful in Ohio and the region. The publications provide operating fertilizer application targets and tips on how to reach them. Targets in the publications are the best available benchmarks. However, it is best to think of them as not fixed in stone and as needing to be validated for individual cropping situations. On-farm validation (adjustment by trial and error) using published, research-based and other reliable benchmarks as starting points saves time, money, and headache.

Indeed, since production conditions change continuously and research-based recommendations require years to develop, evaluating fertilizer programs (material, rate, timing, placement) often is good practice. Like effective crop protection programs, fertilizer ones are not static, they need to be updated as weather patterns, varieties, rotations, fertilizer materials and their costs, and other factors change. Observe crops now and through the remainder of the season and ask if you are convinced their fertilizer programs are optimal. If you aren’t convinced, consider experimenting carefully.

Experiments are most effective when they account for factors that tend to influence their outcomes most significantly and consistently. To refresh my memory on these factors, especially nitrogen application rate effects on watermelon and other Cucurbit crops, I looked at extension resources referenced above and reports from research completed in the U.S. and other countries. I was also very pleased to hear from Ohio growers on the same topic.

That input pointed to the following seven factors as most likely to shape optimal fertilizer, especially nitrogen, application rates for individual farms, soils, crops, and plantings.
1. Soil type and condition. Sandy, loam, or clayey? Organic matter level? Have a prominent plow layer or other condition affecting drainage, etc? Fertilizer programs must be calibrated to soil type and condition since they influence many facets of nutrient availability at any one time.
2. Fertilizer application approach. For example, will fertigation be used? Fertilizer application approaches influence which materials are used, when and where they are applied, and their likely efficiency.
3. Precipitation and irrigation. Soil moisture management is a very large percentage of nutrient management. Are the irrigation and fertilizer programs in sync? Is rainfall cooperating? Can the program be adjusted for weather?
4. Variety(ies). Shifting market expectations (e.g., large to personal-size melon) may have implications for the fertilizer program. Similarly, the program may also need to be adjusted to maximize gains from using grafted planting stock because rootstocks may differ in, for example, their abilities to obtain nutrients and water.
5. Cultural practices. Production on plastic-covered raised beds versus the flat. Standard versus strip- or reduced tillage approach. Row and plant spacings (plant populations). These and other factors are consistently mentioned as factors shaping the four R’s (material, rate, timing, placement) of all fertilizer programs. The fertilizer program may need to be tweaked if any of these factors are changed.
6. Crop growth stage. Especially important for fruiting vegetables, including Cucurbit and Solanaceous crops. Nitrogen and other macro- and micronutrient levels influence many aspects of crop biology directly impacting (fruit) yield and quality from seeding/transplanting to harvest. Metering nutrient availability by crop stage is a proven, essential tactic in soilless greenhouse production. The same level of control is impossible in soil-based field or high tunnel production; however, a realistic application of the principle can be beneficial in both systems.
7. Nutrient credits. There is often little need to apply what is already there. Basing planned applications on current, reliable soil test data is a cornerstone of successful, efficient, cost-effective fertilizer programs.

Finally, setting optimistic but realistic yields goals, especially for non-vegetable rotation crops, if any, is also beneficial. Realistic yield goals help avoid significantly under- or over-applying fertilizer, regardless of crop. Avoiding such deficiencies and excesses enhances the overall return on investments in the current and subsequent crops.

Hardin County Crop Walk

Hardin County – There is a segment of agriculture in southeastern Hardin County that specializes in commercial fruit and vegetable production. Hardin County is also home to the Scioto Valley Produce Auction near Mt. Victory where much of this produce is sold. Hardin County OSU Extension has planned a Fruit and Vegetable Crop Walk program on Friday, July 30 from 6:00-8:00 pm to help with fruit and vegetable production issues. The location of the program will be on a produce farm at 19809 County Road 200, Mt. Victory. It is open to all fruit and vegetable producers, whether they are commercial or home gardeners.

OSU Extension Integrated Pest Management Coordinator Jim Jasinski will provide information on managing insects with produce. OSU plant pathologist Melanie Ivey will provide information on managing plant diseases with fruits. OSU State Vegetable Production Specialist Matthew Kleinhenz will provide an update for growers on vegetable production. Hardin County OSU Extension Educator Mark Badertscher will provide information about Driftwatch; a voluntary communication tool that enables crop producers, beekeepers, and pesticide applicators to work together to protect specialty crops and apiaries through use of mapping programs.

The program will be held outside so bring your lawn chair and umbrella in case of rain. There will be a diagnostic table so be sure to bring along any weeds, plant nutrition problems, plant diseases, and insect specimens in a sealed plastic bag for questions and answers. The program will conclude with a walk through a produce field, pointing out fruit and vegetable issues and steps to properly manage them. There is no cost to attend this event

Cucurbit Downy Mildew Continues to Spread in Northern Ohio

Downy mildew map.

After last week’s very wet weather, downy mildew has appeared on cucumbers in a research plot on the OSU Muck Crops Research Station (Huron County) and on cucumbers and melons in sentinel plots on the OSU CFAES Wooster campus (Wayne County) and the OSU North Central Agricultural Research Station in Fremont (Sandusky County). In addition, downy mildew continues to spread in commercial fields in Seneca County. Downy mildew is likely to be present in cucumbers and/or melons in other northwest and northcentral Ohio counties and growers should protect these crops with appropriate fungicides. Fungicides must be applied preventatively – once plants are infected they will show symptoms within ~5-7 days even if fungicides are applied after infection. Only the fungicide Curzate has moderate “kick-back” activity.

OSU is part of a multi-state cucurbit downy mildew monitoring project, for which this year we have enlisted the help of Master Gardener Volunteers (MGVs) as Citizen Scientists in counties throughout Ohio. Most (25) are monitoring cucumber and squash plants in their gardens, while six groups of MGVs are managing and monitoring full sentinel plots. We have had no reports of downy mildew on cucurbits outside of northern Ohio and none in squash, pumpkins, gourds, or watermelons in any part of Ohio. We will continue monitoring and reporting downy mildew occurrences as they happen.

Cucumber downy mildew – photo by J. Amrhein.

If you suspect cucurbit downy mildew on your farm or in your garden, please send pictures (as close-up as you can) of the tops and undersides of affected leaves to me by text (330-466-5249) or email (  Please include your name and the name of the town or city nearest you.

Downy mildew sporulating in a lesion on the underside of a cucumber leaf. Photo by F. Rotondo.

2021 Pesticide Disposal Dates

The Ohio Department of Agriculture will be sponsoring three collection events for farmers wishing to dispose of unwanted pesticides. This year, the collections are happening in Morrow, Portage and Butler counties on the following days and locations:

  • August 12, 8AM – 3PM: Morrow County, Morrow County Fairgrounds, 195 South Main Street, Mt. Gilead, Ohio 43338
  • August 17, 9AM – 3PM: Portage County, Deerfield Ag Services, 9041 US-224, Deerfield, Ohio 44411
  • August 24, 9AM – 3PM: Butler County, Butler County Fairgrounds, 1715 Fairgrove Avenue, Hamilton, Ohio 45011

The pesticide collection and disposal services are free of charge, but only farm chemicals will be accepted.  Paint, antifreeze, solvents, and household or non-farm pesticides will not be accepted.

The pesticide collections are sponsored by ODA in conjunction with the U.S. Environmental Protection Agency.  To pre-register, or for more information, contact the Ohio Department of Agriculture at 614-728-6987.

Basil Downy Mildew Spotted in Wayne County, Ohio

Basil plants with severe downy mildew symptoms in a big box store garden center in Wooster, OH. Photo by F. Rotondo.

This is shaping up to be a summer of downy mildews in Ohio. Rainstorms, high humidity, overcast skies and cool-ish nighttime temperatures are very conducive to downy mildew occurrence and spread. We reported the first “sightings” of cucumber downy mildew last week in Seneca and Wayne Counties in Ohio, and today OSU diagnostician Dr. Francesca Rotondo spotted a very severe outbreak of downy mildew in potted basil in a big box store garden center in Wooster (see photos). The pathogens that cause downy mildew in cucurbits and basil are different and don’t cross-infect among the two different plant groups.  However, they do respond similarly to environmental conditions.

Basil plants with severe downy mildew in a garden center in Wooster, OH.

The garden center manager in Wooster was notified and will have the diseased basil plants removed and destroyed promptly.

Management options for commercial  growers are 1) resistant varieties and 2) fungicides applied preventatively. Dr. Andy Wyenandt and colleagues at Rutgers University recently published an excellent discussion of available management tactics, including those for conventional and organic commercial basil producers. Information is also available on the Basil Ag Pest Monitor website, including photos of symptoms, management options and a map of basil downy mildew reports.

Management options are limited for home gardeners – resistant varieties are the most viable choice. In established garden basil plantings of susceptible varieties, monitor plants closely and remove and destroy leaves and stems with downy mildew symptoms. This may or may not slow disease progress, depending on environmental conditions and the presence of inoculum in nearby plantings. Leaves without symptoms are safe to eat, so if downy mildew appears in one’s garden basil, it may be time to make pesto or a nice Caprese salad before the disease spreads.