Are Your Cucurbits Yellowing or Wilting?

We are seeing many reports of yellowing and/or wilting squash, pumpkin and other cucurbits in commercial fields and gardens this month. Chances are that the cucurbits have been affected by cucurbit yellow vine decline (CYVD) or bacterial wilt. Both of these diseases are caused by bacteria transmitted to plants during the feeding of their insect vectors. Once infected, the plants cannot recover; these diseases must be managed preventatively by controlling the insect vectors, ideally early in the season. At this point, insecticides may be applied to prevent the diseases from spreading to healthy plants. It is also useful to remove and destroy symptomatic plants that serve as sources of bacterial inoculum.

Sticky bacterial ooze from a cucumber vine with bacterial wilt

Bacterial wilt of melon

Bacterial wilt affects many cucurbits including cucumber, melon, pumpkin and squash. The causal agent, Erwinia tracheiphilia, overwinters in the digestive system of spotted and striped cucumber beetles.  When these beetles emerge in the spring, the pathogen is spread from beetle feces to healthy cucurbits mainly via wounds caused by insect feeding.  Bacterial wilt occurs almost every summer in Ohio, but is less severe after very cold winters that reduce overwintering beetle populations. Symptoms begin as discoloration and wilting of individual leaves.  As the disease progresses, the entire plant begins to wilt and collapse as the bacteria clog the xylem vessels.  When the stem is cut along the base, clear to white elastic strands comprised of the bacteria and “gum” are visible when cut ends of stems are slowly pulled apart. More details can be found here. Insecticides labeled for cucurbits and effective against the beetles can be found in the Midwest Vegetable Production Guide for Commercial Growers. Covering plants with netting or floating row covers until flowering can also protect plants from early infection.

Cucurbit yellow vine decline in summer squash

Cucurbit yellow vine decline in pumpkins.

Cucurbit yellow vine decline (CYVD) is caused by the bacterial pathogen Serratia marcescens, transmitted by squash bugs. It is uncommon in some years but in others can do a lot of damage. Bright yellowing of leaves, followed by by wilting and death of plants is indicative of possible CYVD. If squash bug adults, nymphs or eggs are found on the underside of leaves, this is a good clue that the symptoms are caused by CYVD. A cross-section of the vine may show a light tan discoloration of the vascular tissues. CYVD is managed by applying insecticides (see Guide link above). For both CYVD and bacterial wilt, fields and gardens should be scouted regularly for the insect vectors beginning soon after transplanting or seedling emergence.

The OSU Plant Disease Diagnostic Clinic in Wooster can provide a definitive diagnosis of CYVD using a PCR assay.  Testing for this and other diseases and pests is free of charge for Ohio commercial vegetable growers thanks to financial support from the Ohio Produce Growers and Marketers Association.

Eggs of the squash bug

Cross-section of squash vine with light browning of the vascular system caused by the bacteria

Pumpkin and Sunflower Field Day – August 25

For over 20 years the pumpkin field day has been a source of production and pest management information for both new and experienced growers. This year we will be adding some flair as we begin to tackle the production and pest management issues surrounding the popular trend of sunflower fields for photographs and cut flowers as an additional source of revenue on diversified farms. So if you want to learn about two popular fall attractions, pumpkins and sunflowers, this is a field day that can’t be missed.

Pumpkin and sunflower

The field day will be divided roughly in half, with the first hour focused on sunflower topics ranging from grower experiences in production (Matt Sullivan, grower) to impacts from the ag tourism perspective (Kate Hornyak, OSU). A nine-hybrid sunflower demo strip trial will be in various stages of bloom for attendees to walk through and examine.

The second hour will focus on pumpkins, starting off with managing pollinators in cucurbits (Ashley Leach, OSU), foliar fertilizers and plant nutrition (Bryan Reed, Sunrise) and then a review of powdery mildew fungicide management and a walk through the 24 hybrid trial (Jim Jasinski, OSU).

The field day will be held at the Western Ag Research Station, 7721 S. Charleston Pike, South Charleston Ohio. The field day will begin promptly at 5:30 PM and end at 7:30 PM. Pre-registration is required for attendance and there is a $5 charge per person for handouts and refreshments (and likely a few sunflowers). For more information contact Jim Jasinski,

Pre-register at this link:

More details are listed on the attached flyer. Hope to see you there!

Pumpkin and Sunflower 2022 Flyer

Fruit and Vegetable 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 Tuesday, August 2 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 15237 County Road 209, Kenton. 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 using IPM techniques to control pests with produce. Ashley Leach, OSU College of Food, Agricultural, and Environmental Sciences Assistant Professor of Entomology will provide an update on specialty crops insects. Gary Gao, OSU Extension Small Fruit Production Specialist will provide information on growing grapes and raspberries. Brad Bergefurd, Technical Specialty Crop Agronomist, Brandt Discovery and Innovation will provide an update for growers on vegetable production fertility. 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.

New Cucumber Downy Mildew Reports This Week

Reports of cucurbit downy mildew as of July 21, 2022.

A new report came in this week of cucumber downy mildew in Fulton County, as well as another report from Medina County, this time from a different farm in the Homerville area.  Downy mildew is favored by cooler conditions so despite many hot days, nights were cool enough for the pathogen to get a foothold in northern Ohio. In addition, we have seen a number of storms across the area; spores of the pathogen travel by air and clouds protect them from UV light, while rain drops them to earth.

Cucumber and melon growers in northern Ohio should scout fields for downy mildew and apply appropriate fungicides on a 7-10 day schedule, depending on the fungicide. See this post for fungicide recommendations.

Many thanks to Bill Holdsworth and Frank Becker for reporting these outbreaks.


Downy Mildew Reported on Fresh Market Cucumbers in Seneca County, OH

Cucurbit downy mildew incidence report, July 20, 2022. https:/

Downy mildew was reported on cucumbers in NE Ohio (Medina and Wayne counties) and southern Ontario last week, suggesting widespread occurrence possible in northern Ohio. This morning Marty Hofbauer, CCA and Agronomist at Luckey Farmers, Inc., discovered downy mildew in fresh market cucumbers near Tiffin, Ohio in Seneca County. Marty sent me excellent photos of leaf lesions taken with his smartphone that allowed me to confirm downy mildew without the need to send in a sample. By taking the pictures early in the morning, the sporulation on the undersides of leaves was clearly visible in young lesions. Sometime about mid-late morning the sporangia will be discharged. Older lesions tend to dry out and are not necessarily diagnostic for downy mildew. Several of his pictures are included here as examples of what to look for.  Angular leaf spot, caused by a bacterium, also makes angular lesions, but the grey fuzzy growth and black dots (sporangia) on the lower side of the lesion is diagnostic for downy mildew.

Cucumber downy mildew – young lesions. Photo by Marty Hofbauer.

Underside of cucumber downy mildew lesion showing sporulation of the pathogen. Photo by Marty Bauer.












I continue to be amazed at the increasingly high quality and resolution of smartphone images. For a disease like downy mildew, where quick diagnosis and treatment is crucial, taking high high quality pictures that can be sent to us for confirmation saves both time and money. Ohio cucurbit growers, consultants and others may send me pictures such as these by text (330-466-5249) or email ( for diagnosis. Physical samples may be sent to Dr. Francesca Rotondo in the OSU Vegetable Pathology Lab – see submission instructions here. Vegetable and fruit diagnostics are free to Ohio growers due to financial support from the Ohio Produce Growers and Marketers Association’s Ohio Vegetable and Small Fruit Research and Development Program.

Scouting Notes From the Wayne County IPM Program

Here are our weekly observations from the fields and farms around Wayne County from the week of July 11-15.

Vegetable Crops

Probably the biggest development in our area was the presence of cucurbit downy mildew on a path of cucumbers in southern Wayne County. This means there are active infections in Wayne and Medina counties, and likely the surrounding counties. Ideal conditions for continued progression and infection will exist in the coming days. It is important to take steps now to protect your cucumbers and cantaloupes.

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

Powdery mildew on cucurbits continued to spread rapidly, spurned on by several foggy mornings in the area.

As early plantings of summer squash and other cucurbits are harvested, it is important to practice good sanitation in the fields. Do not allow these areas to become diseased and insect infested, as they will only lead to problems in other areas on your farm. Once you are done harvesting an area, it is best to terminate the crop and either incorporate or remove the residue. 2

Other disease concerns revolved around bacterial diseases on peppers and tomatoes. We started to find some bacterial spot/speck on these crops.

Insect wise, it was an active week. Cole crops are still facing significant pressure from flea beetles and imported cabbage worm. European corn borer was identified in a few pepper plantings. Cucurbit crops saw increased activity from cucumber beetles, squash bug and squash vine borer.

Small Fruit and Orchards

A few diseases like scab and blister spot have started to show up on leaves in apples orchards, otherwise, the majority of any disease pressure has subsided after dealing with several rounds of fire blight outbreaks. Insect pressure in apples has slowed some as codling presence has remained low, however, some orchards are still facing some persistent damage from European red mites.

Some of our oriental fruit moth traps showed a significant flight, with some traps averaging nearly 30 moths per trap. Red mites were still active in the peach blocks as well this week.

The season is wrapping up for some of our raspberry growers, and blueberries won’t be far behind. With blackberries now coming into season, it is still important to be aware of the presence of the spotted wing drosophila, which are still being found in most of our traps. Japanese beetles may also be causing some troubles for small fruit grower, especially those with grape vines. We observed significant defoliation from Japanese beetles on grapes in several areas of the county this week.


Attack of the Killer Tomato (Hornworms)

Yes, this is the title of a 1978 comedy horror film (sans the hornworm part, that was added to provide context to the article).  I have a small garden at home and last week I noticed foliage and fruit chewed along with fairly large frass pellets laying around so I had all the clues needed that hornworms had indeed found at least two of my tomato plants. I began searching diligently but could only find one hornworm, I’m sure there were several more hidden among the foliage digesting their lunch.

Finding these worms at home made me think about scouting the much larger tomato research project at the Western Ag Research Station in South Charleston. Unfortunately, there is no pheromone trap to detect the moth so periodic monitoring of the plants for feeding damage or caterpillars is required. I started looking at the plants and soon discovered there were hornworms infesting about 5% of the plants.

Hornworm damage to tomato plant


Hornworm damage

While there are many types of hornworm moths, commonly referred to as hawkmoths or sphingid moths, there are only two economically important species found in Ohio that feed on tomato plants, the tomato and tobacco hornworm. The key characteristic I use to identify these two species is the shape of the markings on the side of the caterpillar; the tomato hornworm has a sideways “V” called a chevron on each segment while the tobacco hornworm has a slanted white slash that looks like a cigarette (to me). There are other characters to separate the species such as the color of the “horn” on the last segment (black vs. red) but these tend to be less reliable. The tobacco hornworm is usually more common in Ohio tomato fields than the tomato hornworm. The length of the worms found at the research station was up to 3 inches, which is near their maximum size.

Tobacco hornworm, note white slashes on segments


Tomato hornworm, note “V” shape on segments

Hornworms are often found with many small white cocoons stuck on their body. The cocoons show that biological control by natural enemies is in progress. A hornworm covered with cocoons has been parasitized by Cotesia congregata, a small braconid wasp. By the time the cocoons emerge from the larva, the hornworm is close to death and will not reach its pupal stage. One wasp will emerge from each cocoon.

Parasitized hornworm

The threshold for treating this pest is two or more hornworms or fresh damage per 40 plants scouted of any stage, from seedling to fruiting. Whether parasitoid cocoons are seen or not, the chances of biocontrol contributing to the management of this pest are increased greatly by avoiding the use of broad-spectrum insecticides. The best insecticide to use is one of the BTs such as Dipel or Javelin or Xentari, especially if worms are small. If insect pests in addition to hornworns are found in the tomato field, then conventional insecticides will be needed; most insecticides are very toxic to hornworms so the selection of the product should be based on the other pest(s). Products such as carbamates (Lannate, Sevin) and pyrethroids (Asana, Baythroid, Pounce, Warrior) are toxic to hornworms but disruptive to natural enemies like the Cotesia parasitoid. Products such as Radiant, Intrepid, or Neemix are toxic to hornworms but have a more gentle impact on beneficial insects. More insecticide options are listed in the Midwest Vegetable Production Guide (

Part of this article was excerpted from a previous VegNet article posted in 2009.

2nd OH Report of Cucumber Downy Mildew – Wayne County

Cucumber downy mildew July 13, 2022, Wayne County, OH. Photo by OSU diagnostics intern Vansh Khatri.

Quick on the heels of our report of cucumber downy mildew on Monday in Medina County, we have diagnosed the disease on cucumbers in the Fredericksburg area of Wayne County. With thunderstorms rolling across northern Ohio this afternoon, we expect the disease to spread to cucumbers and melons throughout this part of the state. See my post on July 11 for fungicide recommendations.

Reported cucurbit downy mildew, July 13, 2022.

First Report in Ohio of Cucumber Downy Mildew for 2022

Cucurbit downy mildew map, July 11, 2022.

Today OSU plant diagnostician Francesca Rotondo diagnosed the first cucumber sample of the 2022 growing season with downy mildew. Downy mildew has been a bit slow to appear, likely due to the high temperatures and often sunny and dry conditions. Last year our first report of cucumber downy mildew in Ohio was on July 12. I expect that conditions last week – rain and overcast skies in northern Ohio -promoted spore transport, deposition and infection. The sample came from an organic farm in the Homerville area, in Medina County – it was just getting started in the field and disease incidence and severity were low. Cucumber and melon growers in northern Ohio should ramp up their spray programs to include highly effective fungicides against downy mildew such as Orondis Opti, Ranman, Omega, Previcur Flex, and Elumin (see efficacy table below). Curzate was effective in our 2021 tests but has been variable in efficacy over the years. It is recommended to tank mix these products with chlorothalanil. Check the labels carefully for use instructions and restrictions. Remember to alternate products in different FRAC groups. Fungicides must  be applied preventatively – they  are far less effective if applied after  infection.

Growers in central Ohio should intensify scouting of cucumbers and melons and apply a protectant fungicide. Look for yellow or tan angular lesions delimited by veins on the top surface of leaves, and fuzzy grey/brown growth on the undersides of the lesions. With a good hand lens or a smartphone camera with high magnification you may be able to see small dark brown/purple spots within the fuzzy growth. These are the spores of the downy mildew pathogen.

Smartphone image of a downy mildew lesion with the pathogen sporulating on the underside of a cucumber leaf.

If you suspect downy mildew in cucumber or melon please text or email pictures to Sally Miller (330-466-5249; of both sides of lesions, with the underside in the highest possible magnification. I can often confirm downy mildew from photos, but if not will ask you to send a sample to the OSU Vegetable Disease Diagnostic Lab for confirmation. Instructions for sample submission are here. Thanks to financial support from the Ohio Produce Growers and Marketers Association’s Ohio Vegetable and Small Fruit Research and Development Program, there is no fee for this service for Ohio vegetable growers.

Scouting Notes from the Wayne County IPM Program

Here are our weekly crop scouting observations from the week of July 4-July 8.

Vegetable Crops

The warm temperatures and accumulated heat units have kept our insect pests active and building in population. Cucumber beetles, squash bugs and squash vine borer were all active this week in cucurbit plantings and fields. Additionally in squash, we noted our first sighting of powdery mildew in an area of first planting summer squash.

The warm and sunny days have also led to some challenges with sun scald. Unfortunately, the heavy winds and rains from the storms had pushed plants over, which allowed for the first set of vegetables, such as in peppers or tomatoes, to be exposed to direct sun and extreme heat.

Growers with cole crops may still be battling flea beetle and imported cabbage worms. Significant egg laying from the cabbage white butterflies gives us the heads up to scout our cole crops very closely to watch for hatching eggs and young caterpillars.

Generally speaking, the Japanese beetles have begun their entrance into a wide range of vegetable crops. In some cases, isolated cases of heavy feeding damage may severely damage the foliage and stunt young plants. Frequent scouting can help you make timely management decisions, therefore avoiding significant damage from the Japanese beetles.

Small Fruit and Orchards

European red mites were found in apples and peaches this week, and in a few cases, the populations had reached significant levels, with severe feeding damage present on the foliage. As was the case in vegetable crops, the Japanese beetles feeding on orchard trees and small fruit plants started to cause some significant defoliation.

Spotted wing drosophila were found in all of our traps. Accordingly, small fruit growers should be aware that we are now fully into SWD season.

Fire blight in apples has been our main disease concern to this point. We did note a few cases of apple scab on leaves in some orchards around the area.

Overall, fruit development in orchards and small fruit production areas is coming along nicely and should be greatly benefited by the timely rains.