You probably won’t use your sprayer again until next spring. To avoid potential problems, frustration, and major headaches next year, it’s wise to give your sprayer some TLC (Tender Loving Care) this time of year. While there may still be other important matters demanding your attention, don’t forget to winterize your sprayer. Don’t delay if you haven’t done so already. You want to prevent a cracked pump or reduced efficiency caused by not properly winterizing before temperatures drop below freezing. Here are some essential steps to take with your sprayer now.

Rinsing
You probably did the right thing when you last used the sprayer: thoroughly rinsed the entire system (tank, hoses, filters, nozzles). If you didn’t, be sure to do this before storing the sprayer. An unrinsed sprayer after each use, especially after the spraying season ends, can lead to cross-contamination of products applied to different crops next spring. Pay special attention to avoiding cross-contamination, which can cause severe crop damage, especially when using some of the newer 2,4-D and Dicamba herbicides. Another issue caused by not properly rinsing all sprayer parts is clogged nozzles. Once nozzles are clogged and remain that way for a long time, it becomes difficult to restore them to their normal working condition, which is what you expect from a properly cleaned nozzle. Leaving chemical residues in nozzles often causes changes in flow rate and spray pattern, resulting in uneven chemical distribution on the target.

The ease of properly rinsing a tank’s interior depends on its type. It is very simple if the tank is relatively new and has special rinsing nozzles and mechanisms inside. If not, manual rinsing becomes more difficult and can pose safety risks, such as inhaling fumes from leftover chemicals during the process. To avoid these issues, you can either replace the tank with one that has interior rinse nozzles or install an interior rinse system in your current tank.

For effective rinsing of all sprayer parts, circulate clean water through the entire sprayer for several minutes first with the nozzles off, then flush out the rinsate through the nozzles. Rinsing should ideally be done in the field or on a concrete chemical mixing/loading pad with a sump to recover rinse water. In any case, dispose of the rinsate following the instructions on the pesticide labels you have used. Always check the label for specific directions. Most labels recommend the following procedure: if rinsing on a concrete rinse pad with a sump, return the collected rinsate to the tank, dilute it with water, and spray it in the field where it cannot reach ditches or other water bodies. If rinsing is done in the field, make sure you are not flushing rinsate in one area. It’s best to dilute the rinse water in the tank further and spray it on the field in places where it won’t contaminate nearby water bodies or ditches.

Cleaning
Rinsing the system with water, as explained earlier, may not completely remove chemicals from the sprayer. This could lead to cross-contamination issues. Residues of certain pesticides left in the sprayer might cause serious problems when applying a spray mixture containing those residues to a crop highly sensitive to that pesticide. To prevent such issues, it’s best to thoroughly clean and rinse the entire spraying system with a cleaning solution. Usually, a mixture of 1 part household ammonia to 100 parts water works well for cleaning the tank. However, if the tank hasn’t been cleaned for weeks or immediately after the last spraying, you might need to start with a detergent solution. Some chemicals require specific rinsing solutions. Always check the product label for the latest cleaning instructions.

Cleaning the outside of sprayer components deserves equal attention. Remove compacted deposits with a bristle brush. Then flush the exterior parts of the equipment with water. A high-pressure washer can be used if available. Wash the exterior of the equipment either in the field, away from ditches and nearby water sources, or on a specially constructed concrete rinse pad with a sump. Again, the rinsate should be disposed of according to the label recommendations. As I mentioned earlier, most labels recommend the same practice: put the rinsate collected in the sump back into the tank, dilute it with water, and spray it in the field where there is no potential for the rinsate to reach ditches or other nearby water bodies.

Inspecting sprayer during winterization.

Winterizing
Recheck to ensure no liquid remains inside any of the sprayer parts to prevent freezing. The pump, as the core of a sprayer, needs special attention. You don’t want a cracked pump or one that isn’t working properly due to inadequate winterization before temperatures drop below freezing. After draining the water, add a small amount of oil, then turn the pump four or five revolutions by hand to coat the inside. Ensure this oil won’t harm rubber rollers in a roller pump or rubber parts in a diaphragm pump. Refer to the operator’s manual. If oil isn’t recommended, pouring one tablespoon of radiator rust inhibitor into the pump’s inlet and outlet can also help prevent corrosion. Alternatively, use automotive antifreeze with rust inhibitor in the pump and other sprayer parts. This helps protect against corrosion and freezing if any water remains. To prevent corrosion, remove nozzle tips and strainers, dry them thoroughly, and store them somewhere dry. Another option is to submerge them in a can of light oil, such as diesel fuel or kerosene.

Storage
Find ways to protect your sprayer from the harmful effects of snow, rain, sun, and strong winds. Moisture in the air, whether from snow, rain, or soil, causes rust on the metal parts of all types of unprotected equipment. This is especially true for a sprayer, which has various hoses, rubber gaskets, and plastic components. While the sun can help reduce moisture in the air, it can also cause damage. Ultraviolet light weakens and softens rubber parts like hoses and tires, and degrades some tank materials. The best way to protect your sprayer is to store it in a dry building. Keeping sprayers inside also allows you to work on them anytime during the off-season, regardless of the weather. If storing inside isn’t possible, cover the sprayer with a material that shields it from sun, rain, and snow. For trailer-style sprayers, place blocks under the frame or axle and reduce tire pressure during storage.

Finally, double-check all sprayer parts before leaving it behind. Identify parts that may need repairs or replacement. Inspect the tank and hoses for any signs of cracks or damage. Check the painted surfaces for scratches and touch up with paint to prevent corrosion. Also, remember to cover openings to prevent birds from nesting in the sprayer and to keep insects, dirt, and other debris out of the system.

Erdal Ozkan
Professor and Extension State Specialist
The Ohio State University

The powdery mildew fungicide trial plot at South Charleston (WARS) are 100% orange and beginning the natural process of senescence. It has been dry at the station for the past few weeks and the Plectosporium blight has slowed down considerably. In the picture below, the top 15’ is a no-spray untreated check (near the grass border), then the main PM trial treatments and then a few PMT hybrids on the end of each row for comparison. The different susceptibility of Plectosporium to pumpkin hybrids can be seen in the image although now even the relatively tolerant hybrid is now severely infected and collapsing.

Plectosporium damage to powdery mildew trial.

At the station, PM infection in general seems light this year so far. Squash bugs are very active still, with all stages readily found in the field. Some striped and spotted cucumber beetles are feeding on the foliage, flowers and fruit.

Special Guest – Andres Sanabria Velazquez, OSU’s specialty crop plant pathologist, came down from Wooster and toured the plots with me last week. He pointed out many diseased plants which later were confirmed to be bacterial infections, likely bacterial leaf spot.  This disease is common in Ohio, attacking both foliage and then fruit. Unfortunately there is no effective treatment but certain hybrids do have a higher tolerance to the bacterial infection.

The tar spot sweet corn study has been scouted for the past few weeks but no lesions have been reported at any of the locations; Piketon, South Charleston or Willard. A fungicide application was made today on one of the South Charleston trials at full tassel stage despite there not being any tar spot, to see if slowing down other fungal pathogens would make a yield difference.

Spider sprayer going through Tar Spot trial with a fungicide.

While scouting these tar spot plots, it was quite evident that fall armyworm, corn leaf aphids and flea beetles were quite plentiful, damaging the tassels and emerging leaves on a substantial number of plants. There were also quite a few natural enemies feeding on the aphids in particular, including several species of ladybugs and green lacewing larvae.

Fall armyworm larva and leaf damage.

Ladybug with corn leaf aphids in tassel.

Corn earworm numbers have been spiking the past few weeks, with 3-5 day trap catch counts exceeding 120 moths. Sweet corn growers surrounded by drying field corn fields are at higher risk of infestation as their field is functioning like a trap crop due to it’s relative greenness. Recall CEW should be treated at fresh silking stage using a combination of moths caught per day and daily temperature above or below 80F to set the spray interval. Once silks have turned brown, those ears are relatively unattractive to egg laying CEW moths. Recommended products to treat for CEW caterpillars can be found in the Midwest Vegetable Production Guide here: https://mwveguide.org/results/crop/589/pests/3279

CEW treatment table.

Hartstack trap for corn earworm moths.

When people mention the Big Three auto manufacturers in Detroit, Michigan, most people think Ford, GM and Chrysler. When someone mentions the Big Three soil borne diseases in pumpkins, you should think of Phytophthora, Fusarium and Plectosporium. All of these fungal diseases can cause plant death and significant fruit loss. The spores can live several years in the soil, requiring proper moisture and weather conditions to initiate the infection cycle on a susceptible host, such as pumpkin.

This past week at the Western Ag Research Station in South Charleston, there was a spectacular infestation of Plectosporium blight on pumpkin leaves, veins, petioles, vines and fruit handles. This disease has previously been called white speck or Microdochium blight. After weeks of periodic heavy rains splashing infected soil onto the plants, a small percent of lesions were noted on a few plants July 30. Five days later, about 90% of the plants in the trial had a full blown infestation, severely damaging foliage and killing some plants in the trial. Because this disease attacks all parts of the plant, including the fruit handle and rind, it can lead directly to marketable fruit losses. Once infected, the leaves and petioles become very brittle and can snap off easily when handled or moved.

Plectosporium signs on pumpkin leaves. Note tiny white specks / spots on early infestation.

Note spindle or diamond shaped lesions on the lower leaf surface veins and petioles. These lesions will expand and coalesce into a large bleached area as the signs progress.

This infected fruit handle has become bleached over time. Notice all plant parts can be infected (leaves, veins, petioles, vines, fruit and handle) on right hand image.

Lighter colored foliage in this field wide image is infected and will eventually turn necrotic and fall off of the plant. Based on severity of infection, the entire plant may die.

Protectant fungicides used in powdery mildew applications such as Manzate should help prevent infection but after disease is identified, other chemistries such as the strobilurons (FRAC 11) are quite effective at control. Cultural management includes rotation away from cucurbits for at least three years to reduce soil borne inoculum. Biofumigation with mustard cover crops was researched for two years (2019-20) as a potential mitigating practice but was not found effective in reducing plant and fruit losses. A video outlining the biofumigation process can be seen on the OSU IPM Video Library on YouTube (https://youtu.be/Taz-PhDphhA?si=U11CrjsdAJXR01TD).

Cover crops such as rolled or crimped winter rye left on the soil surface forming a mat between the soil and the plants/fruit should help reduce soil splash and therefore limit disease progression on plants. Winter rye should help reduce Fusarium infections by preventing soil contact but will not be very effective against Phytophthora. Most pumpkin hybrids have very little resistance to Plectosporium blight but squash hybrids tend to be more resistant to infection, so looking for resistant hybrids in seed catalogs won’t yield any results.

Older pesticides for disposal.

The Ohio Department of Agriculture (ODA) will be sponsoring three collection events for farmers to dispose of unwanted pesticides. This year, the collections are available in Fulton, Lake, and Greene counties on the following days and locations:

• August 13 – Fulton County Extension
  8770 State Route 108, Wauseon, Ohio 43567, 9 a.m.–3 p.m.
• August 14 – Perry Coal and Feed (Lake County)
  4204 Main Street, Perry, Ohio 44081, 9 a.m.–3 p.m.
• August 27 – Greene County Fairgrounds
  100 Fairground Road, Xenia, Ohio 45385. 9 a.m.–3 p.m.

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.

Pumpkin growers are in the middle of their season now, with plants still flowering, fruit being set, and set fruit sizing up. We’ve been getting steady rains in South Charleston for the past two weeks, and the pumpkin plants are as large as I’ve ever seen. My research plots with small vining hybrids are planted on 15′ centers but are now nearly 12′ wide, even after vine training!

Steady rains have favored pumpkin growth.

Powdery Mildew has been detected at the station on 7/22 but is still at very low levels, under 0.5%. This is the equivalent of 1-2 white powdery colonies per leaf which is a very low level. Growers are encouraged to begin their spray schedule oevery7-14 days when they see the first colonies, as this disease multiplies very fast in the canopy.  For a list of PM fungicides, see the Cucurbit chapter of the Midwest Vegetable Production Guide (https://mwveguide.org/uploads/pdfs/Cucurbit-Crops_2024-12-03-155451_othe.pdf) or take a look at some of the results performed at OSU over the past few years (https://u.osu.edu/jasinski.4/pumpkins/).

Early powdery mildew infections on upper leaf…only a few percent in this image.

While Downy Mildew has been reported in Ohio over the last two weeks, it is the clade that affects cucumbers not pumpkin. Protective applications of chlorothalonil or mancozeb will help protect against infection; recall that FRAC M fungicides like chlorothalonil and mancozeb can be added to every spray with only minimal chance of resistance development. Once DM has been positively identified in a field, switch to more specific and systemic products found in the MVPG.

Squash bug activity has been picking up in the plots over the past few weeks, with all stages readily seen on foliage; eggs, nymphs and adults. The threshold is one egg mass or adult per plant to justify an application. There are not squash bug specific sprays per se, and any insecticide application made at this point needs to consider if the plants are flowering or not. If flowering, legal pollinator protections and guidelines must be followed to minimize impacts on pollinators and other beneficial insects in the field. Applications of pyrethroids or other insecticides will kill many of the beneficial insects and most likely spike secondary pests like aphids. Do not add a blanket insecticide unless you have a specific pest insect above threshold that needs to be controlled. If an insecticide is needed, do not tank mix with a fungicide as this will increase bee mortality in most cases; apply late in the evening to lessen impact on pollinators. Available insecticide options can be found in the MVPG.

Squash bug life stages.

Other News from Around the Research Station and Beyond
The Tar Spot sweet corn study is nearly ready to begin evaluating. Tar Spot is a relatively new disease on corn, first detected on field corn in Ohio in 2018. Currently the plants are at V7. When the plants reach V10, the evaluation for dark brown stroma on leaves will begin. This project is also being trialed at Piketon and Muck Crops station. We’ll keep you updated as the season progresses.

OSU researchers are working with FarmSense to evaluate a new kind of insect monitoring device that does not rely on a sticky card or compartment to trap the insect. Instead, the experimental FarmSense device reportedly can identify the pest moth as it flies through the sensor. Pest detections are then uploaded via cellular connection to the cloud where growers can access trap counts on a website without taking time to visit the trap. This technology is being compared to standard Heliothis traps for squash vine borer and corn earworm. Stay tuned for more results.

FarmSense traps differ from other conventional traps.

Brown Marmorated Stink Bug traps are being set to record the late summer migration toward tree fruit and other vegetables, especially sweet corn, tomato and pepper. Keep an eye out for these pests as you work around your fields.

BMSB traps deployed.

Pumpkin plants continue to grow slowly under the mid 90’s heat of this week. Some rain hit the station mid-week but more is needed to avoid plant stress. Cucumber beetle damage has been minimal given systemic insecticide applications. Cucumber beetles have been reported in high numbers at other locations across the state.

Squash bugs were nearly undetectable but typically increase quickly as plants grow larger and adults find local cucurbit fields.

Squash bug eggs and mating adults.

Squash bug eggs.

No squash vine borer moths have been detected at the station despite the trap being up for two weeks; SVB have been detected in nearby Greene County site and near Akron. They are likely active over most of the state at this point in the season.

Squash vine borer adult on pumpkin leaf.

Around mid-July, begin scouting for powdery mildew on pumpkin, squash and other cucurbits. This disease does not over-winter in Ohio but spores are blown up on wind currents from Southern states. Check the upper and lower leaf surface at the edge and middle of the field for confectionary sugar looking spots to indicate initial infections. Powdery mildew will likely be found lower in the canopy, so be sure to inspect more than the top most leaves. There are many fungicide effective at controlling PM as determined by both lab and field studies by OSU researchers. Results are posted here:

2023 PM Fungicide Trial Results:
https://bpb-us-w2.wpmucdn.com/u.osu.edu/dist/f/4395/files/2025/01/PM-Fungicide-Demo-Report-2024.pdf

2024 PM Fungicide Trial Results:
https://bpb-us-w2.wpmucdn.com/u.osu.edu/dist/f/4395/files/2024/07/PM-Fungicide-Demo-Report-2023.pdf

Initial powdery mildew infestation

Heavy powdery mildew infestation

For a full list of recommended fungicides on PM and other diseases, consult the cucurbit chapter of the Midwest Vegetable Production Guide. https://mwveguide.org/uploads/pdfs/Cucurbit-Crops_2024-12-03-155451_othe.pdf

In other news, Spotted Wing Drosophila, were detected in red raspberries on June 24 in Greene County, check your berry patches for signs of infestation (small, white larvae) in the fruit. Management guidelines and images of these insects can be found here: https://u.osu.edu/pestmanagement/pests/swd/ 

Male and female SWD adults. Note only male has single spot on wings.

Pumpkin research plots at the Western Ag Research Station were finally completed via transplanting and direct seeding on Friday, June 13 while dodging rain drops. A few of the transplants were destroyed by large black cutworm larva within hours of being in the field. These large larva often move onto any green plant when the weeds they are feeding on are disturbed by tillage or herbicide.

Black cutworm cut seedling stem below the cotyledons.

Black cutworm larva resting in transplant plug.

The remaining transplants were intermittently attacked by striped cucumber beetles that have emerged from their overwintering sites. These hybrids were not treated with FarMore FI400, a systemic seed coat insecticide, so they needed to be rescued to reduce severe feeding damage and possible bacterial wilt infection. For foliar treatment options, consult the Midwest Vegetable Production Guide online here: https://mwveguide.org/results/crop/586/pests/474

Striped cucumber beetle feeding damage on pumpkin cotyledon.

The statewide insect trapping network is also ramping up, with Corn Earworm, Squash Vine Borer and Spotted Wing Drosophila traps being deployed in several counties. In Clark county, 10 CEW were captured on June 16. In Greene county, 2 SVB were captured on the same date. SWD samples have been collected but not sorted for positive identification yet.

Striped cucumber beetle adult.

Mating squash bugs.

While most of us have a long holiday weekend, it’s late May which means early season cucurbit pests like striped cucumber beetles and squash bugs will soon exit their overwintering sites and head to crop fields. Based on our biweekly fruit and vegetable conference calls, neither of these pests have been reported but growers should remain vigilant.

As growers begin to plan for direct seeding or transplanting melons, pumpkin, squash, cucumbers and squash, recall that early planted fields will likely be infested soon after emergence or when placed in the field. For growers who purchased seed treated with FarMoreFI400, striped cucumber beetle populations should be controlled for 2-3 weeks. After this period if scouting reveals beetles in excess of plant stage threshold, foliar treatments are an option.  For growers who did not purchase systemic insecticide treated seed, remember to scout plants frequently in multiple parts of the field, edge and interior, and if the damage exceeds the following thresholds (see below), consider treating with a foliar insecticide to knock these pests down. Foliar insecticide options can be found here:

Striped Cucumber Beetle – https://mwveguide.org/results/crop/586/pests/474

Squash Bugs – https://mwveguide.org/results/crop/586/pests/501

Characteristic striped cucumber beetle feeding. FarMoreFI400 should prevent significant feeding and therefore limit bacterial wilt spread.

Systemic Insecticide Use Considerations
Seed treatments containing thiamethoxam (FarMore FI400, Cruiser) offer maximum protection against cucumber beetles and other pests for about 2 to 3 weeks after seedling emergence. Seed treatments offer little protection to transplanted crops. For transplants and direct-seeded plants over 3 weeks old, the concentration of insecticide from seed treatment is no longer strong enough to kill beetles but can still harm bees due to sublethal doses in the pollen and nectar. Treated seed should never be used in combination with at-plant soil drenches with imidacloprid (Admire or generics), or thiamethoxam (Platinum). At-plant soil drenches used alone, with non-treated seed, offer similar protection to treated seed for beetle control. Due to increased residues in nectar and pollen, in-furrow applications should be considered last and applied at the lowest recommended rate that provides control. Non-systemic foliar applications of insecticides can be used to control cucumber beetles if seed or in-furrow treatments were not used, or were ineffective. Once flowers are present, applications should be made in the evening when flowers are closed and bees are not actively foraging, which minimizes the risk to pollinators.

Thresholds range from 0.5 to 1 beetle per seedling, and 1 to 5 beetles per plant for plants after 4 leaf stage. The threshold for cantaloupe melons and cucumber is lower because these crops are susceptible to bacterial wilt, which is vectored by cucumber beetles. Pumpkin, squash, and watermelon have higher thresholds because these crops are less susceptible to bacterial wilt, but beetle feeding can occur on the fruit rind by both adult and larvae, causing marketable loss. Beetles found in pumpkin or squash flowers do not pose a risk to the plant but as flowering decreases, rind feeding may increase.

Thresholds for squash bugs are one egg mass or adult per plant.

Pumpkin playlist on OSU IPM Video Library.

OSU IPM Video Library
Not sure how to identify striped or spotted cucumber beetle? Can’t remember what squash bug nymphs, egg masses or adults look like? Take a few minutes to peruse the OSU IPM Video Library where these resources are housed to help growers identify and manage all key cucurbit pests including squash vine borer.

Videos on weed control, disease control (powdery mildew, plectosporium) and hybrid selection are also in this playlist collection.

https://www.youtube.com/playlist?list=PL0HRPaZDLHyH64oVLKdX5icKQFzqQ5nCA

NEW Pumpkin Resource Guide

Cover shot of new pumpkin guide

If you haven’t seen this announcement, a team from OSU, MSU and Cornell University developed a new 72-page guide, “A Modern Approach to Crop and Pest Management in Pumpkin – ANR 806”. This guide highlights modern IPM practices such as mechanical weed control, cover crops, pollinator protection and negative impacts of certain pesticide mixtures. Basic topics like weed, insect and disease management are also covered, as well as the benefits of natural enemies and a pumpkin enterprise budget to measure overall profitability. In addition to colorful images and layman’s text to explain each topic, QR codes are sprinkled throughout the guide to provide deeper dives on most topics via factsheets, bulletins, websites and videos from specialists around the country.

Copies of the guide can be ordered and purchased at your local Extension county office or online at OSU Extension Publishing (https://extensionpubs.osu.edu/a-modern-approach-to-crop-and-pest-management-in-pumpkin/).

Three weeks ago an article was posted in VegNet outlining a relatively new disease on sweet corn, Tar Spot (https://u.osu.edu/vegnetnews/2025/03/08/tar-spot-on-sweet-corn/).

In order to understand the magnitude and distribution of this disease across Ohio, a short survey was available for growers to anonymously send in their experience with Tar Spot so that a more accurate understanding of this disease could be made, informing potential research in 2025. If you would like to add to our understanding of this disease on your farm, here is the link to follow: https://osu.az1.qualtrics.com/jfe/form/SV_d5NMkdMmASqJza6

Two growers responded to the survey from west central and north central Ohio stating they:

-have had issues with Tar Spot since at least 2023 (primarily “late” planted)
-have sprayed fungicides on the crop since at least 2023
-believe this disease is impacting ear quality and sales

As a result of this information, a group of OSU researchers and Extension educators have decided to go forward with planning a Tar Spot evaluation and yield impact study at three locations in 2025. The study will be guided by Dr. Pierce Paul, Tar Spot researcher, Professor and Chair of Plant Pathology, and Dr. Andres Sanabria Velazquez, Associate Professor in Plant Pathology. Contributing to the study design, data collection and analysis will be Dr. Logan Minter (Associate Professor in Extension, Field Specialist), Jim Jasinski (Professor in Extension), Mike Gastier and Pressley Buurma (Extension Educators).

Sites for the Tar Spot trials will be South Centers at Piketon, Western Ag Research Station (South Charleston), and Muck Crops Research Station (Willard), evaluating both fresh market and shipping sweet corn hybrids. More details of these trials will be released soon.

The past few months have been full of opportunities for growers to attend local, statewide, regional or even national fruit and vegetable conferences to learn new skills and get updates on current production and pest management practices. I recently attended a conference where Dr. Julie Kikkert, Cornell University, gave a very interesting presentation on Tar Spot in sweet corn. During her talk, gears began turning in my head as I considered if this disease was also a problem under the radar for Ohio sweet corn growers.

Crop Protection Network

Tar Spot was initially detected in Ohio in 2018 on field corn and is mostly distributed in the northwest and northcentral parts of the state (https://agcrops.osu.edu/newsletter/corn-newsletter/2020-03/tar-spot-corn). Tar Spot is currently found in 14 states and mostly thought of as a pathogen on field corn, due primarily to the length of exposure as the ear matures on the stalk. Since sweet corn is harvested immature, the question of Tar Spot impacting quality and yield seems remote but possible. Late planted sweet corn in Ohio (ca. late June or early July), is most likely to be affected but other factors such as prior crop, tillage and weather can play a part in the disease severity.

From CORN article

If the prior crop was field or sweet corn then the risk of Tar Spot increases, as does the risk if there was no primary tillage performed which could serve to bury inoculum (old, infected corn leaves).  In the later part of the season, if weather conditions turn cool and wet, this favors disease development. Proximity to large acreages of field corn may also be a factor as air borne spores can travel miles to infect other corn plants. At this time there are no resistant field or sweet corn hybrids but there may be some tolerance among hybrids. Fungicides can be applied to late planted sweet corn crops that are effective against this pathogen but the matter of economics and Pre Harvest Interval comes into play. https://cropprotectionnetwork.org/publications/fungicide-efficacy-for-control-of-corn-diseases

What can be done?

At this point, several members of the OSU Specialty Crops team are looking to set up multiple late planted sweet corn hybrid trials on OSU research stations from southern to northern Ohio to determine the extent of foliar Tar Spot infestation and if any impacts on ear production or quality can be observed.

Since this pathogen is new to Ohio sweet corn growers, we are also interested in feedback from growers who have seen this pathogen on their crop in 2024. In order to collect this information anonymously, please use the 9-question feedback form at this link: https://osu.az1.qualtrics.com/jfe/form/SV_d5NMkdMmASqJza6

 The survey questions are listed below. The last question on the form is open ended if growers have any other thoughts to share on this disease. In a few weeks, I will summarize the observations and concerns of the growers who responded.

Q1. Did you see Tar Spot on sweet corn last year?

Q2. What was the previous crop?

Q3. What tillage was performed in the field?

Q4. What was the planting date of the infected sweet corn hybrid?

Q5. When was the sweet corn harvested?

Q6. What was the name of the sweet corn hybrid?

Q7. Did the Tar Spot infection affect the ear quality in your opinion?

Q8. What county is your farm located?

Q9. Anything else to tell us about Tar Spot on your farm in 2024?