Integrated Pest Management

Ohio State University Extension Specialty Crop Team Newsletter

Editor – Frank Becker, Agriculture and Natural Resources Educator, Wayne County. Contributions made from team members around the state of Ohio. 

Fruit Update

Lingering effects from 2024 drought stress are being reported from various areas of the state. These observations highlight regions where fruit trees continue to struggle to overcome the effects of last year’s drought, with noticeable carryover stress impacting fruit set, tree vigor and fruit development and quality this season. Water management, where you are able, remains a critical factor in maintaining tree vigor and productivity.

The use of broad-spectrum insecticides in some orchards is leading to flare-ups of aphids and mites, as beneficial insect populations are being negatively impacted by the applications. Growers should consider integrating more selective products or IPM-compatible practices to preserve natural enemies.

Harvest of early grape varieties is underway in several regions. Fruit quality appears variable and may impact fermentation decisions for wine and juice production. Growers should also be cautious of the late season products that are applied in the vineyard, as these can also impact juice or wine quality.

We are now in peak adult spotted lantern fly season. Growers should continue to scout for adults, which are active and will soon be laying eggs.

 

Vegetable Update

This season has brought a mix of both expected and unexpected vegetable disease issues: Plectosporium blight in pumpkins, bacterial diseases in multiple crop families, and buckeye rot in tomatoes are being reported by growers across the state. There are also reports of some uncommon or unusual diseases in Ohio such as southern blight, leaf mold in field tomatoes, and pumpkin downy mildew. Some of these diseases challenges can be associated with the abnormally high humidity experienced by much of the state this year.

Squash vine borer (SVB) is causing unusual damage in pumpkins. While not significantly impacting total yield in most fields, the extent and nature of injury are notable. Interestingly, SVB may be partially suppressed by standard sprays targeting cucumber beetles and squash bugs.

Bacterial wilt in cucurbits is persisting into the late season, which is not entirely surprising considering the documented high pressure from cucumber beetles earlier this year.

Populations of corn earworm (CEW) and fall armyworm (FAW) are increasing.

Tar spot has been detected in field corn but has not yet appeared in sweet corn trial plots.

Across all scales of vegetable operations, crop ripening has been slow, contributing to prolonged harvest windows and potentially increasing disease and pest exposure.

Growers utilizing high tunnels have reported facing several key issues this season, including: poor drainage, difficult crop transitions, strategic crop and variety selection decisions.

In field grown vegetables, water-related abiotic disorders continue to show up across the state. These abiotic disorders are often linked to inconsistent irrigation, inconsistent soil moisture or poorly drained soils.

Instances of herbicide drift—some self-inflicted—have continued to be reported. Proper nozzle selection, wind awareness, and sprayer calibration remain critical for minimizing off-target damage.

Pumpkins appear to be ahead of schedule in terms of maturity this year. Growers are preparing for, or already in the midst of an early start to harvest in many locations.

 

Ohio State University Extension Specialty Crop Team Newsletter

Editor – Frank Becker, Agriculture and Natural Resources Educator, Wayne County. Contributions made from team members around the state of Ohio. 

General Update

Pest and disease pressure continues to be a concern, particularly with increased weed pressure this year as well as issues stemming from herbicide drift. While herbicide damage can cause cosmetic damage to perennial crops like fruit trees, it’s important to note that these do not always translate into yield penalties. In areas like orchards and vineyards, patience is key as plants recover from such damage. Please keep in mind that in order for the Department of Agriculture to adequately analyze plant material for herbicide drift, reports to ODA need to be made within 7-1o days of the drift event, and the sooner the better.

Fruit Update

Reports are coming in from several areas about Marssonina leaf blotch affecting apples. This fungal disease thrives in wet conditions and can lead to premature defoliation, weakening the tree. Regular fungicide applications and proper sanitation of fallen leaves can help manage this disease.

Several reports have come in of observed significant loss of raspberry and blackberry plants suspected to be caused by Phytophthora root rot. This is particularly troublesome in raised beds or container plants, where rotation can be difficult to implement. Phytophthora thrives in wet, poorly drained soils, and the disease can rapidly progress if not controlled. It’s important to use resistant cultivars, improve drainage, and avoid overwatering. If you suspect root rot, be sure to send in samples to the Plant and Pest Diagnostic Clinic for a more accurate diagnosis.

Insect activity has been relatively low across most fruit crops, though there have been sporadic reports of spider mites, spotted wing drosophila and third-generation oriental fruit moths (OFM).

Vegetable Update

Cucurbit fields are seeing multiple challenges, including bacterial wilt, which is becoming more widespread. Although the symptoms are visible now, the plants would have been infected with bacterial wilt some time ago via cucumber beetle feeding.  This disease is vectored by the cucumber beetle and can cause wilting and death of the plant. In addition, angular leaf spot has been reported, which is a foliar bacterial disease. Plectosporium has also been observed, primarily in fall vine crop fields. Plectosporium can cause lesions to form on the stems and handles, causing handle integrity issues in these crops. Lesions may also form on the fruit, directly impacting fruit quality and marketability.

Recent field collected samples have shown bacterial issues on dill, which could be a sign of improper plant spacing, moisture issues, or bacterial contamination. The leaves are exhibiting typical signs of bacterial infection, so reducing overhead irrigation and removing affected plants can help minimize spread.

In tomatoes, pressure continues to increase from Septoria leaf spot, early blight and bacterial spot. These diseases tend to show up during wet periods and cause significant defoliation, which can reduce yields. Applying fungicides and bactericides to affected crops and practicing good sanitation and crop rotation can reduce the chances of recurrence.

On the insect side, activity has been relatively light. Some growers have observed garden millipedes feeding on decaying plant material, particularly in areas affected by bacterial wilt. These are only secondary pests in these cases and no control is needed. Flea beetle numbers are sporadic, and both imported cabbage worms and diamondback moths are being seen, but with thorough scouting and timely management decisions, can be effectively controlled.

Onions still in the fields have been under attack from salt marsh caterpillars and thrips. Both pests can cause significant damage, with thrips often being the primary concern due to their ability to spread viruses and cause leaf damage. Regular scouting is critical for managing these pests.

A few growers have reported broad mite issues in certain fields. Broad mites are particularly damaging in high humidity conditions and can cause distorted leaf growth. With the high weed pressure this year, it’s important to monitor how these pests may persist in weed refuges, potentially leading to future problems in subsequent seasons. When selecting miticides, ensure that you are reading the label to confirm that the products are listed for control of broad mites. Products listed for control of only red mites or two-spotted spider mites will not control broad mites.

Ohio State University Extension Specialty Crop Team Newsletter

Editors – Dr. Ashley Leach, State Extension Specialist- Specialty Crop Entomology, and Frank Becker, Agriculture and Natural Resources Educator, Wayne County. Contributions made from team members around the state of Ohio. 

General Note

As issues (biotic or abiotic) are observed throughout the season, growers should consider the importance of supporting plant health through fertility management, both to address deficiencies as well as avoiding over fertilization. This can be especially important in older plantings, such as established perennial fruit crops, where this aspect of management may have been neglected. Taking soil tests and tissue tests is encouraged to get a better picture of overall plant health status. This discussion should also include consideration for the importance of transplant and seedling health management. While these management areas may have some seasonality to them, in reality, they are year round commitments that are foundational to integrated plant health management.

Fruit Crops 

As the summer has progressed, insect issues have continued to be causing frustrations for fruit growers. Spotted wing drosophila have seemed to establish some significant populations, evident by consistently significant trap catches in small fruits. Other insect issues such as stink bugs have been found in the orchards, but populations remain fairly low and are mostly concentrated around the edges. Be sure to walk your blocks and check for any signs of stink bug activity.

Stink Bug trap in an orchard, F. Becker photo.

Codling moth and Oriental fruit moth trap counts have ticked up slightly from previous weeks. Numbers are still low and nearly all sites do not require intervention, but continue to monitor trap catches closely. Keep your apples protected from Apple maggot, which is still active and capable of infesting fruit. If you’re using a yellow card, spray when you catch 1 fly per trap; if using a red baited sphere, spray when you catch 5 flies per trap. Some growers have reported Japanese beetle feeding, particularly around the edges of orchards. This pest rarely causes major issues, but if your planting is young or stressed, consider an insecticide application.

Vegetable Crops 

Photo Credit – Dr. Ashley Leach, OSU

Special to the Specialty Crop Team from Dr. Ashley Leach: Managing pests when pollinators are in the field is challenging, especially in crops like cucurbits, which face pressure from pests like squash bugs and cucumber beetles during bloom. Integrated Pest and Pollinator Management (IPPM) offers a realistic framework for managing pests while minimizing unintended harm to pollinators and beneficial insects.

Key practices include:
  1. Monitor pest pressure and use thresholds when possible to guide insecticide decisions. For example, treating only when beetle densities exceed 1 per plant can reduce sprays, improve pesticide performance, and cut costs.
  2. Choose insecticides with lower toxicity to pollinators—such as kaolin clay (e.g., Surround) or acetamiprid—when applying during bloom. Apply in the late afternoon or evening to reduce bee exposure.

    Photo Credit – Dr. Ashley Leach, OSU

  3. Avoid tank mixes with multiple broad-spectrum products, especially combinations with certain fungicides (e.g., sterol biosynthesis inhibitors), which can increase toxicity to pollinators.
  4. Leave unsprayed refuge areas or field borders, when feasible, to conserve pollinators and natural enemies that contribute to pest suppression.
  5. Rotate insecticides by mode of action to slow resistance and protect natural enemies that help keep secondary pests in check.
IPPM doesn’t have to mean compromising on pest control. With small adjustments, growers can reduce input costs, protect pollination services, and maintain high-quality yields. even during bloom.

Detection of Downy Mildew in Sandusky, Holmes, Ashland County

New downy mildew outbreaks have also been confirmed in Sandusky, Holmes, and Ashland counties, where diagnostic microscopy and spore‐trap monitoring detected abundant Pseudoperonospora cubensis sporangia in each area. In all three counties, plants showing the angular, vein‐limited chlorotic lesions typical of early infection, with sporulation readily visible on the underside of affected leaves during morning dew. Warm days followed by cool, humid nights over the past week have created ideal conditions for pathogen development and spread.

To limit further disease progression, initiate a protectant–curative fungicide rotation, for example alternating chlorothalonil (FRAC M05) or mancozeb (M03) with a systemic such as mandipropamid (FRAC 40) or cyazofamid (U8), and include oxathiapiprolin (FRAC 49) or a Zampro® (ametoctradin + dimethomorph, FRAC 40 + 45) treatment at least once per ten‐day cycle. Apply sprays preventively—before visible symptoms appear—and shorten intervals to seven days if nightly leaf wetness persists. Improve air movement by removing lower leaves and trellising vines to reduce canopy humidity, and humid-prone irrigation should be switched to drip systems or scheduled for early morning to allow foliage to dry quickly. Continue scouting every three to four days, removing and destroying any heavily diseased foliage, and disinfect tools and harvest equipment between fields to minimize local inoculum buildup and cross‐contamination.

Confirmed Downy Mildew (Pseudoperonospora cubensis) in Ohio Cucurbit Fields by County (July 2025)

Confirmed Downy Mildew (Pseudoperonospora cubensis) in Ohio Cucurbit Fields by County (July 2025)

First Detection of Downy Mildew (Pseudoperonospora cubensis) in a Wayne County Cucumber Block

First confirmation of Downy Mildew (Pseudoperonospora cubensis) in Sandusky County

Field view of a cucumber vine leaf exhibiting scattered, vein-confined chlorotic flecks characteristic of early downy mildew infection on the adaxial surface.

Field view of a cucumber vine leaf exhibiting scattered, vein-confined chlorotic flecks characteristic of early downy mildew infection on the adaxial surface.

 

Free Sample Diagnosis 

Please consider submitting fresh or well-preserved samples to the Plant and Pest Diagnostic Clinic.

This process ensures that your management decisions, fungicide choice, cultural controls, resistant varieties, are based on precise diagnosis rather than assumption.

How to Submit:

  1. Complete the online Plant Diagnostic Form:
    https://ppdc.osu.edu/forms/plant-diagnostic-form
  2. Ship or deliver your samples according to the instructions on the form. Samples may be mailed:
    C. Wayne Ellett Plant and Pest Plant Diagnostic Clinic
    Ohio State CFAES Wooster Campus
    c/o Dr. Francesca Rotondo
    234 Selby Hall, 1680 Madison Ave., Wooster, OH 44691
  3. Samples may be hand-delivered:
    Requires coordination with Dr. Rotondo: (330-263-3721) | rotondo.11@osu.edu

 

 

 

Ohio State University Extension Specialty Crop Team Newsletter

Editors- Thomas Becker, Agriculture and Natural Resources Educator, Lorain County and Frank Becker, Agriculture and Natural Resources Educator, Wayne County. Contributions made from team members around the state of Ohio. 

Fruit Crops

As we are on the tail end of blueberry season and entering blackberry season (at least in northern Ohio) we’ve continued to see activity from spotted wing drosophila (Drosophila suzukii) in our traps. Without traps, this is a pest we may not notice in our crop until our pickers or consumers notice soft berries or potentially even berries with live worms. Unless our customers are okay with a little extra protein in their fruit, this could be enough to keep folks from coming back to a farm for their berries. If you are a long-time reader of the Specialty Crop Newsletter, you may recall that one thing that sets these fruit flies apart from others is the fact that the females possess a serrated ovipositor that allows her to lay eggs in ripe fruit on the plant. Our more traditional fruit flies or vinegar flies must wait for fruit to be overripe or rotten before they infest it. Thus, the importance of a good integrated pest management program that utilizes trapping so growers can make timely decisions to manage this economically important pest. Trapping can be critical because the action threshold for spotted wing drosophila (SWD) is 1 fly. What can be tricky for growers is distinguishing between SWD and other fruit flies in the trap. In the Extension office, we have to make use of a microscope to ensure we are getting a proper ID. That is where growers might be able to work with their Extension educator to see if they can assist with trapping or go to the OSU South Centers web page to look at the specialty crops trapping data that is updated in-season. You can find that at this link: https://southcenters.osu.edu/horticulture/eplus/specialty-crops-insect-trapping. Another thing we can do in the field to see if our berries are infested is a saltwater test. Place a sampling of your fruit in a shallow container with some salt water. Smash the fruit a bit to allow the saltwater into the fruit and allow it to set for a few minutes. If the berries are infested with SWD larvae, the larvae will float to the top. If you are looking for a list of effective insecticides, Penn State University provides a list of products with efficacy ratings of good or excellent along with the IRAC codes and pre-harvest intervals for each product. Remember that a good pest management program rotates pesticides based on their group numbers to help prevent resistance building up in pest populations. Paying attention to pre-harvest intervals can be especially important for growers that have U-pick fields. This information can be found here: https://extension.psu.edu/spotted-wing-drosophila-part-4-management.  

Vegetable Crops

Numerous disease challenges have continued to be troublesome for growers all over the state.  

Cucurbit downy mildew has now been confirmed in Medina and Wayne counties. As shared by Vegetable Pathologist, Dr. Andres Sanabria-Velazquez , “Recent climatic conditions, including frequent overnight leaf wetness from dew, daytime temperatures in the mid-70s Fahrenheit, and intermittent rainfall, have created an ideal environment for pathogen development. Although current incidence and severity remain relatively low, the pathogen’s rapid disease progression under these conditions poses a significant threat to yield if left unmanaged. 

Immediate management should be with a protectant fungicide spray program targeting oomycete pathogens and subsequent applications planned at weekly intervals. Canopy thinning can be performed to improve air circulation and reduce leaf wetness. Fields will need to be scouted every three to five days to assess treatment efficacy and adjust application timing. Severely affected foliage can be removed and destroyed to limit inoculum, and equipment sanitation protocols should be reinforced to prevent spread to adjacent fields. 

Recommended active ingredients include chlorothalonil, mancozeb, cyazofamid (Ranman), the ametoctradin + dimethomorph combination (Zampro), and oxathiapiprolin (Orondis Opti). To reduce the likelihood of resistance, these fungicides should be rotated based on their modes of action. Moreover, preventive applications made before pathogen establishment are essential for the most effective disease control. 

Field diagnosis alone can be misleading. Many foliar symptoms overlap, and mixed infections are common. Accurate identification requires observation of the pathogen’s microscopic structures (conidia, sporangia, bacterial streaming, or hyphal morphology) under a compound microscope. Please consider submitting fresh or well-preserved samples to the Plant and Pest Diagnostic Clinic 

Additionally, a grower submitted photo was shared with a county extension educator and while a sample has not yet been processed to confirm, the photo showed clear signs and symptoms typically associated with southern blight of tomatoes. This is a disease that thrives under hot, moist conditions – it is not common in northern Ohio, but we have seen it before in central and southern Ohio. An elongated brown lesion on the lower stem and root rot was accompanied by white mycelium, sometimes clearly in a fan shape, at the base of the stem. Small, round sclerotia eventually form on the surface and serve as overwintering structures. Sclerotia can survive many years in the soil, so it is important to remove diseased plants and accompanying sclerotia from the field. 

Crucifers have also had their fair share of disease challenges. Lab confirmed samples of bacterial head rot and Alternaria leaf blight has growers concerned about next steps to protect their cabbage, broccoli and cauliflower. Alternaria causes round or oval bullseye lesions on leaves and stems of cole crops. Yellowing of tissues surrounding the lesions, as well as leaf drops, may also occur. While Alternaria lesions generally do not progress deeply into the head, they are unsightly and may render the heads unmarketable. Secondary soft rot infections can cause significantly more damage to the heads than the initial Alternaria infection. As for the bacterial head rot, symptoms start as water-soaked areas on small groups of unopened flowers on immature heads. These infected florets become necrotic and turn brown to black in color. The symptoms start to spread to surrounding florets and other areas of the head, eventually affecting larger areas of the head. Soft rot then develops in the infected tissues, meaning that the tissues turn soft and slimy. A bad odor is often associated with this rotting. After the initial infection, secondary bacterial and fungal pathogens can invade, causing further rotting of the tissue. 

Insect pests are also increasing in activity. There has been observed and reported pressure or damage from potato leafhoppers, corn earworm, European corn borer, aphids, spider mites, imported cabbage worm, flea beetles and Colorado potato beetles, among others. We have had ample southern winds and accompanying warm temperatures to allow for migratory pests to arrive in abundance and for all our insect pests to complete their generations and life cycles rather quickly. Frequent scouting or use of insect pest monitoring traps are the best ways to ensure that your crops are not facing economic levels of damage and that any management decisions or applications can be made at the most effective time.  

New Report: Downy Mildew of Cucurbits in Wayne County

Date: July 18, 2025
Location:  Wayne County, Ohio

Samples provided by the OSU Extension were submitted to the campus diagnostic clinic, where microscopic examination verified downy mildew caused by Pseudoperonospora cubensis. In this 2-acre trial block, 8 percent of plants displayed the angular, vein-limited chlorotic lesions typical of early infection, and sporulation was evident on the underside of affected leaves. Concurrently, spore traps deployed within the field captured abundant P. cubensis sporangia, confirming active pathogen dispersal in the canopy. Immediate management measures—including a preventative fungicide application and removal of severely affected foliage—have been initiated to curtail further spread.

Ohio counties with Downy mildew confirmed

Ohio counties with Downy mildew confirmed. Image Credit: Andres Sanabria-Velazquez

 

Downy Mildew sporangia underneath the leaves

Downy Mildew sporangia underneath the leaves. Image Credit: Andres Sanabria-Velazquez

 

Cucumber sample from Wayne County, Ohio

Cucumber sample from Wayne County, Ohio. Image Credit: Francesca Rotondo

Downy mildew causal angent, Pseudoperonospora cubensis sporangia and sporangiophores captured by spore traps confirming active airborne dispersal.

Downy mildew causal agent, Pseudoperonospora cubensis sporangia and sporangiophores captured by spore traps, confirming active airborne dispersal. Image Credit: Andres Sanabria-Velazquez

Management 

Implement a weekly preventive fungicide program rotating FRAC groups (Oxathiapiprolin  and Cyazofamid  have show good control). Improve air flow and reduce leaf wetness, scout the block every three days to catch new lesions early, remove and destroy any heavily diseased leaves, and avoid overhead irrigation during evening hours to minimize canopy moisture.

Please consider submitting fresh or well-preserved samples to the Plant and Pest Diagnostic Clinic.

This process ensures that your management decisions, fungicide choice, cultural controls, resistant varieties, are based on precise diagnosis rather than assumption.

How to Submit:

  1. Complete the online Plant Diagnostic Form:
    https://ppdc.osu.edu/forms/plant-diagnostic-form
  2. Ship or deliver your samples according to the instructions on the form. Samples may be mailed:
    C. Wayne Ellett Plant and Pest Plant Diagnostic Clinic
    Ohio State CFAES Wooster Campus
    c/o Dr. Francesca Rotondo
    234 Selby Hall, 1680 Madison Ave., Wooster, OH 44691
  3. Samples may be hand-delivered:
    Requires coordination with Dr. Rotondo: (330-263-3721) | rotondo.11@osu.edu

 

First Report: Downy Mildew of Cucurbits in Ohio

Downy Mildew of Cucurbits in Ohio
Date: July 15, 2025
Location: Homerville, Medina County, Ohio

Ohio counties with Downy mildew confirmed

Samples provided by the OSU Extension were submitted to the OSU Diagnostic Clinic, where microscopic examination confirmed downy mildew caused by Pseudoperonospora cubensis in a 4-acre cucurbit planting near Homerville. Approximately 10 percent of plants exhibit angular chlorotic lesions with characteristic purple-gray sporulation on the undersides of leaves, and on symptomatic plants disease severity averages 2 percent of total leaf area.

Downy mildew in cucumber.

Downy mildew in cucumber. Small, pale yellow lesions, often confined by the leaf’s veins, so that each spot takes on an angular shape. Image credit Frank Becker

underside of a cucurbit leaf—most likely cucumber—covered in tiny beads of dew. Along the veins you can see angular, brownish to grayish patches where the tissue has died, and within those patches a fine, dark-gray to purplish fuzz is just beginning to develop. That fuzzy growth is the sporulation of the downy mildew pathogen, emerging from the necrotic spots. The overall scene—water droplets on the cell-textured surface, contrasting with the darkened, angular lesions—is textbook for early downy mildew infection on cucurbits.

underside of a cucurbit leaf—most likely cucumber—covered in tiny beads of dew. Along the veins you can see angular, brownish to grayish patches where the tissue has died, and within those patches a fine, dark-gray to purplish fuzz is just beginning to develop. That fuzzy growth is the sporulation of the downy mildew pathogen, emerging from the necrotic spots. The overall scene—water droplets on the cell-textured surface, contrasting with the darkened, angular lesions—is textbook for early downy mildew infection on cucurbits.

Downy mildew in cucumber. Underside of a cucumber leaf. Along the veins you can see angular, brownish to grayish patches where the tissue has died, and within those patches a fine, dark-gray to purplish fuzz is just beginning to develop. That fuzzy growth is the sporulation of the downy mildew pathogen, emerging from the necrotic spots. Image credit Frank Becker

Confirmation in the Diagnostic Clinic. Characteristic sporangia and sporangiophore structures of a downy-mildew pathogen (in this case, Pseudoperonospora cubensis on cucumber). Scattered across the field are dozens of ovoid to ellipsoid sporangia, each roughly 20–30 µm long, with smooth, thin walls and a pale greenish tint. Image credit Francesca Rotondo

Recent climatic conditions, including frequent overnight leaf wetness from dew, daytime temperatures in the mid-70s Fahrenheit, and intermittent rainfall, have created an ideal environment for pathogen development. Although current incidence and severity remain relatively low, the pathogen’s rapid disease progression under these conditions poses a significant threat to yield if left unmanaged.

Immediate management began on July 15 with a protectant fungicide spray program targeting oomycete pathogens and subsequent applications planned at weekly intervals. Canopy thinning was performed to improve air circulation and reduce leaf wetness. Fields will be scouted every three to five days to assess treatment efficacy and adjust application timing. Severely affected foliage will be removed and destroyed to limit inoculum, and equipment sanitation protocols have been reinforced to prevent spread to adjacent fields.

Recommended active ingredients include chlorothalonil, mancozeb, cyazofamid (Ranman), the ametoctradin + dimethomorph combination (Zampro), and oxathiapiprolin (Orondis Opti). To reduce the likelihood of resistance, these fungicides should be rotated based on their modes of action. Moreover, preventive applications made before pathogen establishment are essential for the most effective disease control.

Submit your sample

Field diagnosis alone can be misleading. Many foliar symptoms overlap, and mixed infections are common. Accurate identification requires observation of the pathogen’s microscopic structures (conidia, sporangia, bacterial streaming, or hyphal morphology) under a compound microscope.

Please consider submitting fresh or well-preserved samples to the Plant and Pest Diagnostic Clinic. Our team will:

  • Macerate tissue and plate it on selective media
  • Examine spores, conidia or bacterial cells under the microscope
  • Run confirmatory tests when necessary

This process ensures that your management decisions, fungicide choice, cultural controls, resistant varieties, are based on precise diagnosis rather than assumption.

How to Submit:

  1. Complete the online Plant Diagnostic Form:
    https://ppdc.osu.edu/forms/plant-diagnostic-form
  2. Ship or deliver your samples according to the instructions on the form. Samples may be mailed:
    C. Wayne Ellett Plant and Pest Plant Diagnostic Clinic
    Ohio State CFAES Wooster Campus
    c/o Dr. Francesca Rotondo
    234 Selby Hall, 1680 Madison Ave., Wooster, OH 44691
  3. Samples may be hand-delivered:
    Requires coordination with Dr. Rotondo: (330-263-3721) | rotondo.11@osu.edu

Cucurbit Disease Update: No Downy Mildew Yet but Powdery Mildew, Bacterial Wilt, Angular Leaf Spot, and Alternaria Leaf Spot Present – July 11, 2025

As of July 11, 2025, our sentinel plots and grower reports have yielded no confirmed cases of Downy Mildew on cucurbits in Ohio. Instead, we are observing several other foliar and vascular diseases that can be easily confused in the field:

1. Powdery Mildew
Powdery Mildew typically appears as white, flour-like patches on leaves and stems. Under humid conditions, it can spread rapidly and reduce photosynthetic capacity. Although its symptoms are fairly distinctive, severe infections or mixed diseases can obscure diagnosis.

Figure 3. Advanced symptoms of powdery mildew on Zucchini leaf. Image Credit: Andres Sanabria-Velazquez

Figure 1. Advanced symptoms of powdery mildew on Zucchini leaf. Image Credit: Andres Sanabria-Velazquez

2. Bacterial Wilt

We have detected Bacterial Wilt caused by Erwinia tracheiphila in melon and squash. Infected vines wilt suddenly and irreversibly during the heat of the day. Because early symptoms—such as yellowing of lower leaves—can mimic other wilts, laboratory confirmation is essential. Cucumber beetles transmit the bacteria; therefore, as their populations increase, the incidence of the disease will be higher.

Bacterial Wilt caused by Erwinia tracheiphila

Figure 2. Bacterial Wilt caused by Erwinia tracheiphila. Image Credit: Andres Sanabria-Velazquez

3. Cucurbit Angular Leaf Spot
Identified on cucumber and watermelon, Angular Leaf Spot produces water-soaked lesions that become angular when bounded by major veins. Lesions often exude bacterial ooze in high humidity, but when dry they can be mistaken for other spots.

 

Angular Leaf Spot produces water-soaked lesions

Figure 3. Angular Leaf Spot. Image Credit: Andres Sanabria-Velazquez

4. Alternaria Leaf Spot

  1. Alternaria spp. produce small, brown to black circular to irregular lesions with concentric rings on melon and squash. In heavy infections, leaves may coalesce and blight, reducing yield and fruit quality.

Alternaria Leaf Spot

Figure 4. Alternaria Leaf Spot. Image Credit: Andres Sanabria-Velazquez

Why Submit Samples?

Field diagnosis alone can be misleading. Many foliar symptoms overlap, and mixed infections are common. Accurate identification requires observation of the pathogen’s microscopic structures (conidia, sporangia, bacterial streaming, or hyphal morphology) under a compound microscope.

Please consider submitting fresh or well-preserved samples to the Plant and Pest Diagnostic Clinic. Our team will:

  • Macerate tissue and plate it on selective media
  • Examine spores, conidia or bacterial cells under the microscope
  • Run confirmatory tests when necessary

This process ensures that your management decisions, fungicide choice, cultural controls, resistant varieties, are based on precise diagnosis rather than assumption.

How to Submit:

  1. Complete the online Plant Diagnostic Form:
    https://ppdc.osu.edu/forms/plant-diagnostic-form
  2. Ship or deliver your samples according to the instructions on the form.Samples may be mailed:
    C. Wayne Ellett Plant and Pest Plant Diagnostic Clinic
    Ohio State CFAES Wooster Campus
    c/o Dr. Francesca Rotondo
    234 Selby Hall, 1680 Madison Ave., Wooster, OH 44691Samples may be hand-delivered:
    Requires coordination with Dr. Rotondo: (330-263-3721) | rotondo.11@osu.edu

Ohio State University Extension Specialty Crop Team Newsletter

Editors- Thomas Becker, Agriculture and Natural Resources Educator, Lorain County and Frank Becker, Agriculture and Natural Resources Educator, Wayne County. Contributions made from team members around the state of Ohio. 

Warm and wet conditions across much of the state have continued to drive pest and disease activity in both fruit and vegetable crops. As we hit peak summer production, timely scouting and integrated pest management remain your best tools for maintaining crop health and quality.

Fruit Crops:
Spotted Wing Drosophila (SWD) remains a top concern for small fruit growers. This invasive fruit fly lays eggs inside ripening berries, with larvae feeding internally—causing soft fruit, collapse, and post-harvest losses.

To manage SWD, growers should monitor fields using baited traps placed within the fruiting zone. Traps should be checked regularly, ideally weekly, to assess fly presence. It’s important to harvest fruit frequently and remove any overripe or dropped berries to reduce egg-laying sites. At the first signs of fruit color change, apply protectant insecticides, rotating among different chemical classes such as spinosyns, pyrethroids, and organophosphates to delay resistance development. Post-harvest, rapid cooling of fruit and maintaining cold chain storage can significantly slow larval development and help protect product quality.

Sun Scald was reported in brambles following the extreme heat conditions. White or pale drupelets may appear on raspberry fruit due to intense sun exposure, a condition known as sun scald. While this disorder affects visual quality and salability, it has limited impact on flavor or nutritional value. To minimize sun scald, growers should maintain a healthy canopy by using proper pruning techniques that allow leaves to shield developing fruit. In extreme heat, consider deploying shade cloth or temporary row covers. Consistent irrigation is also critical to reduce plant stress and support recovery from heat damage.

Other pests in small fruit & orchards being reported are leafhoppers, aphids—including woolly apple, green, and rosy aphids—and spider mites (such as two-spotted and European red). These pests are showing up in scouting reports across the state. These pests often thrive during hot, dry spells and can cause significant foliage and fruit damage if left unchecked.

Regular field scouting is essential, especially on the undersides of leaves where many of these pests feed and reproduce. Growers should look for signs like stippling, curling, or honeydew. Maintaining beneficial insect populations such as lady beetles, lacewings, and predatory mites can provide natural pest control. Cultural practices such as avoiding excessive nitrogen applications can reduce lush growth that attracts pests. If pest thresholds are exceeded, selective insecticides or miticides may be used, always rotating products to reduce the risk of resistance.

Vegetable Crops
Phytophthora Root Rot has already been reported in several areas of the state, following some extremely saturated field conditions and heavy rain fall events. Persistently saturated soils have created ideal conditions for root rot diseases, particularly Phytophthora, which affects crops like peppers and cucurbits. This disease thrives in poorly drained soils and can quickly devastate fields if unmanaged. To reduce risk, improve field drainage by planting on raised beds or using plasticulture systems that shed excess water. Where appropriate, choose resistant or tolerant cultivars. Preventive fungicide applications can help protect plants during periods of prolonged soil saturation.

Powdery mildew has been confirmed in several squash plantings. Early symptoms include white, powdery patches on upper leaf surfaces and stems, which can reduce photosynthetic capacity and fruit yield. Management begins with early detection and protectant fungicide sprays.  Ensuring adequate airflow by properly spacing plants and minimizing leaf wetness also helps suppress disease development. After harvest, remove infected plant debris to reduce inoculum for future crops.

Squash bugs, stink bugs, and tarnished plant bugs have been observed feeding on vegetable crops statewide. These insects damage plants by piercing and sucking, which can lead to fruit deformities, discoloration, or aborted development.

For effective management, monitor plants closely for egg masses and early nymph stages, particularly on the undersides of leaves. When practical, remove egg masses by hand and destroy them. Cultural practices like eliminating crop debris and rotating host crops each season will reduce overwintering populations. Insecticide applications are most effective against young nymphs, as adults are often more difficult to control.

Cucumber beetles and Colorado potato beetles remain highly active and continue to pose serious challenges in cucurbit and solanaceous crops. Regular scouting is critical. Consider using sticky traps or direct plant inspections to detect rising populations early. Chemical options should be applied according to threshold guidelines, rotating among different IRAC classes to delay resistance development—especially important in managing Colorado potato beetle, which has a history of rapid resistance buildup.

In sweet corn fields, damage from European corn borer (ECB) has been reported. Monitoring ECB with pheromone traps can help time insecticide applications precisely. Applications are most effective when timed just after egg hatch, before larvae have a chance to bore into stalks and ears where they are protected from contact sprays. For growers planting sweet corn regularly, Bt hybrids are an effective tool for reducing ECB damage.

Ohio State University Extension Specialty Crop Team Newsletter

Editors- Thomas Becker, Agriculture and Natural Resources Educator, Lorain County and Frank Becker, Agriculture and Natural Resources Educator, Wayne County. Contributions made from team members around the state of Ohio. 

Fruit

Pest incidence in orchards has seemingly erupted as we received an abundance of heat unit accumulation and warm winds from the south. Potato leafhoppers have found their way into apple orchards, along with white apple leafhoppers. Both adults and nymphs can currently be found for both of these leafhopper species. White apple leafhopper damage shows up on apple leaves as whitish stippling, which is evidence of feeding via their piercing, sucking mouthparts. Potato leafhoppers feeding on apple leaves typically results in hopper burn with a bronzing of the leave edges and a “v” shaped chlorotic/necrotic region reaching inward toward the mid-vein. If there is not any evident feeding damage evident to determine the species, scouting for adults or nymphs can help differentiate the species. White apple leafhoppers are a very light yellow or pale white color, while the potato leaf hopper adults are a light green color. White apple leafhopper nymphs when startled move in a forward/backward direction. Potato leafhoppers nymphs commonly move in a sideways direction when startled. White apple leafhoppers can overwinter in Ohio while potato leafhoppers have to be blown up into Ohio out of the gulf states. Importantly, a critical time to scout for potato leafhoppers is during and immediately after hay cuttings, typically starting with 2nd cutting hay and each subsequent cutting through late summer. As the hay is harvested, they are flushed out of the fields and can quickly overwhelm and stress young, non-bearing fruit trees.

Wooly apple aphid clusters beginning to show up in apple orchards. F. Becker photo.

Other orchard pests that have been observed include spotted tentiform leaf miner, green apple aphids, wooly apple aphids, and apple sawfly.

Codling moth populations have been steady for quite some time now. Oriental fruit moth catches have shown some moderate activity as well, especially in southern Ohio. For both of these pests, we are at or approaching second generation depending on where you are in the state. Orchard managers should be prepared to scout for apple maggot, stink bugs, mites, and the second generations of oriental fruit moth and codling moth in the coming weeks.

Of note, this is also an opportune time to take an inventory of the beneficial insects present in your orchard. Beneficial natural enemies such as lacewings are currently active in orchards laying eggs and as those eggs hatch, the young of lacewings and lady beetles are prolific feeders on aphids and spider mites. Visual scouting can help to accomplish this observation as can passive approaches (sticky traps, pitfall traps). Another method to observe species that may be present is to use beat sheets to try to catch bugs that fall from shaken tree limbs.

Green lacewing found while scouting apple orchards. F. Becker photo.

Small fruit growers have reported slug damage in strawberries, which is not unexpected in a wet spring. Approved baits may be of interest to growers who are dealing with high levels of slug pressure. Remember, slugs are not insects, so they will not be impacted by insecticide applications. The molluscicides that are available for management of slugs are typically available in the aforementioned bait pellets.

The red raspberry season is just getting underway for some growers, and other brambles won’t be too far behind. As we transition out of strawberry season and into brambles and blueberries, we enter the window of activity for the spotted wing drosophila fruit fly.

Vegetable

One problem that we had confirmed in field vegetables was damping off. Damping off can be caused by several soil-borne pathogens

Symptoms of damping off. T. Becker photo.

including Pythium, Rhizoctonia, Fusarium, and Phytophthora. Plants are most susceptible to damping off as young, tender seedlings. The cool, wet soil conditions that we experienced much of the spring tend to result in slow plant growth. The quicker a seedling grows out of that early seedling growth stage, the less likely it will become infected, but without the right conditions, it remains susceptible. The warming trend we are likely to see in the near future should help move plant development along, and the primary threat of damping off should pass. A common symptom of damping off in seedlings is compromised plant tissue right at the soil line. The stem can look constricted and rotten. This often leads to the death of the plant. Management of this disease can come down to promoting seedling vigor and doing your best to get plants in the field when the conditions are more favorable for plant growth. Moisture management can also be critical as soils that are too wet can be favorable for infection.

Heavy cucumber beetle pressure observed, and photos taken after treatment was applied. F. Becker photos.

As far as insect pests are concerned, this is a busy time of year with a lot to keep your eye on. Massive emergences of cucumber beetles have been reported. Remember, cucumber beetles vector the bacterial wilt disease, and your only chance at effectively limiting the impacts of bacterial wilt is through thorough cucumber management.

Other pests such as flea beetles, imported cabbage worm, Colorado potato beetle, aphids and leafhoppers are also in abundance.

High tunnel growers have reported recent outbreaks of aphids and spider mites, likely spurred on by warm temperatures and dry conditions

Colorado potato beetle larvae feeding on potato leaves. F. Becker photo.

in the tunnels. Keep in mind that when making management decisions, careful consideration should be had when selecting products, not only for approved use in a covered structure, but also for the different species of pests. Insecticides will not control mites, and use may actually result in mite flare ups as the insecticide application kills any predators feeding on the mites. Acaracides or miticides should be used to manage mite populations. Follow up applications may be necessary when dealing with these pests, depending on whether or not the applied products control both eggs and adults, or only one or the other.

General Note:

Cultivating tomatoes was a family affair for this grower. F. Becker photo.

If you suspect herbicide damage on your farm, please contact the Ohio Department of Agriculture as soon as possible after the drift event, either by phone at 614-728-6987 or via the online submission tool at agri.ohio.gov/divisions/plant-health/pesticides/online/use-complaint