Month: June 2021

This is a Year for Bacterial Diseases in Ohio Open Field Vegetables

Numerous intense rainstorms that have moved across Ohio during the 2021 growing season so far have created conditions for the establishment and spread of bacterial diseases. Unseasonably cool weather in early June plus rain favored leaf spots and blights caused by Pseudomonas spp. such as bacterial leaf spot of parsley and peppery spot of crucifers. In late June we are seeing bacterial diseases favored by rain and warmer weather, caused by Xanthomonas spp., such as

Cabbage black rot.

black rot in crucifers and leaf spot of radish. These bacteria enter vegetable crops through infested seeds and seedlings, overwintered crop debris or weeds. Epidemics tend to be more severe when started at the seed or seedling stage. Other bacterial diseases to watch for this summer are bacterial canker of tomato and pepper (Clavibacter), bacterial wilt of cucurbits (Erwinia), yellow vine decline of cucurbits (Serratia), and various soft rots (Pectobacterium).

Microscopic image of bacteria streaming from a leaf lesion.

Bacterial disease symptoms can be similar to those caused by certain fungi or oomycetes, so an accurate diagnosis should be obtained before applying fungicides or bactericides. When in doubt, growers may send samples to us for diagnosis. A simple microscopic evaluation for bacterial streaming from diseased tissue allows us to separate bacterial diseases from others (see image, right). 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 commercial vegetable growers.

Unfortunately, bacterial diseases are very difficult to manage in susceptible varieties at the field stage if rainy conditions persist. The go-to treatment for bacterial diseases in the field has been a fixed copper product with or without mancozeb. However, copper application has never been highly effective due to its inability to reach the inside of plants, relatively low residuals and sensitivity to pH.  It is not uncommon for bacterial populations in a leaf with lesions to exceed 100 million bacterial cells per gram of leaf tissue.  Copper compounds in currently available products are too large to enter lesions and thus high levels of inoculum are protected. In addition, our research and studies conducted in other states have shown high levels of resistance to copper in Xanthomonas spp. causing bacterial spot of tomato and pepper. Other bacterial species also develop copper resistance.

So what can be done if a bacterial disease is found in an open-field vegetable crop? If it is early in the epidemic and few plants with symptoms are observed during scouting, various non-copper-based products can be applied preventatively. These products are listed in my July 18, 2020 post. Many of these products, falling in three categories of 1) plant resistance inducers, 2) antimicrobials and 3) antibacterial viruses have been shown to be partially effective under low- to moderate-disease pressure. If disease pressure is high, and rainy, humid conditions persist, these products are not likely to control a bacterial disease epidemic.

Partnerships, Teamwork, and Persistence Bring New Potato Varieties

Hundreds of new, promising, numbered (unnamed) potato genotypes are evaluated at research station and farm sites each year. Ohio State is one of many institutions involved. In 2021, we are evaluating more than 100 numbered selections from four breeding programs against seven standard industry varieties. The same evaluation techniques we use can be employed by individual vegetable farms.

High-performing varieties are just one of the core raw materials for vegetable production, which also relies on water, mined or manufactured inputs and equipment, and the know-how to use all of them. Whether formal or informal, variety evaluation is essential for individual growers and the vegetable industry. Since now is when differences among varieties of individual crops begin to show themselves on farms and research stations, it’s a good time to discuss traits and processes used to evaluate varieties.

When we evaluate genotypes of potato being considered for naming and release as varieties, we score plant maturity and record total and marketable yield and more than ten tuber characteristics for each entry (e.g., tuber size and shape, skin color and texture, flesh color, eye depth, incidence of internal defects, and specific gravity and chip color). Collaborators in other states evaluate the same genotypes for pest and disease resistance, crop tolerance to heat stress, storage effects on tuber quality, and tuber cooking quality and sensory properties. So, like for other vegetables, developing potato varieties requires teamwork.

Background on the Variety Development Process

Experimental genotypes originate in public-sector breeding programs based at universities and the USDA. In fact, although varieties developed by private companies (e.g., major processors) contribute significantly, the U.S. potato industry (especially the fresh/tablestock and chip sectors) has long relied on varieties developed in the public sector. Public-sector varieties are developed by large teams led by universities, USDA, and/or state industry associations or organizations and account for most of the available varieties, acreage, and value of production.

Whether public or private, variety development teams include breeders/geneticists, agronomists/horticulturalists, plant pathologists, entomologists, food scientists, farmers, processors, and people with expertise in related areas.

Potato varieties are named, released, and made available for commercial use only after years of comprehensive, widespread testing, beginning with just a few plants and concluding at farm scale. Once released, varieties support processing (i.e., chip, fry), fresh market/tablestock, and/or breeding programs. The varieties ‘Atlantic’ (released in 1976), ‘Dark Red Norland’ (1957), ‘Katahdin’ (1932), ‘Kennebec’ (1948), ‘Red LaSoda’ (1953), ‘Superior’ (1962), and ‘Yukon Gold’ (1981) are just a few examples of public-sector varieties that have been planted to many thousands of acres over decades of production. Varieties like these set the bar for and/or are found in the “family trees” of newer, increasingly popular varieties.

Still, markets, production conditions, and industry factors change continuously. Therefore, variety development must be ongoing and once-popular varieties are eventually displaced by new, more farmer-, processor-, and consumer-friendly ones. The process is designed to enhance industry success and consumer satisfaction.

Evaluation is nearly continuous since sites are located throughout the U.S. and the process begins before planting and ends long after harvest. Groups based in the East, Midwest/Upper Midwest, West and Pacific Northwest, and South often coordinate the work. Ohio State and Ohio farmers and processors have participated annually for more than fifty years. We emphasize the evaluation of genotypes originating in eight breeding programs and with potential value in fresh and chip markets and have contributed to the release of multiple varieties used in Ohio and elsewhere.

Sharing Results

Data from our 2021 trials will be summarized in a report available at https://u.osu.edu/vegprolab/technical-reports/ with data from 2020 and previous years available at https://neproject.medius.re/trials/potato/ne1731 and https://neproject.medius.re/. Later, we will join team members from Maine, New York, Pennsylvania, North Carolina, Virginia, Florida, and USDA and industry partners to discuss evaluation outcomes and begin selecting new entries and others to be evaluated again or dropped from the program. With information reflecting variety or experimental selection performance in the field and on the plate, the breeder and team have key information when making the thumb-up/thumb-down decision on each entry.

Still, for all crops, the performance of each variety (or experimental genotype) hinges on how it is managed, the know-how allowing growers to get the most from each variety. Planting and harvest dates, plant populations (spacings), irrigation and fertility programs, etc. influence variety performance and, therefore, whether a grower will select the variety again. So far, potato genotype evaluations at Ohio State have been completed without irrigation and this approach has clearly affected tuber yield and quality. We are rethinking this approach and look forward to speaking with vegetable and potato growers about their use of irrigation.

Wayne County IPM Notes From the Week of June 21 – 25

 

Imported cabbage worm eggs in the red circles and a recently hatched caterpillar circled in yellow.

Vegetable Crops

            Imported cabbage worm butterflies are laying a lot of eggs on cole crops. It is important to scout the crops for the eggs as well as the larvae, in order to have a better grasp on when the larvae are hatching and causing damage. This will also help ensure efficient and timely insecticide applications.

Aphids are continuing to be present in many of the vegetable crops that our IPM program scouts,

Thrips feeding in on onion leaves in the center of the plant.

however, we are finding a lot of beneficial insects that are feeding on the aphids and helping to either maintain or eliminate populations. Japanese beetles also are present now in many of the crops in our area.

This week was also the first week that we really noticed an increase in thrips in onion plants. As the leaves get larger and offer more shelter for the thrips, the populations are able to multiply rapidly.

Some sweet corn in the area is tasseling, silking and in some cases, nearing harvest. We have noted some European Corn Borer feeding in tassels. If 10% of silking plants are damaged by ECB, a treatment is warranted. In some fields, this threshold was met, and growers started on a spray program for their tasseling and silking corn.

Small Fruit and Orchards

Aphids in the apple trees continued to be the main pest this week. We found more clusters of wooly apple aphids, which are now working their way out onto the new shoots and green growth. Our trap counts for OFM remain well below threshold.

OFM traps in peach blocks were also well below threshold, however, we did see an increase in the trap counts of Greater and Lesser Peach Tree Borer.

Strawberry season is winding down. Our SWD traps in strawberry patches yielded 0 SWD. Harvest is starting in some area blueberry and bramble patches. Grape clusters are developing nicely and starting to put on some size.

Landowner Club

Land is an expensive and important investment that is often handed down through generations. As such, it should be cared for and maintained to remain profitable for future generations. Whether it is a change in regulations or a loss of knowledge with the loss of a generation, it can be difficult for landowners to stay on top of everything.

To help, OSU Extension and Farm Bureau in Champaign County have started the Landowner Club designed to help farmland owners understand critical conservation and farm management issues. Topics will range in expertise level from beginner to advanced, so landowners of all experience levels can gain knowledge, skills, and confidence to implement, or talk with tenants about, farming and conservation practices.

The Landowner Club will meet on the 4th Thursday of the month from 8-9 am (with a few exceptions) in the Champaign County Community Center. The kick-off event is on June 24. Peggy Kirk Hall, Ag Law Specialist, will discuss the noxious weed law and landowner liability. Future topics can be found on the registration site.

The series is free to Farm Bureau members and $5 for non-members. A light breakfast will be served. Register online at http://go.osu.edu/Landowners.

The club organizers are interested in learning what topics are important to landowners, so please send your suggestions to Amanda Douridas at Douridas.9@osu.edu or bring them with you to a meeting.

Cucurbit Downy Mildew Fungicide Efficacy in Ohio 2018-2020 and Recommendations for 2021

Now that we know cucumber downy mildew has appeared in the Great Lakes Region (Ontario report – see my post on 6/17/2021), cucumber and melon growers should prepare for fungicide applications. There are a number of products labeled for downy mildew management in cucurbits, but not all are consistently effective due to development of fungicide insensitivity in downy mildew pathogen populations.

The OSU Vegetable Pathology Lab conducts bioassays each summer to assess the efficacy of fungicides commonly used to manage cucurbit downy mildew. We treat potted young cucumber plants with fungicides individually at the labelled rate or with water alone, and the next morning place the plants in a cucumber field with active downy mildew. Depending on the year, tests were conducted in Wayne, Sandusky and Huron counties, all in northern Ohio. After 48 hrs of exposure the plants are returned to the greenhouse and rated for symptom severity 7 days later.  The results for 2018, 2019 and 2020 are shown in the table.

Click to enlarge.

The fungicides Previcur Flex, Ranman, Omega and Orondis were highly effective against cucumber downy mildew for all three years. Zing! and Elumin were only tested in 2018 and 2019/2020, respectively, and both were highly effective. One or more of these fungicides should be part of a downy mildew management program.

Curzate, Forum, Presidio, Quadris and Zampro were inconsistence across years and location and were ineffective in a least one location in one of three years. Revus was consistently ineffective.

Spray Program Recommendations for Northern Ohio Cucumber and Melon Growers

  1. Apply a protectant fungicide such a chlorothalanil (Bravo, Equus, etc.) on a 7-10 day schedule now.
  2. When downy mildew is reported on cucumbers or melons in northern OH, SE MI or western PA add effective fungicides shown in green to the spray program. Tank mix with a protectant fungicide, alternate fungicides with different modes of action (FRAC codes) and follow the label restrictions and requirements. Shorten the application interval to 7 days under favorable weather for downy mildew: rain, overcast skies, high humidity, and cooler day and/or nighttime temperatures. Follow this blog, Twitter @OhioVeggieDoc or the Cucurbit Downy Mildew IPM PIPE for downy mildew reports.
  3. Forum, Presidio, Quadris, Zampro and Revus are not recommended. Curzate may be moderately effective in some locations.

Wayne County IPM Notes From the Week of June 14-18

Vegetable Crops

            This growing season, so far, has been all about the bugs. We have not had a huge amount of disease pressure

Squash bug eggs on summer squash.

on the vegetable crops in our area. We have, however, continued to find more insects impacting local crops.

Newly spotted insect pests this week included Japanese Beetles, thrips, and squash bugs. The Japanese Beetles were found in silking sweet corn, the thrips are being found in onions and the squash bugs are being found laying eggs in summer squash plantings.

 

Japanese Beetle found in a sweet corn stand.

In green beans we are still seeing a light population of potato leaf hoppers and a few bean leaf beetles feeding here and there. Cucurbits still have some cucumber beetles feeding, as well as some aphids. Aphids are not picky about which crops they are in, as we continue to find them in a variety of crops, including peppers and tomatoes. Both eggplant and potatoes are dealing with flea beetle and Colorado potato beetle. The Colorado potato beetle larva are becoming very prolific in some areas and causing significant defoliation. Cole crops, while also dealing with pressure from flea beetle, are now seeing an increase in activity from the imported cabbage worm caterpillar.

Small Fruit and Orchards

Aphids and mites are being found in fruit trees, primarily apple trees. This week, we began to find European red mites, green apple aphids and wooly apple aphids. Trap counts for CM in apples and OFM in peaches were all below threshold, with many traps reporting zeros.

The biggest update in our pest outlook in small fruit was not an insect, instead it involved birds. There was bird damage being found in strawberries, as well as in blueberry areas where the berries are starting to color. Some growers are using netting to exclude the birds from blueberry plantings. This is a lot of work but saves a lot of berries from being damaged.

Cucumber Downy Mildew Confirmed in Ontario – Cucumber and Melon Growers in Northern Ohio Should Intensify Scouting

Downy mildew was reported on cucumbers in Ontario today. This is the first report for 2021 of cucurbit downy mildew in the Great Lakes region. There have been no reports of cucurbit downy mildew in Ohio or Michigan, although the Hausbeck lab at Michigan State University has detected spores of the pathogen in their spore traps for several weeks now. The storm system currently in the upper Midwest is moving in an east/southeast direction, and as it moves through Ontario may pick up spores and drop them further south. Historically cucumbers in the northern approx. 1/3 of Ohio have been the first in the state to show symptoms of downy mildew. Growers should intensify scouting of cucumbers and melons and apply a protectant

Top left: early downy mildew lesion on cucumber; top right: advanced cucumber downy mildew; lower left: underside of cucumber leaf with spores of the pathogen; lower right: microscopic image of downy mildew spores.

fungicide such as chlorothalanil. Look for yellow or tan angular lesions delimited by veins on the top surface of leaves, and sparse fuzzy 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.

If you suspect downy mildew in cucumber or melon please text or email pictures to Sally Miller (330-466-5249; miller.769@osu.edu) 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.

Custom Farming Rates

Farming is a complex business and many farmers utilize outside assistance for specific farm-related work. This option is appealing for tasks requiring specialized equipment or technical expertise. Often, having someone else with specialized tools perform a task is more cost-effective and saves time. Farm work completed by others is called “custom farm work” or more simply, “custom work.” A “custom rate” is the amount agreed upon by both parties to be paid by the custom work customer to the custom work provider.

This publication reports custom rates based on a statewide survey of 377 farmers, custom operators, farm managers, and landowners conducted in 2020. These rates, except where noted, include the implement and tractor if required, all variable machinery costs such as fuel, oil, lube, twine, etc., and the labor for the operation.

Ohio Custom Rates

Indiana Custom Rates

Recognize and Mitigate Crop Heat Stress

Recent conditions in some areas (soaked soil, fog- and dew-filled mornings, high daytime humidity) can give a different impression about the season so far than weather data at https://www.oardc.ohio-state.edu/weather1/ and various forecasts. Temperature, rainfall, and other data are collected around the clock at OSU vegetable (and other) research sites in Fremont, Celeryville, Wooster, and Piketon and have been for decades. So far in 2021, these four locations have accumulated less precipitation and more growing degree days (GDD) than their historical averages. Also, climate and weather authorities reported on June 11 that the Upper Midwest, including Ohio, is set to experience hot, droughty conditions. Most agree that a dry year is less problematic than a wet one — provided irrigation is possible. However, it can be difficult for vegetable growers to escape the unwanted effects of excessively high temperatures. A way to separate potentially minor, moderate, and severe heat stress, example effects of moderate-severe heat stress, and main strategies for mitigating heat stress during production are summarized below.

Five Major Factors Influencing Whether Heat Stress is Minor, Moderate, or Severe

  1. Crop and variety (sensitivity 1). All crops and varieties have a range of temperature in which they perform best. A crop’s genetic past (i.e., heritage/Center of Origin) and level of improvement through breeding matter. Individual crops and varieties are thought or proven to be relatively heat tolerant or intolerant.
  2. Timing (sensitivity 2). When high temperatures occur in the crop cycle is key. Crop plants can tolerate high temperatures more reliably at some stages than others. Even relatively tolerant varieties can be impacted by temporary spikes in temperature at the “wrong” time.
  3. Intensity. The extent to which actual temperatures exceed the crop’s and variety’s optimal range is important … 5 degrees? 15 degrees?
  4. Duration. The length of time the temperature was consistently above optimal. Short periods of intense stress can be problematic although the effects of prolonged moderate stress typically accumulate.
  5. Mitigation: were steps taken to lessen the stress?

Combinations of these five factors represent common scenarios. For example, for vegetables for which pollination is required, excessively high temperatures lasting only hours can disrupt pollination or trigger flower or fruit drop or interruptions in normal developmental patterns. The result can be loss of a “set” (dip in production) and/or malformed or misshapen units to be harvested (e.g., pods, fruits, roots, stems, leaves, tubers). Longer periods of above-optimal temperatures can speed (e.g., bolting) or delay (e.g., prolonged vegetative state) maturity depending on the crop and when they occur in the crop cycle. Heat stress is also implicated as a contributing factor in fruit ripening and physiological disorders (e.g., blossom-end rot). Above-optimal temperatures can also trigger changes in the chemical composition of plant tissues, possibly affecting the color and/or taste of marketable units. Similarly, prevailing temperatures can influence a crop’s tolerance to typical inputs and protectants.

Irrigation and shading are among the most common strategies for mitigating the effects of excessively high temperatures in field and high tunnel vegetable production. Irrigation is essential for the obvious reason that evapotranspiration is the crop’s primary means of cooling itself. A warm period or season calls for the best irrigation (scheduling) practices, not just pouring water on because, as we know, excessive irrigation (soil moisture) disrupts water uptake, compounding the heat stress problem. Circumstances allow some growers to shade the crop (e.g., in high tunnels) as they attempt to reduce the temperature around it.

At this time, 2021 has not earned the label as a “hot or heat stress” year. Let’s hope that remains true even as we remain aware of factors contributing to heat stress and ways of addressing it. In addition to proper irrigation, shading (if possible), and careful application of inputs and protectants, consider tracking variety performance closely to aid in variety selection going forward.

Wayne County IPM Program Scouting Notes From the Week of June 1- June 4

Vegetable Crops

Cucumber beetle feeding on the foliage of a summer squash plant.

Insects continue to be the main headline in the vegetable crops in our area. Of greatest concern is the cucumber beetle. The populations continue to increase in number and the efficacy of seed treatments or in-furrow applied insecticide starts to decline 4-6 weeks after the seed germinates or after the insecticide is applied. This means that more of the beetles are feeding without being affected by the insecticide. Be sure to scout cucurbit crops frequently and carefully to get accurate counts of the beetles. The thresholds for cucumber beetles are as follows: Cotyledon stage – .5 beetles per plant, 2-4 leaf stage – 1 beetle per plant, greater than 4 leaves – 3 beetles per plant. Limiting the amount of feeding that cucumber beetles do will also limit the amount of bacterial wilt occurring in these plantings. Do be cognizant of the plants that are in bloom and limit your spraying to a time when it will be least impactful on the pollinators.

 

Colorado potato beetle larva feeding on a potato plant. Tommy Becker photo.

Other insects that were spotted this week include Colorado Potato Beetle larvae and imported cabbage worms. Both of these pests can cause significant damage in their respective crops when left unchecked. Flea beetles also continue to feed on plantings of cole crops, preferring young transplants versus older, more established plantings, although both should be inspected for beetles.

Sweet corn plantings are growing quickly and some plantings that were done into plastic mulch and covered this spring already have a few tassels poking out. Overall, there has been no major concerns in the sweet corn plantings so far, however, do your best to keep up on weed control. Weeds such as bindweed, thistle, and ragweed can not only compete for resources, but can also make harvest difficult and may serve as refuge locations for insect pests to retreat to.

Small Fruit and Orchards

We are beginning to enter a critical period for managing diseases in grapes. This period, which extends from immediate pre-bloom through four to five weeks post bloom, is a critical time to control fruit infections by the pathogens which cause black rot, powdery mildew, and downy mildew. According to the 2021-2022 Midwest Fruit Pest Management Guide, the fruit of the most commonly planted varieties becomes resistant to infection by these diseases by four to five weeks after bloom.

In strawberry plantings we are seeing a lot of green fruit and in some locations, harvest is beginning to ramp up. Overall, there have been very few concerns in the

Blueberries starting to enter the “fruit coloring” stage.

strawberries to this point, with just a few slugs here and there and a spotting of powdery mildew on a few plants. Powdery mildew is managed by spraying either pre-bloom or during the early bloom through bloom stage.

Other small fruit like blueberries and brambles look to have a heavy fruit set this year. Blueberries are beginning to get some color to them, and the blackberry and raspberries are either in bloom or in fruit development.

In apple and peach orchards, the fruit are noticeably starting to increase in size. We are finding some aphids in apple trees, feeding on the leaves and new shoots. In peaches, we did find a few instances of powdery mildew affecting the fruit. Trap counts for OFM and CM were under threshold in all of our traps this week. The counts are down after last week with several orchards above threshold for CM and OFM counts.