Midwest Vegetable Production Guide Now Available

If you are a vegetable grower in Ohio, the Midwest Vegetable Production Guide, is an essential resource to keep on top of the latest fertility, horticultural management, and pesticide recommendations for your operation. Each year the guide is edited and updated by specialist’s in eight states to bring you the most current information possible at the time of printing.

What’s new to the guide in 2020? Within the 262 spiral bound pages there is an updated Organic Production section plus updated sections on disease, weed and insect management on 45+ vegetable crops, from Asian vegetables to Zucchini.

The MVPG is also more mobile friendly now with an improved interface designed to get your crop production question addressed quickly. Enter your crop and pest information and receive cultural and pesticide recommendations matching your request. Try it out on your computer, tablet or smart phone at https://mwveguide.org. The site will default to the new interactive mobile friendly interface but if you want to access individual pdf chapters of the guide, click on the drop down and select “Production Guide.”

MVPG new and mobile friendly interface.

To get a traditional hard copy of the guide, contact your local Extension office and they can order a copy from main campus. Cost will be around $15.

MVPG cover for 2020. 

If you want to order a guide online through the new Extension publications website, here is the link https://extensionpubs.osu.edu/2020-midwest-vegetable-production-guide-for-commercial-growers/. If you order the guide online and have it mailed to your house, it will cost $21.25 plus shipping.

Be sure to purchase your guide soon, there are only 90 copies left in inventory at OSU! Best of luck for a productive season!

 

 

 

Plant health check – get to the root of it

Root-knot nematode galls on tomato

As the vegetable growing season winds down, now is a good time to dig up plants in high tunnels and open fields and determine the health of the roots. Root diseases that may not kill plants outright can nonetheless stunt plant growth and reduce yields. Look for plants that appear less vigorous than others and remove them with a shovel, taking care to maintain root integrity. Shake off the soil and rinse the roots gently with water. Then examine roots for symptoms.

While some soilborne diseases such as Phytophthora blight can “explode” in the field from relatively low initial inoculum levels, many others build up slowly from season to season. Root-knot, caused by the the plant pathogenic nematode Meloidogyne spp., is increasing in prevalence in Ohio in high tunnel tomatoes and other crops in open fields. Root-knot is fairly easy to identify – galls are clearly visible on roots. The Northern root-knot nematode, which predominates in northern Ohio, causes small galls, while the southern species, which occurs in southern Ohio, causes large galls. Since root-knot nematodes have a very broad host range, crop rotation may not be helpful, although certain cover crops such as sudangrass are toxic to nematodes, and wheat and corn are not hosts of northern root-knot nematodes. Anaerobic soil disinfestation (ASD) is highly effective against root-knot.

Corky root rot of tomatoes

End-of-season root health checks are especially important for high tunnel tomatoes, which are often produced in the same soil year after year. Root-knot, Verticillium wilt, corky root rot, black dot root rot, and Pythium root rot are among the root diseases that can predominate in long-term non-rotated tomatoes.  The roots should be evaluated every year to assess disease development and the need for control measures such as grafting on disease-resistant rootstocks and ASD.  A fact sheet describing  tomato soil borne diseases and their management can be found here.

 

Downy mildew on pumpkins in Ohio

Downy mildew was found this week in organic pumpkins in Harrison County. Options for downy mildew control are limited in organic cucurbits, and at this point in the growing season the damage may not significantly affect yield. Downy mildew affects pumpkin leaves but not vines or fruit.  The main danger, once fruits have matured, is defoliation and subsequent sunburn of the fruit. If plants are defoliated, and sunny weather is expected, fruits should be removed from the field and stored in the shade.

Previously this summer we found downy mildew on cucumbers and cantaloupes in our sentinel plots and on commercial farms.  The disease appeared on cucumbers/melons much later in the growing season than expected, first detected on August 22.  The strain of the downy mildew pathogen that appears early, usually in early July, is thought to originate in greenhouses in the Great Lakes region.  This strain only affects cucumbers and melons, and we don’t know why the early introductions did not happen this year. The strain that infects all cucurbits originates in the South, always arrives in August or later, and is likely the main culprit this year. We are currently testing isolates to identify the strain type from plants we’ve collected in Ohio.

 

Cucumber Downy Mildew Confirmed in Northeast Ohio

cdmipmpipe.org, August 22, 2019

Following reports this week of downy mildew on cucurbits in Michigan, central Pennsylvania, Wisconsin and Indiana, we have our first confirmed report of downy mildew on cucumbers in northern Wayne County. This is very late for this area – we usually see downy mildew on cucumbers in early July in northern OH. Many growers have been spraying preventatively due to the seriousness of downy mildew on cucumbers and other cucurbits. All of the reports this week from MI, WI and PA were from cucumber, although the report from southwestern Indiana was from watermelon.

Cucurbit growers who have not transitioned from applying only protectant fungicides such as chlorothalanil or mancozeb to downy mildew fungicides should now do so.  The environmental conditions – cooler temperatures, high humidity, overcast skies and rain showers- expected in much of Ohio during this part of the season are conducive to downy mildew. Effective fungicides against downy mildew are Ranman, Elumin, Orondis Opti and Zampro.  Tank mix these with chlorothalanil or mancozeb, with the exception of Orondis Opti, which includes chlorothalanil inn the pre-mix.

Alternate products on a 7-10 day schedule.  Follow the label regarding limitations on number and timing of applications.  If you have already applied Orondis Ultra or Orondis Gold for Phytophthora blight management you may have reached the limit on Orondis applications.  Cucurbit crops must be protected from downy mildew in advance – applying fungicides after the disease is well-established is not effective and yield losses are likely.

Tips for a Successful Zucchini, Squash and Cucumber Harvest

For many backyard growers, community gardeners and urban farmers, growing the cucurbits can be a challenge.  This vegetable (fruit?)  family is affected by a large number of garden insects as well as both bacterial and fungal disease.  There are a few tips and tricks that can be used to make sure some harvest makes it to the table or sales booth in 2019.

First thing to do is mind your pollinators.  Cucurbits are commonly dependent on pollinators as they have separate male and female flowers.  Once the flowers emerge, use of pesticides can damage pollinators and lead to decreased harvest.

 

The male flower is at the bottom right. It is simply a flower at the end of the stem. The female flower of this yellow summer squash is behind the male flower and has an immature fruit at the base.

 

Scouting is a very important part of the Integrated Pest Management strategy.  I had not seen cucumber beetles in large numbers until the July 4th holiday weekend.  Then I started to see them in moderate to large numbers on my summer squash in central Ohio.

 

Adult Striped Cucumber Beetle. This bug will damage leaves, stems, flowers, and fruit while feeding. It also transmits a bacterial wilt that can rapidly cause death in cucurbit plants.

 

 

This is an adult squash vine borer. They lay eggs at the base of the stems and their larvae then tunnel through the stem of the plant disrupting vascular flow and often killing the plant.

These plantings of winter squash, both Waltham Butternut and Buttercup, died over the last weekend in July while the summer squash persisted. Suspects include squash vine borer damage or bacterial wilt from cucumber beetles.

Squash bugs are another common pest of cucurbits that can be present in large numbers in plantings.

Squash bug eggs are laid white, then rapidly change color to bronze. They are commonly found on the underside of cucurbit leaves and should be removed immediately when discovered and discarded away from the plants.

 

This is the juvenile form of squash bugs. They can achieve large numbers fairly rapidly.

 

One great strategy to get a harvest of summer squash is to plant a summer planting now for a fall harvest.  Many of the pests of cucurbits will be transitioning to their over-wintered habitat and become less of a problem in fall.

Responses to Pumpkin/Squash/Melon Grower Stress Survey

On July 5th I posted an article acknowledging the difficult spring and early summer planting conditions most Ohio growers faced, and asked to let us (OSU specialists and Extension educators) know what kind of issues you were experiencing. Once these issues were identified, I began researching possible solutions in order to help growers salvage as much of the season and market as possible. Attached at the end of the article is a PDF with my responses to your questions.

I wanted to thank the 36 growers farming just over 500 acres who took time to respond to the survey. In general, most growers were delayed 2-4 weeks but had a crop in the ground now. The biggest concern besides the ability the control the weather, was that OSU specialists continue to post current information about crop management, pest management, and markets. Several articles along those lines have recently been posted to the VegNet Newletter and we will continue to do so, but if there is a specific topic that has not been addressed, please reach out and contact that specialist directly. Below is a list of OSU specialists and Extension educators with their contact information.

Best of luck to you for better weather this summer and a fair harvest this fall.

Specialist                    Area                            Contact

Doug Doohan              Weeds                        doohan.1@osu.edu

Celeste Welty              Insects                         welty.1@osu.edu

Sally Miller                  Diseases                      miller.769@osu.edu

Jim Jasinski                   IPM/Insects                  jasinski.4@osu.edu

Brad Bergefurd             Horticulture                  bergefurd.1@osu.edu

Matt Kleinhenz             Horticulture                  kleinhenz.1@osu.edu

Steve Culman                Fertility                         culman.2@osu.edu

In case you are not aware, we are having a Pumpkin Field Day on Aug. 22 at the Western Ag Research Station. Read more about it here http://u.osu.edu/vegnetnews/2019/07/25/pumpkin-field-day/

Response to Cucurbit Growers Early to Mid Season

 

Look-alikes Spotted but No Cucurbit Downy Mildew in Ohio Yet

Cucurbit downy mildew has been moving up the east coast, with some westward movement in the South, but there have been no reports of downy mildew on cucurbits in Ohio, its surrounding states, or Ontario. Downy mildew pathogen (Pseudoperonospora cubensis) spore trap counts from the Hausbeck Lab at MSU have been very low – and only a few (8) P. cubensis spores were counted from one location on June 28, and none before or since.

We have seen many, many examples of bacterial diseases in vegetable crops this season, a consequence of excessive rainfall this spring and summer. Some bacterial diseases cause leaf spots that can be mistaken for those caused by fungi or oomycete pathogens. Angular leaf spot of cucumber is a prime example: the angular lesions are very similar to those of downy mildew. In downy mildew, the spores of the pathogen may be observed on the lower side of leaves with a good hand lens, but sometimes they are difficult to find. If downy mildew is suspected but can’t be confirmed with a hand lens, it should be confirmed with a lab microscope. Downy mildew spores can be visualized easily with a microscope. If on the other hand the symptoms are caused by bacteria, bacterial streaming from the lesions can be seen using a microscope. This process can be completed in minutes in an experienced lab. Ohio vegetable growers can send or drop off samples for diagnosis to the OSU Vegetable Pathology Lab in Wooster; a fillable PDF sample submission form can be found here.  Samples can also be dropped off at OSU-OARDC Experiment Stations in Celeryville or Fremont, or on the OSU main campus in Columbus (Kottman Hall).

Downy mildew of cucumber

Angular leaf spot of cucumber – a bacterial disease

Applying fungicides is an important tactic in downy mildew management, but spraying them when the disease is caused by a bacterial pathogen is a waste of time and money. Regular scouting, confirmation of symptoms and being alert to reports of outbreaks of downy mildew in the vicinity should be the focus now.

Cucurbit Powdery Mildew – Start Scouting Now

Powdery mildew arrived this week on squash in Wayne County, Ohio. It is early – usually we see it first in mid-July. The fungus that causes cucurbit powdery mildew does not overwinter in Ohio, so the disease does not appear until spores arrive on wind currents from warmer growing areas. Signs of infection are small circular powdery growths (mycelium and spores of the pathogen) on either side of the leaf. These spots enlarge and can eventually cover most of the leaf surface and kill the leaves. Stems and leaf petioles are also susceptible, but the disease is not observed on fruit. In pumpkins, powdery mildew may also attack the “handles”, which can be further damaged by secondary pathogens.

Powdery mildew is managed using disease-resistant varieties and fungicides. Organic production systems need to rely heavily on resistant varieties but there are OMRI-approved fungicides and biologicals that can reduce disease severity.  These options were summarized in this blog in 2018.  In conventional systems, insensitivity to overused fungicides is common in populations of the fungus that causes this disease, so it is important that a fungicide resistance management program is followed. Remember to alternate fungicides in different FRAC (Fungicide Resistance Action Committee) groups, indicating different modes of action against the fungus. It is important to apply fungicides when the disease first appears and incidence is low. Fungicides that are effective against cucurbit powdery mildew can be found in the Midwest Vegetable Production Guide for Commercial Growers; product ratings and FRAC codes are on page 128. Our evaluations of efficacy of powdery mildew fungicides in Ohio in 2018 indicated that Inspire Super, Procure, Rally, Aprovia Top and Quintec provided very good control of powdery mildew on pumpkins in all three locations (click on graph to enlarge).  In this test, a bioassay, Bravo Weather Stik and Fontelis provided moderate control and Pristine provided poor control. Merivon Xemium and Torino did not perform well in this test (data not included); however efficacy ratings in the Midwest and Southeast vegetable production guides are “good”. Growers should take this into account when choosing products for powdery mildew management.

Keeping Tomatoes Healthy in Wet Weather

We are in the middle of a period of wet weather that is predicted to deliver multiple inches of rain to central Ohio and even more to other soaked parts of our state.  Tomatoes are a crop that can suffer several problems related to heavy rainfall that can shorten the harvest period and affect yield.  There are a few things that the backyard grower, community gardener and urban farmer can do to keep their tomato plants healthy and productive though heavy rain periods.

Key Garden Tasks to Keep Tomatoes Healthy in Wet Weather

  • Mulch – organic or non-organic can both be used.  Be careful if your plasticulture is not permeable to air and water,  the heavy constant rainfall may saturate the soil and drown the roots if the soil cannot dry out. Mulch also acts as a barrier to keep soil borne fungal spores off lower tomato leaves.
  • Fertility – contstant rainfall can leach fertility from soil making it unavailable to the plants. Make sure to monitor plant growth and health carefully to avoid a nutrient deficiency.  Foliar feeding can be used when the ground is too saturated to irrigate with water soluble fertilizer.
  • Pruning – promote air circulation by pruning lower leaves.  Try to minimize lower leaf contact with soil.  Use sterilized pruners to remove any diseased leaves and make sure to put diseased leaves in the garbage and not the compost after pruning.

 

This plant needs mulched around the base to prevent soil borne fungal spore contact with leaves. Pruning of the lower leaves will also promote air circulation to assist in disease prevention.

 

These discolored leaves suggest fungal disease in this tomato plant. The leaves need pruned with sterilized pruners and then discarded into the garbage and not the compost pile.

 

This tomato has both organic and plasticulture mulch at the base to keep fungal spores in the soil and off plant leaves. Pruning needs to be done to allow air circulation at the base of the plant.

 

This tomato plant has had lower leaves removed for air circulation with a combination of compost and plasticulture mulch at the base of the plant.

 

Monitor tomatoes carefully for signs of blight, remove the diseased leaves promptly with sterilized pruners and dispose of disease materials in the garbage, not the compost pile.

Make sure to address fertility needs as production increases.  Heavy rain can leach nutrients into the subsoil where they are unavailable to plants, decreasing yield as the season progresses.

Ohio State University Extension has an excellent fact sheet on Growing Tomatoes in the Home Garden.   There is also a plant disease diagnostic laboratory on campus where the grower can send samples if an accurate diagnosis needs confirmed on possible diseased leaves.

Introduction to Using Mustard Cover Crops for Biofumigation in Pumpkin

This article is an introduction to the general processes and basic steps of how to use mustard cover crops to reduce soil borne diseases, such as Plectosporium, in pumpkin. Research using mustard plants to naturally biofumigate soil to allow for more normal yield and fruit quality, has been conducted in several states and Canada, sometimes with mixed results. The results of this trial will be released in a report later in the season.

Mustard cover crop in full bloom.

The field intentionally selected for this trial was cropped to pumpkin in 2018 and exhibited high amounts of Plectorsporium infections on both plant and fruit. The general recommendation for a field infested with this disease would be to rotate away from cucurbits for 3-5 years. Instead of rotation, we are investigating the use of biofumigation as a means to reduce disease incidence.

In mid-April when conditions were suitable for direct seeding, Pacific Gold (6lb/A), Caliente 199 (10lb/A), and a 50/50 blend of the two were drilled into plots at the Western Ag Research Station in South Charleston. Prior to seeding, 100 lb/A of urea and 34 lb/A ammonium sulfate were broadcast and incorporated to increase the biomass and glucosinolate levels of the cover crop. Glucosinolates are the compounds responsible for the biofumigation effect and are released when the mustard plant tissue is macerated and incorporated into the soil. The production of these compounds peak during flowering.

Once peak bloom has been reached it is necessary to mow the plants, immediately followed by incorporation (such as rototilling), packing, and then sealing the soil with water. Once these steps have been performed, the glucosinolates are broken down into other compounds in the soil such as isothiocyanates, where they begin the biofumigation reactions. It is recommended to wait 7-10 days after incorporation to either direct seed or transplant. We seek to confirm the necessity of the waiting period by both seeding and transplanting pumpkins one day after incorporation; we’ll report if any negative effects are seen on the germination rate or growth of the transplants.

To hear more details about the trial and see all steps including the incorporation of mustard cover crop, watch this video posted to the OSU IPM YouTube channel: https://youtu.be/Taz-PhDphhA

If you have worked with mustard cover crops before and have any experiences positive or negative to share, please send them to me at jasinski.4@osu.edu.