High Tunnel Tomato Root and Soil Health Checkup

Verticillium wilt symptoms in high tunnel tomatoes. Photo by Anna Testen.

Tomatoes are prone to damage by many foliar, fruit and root diseases. While producing tomatoes in high tunnels protects them from diseases spread by rainsplash such as bacterial spot and Septoria leaf spot, diseases favored by high humidity, including  Passalora leaf mold and Botrytis grey mold, can be exacerbated. Producing tomatoes year after year in high tunnels often results in a slow decline over the years in crop productivity due to a buildup of soilborne tomato pathogens. In Ohio, corky root rot, black dot root rot, Fusarium wilt, Verticillium wilt and root-knot nematode are quite common. Our fact sheet describing these diseases can be found here. Our research has shown high levels of these diseases in Ohio high tunnel tomatoes.

Corky root rot symptoms in high tunnel tomatoes. Photo by Anna Testen.

If tomatoes have been produced year after year in the same place, even if there are no obvious aboveground symptoms, a few plants in the high tunnel should be dug up as the season comes to a close and their roots washed off and inspected. Healthy roots are abundant and white with an intact taproot and many smaller feeder roots. Plants with corky root rot, for example, may have rotted tap roots and banded dark or “corky” lesions.

What to do if tomato roots appear diseased?

First, find out which diseases/pathogens are present. The Ohio State University Vegetable Pathology Lab and the USDA-ARS Application Technology Research Unit in Wooster are offering free soil testing this Fall for soilborne tomato pathogens.  See the flyer here: Soil_testing_flier_1Sep2022

Secondly, consider management tactics for next season. Anaerobic soil disinfestation (ASD) is a non-chemical soil treatment that reduces the populations of soilborne plant pathogens. It is very suitable for conventional and organic high tunnels but should be done while the soil is fairly warm; in Ohio this means ASD treatment should begin by late September. More information on ASD can be found here (factsheet) and here (step by step video).

Once the pathogens have been identified, growers can also choose disease-resistant rootstocks and produce or purchase grafted seedlings. Information on rootstocks and propagators can be found here (see Resources).

Cucumber Downy Mildew Now in Sandusky County, Ohio

Cucumber downy mildew in a sentinel plot at OSU NCARS, Sandusky County. Photo by our intern Raven Schaffter.

Northern Ohio counties are falling like dominoes to cucumber downy mildew. The disease was detected today in our sentinel plot on the OSU North Central Agricultural Experiment Station in Fremont, Sandusky County. This is the sixth county in northern Ohio for which we have confirmed reports of cucumber downy mildew. Management information can be found in yesterday’s post and previous posts on this site.

Are Your Cucurbits Yellowing or Wilting?

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

Sticky bacterial ooze from a cucumber vine with bacterial wilt

Bacterial wilt of melon

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

Cucurbit yellow vine decline in summer squash

Cucurbit yellow vine decline in pumpkins.

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

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

Eggs of the squash bug

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

New Cucumber Downy Mildew Reports This Week

Reports of cucurbit downy mildew as of July 21, 2022. cdm.ipmpipe.org

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

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

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

 

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

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

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

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

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

 

 

 

 

 

 

 

 

 

 

 

I continue to be amazed at the increasingly high quality and resolution of smartphone images. For a disease like downy mildew, where quick diagnosis and treatment is crucial, taking high high quality pictures that can be sent to us for confirmation saves both time and money. Ohio cucurbit growers, consultants and others may send me pictures such as these by text (330-466-5249) or email (miller.769@osu.edu) for diagnosis. Physical samples may be sent to Dr. Francesca Rotondo in the OSU Vegetable Pathology Lab – see submission instructions here. Vegetable and fruit diagnostics are free to Ohio growers due to financial support from the Ohio Produce Growers and Marketers Association’s Ohio Vegetable and Small Fruit Research and Development Program.

Scouting Notes From the Wayne County IPM Program

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

Vegetable Crops

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

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

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

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

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

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

Small Fruit and Orchards

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

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

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

 

First Report in Ohio of Cucumber Downy Mildew for 2022

Cucurbit downy mildew map, July 11, 2022. cdm.ipmpipe.org

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

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

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

If you suspect downy mildew in cucumber or melon please text or email pictures to Sally Miller (330-466-5249; 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.

Scouting Notes from the Wayne County IPM Program

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

Vegetable Crops

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

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

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

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

Small Fruit and Orchards

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

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

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

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

Septoria Leaf Spot in Commercial, Organic and Garden Tomatoes

An old post updated:

Septoria leaf spot has been found in Ohio recently, not surprisingly after heavy rains in many areas. This excellent photo taken by Dr. Francesca Rotondo is diagnostic for Septoria leaf spot: round tan to brown spots on the leaves and leaf yellowing. In the more mature spots, margins are dark brown and small round black dots can be seen in them through a hand lens or the lens of your smartphone camera. The tiny black dots are called pycnidia, the fruiting bodies of this fungus. Pycnidia are flask-shaped structures with a small hole at the top, partially submerged in leaf tissue. Pycnidia contain large numbers of spores held in a gelatinous matrix; when humidity is high or free water is on the leaf surface, the spores ooze out of the pycnidia like toothpaste being squeezed out of a tube. The spores are dispersed by rain or irrigation water to other leaves on the same plant and to other nearby tomato plants.

Septoria lycopersici is seedborne and also survives at least 1-2 years in soil. Septoria leaf spot is favored by moderate temperatures, high humidity and rain or overhead irrigation. While Septoria does not cause spots on tomato fruit, it can rapidly defoliate the plant. If this happens early the plant is likely to die. Later on, defoliation leads to small fruit, poor ripening and problems with sunscald. Even large, previously healthy, vigorous plants can be completely defoliated.

Commercial growers can manage Septoria leaf spot by including a strobilurin fungicide such as Quadris or Cabrio in a fungicide program that also includes a protectant such as chlorothalanil or mancozeb. A list of labeled fungicides to manage Septoria leaf spot can be found in the Midwest Vegetable Production Guide for Commercial Growers. Cultural practices to minimize Septoria leaf spot should be undertaken, including crop rotation of 3 years or more, planting tomatoes on raised beds, using adequate spacing, using drip irrigation, pruning foliage to allow good air movement through the canopy, and removing diseased plants from the field. Septoria leaf spot is rarely a problem in high tunnels, greenhouses and other structures that protect plants from rain.

Organic growers need to follow the cultural practices described above and may consider growing tomatoes in protected culture. Copper-based fungicides formulated for organic production can suppress disease development if applied soon after initial symptoms appear.

Home gardeners should adopt the cultural practices described above and should also remove and destroy leaves with symptoms. This is really only effective when symptoms first appear. Always avoid the foliage when watering plants. Fungicides containing chlorothalanil or copper can be applied to slow disease spread.

Blossom End Rot of Tomatoes and Peppers

Blossom end rot of bell pepper

The very hot temperatures and dry periods over the last month have been stressful for peppers and tomatoes, resulting in the appearance of blossom end rot. While blossom end rot, as the name implies, typically occurs on the blossom end of tomato fruits, in some cases (see figure) it occurs on the shoulder and sides of the tomato fruit. In peppers it occurs commonly on the sides of the fruit but can appear anywhere on the fruit surface.

Blossom end rot is the result of plant stress brought on by periods of dry vs moist soil.  Calcium deficiency in the plant is the cause but applying calcium to the foliage won’t help.  Calcium is relatively insoluble and plants under stress can’t move it to flowers and developing fruit.  It is a vital component of plant cell walls and the matrix that holds the cells together. When fruits start to form without sufficient calcium the tissues soften and die.  Secondary molds often colonize the dead tissue.

Severe case of blossom end rot of a green tomato, starting at the blossom end.

Blossom end rot of a green tomato.

The disorder is especially disappointing to home gardeners, because fruits with blossom end rot are often the first to ripen but usually inedible. I don’t recommend cutting off the affected parts and consuming the rest due to the risk of mold growth and presence of potential toxins to which some people may be sensitive.

Blossom end rot becomes less problematic with more consistent soil moisture and as the plants grow and develop their root systems.

Thanks to Carri Jagger for the blossom end rot of pepper photo.