Northern 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 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.
As of Monday, most reports of downy mildew in our neighboring states – MI, KY, PA – were in cucumbers, as were our previous reports. However, we found downy mildew on acorn squash in our sentinel plot on the OSU North Central Agricultural Experiment Station in Sandusky County and on cantaloupe in our sentinel plot on the OSU Muck Crops Experiment Station in Huron County. While we have not had reports from most Ohio counties, it is likely that downy mildew is widespread in Ohio. Now we have evidence that the strain that infects most cucurbits, including squash and pumpkins, is present here. The cucurbit growing season is winding down, but if cucurbit crops are expected to be in the field in the next few weeks they should be protected with fungicides. See my blog post on August 22 below for fungicide recommendations.
The downy mildew pathogen does not infect cucurbit fruits but if plants are defoliated the fruits are at risk of sunburn. Sunburn may not be obvious immediately in the field but may develop in storage. In fields with significant defoliation, pumpkins and winter squash should be removed from the field and into shade for curing.
Finally, the downy mildew pathogen does not survive over the winter in the absence of living cucurbit plants. However once harvesting is completed, plants should be disked as soon as possible to kill remaining green tissues that may otherwise be infected and serve as sources of inoculum. This will reduce downy mildew inoculum that can spread to cucurbit crops near and far.
Do you have a bird problem on your farm? Do you want to encourage beneficial birds as an IPM tool? If so, consider attending this free webinar. Registration information below:
Webinar: Supporting Beneficial Birds and Managing Pest Birds
Supporting Beneficial Birds and Managing Pest Birds
Webinar: Tuesday, October 1 at 11AM Pacific, 12PM Mountain, 1PM Central, 2PM Eastern Time
Register in advance at https://oregonstate.zoom.us/webinar/register/WN_Yey2HdAZQ8S3CSKUuR8FIg
Join eOrganic for the first webinar of our fall season! The topic is Supporting Beneficial Birds and Managing Pest Birds, by Jo Ann Baumgartner of the Wild Farm Alliance, Sara Kross of Columbia University, and Sacha Heath of the Living Earth Collaborative.
Beneficial birds can help farmers keep pest insects, rodents, and pest birds at bay. They act the same way that beneficial insects do in helping with pest control. The overwhelming majority of songbirds are beneficial during nesting season because they feed pest insects to their voracious nestlings. Farmers may be able to reduce their pest-control costs by providing habitat for these beneficial birds and by only targeting detrimental birds at the right time and place. Wild Farm Alliance and two avian ecologists will present on: a) How birds’ diets, foraging strategies, and nesting periods affect the farm, b) How best to manage and co-exist with pest birds, c) Why on-farm habitat and the surrounding landscape influences pest control, and, d) What farmers can do to make farms more bird-friendly and resilient. With this webinar and the associated Supporting Beneficial Birds and Managing Pest Birds booklet, we aim to help all farmers and farm consultants make the most of birds on farms.