Downy Mildew Reported on Cantaloupe and Acorn Squash 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.

Pumpkins: Time to Pass the SPF 45

About 10 days ago we harvested a few pumpkin trials at the research station. After weighing and grading the fruit, they were set back in the row but not in the leaf canopy. Last week I drove by some of the plots and noticed some fruit were sunburned. Such is the fate of many pumpkin fruit exposed to direct sun and not covered by leaf canopy. Sunburned fruit have a reddish area facing the sun which will eventually soften and rot.

Reddish area on near fruit, sunburn.

Over the year’s growers have asked me, how long into the season should they treat the foliage with fungicides? I would respond as long as you plan to harvest fruit. Avoiding sunburned fruit is the primary reason to keep the foliage healthy later into the season. Given our increasingly warmer and sunnier fall season, growers should expect to incur significant losses if the foliage is degraded by bacterial or fungal pathogens.

Conditions that favor sunburn include thin leaf canopies, fruit that have been clipped off of the vine but left in the field to cure or be packed at a later date, and clear sunny days with highs above 80-85F.  The weather forecast for the next week in southwest Ohio include max temperatures in the mid 80’s to low 90’s…let’s hope periodic cloud cover spares growers from excessive fruit losses.

Harvests of Data Hopefully Increase Harvests of Money

Experiments planned in Fall-Winter 2018-2019 and initiated this spring at the OARDC in Wooster, OH are now yielding crop-based data. Additional experiments initiated this past week or to be initiated within several weeks will provide additional numbers of potential value to growers. Overall, these experiments are supported by: (a) the USDA-NIFA Specialty Crop Research Initiative (https://nifa.usda.gov/program/specialty-crop-research-initiative-scri), (b) the USDA-NIFA Organic Transitions Program (https://nifa.usda.gov/program/organic-agriculture-program), (c) the USDA-NIFA Potato Breeding Research support program (https://nifa.usda.gov/funding-opportunity/potato-breeding-research), (d) North-central SARE (https://www.northcentralsare.org/), and (e) companies. Along with our collaborators, through these experiments, we look to provide growers and other members of the industry with information they can use beginning immediately, especially when making decisions involving the use of grafted plants, microbe-containing crop biostimulants, reduced-tillage approaches, high tunnels, and/or new potato varieties. Ideally, this information will increase the yield of money on Ohio farms.

Two ongoing experiments will help identify the optimal growing practices when grafted watermelon plants are used. Grafted watermelon plants are showing high potential in- and outside Ohio. However, their wider use has been slowed by their higher cost and the fact that yields from them are not always higher than from standard ungrafted plants. Importantly, an increasing amount of evidence provided by researchers and farmers suggests that growing practices may have to be altered in order to get the best return on investment from grafted watermelon plants. Studies and farmer experience point to changes in plant density, and/or nutrient and/or irrigation management as possibly beneficial. This is reasonable given characteristics of some watermelon rootstocks. So, since 2018, like others, we have been asking if yield can be maintained or increased even as grafted plant density or fertilizer inputs are modified. These two experiments total twelve variety-fertility program and eight variety-plant density treatments. On 8/21/19, the VPSL and OARDC Farm Crew harvested 849 “Jade Star” watermelon fruit from the forty plots spanning roughly 0.7 acre (including pollenizer plants). The 849 fruit totaled 6.2 tons (11 over-filled pallet boxes) and averaged 255 lbs/plot (nine plants). “Fascination” fruit will be taken from the same experiments the week of 8/26, fruit quality will be evaluated in the lab, and the harvest-evaluation process will be repeated for the same experiments to capture total crop yield potential. At the same time, we will continue to focus on: (a) tomato experiments testing grafting, strip-tillage, and/or microbial inoculant effects on fruit yield and quality; (b) butternut squash, carrot (fall high tunnel), and spinach (fall high tunnel) experiments testing microbial inoculant effects on yield and quality; and (c) potato experiments completed in cooperation with breeders at USDA, the University of Maine, Cornell University, and North Carolina State University.

What’s Chewing on my Sweet Corn?

While walking through a sweet corn plot this morning looking at how many plants were tasseling, I saw a few interesting things to quickly comment on in case growers are seeing these things in their fields.

I saw some rough chewing damage on the leaf and immediately thought, wow, it looks like we have some Fall armyworm in this plot (despite having a FAW pheromone trap nearby that has caught zero moths for weeks). Upon closer inspection, it was a grasshopper inside the rolled up leaf.  As I looked at the grasshopper, I noticed the frass around the leaf damage was not wet and messy typical of the pest but rather thinner, pelletized and fairly cylindrical. So even if the grasshopper had left the leaf, the “frass” would be a good clue it wasn’t a caterpillar.

Leaf damage caused by grasshopper.

As I began inspecting the tassels, I saw a lot of corn leaf aphid on just about each tassel. This sucking pest can be a problem if it exudes too much honey dew (sugary liquid waste excretion) on the tassel and it interferes with pollen shed and possibly pollination. While you can spray insecticides to knock down the aphids, be sure to take a look for natural enemies such as  ladybug adults and larvae, green lacewing larvae, and hover fly larvae.

Corn leaf aphid on tassel and ladybug adult (multi-colored Asian ladybeetle) feeding on aphids.

One of the biggest pests of sweet corn has been a little quiet for the past few months according to our trapping network, but we expect it to pick up in the next few weeks so be sure to have your corn earworm trap out near fresh silking corn with a fresh lure. See the nice summary below by Celeste Welty a few weeks ago with reference to spray frequency of CEW.

The corn earworm moths will be laying their eggs on (fresh) silks of sweet corn. Sweet corn can be protected from corn earworm infestation by insecticide sprays during silking. When the number of CEW moths caught in traps is moderate  (1 to 13 moths per day, or 7 to 90 moths per week), then sprays should be applied every 4 days if the daily maximum temperatures is below 80 degrees F, or every 3 days if the daily maximum temperatures is above 80 degrees F. More information about CEW, traps, and trap-based spray schedules is available using this link: http://u.osu.edu/pestmanagement/crops/swcorn/ .

New Video Resource on Herbicide Drift and Sensitive Crops

Ohio grain farmers are using dicamba and 2,4-D more frequently against herbicide-resistant weeds. These herbicides are stronger and prone to off-target drift. A new video from Ohio State discusses the high cost of drift damage on specialty crops, ranging from lower yields to delayed or lost harvests and even the loss of long-term investments like grape vines or certification status.

2,4-D and dicamba are synthetic auxins, herbicides that affect multiple growth processes by mimicking natural plant hormones. Not all plants are highly sensitive to synthetic auxins, but most will react to exposure in characteristic ways (see photos). Damage is usually characterized by severe distortion of stems and leaves but can also cause delayed or uneven fruit ripening and plant loss.

Good Neighbors: Herbicide Drift Issues and Sensitive Crops
Running time 7:36 minutes
http://go.osu.edu/drift_video

Final Call – Pumpkin Field Day

The 2019 Pumpkin Field Day is designed to help beginning and experienced growers with production and pest management challenges. The field day is scheduled for Aug. 22 from 6-8 PM at the Western Ag Research Station (7721 S. Charleston Pike) in South Charleston. Pre-registration using this link (https://www.surveymonkey.com/r/pumpreg19) is required by Aug. 19th.

Due to our later than normal planting date, not all of the 27 hybrids have fully matured yet. Here is an updated list of what pumpkins/squash in the hybrid trial HAVEmature fruit:

Bayhorse Gold, Hybrid Pam, Carronado Gold, Orange Sunrise, Blanco, Blue Doll, Hermes, Indian Doll, Sanchez, Warty Gnome, Red Warty Thing, Moonshine, 20Kt Gold, Cinnamon Girl, Half Pint, Snowball and Knucklehead.

All of the hybrids have some fruit, and I expect a few more to mature by the field day next week.

Celeste Welty, Jon Branstrator, and myself will be on hand to present information and answer questions as they arise on the two hour tour.

The full details of the field day can be found here:

https://u.osu.edu/vegnetnews/2019/07/25/pumpkin-field-day/

Looking forward to seeing you next week!

July 29, 2019 cdm.ipmpipe.org

Downy mildew was confirmed today in cucumbers in an unsprayed MSU research plot in Benton Harbor, MI. In our experience, when downy mildew is identified in Michigan, it is probably already or soon to be seen in Ohio, and vice versa.  Cucurbit growers should have been applying protectant fungicides such as chlorothalanil or mancozeb , but should now consider transitioning to downy mildew fungicides.  Moderate temperatures, humidity, overcast skies and rain showers expected in much of Ohio in the next few days are conducive to downy mildew spore movement, deposition and infection. MSU’s recommendations for effective fungicides against downy mildew are shown here:

  • Ranman + chlorothalonil or mancozeb
  • Orondis Opti (chlorothalonil is part of the premix)
  • Elumin + chlorothalonil or mancozeb
  • Zampro + chlorothalonil or mancozeb

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.

Pumpkin Field Day

The 2019 annual Pumpkin Field Day will be held from 6-8 PM on Aug. 22 at the Western Ag Research Station in South Charleston (7721 South Charleston Pike, South Charleston, 45368). This is the 20th anniversary of the field day and no better way to celebrate than to come out and see what kind of research and demonstration trials we have set up this year! We cater to both beginner and experienced growers so prepare to leave with more pumpkin knowledge than when you arrived!
This year we have our standard powdery mildew fungicide trial where we are looking at some new compounds (Trionic, Miravis Prime, Inspire Super). This spring we barely got our mustard cover crop biofumigation research trial planted due to the heavy rains with the goal of reducing Plectosporium infections on the foliage and fruit. We have some strip trials of cover crops and several combinations of plant bio-stimulant products for review. Lastly we have a 27 entry pumpkin and squash hybrid variety trial. Since the rain caused us to plant a few weeks later than normal, it’s likely not all hybrids will have mature fruit by the field day.  A detailed report will be given later as to what hybrids will have mature fruit.
In terms of specialists who be at the meeting, Celeste Welty will be presenting information about insect control. Jon Branstrator is a local grower who will share his experiences (positive and not so positive) with cover crops. Jim Jasinski will host the event and squeeze in a few words about the fungicide trial, mustard biofumigation trial, and bio-stimulants demonstration. As always we hope this field day allows you to mix and meet other growers from around the state.
We ask that you pre-register for the event by Aug. 19th using this link:
https://www.surveymonkey.com/r/pumpreg19
There is a $5 fee per person, and the field day will include some beverages and hand outs. We start registration at 5:30 PM and the tour begins promptly at 6:00 PM. For more information please contact Jim Jasinski, jasinski.4@osu.edu, or 937-462-8016.  Hope to see you out here!

Attention pumpkin, squash, melon, and cucumber growers

We all know this has been one of the most challenging spring and early summer seasons in the past 20-25 years. Ohio State researchers and Extension educators are aware of this and are trying to understand what are your most pressing production needs, so that we can begin to address them as best as possible.
Below is a link with 7 questions that will allow you to report your crop status and any issues you are facing or needing assistance with. We do not ask for your name or farm but we are trying to understand where these issues are occurring, so we do ask for your county; your response is of course optional. All responses are anonymous.
Please take just 2-3 minutes to help us understand your situation, so we can help you in return.  Thank you.

Persistently-wet Soils Early in the Season: Consequences and Mitigation

The Problem

Too much rain has fallen. Beginning in late autumn 2018, conditions turned wet and have persisted throughout the winter and spring seasons of 2019. For example, the OARDC-Wooster weather station (https://www.oardc.ohio-state.edu/weather1/) registered rainfall on 47 days of the 88-day period April 1 – June 27, totaling 13.4 inches over the period (an average of nearly one-third inch of rainfall per day with rain). Not surprisingly, impacts have been accumulating. Much has been lost directly due to rain and rain-related delays: time, topsoil, fertilizer, targeted levels of stand establishment, and opportunities to start well with weed, pest, and disease management, and other operations. These primary consequences have had secondary ones. Field preparation and stand establishment is always a hectic phase and outcomes are never certain, even in years when weather is largely a neutral factor. Still, routines and schedules can follow a familiar timeline. Not so for many in 2019. Timelines and various common expectations have gone out the window (or, into the drainage ditch, as it were) and management has been more “seat of the pants” than many prefer. We’ve been required to reconsider what to do, when, how, etc.

A Set of Partial Solutions

Conditions can improve with a little cooperation from the weather and strategic action. What follows is a brief overview of factors to consider and steps to take when given a chance: (a) to kick-start or rejuvenate a stand or crop set back by persistently wet or saturated soil since seeding or transplanting or (b) to limit the recurrence of the same problem in future seasons. The amount of detail available for each factor and step could fill at least several VegNet articles. This article is more broad than deep and it draws from experience and excellent references developed through the years by members of the industry and vegetable research-extension community.

For 2019

1. Surface cultivation. Persistent or pounding rain can lead soil to crust. Crusting prevents seedlings from emerging, air from entering the soil, and some wastes in the soil from leaving it. Breaking the crust with light surface cultivation can help reverse these conditions. Choose the right time and equipment for the operation in order to maximize its benefit while minimizing the potential for creating compaction while heavy equipment is taken across the field with subsurface soil moisture levels still relatively high.

2. Careful cultivation and irrigation. Many now face a situation in which leggy, under-nourished, and generally weak transplants were set into soils wetter than ideal and which remained wet for long stretches thereafter. Not good. Root-shoot ratios are not ideal and root systems may be small and shallow, concentrated near the soil surface. This makes root systems prone to damage due to cultivation and ironically, plants susceptible to LOW moisture stress, especially if weather turns dry AND warm. Keep alert when cultivating, maintain the proper depth and distance from the crop. Also, as we shift toward a more summer-like pattern of scattered but intense rainfall, treat it as an opportunity to encourage root systems to expand and deepen. Doing so may require “weaning” plants off the saturated conditions many have experienced since planting. Guard against strict adherence to irrigation schedules based on a “normal” year with normal stand establishment conditions. Modify how often you irrigate and for how long the water flows each time according to soil and plant conditions, monitoring both carefully. Again, shallow- and small-rooted plants need time to adjust to drier conditions and the process largely cannot be rushed. Consider lengthening the time between irrigations gradually until you are confident the crop has, more or less, fully recovered and “toughened up” and you have reached an adequate level of control over soil moisture and other conditions.

3. Replant. Recall that the growth and productivity of individual plants can hinge on how many neighbors it has and where they are located, i.e., the plant population or density. Compensation allows some crops to produce similar yields across a wide range of plant populations. For these crops, thin stands can be less problematic because yield potential is maintained. However, for non-compensators (e.g., fresh market sweet corn), one less plant clearly results in less yield (e.g., one less ear to sell). Replanting may be more beneficial with crops that do not compensate. Regardless, check records, estimates of days to maturity, etc when selecting varieties and choosing to replant. Also, when replanting flooded-out portions of large plantings, be aware that the crop maturity in these replanted, “pieced in” areas will be different than the main crop but may maintain income potential that would be lost otherwise. These areas may also require slightly different management (e.g., fertilizer, irrigation, protection) than nearby areas planted earlier.

4. Replace. IF and only IF circumstances call for it and allow, replace the vegetable planting with a cover crop, forage/feed crop, or clean fallow program. This step has huge implications for the business and others for the soil. If the very weak or absent vegetable planting can be replaced by clean fallowing or a crop involving less expense, time, and effort but offering some soil building and/or cash-flow potential, this option may represent taking two steps forward starting from one back, i.e., a net gain compared to replanting or continuing with a very weak vegetable crop.

5. Keep planting. Vegetable and grain farmers have been hit hard by the weather so far. One aspect of vegetable farming that can help farmers through these difficult times is that many vegetable crops can be harvest-ready in much less time than full-season corn, soy, and other crops. Enough season remains to plant and harvest a profitable vegetable crop. Talk with your produce buyers. Discuss the possibility of adjusting marketing/delivery scenarios and schedules with, for example, late plantings of early-maturing crops such as sweet corn, green beans, peas, transplanted cole crops, radishes, turnips, daikon radish, zucchini and yellow squash, cucumbers and pickles. Recall that most concentrated-set pickle varieties can be harvested 60 days from planting and northwest Ohio farms traditionally plant through early July.

6. Fertilizer application. Excess rain during stand establishment like many have experienced limits root growth and can allow fertilizer applied before or at planting to leach, runoff, or change form and become unavailable or taken-up less efficiently. Therefore, nutrient deficiencies, especially of nitrogen and potassium, may develop soon after growing conditions improve. Research and experience have shown that applying carefully determined, low amounts of N and K through fertigation, or as a sidedress, broadcast, or foliar treatment, can limit the progression of yield reductions caused by excessive soil moisture. Use plant tissue testing and petiole sap analysis to monitor plant nutrient levels useful in determining if fertilizer applications are needed. Review https://edis.ifas.ufl.edu/pdffiles/EP/EP08100.pdf and similar resources for additional information.

7. Support. Anchoring the plant is one of the six major functions of root systems. Anchoring is difficult in saturated soils and/or when root systems are small, especially compared to the canopy. Don’t underestimate the value of a trellis in supporting upright fruiting crops (e.g., tomato, pepper). It lowers the risk of lodging and wind-whipping (wind-whipping is more likely when transplants were particularly leggy).

For Future Seasons

8. Lengthen rotations and build soil internal drainage and moisture holding capacity. All the familiar approaches – e.g., cover cropping, soil amendments, tiling – apply here. Reduced-tillage approaches are less familiar to some but gaining attention.

Clean fields planted on the flat or then formed into raised beds topped with drip tape and plastic mulch are the current standard among commercial growers throughout much of the world. These standard systems have been very reliable and productive. Reduced-tillage systems, on the other hand, offer various benefits although, historically, their yields are often lower than yields in standard systems. Research by farmers and others has focused on retaining the benefits of reduced-tillage approaches while increasing the yield of systems involving them. For example, at OARDC, we have been investigating whether the use of grafted plants and/or microbe-containing crop biostimulants can enhance yield of tomato grown in a flat-ground, strip-till system. Results have been promising; using one or both treatments has narrowed the gap between yields of the strip-till and standard systems. Regardless, our experience and data collected by others also suggest that soils in strip-till plantings can be more resistant to flooding and resilient when flooding conditions develop.

9. A genetic solution to flooding. Flooding is a problem worldwide in agriculture and plant breeders have taken note. Flooding tolerant rootstocks are available for tomato and ones may become available for other crops that are routinely grafted (pepper, watermelon, cucumber, cantaloupe). Pay attention to flooding tolerance and other grafting-related developments.

10. Study up. It will also remain important to pay close attention to information provided by the climate services community, which includes agroclimatology and other experts. Descriptions of historical trends and projections of future scenarios are constantly improving. My non-expert reading of some recent reports (e.g., see June 8 VegNet) suggests that conditions so far in 2019 are consistent with projections outlined in those reports – e.g., intense rainfall events occurring more often and becoming stronger, allowing for fewer days to complete field work. No one knows for certain that conditions many have encountered so far this season will repeat (weather variability). Still, for planning purposes, a broad reading of various reports can lead one to conclude that conditions so far in 2019 are better viewed as an extreme version of an emerging trend, not a fluke or once in a career scenario.

Brad Bergefurd of OSUE and Jason Cervenec, Education and Outreach Director of the Byrd Polar and Climate Research Center (BPCRC) and Aaron Wilson, Research Scientist with OSU Extension and BPCRC, both with the State Climate Office of Ohio (https://climate.osu.edu/), contributed to this article.