Upcoming Session to Focus on Long-term Success in High Tunnel Production

Investments in high tunnels and high tunnel production are among the most significant growers can make, especially if the tunnels are stationary (not designed to move) and income from the tunnels is critical to the farm. Getting the most from tunnels from the start and over the long run is important. A session summarizing steps toward that goal will be held on Thursday April 23, beginning at 12 PM ET. The session is part of the OSUE Ag Madness series (https://go.osu.edu/agmadness) and will focus on major challenges and emerging opportunities in high tunnel production. Specific topics will include soil health, and new crops and high tunnel technologies — information for all high tunnel users, regardless of experience. Please see https://agnr.osu.edu/events/agriculture-and-natural-resources-madness to connect and contact Matt Kleinhenz (kleinhenz.1@osu.edu; 330.263.3810) for information. We look forward to seeing you there!

OSU Plant Disease Diagnostic Services for Commercial Vegetables Will Resume April 13

Septoria leaf spot on tomato transplants

The OSU Vegetable Pathology Lab will resume plant disease diagnostic services in Wooster on Monday April 13 on a limited basis (see below). This service is provided at no cost to Ohio commercial vegetable growers. Dr. Francesca Rotondo will carry out the usual diagnostic procedures during the limited time she is in the lab. If possible, please contact us with digital samples before sending physical samples:

  1. Send photos or short videos that represent the problem via text or email to Dr. Sally Miller (330-466-5249/miller.769@osu.edu) AND Dr. Francesca Rotondo (865-640-5621/rotondo.11@osu.edu).  If we can’t diagnose the problem from the digital samples we will ask you to send a physical sample.  Growers who can’t access/don’t use digital technology should call Dr. Miller or Dr. Rotondo.
  2. No drop-off samples can be accepted. Ship samples Monday through Thursday via overnight delivery (USPS, FedEx, UPS or other courier) to the OSU Vegetable Pathology Lab, c/o Dr. Francesca Rotondo, 234 Selby Hall, 1680 Madison Ave., Wooster, OH 44691 (330-466-5249).

Please see the Vegetable Pathology Lab website before sending samples, for more information and to access the Plant Sample Submission Form.

Freeze / Frost Potential in Ohio – Aaron Wilson, Jim Jasinski

Now that the calendar has turned to April and warmer temperatures are becoming more frequent, those with horticultural interests are eager for the start of the growing season. But April can be a fickle month, with both warm spring rains and lingering cold nights that bring hard freezes and frost and occasionally, even a late-season snowfall. The threat of spring cold temperatures on horticultural production and operations (seeding, transplanting and flowering/fruit) can be greater following early season warmth, where phenological conditions may be advanced for this time of year.

Winter (December 2019 – February 2020) averaged 2-8°F above average compared to the climatological normal (1981-2010; Fig. 1). This warmth continued throughout March as well, with temperatures 4-8°F (west to east) above average. As a result, growing degree day accumulations range from the mid-60s (Ashtabula County) to nearly 200 (Lawrence County) after the first week of April 2020, with our landscapes, fruit trees, and gardening equipment coming to life.

Figure 1: Departure from average (1981-2010) temperatures for December 2019 – February 2020. Figure generated by the Midwest Regional Climate Center (http://mrcc.illinois.edu).

Frost and Freeze Potential

What is Ohio’s typical expectations regarding freeze (≤32°F) conditions in April and May? On average, locations throughout Ohio experience their last seasonal freeze from mid-April (southern Ohio) through mid-May (northeastern Ohio). Timing varies year to year and across Ohio. For a regional analysis, we have selected 8 locations from around Ohio to compare typical last seasonal freeze conditions (Fig. 2).

Figure 2: Selected locations around Ohio for freeze potential analysis displayed in Fig. 3.

Figure 3 shows the probability of experiencing a later freeze in Spring than indicating by the line graphs. All locations show probability based on the most recent 30-year period (1990-2019) except for 7-Lancaster (1996-2019). For each location, five temperatures are displayed (20°F-purple, 24°F-blue, 28°F-green, 32°F-yellow, and 36°F-red). For the purposes of this article we will focus on 32°F and 28°F (considered a hard/killing freeze). The bottom (x-axis) shows the probability that each of these temperatures will occur after a given date (indicated by the left or y-axis).

Figure 3: Probability of a later freeze in the spring for various locations (Fig. 2) around Ohio. Graphs generated by the Midwest Regional Climate Center (http://mrcc.illinois.edu).

Let’s run through an example of how to use Figure 3. For 1-Wauseon, we see that there is a 50% climatological probability of experiencing a 32°F temperature (yellow) after April 27, and this probability decreases to 20% by May 10. The colder, more damaging temperature of 28°F occurs 50% of the time after April 16, with only a 20% chance of seeing 28°F after April 27. For a southern location like 8-Marietta, these dates occur earlier in the season. Here, there is a 50% climatological probability of experiencing a 32°F temperature after April 18 with 28°F occurring 50% of the time after April 2.

Besides latitudinal (north of south) position, what other factors can influence springtime minimum temperatures? Colder air is more dense than warmer air, meaning it wants to remain close to the ground and will flow over the terrain like a fluid to settle in areas of lower elevation. If your location is in a valley or low-lying area, the climatological dates will likely be shifted later to account for more freeze potential later in the spring. Water bodies are typically colder than the surrounding land areas in spring which may keep temperatures in the immediate vicinity a little colder. For 2020, water and soil temperatures are above average, so they are likely to have a moderating impact this year. Cloud cover and higher humidity in the spring will keep air temperatures warmer due to their absorption of terrestrial (from the surface) radiational effects. Finally, late season snowfall combined with clearing skies overnight can also cause the surface to cool rapidly and lead to damaging freeze potential as well. All of these factors should be considered when comparing your location to those selected in Fig. 3.

April 2020 Outlook

At the time of this writing, the National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center (https://www.cpc.ncep.noaa.gov/) outlook for April 10-20, 2020 calls for increased probability of seeing below average (unseasonably cold air) settling into the Upper Great Plain, Midwest, and Ohio Valley (Fig. 4) with a moderate risk of experiencing much below average minimum (nighttime) temperatures. Given the warm start to the year and current phenological conditions, those with horticultural assets should monitor this freeze potential closely and be prepared to mitigate when necessary to avoid losses. For a weekly climate update, please visit the State Climate Office of Ohio’s website (https://climate.osu.edu).

Figure 4: 8-10-day (April 13-19, 2020) temperature outlook. Figure courtesy of NOAA’s Climate Prediction Center.

Aaron Wilson is a research specialist with the Byrd Polar & Climate Research Center and a climate specialist with the Department of Extension. You can also follow Aaron on social media: @dwweather-Facebook or @drwilsonsWx-Twitter.