Welcome to this week’s issue of our 2024 season UF/IFAS Extension Suwannee Valley Watermelon Crop Update. These updates will be summarized by Bob Hochmuth, Regional Specialized Extension Agent- Vegetable Crops, with input from Suwannee Valley Extension Agents: Mark Warren (Levy), Tyler Pittman (Gilchrist), Tatiana Sanchez (Alachua), Luke Harlow (Bradford), Dan Fenneman (Madison), Keith Wynn (Hamilton), Emily Beach (Lafayette), Jim Devalerio (Union), De’Anthony Price (Jefferson), Raymond Balaguer(Suwannee), Kevin Athearn (RSA-Agri- business), Shivendra Kumar (RSA-Agronomic Crops), Jay Capasso (RSA- Water Resources), and Bob H. covering vacant Columbia County position.
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Gummy Stem Blight and Powdery Mildew Strategies
We have only confirmation of gummy stem blight in the Suwannee Valley, as of April 15th, no powdery mildew or downy mildew have been detected to date. Surprisingly, bacterial leaf spot and Alternaria leaf spot have not been an issue yet either. Even though we have not seen much disease activity up to this point, other than some occasionally gummy stem blight confirmations, we would all be wise to think about upcoming strategies primarily for gummy stem blight and powdery mildew, especially in very early planted fields. This is the time of the season to be on the lookout for both diseases. Of course, most fields do not have gummy or powdery yet, but both diseases are serious enough that we want to be proactive. Curing these two diseases after they appear is much more difficult. Since the strategy of a spray program needs to be laid out well in advance, we are sharing our thoughts and considerations just as we did last year at this time. For late planted fields at first fruit set or later, chlorothalonil may still be your best choice.
But for early planted fields, and later planted fields as they start sizing up fruit, we have some guidance to share, if gummy stem blight or powdery mildew are a concern in your fields. If gummy stem blight is not present in your fields yet, this would be the best time to use Miravis Prime, as it is better positioned ahead of infection, not after gummy has gotten well established. Miravis Prime has some activity on powdery mildew too, but we encourage you to add a material like Quintec, Procure, or Rhyme to Miravis Prime to get ahead and stay ahead of powdery mildew. We have added Rhyme to our recommended powdery mildew list for 2024, based on university research trials in the Southeastern US. This could be followed by mancozeb and possibly tebuconazole, plus alternating powdery mildew material (Quintec, Procure, or Rhyme). UF/IFAS consistently ranks Inspire Super in the top performer category for gummy stem blight as a curative spray, but it has a 7-day preharvest interval (PHI). So, as you approach harvest, remember you need 7 days before your harvest. However, once you get into harvest season, and if you have already sprayed Inspire Super, or are at less than 7 days to next harvest, what should you use? In those cases, Aprovia Top would be a good option. Aprovia Top has performed very similarly to Inspire Super in most trials and Aprovia Top has a 0-day PHI on the label. The main caution is that both Inspire Super and Aprovia Top have FRAC Group 3 fungicides in their ingredients, so we want to minimize the number of applications of these two in rotation. Keep in mind Aprovia Top is a great option, if needed, once you start the harvest season. A final note regarding spray programs once harvests start, pay close attention to pre-harvest intervals (PHI). Common rotations after harvests begin will include the following materials: Mancozeb (Manzate, Penncozeb) which have a PHI of 5 days, Quintec 3-day PHI, Procure 0-day PHI, and Rhyme 0-day PHI. Aprovia Top has a 0-day PHI and Miravis Prime has a 1-day PHI. But other materials like tebuconozole, Inspire Super, and Luna Experience all have a 7-day PHI, so be alert to the PHI and your harvesting schedule and food safety records. Because Inspire Super and Aprovia Top both share difenoconazole, you need to remember not to exceed the 0.46 lbs a.i/A/year. (updated by Bob Hochmuth 2024, from Tatiana Sanchez-Jones, and Mathews Paret in 2023).
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Slower than expected growth
During this past week, there were several questions concerning plants that “just were not growing very much”. In all cases the plant leaf or petiole-sap test results were good or even high in some cases. I believe the cool or cold nights and the relatively cloudy days were the reason for our slow growth in certain fields. Temperatures have been in the 40s and low 50s many if not most nights in the past 10-14 days, and many days have been cloudy or overcast for much of the days. As a result, the soil temps have not been as high as we normally expect. Soils started off cool and have never maximized soil temps because the sun was not heating up the plastic or paper mulches very much. However, the forecast this week with temperatures every day in the mid-80s to low-90s should kick everything into higher gear. So, my advice is to be patient and see if these high temps take care of the concerns.
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Produce Safety Alliance Grower Food Safety Training in the Suwannee Valley
April 25, 2024 – 8:00am – 5:00pm
UF/IFAS NFREC – Suwannee Valley
8202 County Road 417 • Live Oak, FL 32060
Who Should Attend – Fruit and vegetable growers and others interested in learning about produce safety, the Food Safety Modernization Act (FSMA) Produce Safety Rule, Good Agricultural Practices (GAPs), and co-management of natural resources and food safety are encouraged to attend. The PSA Grower Training Course is one way to satisfy the FSMA Produce Safety Rule requirement.
Benefits of Attending: The course will provide a foundation of Good Agricultural Practices (GAPs) and co-management information, FSMA Produce Safety Rule requirements, and details on how to develop a farm food safety plan. After attending the entire course, participants will be eligible to receive a certificate from the Association of Food and Drug Officials (AFDO) that verifies they have completed the training course.
Cost to Attend: $40. Please register at: https://psa042524.eventbrite.com. Cost includes training materials, lunch, refreshments, and certificate of attendance issued by AFDO. Seats are limited. Registration closes 1 week prior to training date (April 25). For questions, email Sarah McCoy at sarahmccoy@ufl.edu.
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If you know someone who wants to be added to this weekly notice, contact your Extension Agent or Mark Warren (352-949-8288) if you want to be added to the regional watermelon group text app.
We have initiated a more formal way to support our watermelon growers with a rapid diagnostics system through Suwannee Valley Regional and County Extension Agents. This industry-funded program allows Extension Agents to submit and pay for watermelon grower’s plant disease and other diagnostic samples. This SV Rapid Diagnostic Watermelon Program will help us to get quicker diagnostic results, helping to give early alerts to everyone, and not have to charge the growers directly. Plant disease samples are typically $40 and leaf tissue analyses are typically $20. We are currently extending our solicitation of those industry reps interested in sponsoring this effort. The past year’s sponsorships have ranged from $200 to $2,000 per company. Sponsors will be recognized every week beginning this week. Those interested in being added as a sponsor can contact Bob Hochmuth at bobhoch@ufl.edu or 386-288-6301.
Current 2024 sponsors of our Watermelon Rapid Diagnostics Program include Valdosta Plant Company, Mayo Ag Services, Gowan USA, Harrell’s Fertilizer, Triest Ag, Syngenta Crop Protection, WestRock Paper Company, and Orbia Netafim. Others are still welcome to join.
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