UF/IFAS Extension Suwannee Valley Weekly Watermelon Crop Update –  summarized by Bob Hochmuth with input from Extension Agents: Mark Warren, Tyler Pittman, Tatiana Sanchez, Luke Harlow, Jay Capasso, Sylvia Wills, Dan Fenneman, Keith Wynn, Danielle Sprague, Kevin Athearn, and Charles Barrett.

Cold front coming this week:

Weather forecasts for this Thursday and Friday nights have caught out attention. Forecasts are predicting upper 30s to low 40s, depending on the source. Rain ahead of the cold temps will actually be helpful to add water to the row middle soil so heat can build up in that moist soil ahead of the cold. A moist soil takes longer to cool that a dry soil, so some rainfall Tuesday or Wednesday may be helpful. As we mentioned in our week 1 addition, make sure you keep adequate moisture in the beds ahead of the cold nights so the moist soil can warm during the sunny days under the black plastic. The same principle apples here, a moist bed will stay warmer longer. Overnight drip irrigation events are not proven to be of any benefit to temperatures but have a major negative impact by leaching fertilizer. (Bob Hochmuth)

First detection of bacterial lesions (recap):

Isolated symptoms of bacterial disease were found this past week (black lesions areas that appear wet). We suspect this symptom corresponds to Pseudomonas species and diagnosis confirmation will follow. Since this bacterial disease appears following a cold/moist period like the one we had over the last weekend in most of the region and a similar forecast late this week, be ready to scout intensively later this week. At this point, we only recommend spraying fields where symptoms are observed with a low to medium rate of copper in combination with mancozeb (Manzate, Penncozeb, etc). Remember high rates of copper are toxic to watermelon plants (Tatiana Sanchez).

Watermelon transplants infected with Pseudomonas leaf spot. Note the lesions in leaf margins that expand and later result in defoliation Photo credit: NCSU Plant Disease and Insect Clinic.

Petiole sap testing service:

The Suwannee Valley Extension Agents are all equipped to run watermelon petiole sap tests for farmers. Fields with runners that are about 12 inches long are ready to be sampled. We can test for nitrogen and potassium only. The most recently matured leaf petioles are the ones we sample. This it typically the 5th or 6th leaf back from the tip and we need at least a dozen leaf petioles from random areas of a field. Once the leaf sample is taken, remove the leaf blade from the petiole immediately to keep the sap fresh in the petiole and keep the samples cool until the test is run. I can speak for all of us agents, that if you can collect the samples, we can cover more fields in a timely manner. Communicate with your agents to get lined up for this service. (Bob Hochmuth)


Thank You to the Suwannee Valley Rapid Diagnostic Watermelon Program and Its Industry Sponsors:

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 plant disease and other diagnostic samples. This SV Rapid Diagnostic Watermelon Program will help us to get quicker diagnostic results and not have to charge the growers directly. Plant disease samples are typically $40 and leaf tissue analyses are typically $20. We want to thank the initial sponsors of this program: Syngenta Crop Protection, Harrell’s Fertilizer, Koppert Biological Systems, Seedway, BASF Vegetable Seeds, Bayer Crop Science, and Gowan Seed for sponsoring this effort. Other industry reps interested in sponsoring this effort can contact Bob Hochmuth at bobhoch@ufl.edu or 386-288-6301.

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