Watermelon planting decisions involve multiple risks

Watermelon farmers in Florida consider multiple uncertain risk factors when deciding when to transplant watermelon in a field. Early planting (late February or early March) is associated with higher risk of freeze damage and higher incidence of fusarium wilt disease, but typically finds more favorable markets. Late planting (late March or early April) can decrease the chances of freeze damage and diseases to the watermelons but results in later harvest, which brings lower prices and higher risk of losing market access.

Research was conducted by scientists at the University of Florida to compare the risks and returns from early, middle, and late planting windows. Researchers also wanted to evaluate whether late planting would be a favorable strategy for managing fusarium wilt disease.

Nine scenarios were examined, considering three transplanting windows (i.e., early, middle, and late) and three fusarium wilt risk levels (i.e., low, medium, and high). The 1-week planting windows and associated 3-week harvest windows were identified based primarily on the practices of commercial growers. Planting windows common for north Florida growers are 22–28 February (early), 11–17 March (middle).The 28 March–3 April (late) window, is less common but is proposed as a way to reduce fusarium wilt risk.

Harvest windows are 17 May–6 June (early), 25 May–14 June (middle), and 2–22 June (late). Typically, a watermelon field is harvested three or four times over a 3-week period. The number of days between transplanting and harvest can vary depending on watermelon variety and growing conditions.

Later planting typically has fewer days until harvest than earlier planting, but reliable growing-degree-day calculations to estimate days until harvest are not available. Harvest windows are determined based on interviews with growers and dates of price reports for shipments from north Florida packinghouses.

Researchers found that the middle planting window (mid-March) appears to be the least risky, having the lowest chance of negative net return. Late planting has a higher probability of negative net return than early planting, except in the highest fusarium wilt risk scenario. It was concluded that market factors make early and middle planting windows most favorable in most scenarios.

Further research on pre-season fusarium wilt risk assessments could help inform farmers' planting decisions. Because of market factors, however, farmers may prefer other disease management strategies, rather than planting late.

According to author Kevin Athearn, "Farmers must consider multiple risk factors in choosing planting dates. A simulation analysis of risks and returns for north Florida watermelon growers identifies preferred planting windows. Risk of market losses from late planting appear to outweigh potential benefits of reduced disease risk."

The research is published in the journal HortTechnology.