Fusarium wilt caused severe disease in our standard-size seedless watermelon variety trial in 2021. This is one of the most severe diseases in watermelon production in Indiana. The fungus survives in soils for many years without a host. Our seedless watermelon variety trial at Southwest Purdue Agricultural Center follows a four-year rotation. After doing the trial for almost 30 years, Fusarium wilt showed up a few years ago in the rotational lands. We have been trying to address the issue through fumigation and using drip-applied fungicide. None of the approaches has completely solved the problem. Since some of the varieties in the trial were very susceptible to the disease, even low disease pressure can cause significant damage. We are currently exploring new ground for future seedless watermelon variety trials. I hope the new land will give the variety trials a break from this disease
Fusarium wilt causing watermelon wilt in the 2021 watermelon variety trial at Southwest Purdue Agriculture Center
After evaluating watermelon varieties under the disease pressure for a few years at the Southwest Purdue Agricultural Center, it is clear that commercial watermelon varieties vary in their resistance/susceptibility toward this disease. However, information from both seed companies and university trials can sometimes be confusing. Part of the puzzle is due to the existence of multiple pathogen races. It is challenging to evaluate varieties or breeding lines for seed companies and university trials under the pressures of all races. Plus, the population of the pathogen could change over time. In a naturally infested field, the pathogen is distributed unevenly, thus such trials often fail to find significant differences.
At the 2022 Watermelon Research and Development Group meeting, Dr. Jonathan Schultheis presented watermelon cultivar incidence and yield response in North and South Carolina fields with Fusarium with of watermelon. The two locations evaluated the same nine popular seedless watermelon cultivars under disease pressure. We combined North and South Carolina results and what we have observed in Indiana from the past years. We are confident that Embasy and Fascination were relatively more resistant to the disease in field conditions. Traveler also did well under the disease pressures in Indiana, but the cultivar was not included in North and South Carolina trials. Shoreline and Joy Ride were more susceptible to the disease across all the trials. Grafted plants continue to be the most resistant plant compared to non-grafted varieties.
We hope the variety information is helpful for farmers who are struggling with Fusarium wilt. It is also important to understand that none of the seedless watermelon varieties are entirely resistant to all the races. A complete management approach will depend on integrated use of multiple tools including variety selection, chemical control and rotation. Using grafted plants is probably the most reliable approach in controlling Fusarium wilt, but the cost of grafted plants makes the practice hard to be accepted by many watermelon farmers.
The full 2021 standard-size triploid watermelon variety trial report can be found at https://docs.lib.purdue.edu/mwvtr/228/