- Fruits: melons
- Crop Production: cover crops, application rate management, tissue analysis
- Education and Training: demonstration, extension, on-farm/ranch research, participatory research
- Farm Business Management: budgets/cost and returns
- Pest Management: chemical control, cultural control, eradication, integrated pest management, mulching - plastic
- Soil Management: green manures, organic matter
A hairy vetch winter cover crop was compared with rye, fallow, and vetch plus methyl bromide fumigation for managing Fusarium wilt of seedless watermelon on a private farm. Wilt was lower with vetch plus fumigation than in all other treatments. Early season yield of watermelon was similar in vetch alone and vetch plus fumigation. Cover cropping with vetch produced a net return of $2,675/acre, whereas fallow and rye lost an average of $410/acre. The poor stand of vetch in no-till corn stubble may have limited the potential benefits of hairy vetch.
Tables, figures or graphs mentioned in this report are on file in the Southern SARE office.
Contact Sue Blum at 770-229-3350 or
email@example.com for a hard copy.
Fusarium wilt is the most wide-spread, damaging soilborne disease of watermelon in the South. Cropping the same fields again and again to watermelon without rotation or with short rotations selects the specialized form of the soilborne fungus Fusarium oxysporum, F. oxysporum f. sp. niveum (abbreviated FON), that attacks watermelon (Hopkins et al., 1992). Fusarium wilt kills individual vines or whole plants, directly reducing the number of fruit produced. In addition, this fungus lasts indefinitely in infested soil. It can reduce the yield, acreage, and economic return of watermelon crops, both crops grown now and those planted in the future.
As of 2006, there are four races of FON that are separated by the cultivars they attack. Race 0 is pathogenic only on older and heirloom watermelon cultivars that have no resistance. Many diploid, seeded hybrid cultivars have resistance to race 1. Previously, race 2 was limited to Texas, Oklahoma, and Florida. Since 2000, race 2 has been found in five new states: Indiana, Maryland, Delaware, Georgia, and South Carolina (Egel et al., 2005; Keinath, 2009).
Traditionally, 7-year rotations have been used to manage Fusarium wilt. However, today’s watermelon growers specialize in watermelon production and cannot afford to leave much acreage out of production for more than one or two years. In South Carolina, all seedless watermelons and a majority of seeded watermelons are irrigated. Growers are limited to planting in fields that they have equipped with wells, pumps, or center pivot irrigation. In addition, rotations with agronomic crops, such as wheat and soybean, do not reduce FON in soil (Zhou and Everts, 2004).
Although hybrid seeded cultivars resistant to race 1 were useful in the past, the watermelon market has shifted to seedless cultivars, which are susceptible to Fusarium wilt. Two seedless watermelon cultivars, ‘Matrix’ and ‘Revolution,’ have resistance to race 1, but they are not grown because their fruit types are not acceptable to produce buyers. Both cultivars are susceptible to FON race 2 and thus would perform like susceptible cultivars in fields infested with a mixture of races. In addition, the O’Neal’s cannot grow these cultivars because oblong fruit do not fit in their state-of-the-art packing line.
Methyl bromide was used in the past to manage Fusarium wilt. During the phase-out, some growers tried other fumigants, such as Telone-C35 (1, 3-dichloropropene plus 35% chloropicrin). However, restrictions on use of Telone have been imposed as a result of FQPA review, and few watermelon growers currently use Telone.
To summarize the problem, there is a lack of commercially viable control options for Fusarium wilt of watermelon. Therefore, watermelon growers in the South and other regions of the U. S. need sustainable controls that fit their production practices and are effective against all races of FON.
- Determine the level of Fusarium wilt in treatments;
Measure the yield (number) of marketable-sized fruit;
Calculate the cost and economic return of each treatment;
Determine the level of the Fusarium fungus in soil collected from treated plots;
Communicate results to stakeholders