- Agronomic: canola, rye
- Fruits: melons
- Crop Production: biological inoculants, cover crops, fallow, tissue analysis
- Education and Training: technical assistance, demonstration, extension, on-farm/ranch research
- Pest Management: biological control, biorational pesticides, botanical pesticides, cultural control, integrated pest management, mulches - killed, mulching - vegetative
- Soil Management: green manures
Three years of trials were implemented on a commercial watermelon field leased from a local grower and greenhouse/laboratory experiments conducted to determine the biology of and management techniques for Mature Watermelon Vine Decline (MWVD). It was determined in greenhouse experiments that a biological factor in the soil is responsible for MWVD. The onset and severity of MWVD appears to be correlated with excess soil moisture. Canola used as a cover crop may mitigate the severity of MWVD. Although biological inoculants used in the early season increased the vigor of watermelon plants, the severity of MWVD was not reduced.
Since the mid-1980s, watermelon fields in southwestern Indiana have experienced outbreaks of a disease syndrome known as Mature Watermelon Vine Decline (MWVD). The disease was a limiting factor in production and reduced yields in many fields in 1989, 1995, and 1999. In 2000, it was especially severe, affecting more than 50 percent of watermelon acreage in southwest Indiana, and reducing total estimated yield by 20 percent. (Egel et al., Plant Health Progress, 2000 doi:10.1094/PHP-2000-1227-01-HN).
Initial MWVD symptoms include necrosis and wilting of leaves, followed by the wilt and collapse of the vines. Vine collapse reduces fruit quantity, size, and quality; prevents normal ripening; and exposes fruit to sunburn. On symptomatic plants, the root systems are generally sparse — the primary roots are necrotic (dead tissue) and the plant has few secondary roots.
Symptoms often appear on mature plants in low, poorly drained areas. Under the right conditions, MWVD incidence will increase through the summer, often resulting in the collapse and decline of large portions of affected fields. Plants with MWVD often yield no marketable fruit.
Management of MWVD is dependent on knowing whether the cause is biological in nature or the result of environmental factors and compromised root systems. More information about how and why MWVD occurs will assist management.
Cover crops in the Brassica family release a biofumigant (thiocyanate) upon degradation in the soil. For this reason, Brassicas have been used for management of soil borne diseases (Managing Cover Crops Profitably, 3rd edition, SARE). Experiments conducted here were designed to determine whether watermelon benefit from using canola as a cover crop to reduce the severity of MWVD.
Biological inoculants are products containing live microorganisms and are used for pest management and/or to increase nutrient up-take and other benefits. Growers have long wondered if such products have the capacity to add back to the soil some of those properties that human cultivation has taken away. Several such products were used in these trials for possible management of MWVD.
- Determine whether the cause of MWVD is biological in nature.
Determine the efficacy of cover crops and biological inoculants in the management of MWVD.
Communicate the results to stakeholders