2. Use Urea fertilizer instead of Sulphate of Ammonia, to supply plants with nitrogen. This helps to delay increased soil acidity which helps the development of the fungus.
In Jamaica, watermelon and other melons (Canteloupe, Honeydew etc.) are grown largely on the southern plains of St. Elizabeth and Manchester. Over the years, farmers in these areas have successfully developed systems to profitably produce these crops, which represent a major source of income to them.
Several pests affect the crop but farmers have successfully managed these, using mainly pesticides. In recent years, however, one pest has caused a serious disease problem in St. Elizabeth, as no chemical will arrest its development and spread. This resulted from continued replanting of these crops in the same fields each season, partly due to unavailable lands. It has highlighted the need for farmers to manage these and all crops, in a more balanced way. RADA promotes the use of Integrated Pest Management (IPM), now broadened to Integrated Crop/Pest Management (ICM/IPM). This approach helps farmers to avoid such problems: It allows sustainable, profitable farming, producing safe, wholesome food. At the same time it protects human health and the environment from harmful chemicals and environmental degradation.
The Disease
The disease, Fusarium Wilt, is caused by Races/strains of 3 pest fungi known as Fusarium, which are found in soils.
· Fusarium oxysporum niveum affects only watermelon.
· Fusarium oxysporum melonis affects only melons.
· Fusarium solani affects both and many other crops as well.
· The disease appears on plants scattered (singly or in patches) over the field.
· Seedlings may die early (seedling blight).
· Leaves on older plants become yellow and later wilt.At first, this usually happens to only one vine on the plants.
· Brown gummy droplets may ooze from affected vines.
· Some plants become stunted.
· Affected plants produce poorly.
· Over time, the entire plant wilts and dies, causing losses to the farmer.
· Planting these crops repeatedly in the same field causes a buildup of the fungus in the soil.
· Small infested spots in the field spread out each time these plants are grown there
· After a few years, the entire field gets infested. This has happened to several fields and now the crops can no longer be profitably grown in them.
· Too much rain or drought worsens the problem.
ICM/IPM manages the Fusarium wilt problem as follows:
1. Always practise crop rotation: Do not plant melon/watermelon after melon/watermelon. Instead, follow these crops with others which are not affected by the fungus. Guinea Grass, escallion, onion, peanut, cauliflower and several others may be used (check with your extension officer). Some farmers have done this with good results.
3. Check soil pH. If soil is too acid (pH less than 5.5) apply 375-500 kg/ha (3-4 cwt/ac) hydrated lime and mix well into the soil. Water is necessary for proper action. This treatment takes some time to act properly. After several months, test again and re-treat if necessary (check with your extension officer).
Farmers, seed suppliers, RADA and MinAg Plant Protection Research Section are working to find disease-resistantvarieties suited for the local conditions and other effective management practices. To this end, field observation plots have been established by two farmers. RADA and Plant Protection Research Section will establish two trial plots in March, in the major affected areas.
Field officers and the Plant Protection Unit in RADA , will continue to advise and train farmers in the affected areas.
References:
· Compendium of Cucurbit Diseases American Phytopathological Society, 1996.
· Identifying Diseases in Vegetables Pennsylvania State University, 1983.
· Fusarium wilt in muskmelons European Plant Protection Organization, 1994.
· Personal communication Vincent Campbell, MinAg Rural Physical Planning Div., 2002.