Vegetable production is an important sector of economy for farmers in Nepal. With 65.1 percentage of people engaged, agriculture contributes 31.23% to National Gross Domestic Product (GDP) where horticulture sub-sector has the most significant role sharing 21.42 percent. Vegetable production alone contributes around 9.71% to total Agricultural GDP. Vegetable farming has been widely adopted by the people across the country as a part of their employment. More than 55 different vegetable crops are being cultivated by people in Nepal.
Although Nepal has tremendous potential for commercial vegetable crops production due to agro-climatic diversity available here in different regions of the country, but the vegetable production has not been up to mark due to which we are forced to import huge tons of vegetable from our neighbouring country India every year and large amount of country's currency is being spent on importing those commodity. Among the various hindering factors of vegetable growers, one of the most damaging groups of plant nematodes called root knot nematodes of vegetables has been a serious problems and a threat to vegetable farmers.
Root-knot nematode, Meloidogyne spp. is a major obligate plant-parasitic nematode species affecting more than 200 plant species including vegetable, horticulture and woody plants. It has been a serious problems for vegetable growers all around Nepal. It can be easily found in our homegarden, rooftop farms, greenhouse, vegetables fields and in areas with warm or hot climate and short or mid-winter. These nematodes are affecting the quantity and quality of the vegetable production in many annual and perennial vegetable crops. Infected plants show typical symptoms including root galling, stunting and nutrient deficiency, particularly nitrogen deficiency.
Among the cultivated vegetables, tomato, eggplant, okra, radish, peppers, gourds and melons are highly susceptible to root knot nematode. Tomato and radish fall among the top five most grown vegetables in the country. In tomato and eggplant 20-40% loss is caused by root knot nematode which shows the condition is so alarming to farmer. This disease has not only reduced the yield of vegetables in the country but also has been responsible for increasing the severity of other diseases like wilt, damping off and root rot. So, the control of root knot is very important to enhance the overall productivity of vegetable sector.
As, most of the Nepalese farmer are poor and small land holder & farming practices here are typically diverted towards organic, the control of this disease through inorganic means can't be a long-term solution. Since, the chemical pesticides cause hazard to the biodiversity, the control of this disease with inorganic means is unsustainable and costlier as well. Looking at the future of soil, environment and the health of people, organic control measures for root knot of vegetable is only a way to go forward in Nepal. Some of the organic measures that can be applied to control and combat with root knot disease of vegetables in Nepal are:
* Clean cultivation practices should be followed while growing any vegetables in the field. Weed host should be eradicated from the vicinity of vegetable fields. Seedlings should be raised in nematode free nursery beds.
* Use of organic amendments i.e.use of oil cake sand saw dust @25qt/ha can be useful incontrolling root knotnematodes. Neemoilcanalso acts as a good organic amendments to the nematode in festeds oil.
* Intercropping the main vegetables crops with the antagonistic plants like marigold so that the root exudate produce alpha-terthienyl which acts asallelopathic effect for nematodere production.
* Soil solarization should be done in mid-summer by tightly covering the soil with a clear plastic and letting the soil to expose to the scorching sunlight for 4-5 weeks.
* Rotate the crop with non-host crop. Some green manure crops as well as cover crops such as mustard and rape, produce compounds that suppress root-knot nematodes.
* Use of resistant varieties like pusa ruby for tomato and pusa purple long for brinjal can be used to control root knot of nematodes.
* Flooding the field for more than one month helps creating anaerobic condition and destroy the nematodes eggs present in the soil.
* Incorporate the compost in the soil to enhance the biological activity of the soil as increase in organic matter in the soil helps to suppress root-knot nematode populations.
* Use leguminous plants as a trap crops to trap the root knot nematodes of fields into the roots of legumes before planting the main crops in the field.
* Biological control with bacterium Pasteuria penetrans, an obligate parasite of root knot nematode and soil fungal Paecilomyces liliacinus & application of different species of Trichoderma has been found efficient in controlling it.
* If you have any doubts about the infestation of root knot nematodes in your vegetable field, then dig up the suspected plants, wash soil off the roots and carefully inspect for swellings. If root-knot is strongly suspected have your soil tested and follow above organic control methods for it.
(Suman is a student of the “Institute of Agriculture and Animal Science” Collage)