Abstract:
Onion is an important cash crop in Sri Lanka Among the onion varieties, small onion is
mostly cultivated by farmers in Jaffna because it gives high profit. Even though, pests and diseases
are the major limiting factors. Among the onion pests; stem bulb nematode and bulb mite
reported as very important and management is very difficult and mainly depend on chemicals.
Therefore, a research was aimed to evaluate the effects of different green leaf manures on the
population of Ditylenchus dipsaci and Rhizoglyphus spp in the onion. A nematode infected farmer
field was selected for the field trial. Well prepared land was treated with different green leaf
manures such as Gliricidia maculate, Calotropis gigantia, Glycosmis pentaphylla, Thespesia
populnea and Azadiracta indica and allowed for fifteen days for complete decomposition. Onion
bulbs were planted. Onion bulb samples were collected weekly and analyzed for nematode and mite
population by using stereomicroscope in the laboratory. The results showed that G. maculate
reduced the nematode population in significant amount from second to sixth week in the onion
bulbs. Mite population was also reduced in significant amount by the G. maculate from second to
sixth week in the onion bulbs. C. gigantia, T. populnea and A. indica showed considerable reduction
in nematode and mite population.
