IN VITRO STUDIES IN TO THE EFFICACY OF CITRUS PEELS (ORANGE, LEMON AND GRAPE) CONTROL OF THE ROOT-KNOT NEMATODES
ABSTRACT
The extracts of fresh peels of lemon, orange, and grapefruit showed significant nematostatic effect against M. incognita second stage juveniles after 48 h treatment. The nemticidal activity was very low in all the extracts of fresh peels but was greatly enhanced in the extracts of stored pulpified peels with 90.8 %, 93.5 %, and 85.0 % mortality of nematodes for lemon, orange, and grapefruit,
respectively. The data indicated the possibility of essential oils from the citrus peels might have released in the extracts during storage of the pulpified peels. The egg hatch inhibition of the extracts from stored pulpified peels was 85.7 %, 91.0 %, and 78.3 % for lemon, orange, and grapefruit, respectively. The reversible tests revealed that the effect of extracts on the hatch of eggs was not permanent. The hatching partially resumed after the removal of the extracts but was still significantly lower than the control. The infection of M. in cognita second stage juveniles on mung bean roots was significantly inhibited by the extracts of the refrigerator-stored pulpified peels of lemon, orange, and grapefruit. The findings provide an alternative to chemical nematicides for organic farming and help the disposal of citrus juice processing waste as well as the fallen fruits in the orchards in the typhoon season.
CHAPTER ONE
Introduction
1.1 Nematodes
Nematodes are a diverse group of worm-like animals. They are found in virtually every environment, both as parasites and as free-living organisms. They are generally minute, but some species can reach several meters in length. This topic focuses specifically on plant parasitic nematodes, which are very small or microscopic, can cause significant damage to crops, and are extremely widespread (Agrios, 2005). Because nematodes are difficult or impossible to see in the field, and their symptoms are often non-specific, the damage they inflict is often attributed to other more visible causes. Farmers and researchers alike often underestimate
