Plant Parasitic Nematodes Associated with Longan Decline

Abstract

Plant parasitic nematode populations were observed in three types of longan orchard conditions. They were classified as flooded lowland when receiving heavy amount of rainfall, normal land without flooding and highland commonly obtained insufficient amount of water during dry period. Soil samples of 1-5 points of 500 grams each were randomly collected in the vicinities of longan canopies of normal and declined trees in 10 selected orchards in Chiang Mai and Lam Phun areas. Ten plant parasitic nematode species with varying in numbers were obtained in all types of orchard conditions. The four most prevalent species were comprised of Rotylenchulus reniformis, Macroposthonia sp., Tylenchorhynchus sp. and Helicotylenchus sp. As a high number of Rotylenchulus reniformis were detected in declined orchards, it was presumed that this species of nematode might be directly involved with longan decline or acted together with other factors to cause complex declined symptoms. Further study on the Rotylenchulus reniformis nematode in relation with longan decline should be carried out.