An ecological study of a nematode complex in a Florida citrus grove

Abstract

The presence of ectoparasitic nematodes in citrus groves is rarely apparent in any symptoms in the trees aboveground. The role of the ectoparasitic nematodes in tree decline is difficult to assess and, so far, little is known about the tolerance of citrus to them. A citrus grove naturally infested with an ectoparasitic nematode complex, including Belonolaimus longicaudatus Rau, was pulled out and used to evaluate preplant fumigation. Increased tree growth and significantly higher fruit yields were observed for five crop seasons (Bistline et al., 1967). Pratylenchus brachyurus (Godfrey) Filipjev et Schuurmans-Stekhoven, a migratory endoparasitic nematode, is widespread in Florida citrus (Feldmesser et al., 1956); however, the population density in roots rarely exceeds 100 nematodes per g fresh root-weight, indicating that citrus is a poor host. Results from a chemical control experiment in a citrus grove naturally infested with P. brachyurus have shown that nematode control induced a tree response in young trees, whereas mature trees were less severely affected, as damage decreased with plant growth (O'Bannon et al., 1974). This paper reports our findings on seasonal population variation of several nematode genera associated with citrus roots in a 50-year-old established citrus grove.