Aspects of the Biology of Pratylenchus Brachyurus and P. Zeae

Abstract

Vertical migration of P. bracbyurus and P. zeae was best between 15° and 35°: P. brachyurus moved fastest in coarse particled sand and P. zeae faster in a finer particled sand than P. brachyurus. P. zeae developed faster than P. brachyurus at all temperatures tested: both species developed fastest at 30° and 35°, one generation in P. zeae taking 3 weeks, and 4 weeks in P. brachyurus. Reproduction of both P. brachyurus and P. zeae was greatest at 30°. More P. zeae invaded roots at all inoculum levels than P. brachyurus. Both P. brachyurus and P. zeae occupied all parts of excised maize roots, including the stele. Cavities were formed in the cortex with little accompanying necrosis and in the stele with much, including the deposition of a dense staining substance that occluded xylem vessels and phloem tissues. P. zeae caused more mechanical damage but less necrosis than P. brachyurus, which also greatly decreased the growth of excised maize roots.