The nematode Pratylenchus brachyurus is considered to be pathogenic on cotton; however, there are few reports documenting the response of cotton to infection. This study determined the reproductive potential of P. brachyurus on cotton and the response of cotton to infection by the nematode.

In greenhouse tests the nematode reproduction index (RI = final nematode population/initial nematode population) was less than 1.0 an 'TAMCOT SP3', 'Rowden', 'Lankart LX571', and 'Stoneville 213' eight weeks after inoculation. When TAMCOT SP37 seedlings were inoculated with 1000, 2000, 4000, 8000, or 16000 nematodes per seedling, fresh weight of roots after six weeks was suppressed. Root weight was correlated with the initial inoculum level (r = 0.79, P = 0.05). No significant correlation was observed between nematode inoculum levels and shoot weights although the highest nematode inoculum level did suppress shoot growth as compared to the noninoculated controls. Nematode invasion of cotton roots resulted in the development of necrotic root lesions. In microplot tests the RI for P. brachyurus on TAMCOT SP37 was 1.5 with initial populations of 18 nematodes per 100 cm³; at higher initial nematode populations the RI was reduced. No suppression of seed cotton yields, was observed with initial populations of 54 nematodes per 100 cm³ soil.

These data suggest that cotton is a poor host for brachyurus but that at high initial nematode population densities some growth suppression of cotton may result.