Interaction of Pratylenchus Penetrans and Fusarium Oxysporum Forma Pisi Race 2 and of Rotylenchus Uniformis and F. Oxysporum F. Pisi Race 1 On Peas

Abstract

Wilting of peas, var. 'Rondo', caused by Fusarium oxysporum forma pisi race 2 was enhanced by Pratylenchus penetrans attack at an initial density of this nematode of about 500 or more nematodes per 500 g soil. Some wilting occurred in the absence of the nematode but none at any nematode density in the absence of the fungus. P. penetrans alone possibly reduced stem and seed weight at initial densities exceeding 20,000 nematodes per 500 g soil. P. penetrans + Fusarium did not reduce stem weight but reduced seed weight below that which occurred at smaller initial densities at about 500 and more nematodes per 500 g soil. Seed weight in pots with P. penetrans + Fusarium at 0 to 500 nematodes per 500 g soil was about 80% of that at the same nematode densities in pots without Fusarium. The presence of the fungus probably reduced the rate of multiplication of P. penetrans at all initial densities of this nematode. Rates of multiplication at high initial densities indicate that the attack by the nematodes reduced the quantity of food available to them by damaging the roots. This damage was not reflected in the weight of the above-ground parts of the plants. At low initial densities the rate of multiplication of the nematode was reduced because of underpopulation. The rate of multiplication of Rotylenchus uniformis on pea (var. 'Rondo') was increased by the presence of F. oxysporum forma pisi race 1.