Analysis of Crop Losses in Tomato Due to Pratylenchus penetrans


  • J. W. Potter
  • Th. H. A. Olthof


The effects of Pratylenchus penetrans upon yields of 'Veebrite' tomato were studied at initial soil population densities (P[subi]) of 360, 2,010, 4,580, and 14,360 nematodes/kg of soil in 20-cm (i.d.) clay-tile microplots. The lowest P[subi] appeared to stimulate fruit production. Higher P[subi]'s suppressed fruit production (total weight of marketable tomatoes and numbers of intermediate- and large-sized fruits), in comparison to control yields, the highest P[subi] resulted in 38% fewer fruits which weighed 44% less. These losses were at least partly due to a delay in fruit ripening, caused by the nematodes, which did not become apparent until the fourth week. Nematode populations in the soil increased at all but the highest P[subi]; final populations were around 7,000/kg of soil. Nematode populations in roots ranged from 230-590/gm of root at the completion of the experiment. Nematode control by fumigation would definitely be warranted at soil population densities of 2,000/kg or higher; with 500-2,000/kg, the decision to fumigate would depend on soil type and economic and hiological factors. Key Words: root-lesion nematodes, populations, Lycopersicon esculentum.