title: Analysis of crop losses in tomato due to Pratylenchus penetrans.
abstract: The effects of Pratylenchus penetrans upon yields of 'Veebrite' tomato were studied at initial soil population densities (P(i)) of 360, 2,010, 4,580, and 14,360 nematodes/kg of soil in 20-cm (i.d.) clay-tile microplots. The lowest P(i) appeared to stimulate fruit production. Higher P(i)'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(i) 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(i); 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.
authors.forename: J W
authors.initials: JW
authors.lastname: Potter
authors.forename: T H
authors.initials: TH
authors.lastname: Olthof