Effect of marigold (Tagetes patula) on population dynamics of Pratylenchus penetrans in a field

Abstract

AbstractThe effect of a sequence of host and non-host crops on the population dynamics of Pratylenchus penetrans was monitored for 2 years in a field. The sequence was pea (Pisum sativum, 25% cv. Colombia and 75% cv. Coca), French marigolds (Tagetes patula nana cv. Sparky); fallow; carrot (Daucus carota, cv. Amsterdamse bak); bean (Phaseolus vulgaris, cv. Avignon) and again fallow. Samples were taken every 21 days during the marigold crop and following fallow, and at planting and harvest for the other crops. From five 2 × 5 m2 plots, 15 cores were taken per plot to a depth of 70 cm and split into seven segments of 10 cm each. Within the plots, segments from corresponding depths were pooled and nematodes were estimated from a 200 g subsample. Densities of P. penetrans increased 2.2-fold under pea, but decreased by 90% after marigolds had been grown for 105 days. The P. penetrans population was reduced by about 90% in the soil layer above 40 cm while the reduction was about 80% below 50 cm after 105 days of marigold culture. Densities of P. penetrans declined exponentially in time under marigold and fallow. The effect of marigold was persistent as no increase in P. penetrans densities over the whole soil profile was noticed after two crop cycles of host plants.