Population dynamics and damage potential of the root-lesion nematode, Pratylenchus bolivianus, on Alstroemeria

In a 40-week pot experiment, population development and reproduction of Pratylenchus bolivianus on Alstroemeria cv. Jubilee were investigated. Thirty-two weeks after planting in soil initially infested with 24 P. bolivianus/ 100 cm 3 soil, nematode populations in subterranean plant parts and soil reached maxima of 3,350/10 g and 266/ 100 cm 3 , respectively, giving an overall reproduction factor of x59. In a 2-year pot experiment, population development, reproduction and crop damage were investigated in relation to four initial inoculum levels (Pi): 0, 24, 1 19 and 468 nematodcs/ 100 cm 3 soil. After two years the lateral roots of the infested treatments contained about 20,000 P. bolivianus/10 g and the soils of Pi=24, 119 and 468 were infested with 299, 485 and 1,284 P. bolivianus/ 100 cm 3 and resulted in reproduction factors of ×97.1, ×23.8 and ×3.4, respectively. All infested treatments affected root growth and flower production, with reductions in root weight, number of flowers, weight/flower, length of flower stem and weight/cm of flower stem ranging from 18-75%, 8-17%, 16-22%, 10-13% and 10-17%, respectively. The greatest reductions were found in the treatment with the highest Pi. Although P. bolivianus caused modcrate yield losses, the damage threshold density is less than 24 P. bolivianus/100 cm 3 soil at planting. No specific leaf symptoms were noticed, but lesions on subterrancan stem parts were related to infection with P. bolivianus.