In glasshouses practising monoculture of butterhead lettuce in Belgium, high densities of pin nematodes (Paratylenchus spp.) are frequently associated with reduced plant growth. Growers currently apply chemical soil disinfestation measures to manage this problem, although stricter phytosanitary regulations are forcing a shift towards integrated management. Efficient implementation of such management requires knowledge about the factors influencing nematode population dynamics, and the damage threshold for lettuce. The nematode populations in five Belgian glasshouses were monitored for at least 1 year by frequently soil sampling at 0–30 cm and 30–60 cm depth. An undescribed species of Paratylenchus was identified in all glasshouses based on morphological and molecular features. High nematode densities (>20,000 (100 ml soil)⁻¹) occurred in winter and spring. Chemical soil disinfestation lowered these populations greatly, although up to 14% survived in the deeper soil layer. After soil steaming under negative pressure, no pin nematodes were found. After 2 months of black fallow pin nematode densities were reduced by 50%–76%. Lamb's lettuce, parsley and wild rocket were found to be poor hosts in a pot experiment, while reproduction factors (P_f/P_i) on lettuce cultivars varied between 1 and 3. In three experiments with butterhead lettuce ‘Cosmopolia’ in pots with a series of 9 or 10 densities of Paratylenchus sp. [up to 35,000 (100 ml soil)⁻¹], no damage to lettuce heads was observed. However, root weight and root quality were reduced, and the corresponding damage thresholds were rather low [1,754 and 362 Paratylenchus sp. (100 ml soil)⁻¹, respectively]. Management strategies such as crop rotation, soil disinfestation or fallow are recommended to avoid pin nematode population build‐up.

中文翻译：

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深入研究Paratylenchus sp。在温室生菜中：特征，种群动态，寄主植物和破坏阈值是其综合管理的关键

在比利时从事油头莴苣单一栽培的温室中，高密度的线虫（Paratylenchus spp。）常常与植物生长减慢有关。尽管更严格的植物检疫法规正迫使人们朝着综合管理的方向发展，但种植者目前仍采用化学土壤杀虫措施来解决这一问题。有效实施此类管理需要了解影响线虫种群动态的因素以及生菜的危害阈值。通过频繁在0–30 cm和30–60 cm深度进行土壤采样，对五个比利时温室的线虫种群进行了至少1年的监测。副伤寒物种根据形态和分子特征在所有温室中被鉴定出来。冬季和春季出现高线虫密度（> 20,000（100 ml土壤）^-1）。化学杀虫剂大大降低了这些种群，尽管在更深的土壤层中存活了多达14％的种群。在负压下蒸煮土壤后，未发现针状线虫。经过两个月的黑色休憩针线虫密度降低了50％–76％。在盆栽实验中发现羔羊的生菜，欧芹和野菜是不良的寄主，而生菜品种的繁殖因子（P _f / P _i）在1到3之间变化。在三个试验中，使用黑头莴苣'Cosmopolia'的盆栽实验系列的9或10密度的副伤寒sp。[至多35,000（100ml土壤）^-1 ]，未观察到生菜头的损坏。但是，根重和根质量降低了，相应的损伤阈值也很低[1,754和362 Paratylenchus sp.。（分别为100 ml土壤^-1）]。建议采取作物轮作，土壤除草或休耕等管理策略，以避免针状线虫种群的增加。