Water hyacinth, Eichhornia crassipes (Mart.) Solms (Commelinales: Pontederiaceae), is an important aquatic weed worldwide. Previous studies demonstrate that releases of Neochetina bruchi Hustache (Coleoptera: Curculionidae) provide biological control in many locations, but not all. Notably, N. bruchi were unsuccessful at regulating water hyacinth in tidal brackish waters. Abiotic factors, including salinity and nutrients, affect water hyacinth growth, but little is known about the impact of salinity on weevil survival. We hypothesized that N. bruchi has a relatively low salinity tolerance. In a mesocosm experiment, we assessed weed growth in response to a range of salinity and nutrient concentrations. In a laboratory, we assessed adult N. bruchi mortality in response to various salinity concentrations. Results indicate that increasing nutrient concentration increases weed growth. When both nutrient and salinity levels were varied, nutrients increased leaf count, but not biomass, while salinity reduced growth and increased mortality. Increasing salinity concentrations increased adult weevil mortality; required concentrations were higher than that for weeds. Thus, these results did not provide support for the suggested hypothesis. Potential effects of salinity via other exposures to weevils need to be investigated. Elucidating abiotic factors important for weed growth and weevil survival may increase effectiveness of water hyacinth management practices.

中文翻译：

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盐度和养分对水葫芦及其生物防治剂 Neochetina bruchi 的影响

水葫芦，Eichhornia crassipes (Mart.) Solms (Commelinales: Pontederiaceae)，是世界范围内重要的水生杂草。以前的研究表明，Neochetina bruchi Hustache（鞘翅目： Curculionidae）的释放在许多地方提供了生物控制，但不是全部。值得注意的是，N. bruchi 在调节潮汐微咸水中的水葫芦方面没有成功。非生物因素，包括盐度和营养物，会影响水葫芦的生长，但人们对盐度对象鼻虫生存的影响知之甚少。我们假设 N. bruchi 具有相对较低的盐度耐受性。在中观实验中，我们评估了杂草生长对一系列盐度和营养浓度的反应。在实验室中，我们评估了不同盐度浓度下成年布鲁氏猪笼草的死亡率。结果表明，增加养分浓度会增加杂草的生长。当养分和盐度水平发生变化时，养分会增加叶数，但不会增加生物量，而盐度会降低生长并增加死亡率。增加盐度浓度会增加成虫的死亡率；所需浓度高于杂草。因此，这些结果没有为建议的假设提供支持。需要调查盐分通过其他暴露于象鼻虫的潜在影响。阐明对杂草生长和象鼻虫存活很重要的非生物因素可能会提高水葫芦管理实践的有效性。增加盐度浓度会增加成虫的死亡率；所需浓度高于杂草。因此，这些结果没有为建议的假设提供支持。需要调查盐分通过其他暴露于象鼻虫的潜在影响。阐明对杂草生长和象鼻虫存活很重要的非生物因素可能会提高水葫芦管理实践的有效性。增加盐度浓度会增加成虫的死亡率；所需浓度高于杂草。因此，这些结果没有为建议的假设提供支持。需要调查盐分通过其他暴露于象鼻虫的潜在影响。阐明对杂草生长和象鼻虫存活很重要的非生物因素可能会提高水葫芦管理实践的有效性。