ABSTRACT Invasion from giant salvinia (Salvinia molesta Mitchell, Salviniaceae) blocks sunlight entering waterbodies, reducing submerged aquatic macrophytes, thus lowering dissolved oxygen and stressing aquatic organisms. Due to its rapid growth and ease of dispersal through fragmentation, giant salvinia can quickly become problematic and difficult to eradicate. Since invasion of giant salvinia is persistent, land managers need a cost-effective method of control. Biological control by the salvinia weevil (Cyrtobagous salviniae Calder and Sands, Coleoptera: Curculionidae) has proven successful in controlling giant salvinia, and at a fraction of the cost of chemical and mechanical control. To maintain a source of salvinia weevils for field releases, mass rearing in outdoor ponds by natural resource managers is common practice in tropical regions. Using number of freezing hours and degree-day calculator, we examined how winter and spring conditions impacted the production of weevils in mass rearing ponds across southern Louisiana, USA. We found that winter temperature determined adult weevil mortality while spring temperature dictated reproduction, larval appearance, and timing of pond harvest. During winters with <55 h of freezing temperatures, ponds maintained densities of at least 13 adult salvinia weevils kg−1. Winter with >200 hours of freezing temperature reduced adult density in the ponds nearly extirpating the population. Larvae were found on samples on average at 89 degree-days which began accumulating in January 1st. This study suggested that winter and spring conditions are critical for mass rearing operations and population growth of C. salviniae.

中文翻译：

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冬季和春季条件决定了丹参象甲大规模饲养计划的产量

摘要 巨型丹参（Salviniamoleta Mitchell，Salviniaceae）的入侵阻止阳光进入水体，减少沉水水生植物，从而降低溶解氧和压力水生生物。由于其快速增长和易于通过破碎分散，巨型丹参很快就会出现问题并且难以根除。由于巨型丹参的入侵持续存在，土地管理者需要一种具有成本效益的控制方法。丹参象鼻虫（Cyrtobagous salviniae Calder and Sands, Coleoptera: Curculionidae）的生物控制已被证明在控制巨型丹参方面是成功的，而且成本只是化学和机械控制的一小部分。为了维持用于田间释放的丹参象鼻虫的来源，自然资源管理者在室外池塘大规模饲养是热带地区的常见做法。我们使用冻结小时数和度数日计算器，研究了冬季和春季条件如何影响美国路易斯安那州南部大规模养殖池塘中象鼻虫的产量。我们发现冬季温度决定了象鼻虫的成虫死亡率，而春季温度则决定了繁殖、幼虫外观和池塘收获的时间。在冰点温度 <55 小时的冬季，池塘保持至少 13 只成年丹参象鼻虫 kg-1 的密度。冬季超过 200 小时的冰冻温度降低了池塘中的成鱼密度，几乎使种群灭绝。幼虫在 1 月 1 日开始积累的平均温度为 89 度日时被发现。该研究表明，冬季和春季条件对丹参的大规模饲养作业和种群增长至关重要。