Amaranthus palmeri S. Watson is a competitive weed native to North America with many herbicide-resistant biotypes that have been spreading around the world. Due to its fast growth, farmers need to optimise control timing to reduce the risk of escapes. This study tracked A. palmeri emergence and phenology using days or growing degree days (GDD, T_base = 15°C; thermal time or hydrothermal time). While A. palmeri has been observed emerging throughout the summer growing season, this study found that 90% of total season A. palmeri emerged before July in the absence of a crop canopy. Using thermal time, emergence could be predicted in different locations and years: reaching 10%, 50% and 90% at 77, 278 and 593 GDD from January 1, respectively. From the time of emergence, 10% of A. palmeri were 10 cm tall after 148 GDD, showed first signs of inflorescence by 212 GDD, and open florets by 419 GDD. Also, 50% of A. palmeri plants had reached the respective stages by 244, 394 and 796 GDD. Using the probability of A. palmeri to reach different phenological stages over time as a function of emergence prediction, critical control windows were determined based on thresholds for risk of escapes. Many tactics and times of action are important for managing this weed. Information about A. palmeri biology indicates these actions could be timed more effectively using weather data and predictive models.

中文翻译：

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使用出现和物候模型控制掌palm菜（Amaranthus palmeri）的作用窗口

Amaranthus palmeri S. Watson是北美洲的一种竞争性杂草，具有许多抗除草剂生物型，已在世界范围内传播。由于其快速增长，农民需要优化控制时机以减少逃生的风险。这项研究使用天数或生长度数天（GDD，T_基准 = 15°C；热时间或热液时间）跟踪了棕榈棕榈的出现和物候。虽然已观察到整个棕榈科植物在整个夏季生长，但这项研究发现，整个棕榈科植物的90％在没有作物冠层的情况下出现在7月之前。使用热时间，可以预测不同地点和年份的出现：从1月1日起分别达到77、278和593 GDD的10％，50％和90％。从出苗之时起，148 GDD后10％的A. palmeri高，在212 GDD时显示出第一个花序征兆，在419 GDD时显示出小花。而且，到244、394和796 GDD时，有50％的棕榈棕榈植物已经达到了相应的阶段。使用随时间变化的棕榈果树的出现概率来预测出不同的物候阶段，根据逃生风险的阈值确定关键控制窗口。许多策略和行动时间对于控制这种杂草很重要。相关信息A. palmeri生物学表明，使用天气数据和预测模型可以更有效地计时这些动作。