Bock C H, Parker P E, Gottwald T R
USDA-ARS-USHRL, 2001 S. Rock Rd., Ft. Pierce, FL 34945.
Center for Plant Health Science and Technology Pest Detection Diagnostics and Management Laboratory, USDA-APHIS, Moore Air Base, Edinburg, TX 78541.
Plant Dis. 2005 Jan;89(1):71-80. doi: 10.1094/PD-89-0071.
Dynamics of dispersal of the bacteria that causes citrus canker (Xanthomonas axonopodis pv. citri) were assessed in simulated wind-driven rain splash. The wind/rain-splash events were simulated using electric blowers to generate turbulent wind (15 to 20 m s) and sprayer nozzles to produce water droplets entrained in the wind flow. The splash was blown at an inoculum source of canker-infected trees 1 m downwind. The splash downwind of the source of the infected trees was collected by vertical panel samplers and funnel samplers. The duration over which bacteria were dispersed in spray was assessed in continuous wind at intervals from 0 to 52 h after commencing the simulated rain splash event. In one experiment on 11 February 2003, a total of 1.48 × 10 bacteria were collected by panels 1 m downwind from the inoculum source during the first 10 min of dispersal, but the numbers declined to 3.60 × 10 bacteria after 1 h and ranged between 1.42 × 10 and 1.93 × 10 up to 52 h. In a more detailed study (15 July 2003) of dispersal duration over 4 h, the greatest quantity of bacteria collected by panel samplers were dispersed in the first 5-min period (1.01 × 10 bacteria collected). By 10 min after initiation of dispersal, approximately one-third (3.09 × 10 bacteria collected) of the initial number was being dispersed, and by the end of the first hour, only one-tenth (1.31 × 10 bacteria collected) of the initial quantity was dispersed. Funnel samplers placed at ground level under the trees showed a similar trend. The distance to which bacteria were dispersed in wind-blown splash was also tested under simulated conditions: on 18 September 2003, bacteria were collected by panel samplers at all distances sampled (1, 2, 4, 6, 8, 10, and 12 m) with the greatest number of bacteria deposited at 1 m (4.93 × 10 bacteria collected), while 2.22 × 10 bacteria were deposited over a 10-min period 12 m from the inoculum source. Wind speed declined from 19.5 m s upwind of the trees to 2.8 m s 1 m downwind, and by 4 m downwind from the inoculum source, movement was similar to the surrounding air. The data on duration and distance of dispersal were best described by power law regression models compared to exponential models. Citrus canker is readily dispersed in wind-driven rain and is dispersed in large quantities immediately after the stimulus occurs, upon which wind-driven splash can disperse inoculum over a prolonged period and over a substantial distance.
在模拟的风雨溅射中评估了引起柑橘溃疡病的细菌（柑橘溃疡病菌）的传播动态。使用电动吹风机产生湍流风（15至20米/秒），并通过喷雾器喷嘴产生夹带在风流中的水滴来模拟风雨溅射事件。将溅射物吹向溃疡病感染树木的接种源，该接种源位于下风向1米处。通过垂直平板采样器和漏斗采样器收集感染树木源下风向的溅射物。在开始模拟降雨溅射事件后的0至52小时内，以连续的风速评估细菌在喷雾中传播的持续时间。在2003年2月11日的一项实验中，在下风向1米处的平板采样器在传播的前10分钟内共收集到1.48×10⁶个细菌，但数量在1小时后降至3.60×10⁵个细菌，并且在长达52小时的时间内数量在1.42×10⁴至1.93×10⁵之间。在一项更详细的关于4小时传播持续时间的研究（2003年7月15日）中，平板采样器收集到的细菌数量在最初的5分钟内最多（收集到1.01×10⁶个细菌）。在传播开始后10分钟，初始数量的大约三分之一（收集到3.09×10⁵个细菌）正在传播，到第一小时结束时，仅初始数量的十分之一（收集到1.31×10⁴个细菌）被传播。放置在树下地面的漏斗采样器显示出类似的趋势。在模拟条件下还测试了细菌在风雨溅射中传播的距离：在2003年9月18日，在所有采样距离（1、2、4、6、8、10和12米）处通过平板采样器收集到细菌，在1米处沉积的细菌数量最多（收集到4.93×10⁶个细菌），而在距离接种源12米处的10分钟内沉积了2.22×10⁵个细菌。风速从树木上风向的19.5米/秒下降到下风向1米处的2.8米/秒，并且在距离接种源下风向4米处，气流运动与周围空气相似。与指数模型相比，幂律回归模型最能描述传播持续时间和距离的数据。柑橘溃疡病菌很容易在风雨溅射中传播，并且在刺激发生后立即大量传播，在此之后，风雨溅射可以在很长一段时间内和相当远的距离内传播接种体。
