Abstract Cassava brown streak disease (CBSD) is arguably the most dangerous current threat to cassava, which is Africa's most important food security crop. CBSD is caused by two RNA viruses: Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV). The roles of the whitefly Bemisia tabaci (Gennadius) and farmer practices in the spread of CBSD were investigated in a set of field and laboratory experiments. The virus was acquired and transmitted by B. tabaci within a short time (5–10 min each for virus acquisition and inoculation), and was retained for up to 48 hr. Highest virus transmission (60%) was achieved using 20–25 suspected viruliferous whiteflies per plant that were given acquisition and inoculation periods of 24 and 48 hr, respectively. Experiments mimicking the agronomic practices of cassava leaf picking or the use of contaminated tools for making cassava stem cuttings did not show the transmission of CBSV or UCBSV. Screenhouse and field experiments in Tanzania showed that the spread of CBSD next to spreader rows was high, and that the rate of spread decreased with increasing distance from the source of inoculum. The disease spread in the field up to a maximum of 17 m in a cropping season. These results collectively confirm that CBSV and UCBSV are transmitted by B. tabaci semipersistently, but for only short distances in the field. This implies that spread over longer distances is due to movements of infected stem cuttings used for planting material. These findings have important implications for developing appropriate management strategies for CBSD.

中文翻译：

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粉虱、粉虱 (Gennadius) 和农民实践在木薯褐色条纹 ipomoviruses 传播中的作用

摘要 木薯褐条病 (CBSD) 可以说是目前对木薯最危险的威胁，木薯是非洲最重要的粮食安全作物。CBSD 由两种 RNA 病毒引起：木薯褐色条纹病毒 (CBSV) 和乌干达木薯褐色条纹病毒 (UCBSV)。在一组田间和实验室实验中研究了粉虱 Bemisia tabaci (Gennadius) 和农民实践在 CBSD 传播中的作用。病毒在短时间内由烟粉虱获得并传播（病毒获得和接种各 5-10 分钟），并保留长达 48 小时。最高的病毒传播 (60%) 是使用每株植物 20-25 只疑似带毒粉虱实现的，这些粉虱的采集和接种时间分别为 24 小时和 48 小时。模仿木薯叶采摘或使用受污染工具制作木薯茎插条的农艺实践的实验并未显示 CBSV 或 UCBSV 的传播。坦桑尼亚的筛网和田间试验表明，CBSD 在撒布机行旁边的传播很高，并且传播速度随着距接种源距离的增加而降低。该病害在田间蔓延，在一个作物季节最大可达 17 m。这些结果共同证实了 CBSV 和 UCBSV 是由烟粉虱半持久性传播的，但仅在田间短距离传播。这意味着更远距离的传播是由于用于种植材料的受感染茎插条的移动。这些发现对于为 CBSD 制定适当的管理策略具有重要意义。