Kalyebi Andrew, Macfadyen Sarina, Hulthen Andrew, Ocitti Patrick, Jacomb Frances, Tay Wee Tek, Colvin John, De Barro Paul
National Crops Resources Research Institute, P.O. Box 7084, Kampala, Uganda.
Mikocheni Agricultural Institute, Dares Salaam 6226, Tanzania.
Insects. 2021 Mar 22;12(3):269. doi: 10.3390/insects12030269.
Cassava ( Crantz), an important commercial and food security crop in East and Central Africa, continues to be adversely affected by the whitefly . In Uganda, changes in smallholder farming landscapes due to crop rotations can impact pest populations but how these changes affect pest outbreak risk is unknown. We investigated how seasonal changes in land-use have affected population dynamics and its parasitoids. We used a large-scale field experiment to standardize the focal field in terms of cassava age and cultivar, then measured how populations responded to surrounding land-use change. Sub-Saharan Africa 1 (SSA1) was identified using molecular diagnostics as the most prevalent species and the same species was also found on surrounding soybean, groundnut, and sesame crops. We found that an increase in the area of cassava in the 3-7-month age range in the landscape resulted in an increase in the abundance of the SSA1 on cassava. There was a negative relationship between the extent of non-crop vegetation in the landscape and parasitism of nymphs suggesting that these parasitoids do not rely on resources in the non-crop patches. The highest abundance of SSA1 nymphs in cassava fields occurred at times when landscapes had large areas of weeds, low to moderate areas of maize, and low areas of banana. Our results can guide the development of land-use strategies that smallholder farmers can employ to manage these pests.
木薯（克兰茨）是东非和中非一种重要的商业和粮食安全作物，持续受到粉虱的不利影响。在乌干达，由于作物轮作导致的小农耕作景观变化会影响害虫种群，但这些变化如何影响害虫爆发风险尚不清楚。我们调查了土地利用的季节性变化如何影响粉虱种群动态及其寄生蜂。我们进行了一项大规模田间试验，以使目标田块在木薯年龄和品种方面标准化，然后测量粉虱种群对周围土地利用变化的反应。通过分子诊断确定撒哈拉以南非洲1号（SSA1）是最普遍的物种，在周围的大豆、花生和芝麻作物上也发现了相同的物种。我们发现，景观中3至7个月龄木薯面积的增加导致木薯上SSA1数量的增加。景观中非作物植被的范围与若虫的寄生率之间存在负相关关系，这表明这些寄生蜂不依赖非作物斑块中的资源。木薯田中SSA1若虫数量最多的时候，是景观中有大面积杂草、中低面积玉米和低面积香蕉的时候。我们的研究结果可为小农户管理这些害虫时可采用的土地利用策略制定提供指导。
