The bean leaf beetle (BLB) (Ootheca spp.) is a polyphagous pest causing significant yield losses in Uganda, particularly in the Northern and Eastern regions on various hosts plants. Despite its polyphagous behaviour, the BLB exhibits preferential feeding, offering an opportunity for targeted pest management. This study explored its feeding preferences across seven crops: common bean, cowpea, greengram, okra, roselle (malakwang), groundnuts, and soybean. This study was conducted in Arua and Lira districts using a randomized complete block design for two rainy seasons (2018A and 2018B). The results showed significant differences in BLB abundance and foliar damage among host crops, locations, days after planting and seasons. Cowpea was the most preferred crop while groundnuts was the least preferred. Therefore, cowpea can be recommended for use as a trap for managing Ootheca spp. in gardens where it is not the main crop. There was a higher pest abundance in Arua than in Lira. There was also a higher pest abundance in 2018A than in 2018B. These findings highlight the importance of understanding BLB’s feeding preferences for implementing effective IPM strategies, emphasizing the potential role of trap cropping, especially with cowpea, to minimize BLB damage in resource-constrained agricultural settings.

Bean leaf beetles (BLBs) (Ootheca spp.) are serious legume pests in Uganda and sub-Saharan Africa, but their ecology is not well understood. We planted host plants, viz., common bean, cowpea, and soybean, in an experiment in the hotspot areas of Arua and Lira districts in Northern Uganda in order to assess their influence on the density of adults and immature stages of BLBs in different seasons. Overall, the number of adults, larvae, and pupae were higher in cowpea than common bean and soybean plots. The number of adults were highest in cowpea (29.5 adults/15 plants) in Arua during the long rainy season (2018A). The number of adults did not differ significantly during short rains (season B) in 2017 and 2018. Similarly, in Lira district, the highest number of adult BLBs was in cowpea (4.6 beetles) compared to the common bean (2.7 beetles) and soybean plots, with a peak at four weeks after planting (WAP). During 2018A, larvae of BLBs first appeared at five WAP and seven WAP and peaked at 13 WAP and 11 WAP in Arua and Lira, respectively. The pupae were present in the soil after the harvesting of crops during 2018A, but peaked at seven WAP and eight WAP in 2018B season in Arua and Lira, respectively. The occurrence of below-ground adults in 2018B followed the peak abundance of pupae, although this was delayed until six WAP in Arua compared to Lira. We conclude that cowpea is the most preferred by adults and larvae compared to common bean and soybean. Similarly, the first rain season (2018A) attracted higher abundance and damage than the second rain season. Management of the BLBs should thus take into consideration avoidance of host crop rotation and dealing with the below-ground stages.

Common bean (Phaseolus vulgaris L.) is a major source of food and income for people in sub Saharan Africa. Attack by Bean Leaf Beetles (Ootheca spp. Chev.) is one of the major causes of yield loss to the crop, causing up to 48.9% grain yield loss. Despite the damage, there is limited information on the biology, including preferred oviposition sites and development, of Ootheca spp. This information provides strategic entry points to potential control interventions. The objective of this study was to investigate the oviposition and development duration of O. mutabilis, which is the most abundant and damaging species of Ootheca on common bean in Uganda. A screenhouse study was conducted during 2019, using the common bean variety, NABE 16. Parameters monitored included type of oviposition sites, egg cluster size, and morphological changes and development duration for each stage. The beetles preferred to lay clustered eggs than singly, and oviposited in crevices or cover surface, and near plant stalks or roots, which protects the eggs and ensuring the neonates easily find their food. Development of O. mutabilis took 120 days with the larval stage lasting the longest; followed by pupae and eggs at 75, 24 and 22 days, respectively. This long biological cycle of the beetle goes beyond that of most common bean varieties of the bush type, implying that juvenile stages of the beetles remain in the soil after bean harvest. As a management strategy, we recommend rotation with non-host crops such as maize in order to break the biological cycle of the beetles, and open tillage to expose the beetles in the soil to extreme weather and natural enemies. Further studies will be needed on the fertility, longevity and diapause mechanisms.