Tomato is an important vegetable crop that is cultivated for the domestic market in Kenya and other East African countries. Thrips are one of the key pests hampering the production of tomato, both by direct damage to the crop and as vectors of tospoviruses. Field experiments were carried out over two planting times to evaluate the use of sticky traps for monitoring thrips infesting tomato in East Africa. Blue, yellow, and clear sticky traps with and without a thrips lure (Lurem-TR) were tested. Field observations for thrips catches on the sticky traps were made weekly until crop senescence. Sticky traps were replaced with new ones at each observation time. Additionally, both destructive and non-destructive samplings for thrips were done at each observation. Frankliniella schultzei (Trybom) and Ceratothripoides brunneus (Bagnall) were more attracted to blue than yellow traps. Frankliniella occidentalis (Pergande) attraction to blue and yellow traps was not distinctive. The addition of Lurem-TR on traps increased captures of F. schultzei and F. occidentalis but not of C. brunneus. Blue traps with Lurem-TR captures had the highest correlation with absolute estimate of thrips density on the plants. Rainfall had significant negative correlation with thrips population on the crops. Our results show that blue traps and Lurem-TR have strong potential for improving monitoring and management of thrips on tomato.

Xylosandrus compactus (Eichhoff) is a serious pest of Coffea canephora and Theobroma cacao in Uganda and also attacks several common shade tree species often associated with these crops. Seedlings of 10 common hosts of X. compactus were screened for preferential infestation by X. compactus, with a view to analysing the potential role of the shade trees in escalating incidence and damage by the pest. The experiment was conducted for 8 weeks in a garden of mature C. canephora infested by X. compactus that served as a natural source of infestation for the seedlings. The seedlings that became infested by X. compactus were counted weekly and the counts subjected to generalized linear modelling. Results show marked host preference by X. compactus, with T. cacao and C. canephora being the most preferred, while Eucalyptus sp. and Albizia chinensis being the least preferred. Four simulated scenarios of incidence and damage by X. compactus on a preferred crop such as C. canephora are discussed. It is suggested that it is most unlikely for unpreferred alternate host shade tree species to markedly increase populations of X. compactus on shaded preferred host plants. However, these simulations, which are based on results from potted seedlings, need to be validated in a real field situation, taking into account other ecological parameters that are likely to influence pest populations.

Natural habitat degradation often involves the reduction or disappearance of bee species. In Africa, stingless bees are hunted for honey, which is used as food, for medicinal purposes, and for traditional rituals. Severe habitat degradation due to human settlement is hypothesized to have a negative impact on the species diversity of the African stingless bee species. In this paper, we assess the impact of habitat degradation on the diversity of five stingless bee species across different habitats in the tropical rainforest of Kenya (indigenous forest, mixed indigenous forest) and its neighbouring landscape (grassland, village) in western Kenya. The species fauna, nest occurrence, and species diversity of the stingless bee species varied across the different habitats. The number of nesting habitats of the meliponine species varied between habitats in the tropical rainforest. Meliponula ferruginea (reddish brown) nested in five habitats, while Meliponula bocandei and Meliponula ferruginea (black) nested only in two habitat types. The species richness decreased within the different types of habitats and the indigenous and mixed indigenous forest contained more species than other habitats. The fauna composition in both homesteads was exclusively similar, while the indigenous and mixed indigenous forests were mostly similar. Similarity in habitat preferences for nesting was revealed between M. bocandei vs Plebeina hildebrandti and M. ferruginea (reddish brown) vs Hypotrigona gribodoi. The natural native indigenous forest had the most diverse community compared to the degraded habitats. There are taxon-specific responses to habitat change; and in our study, there is clear value in conserving the native indigenous forest.

Onion thrips, Thrips tabaci (Lindeman), is a prominent species infesting onion and tomato in the northern highlands of Tanzania. It causes considerable leaf damage by direct feeding and also transmits the Iris yellow spot virus (IYSV). Hence, one of the objectives of this study was to identify the most resistant onion entries against T. tabaci. One highly resistant (VI038552) and two resistant onion entries (VI038512 and AVON 1067) were identified against T. tabaci. Besides thrips resistance, the bulb size of VI038512 was also equivalent to one of the commercial varieties, Texas. The highly resistant VI038552 recorded the highest yield, followed by the resistant entry, VI038512. However, the yield of AVON 1067 was significantly lower. Elucidation of the biophysical bases of resistance revealed that there was a significant negative correlation between leaf angle as well as leaf toughness and thrips damage. The total epicuticular wax content in the leaves had a weak and non-significant negative relationship with thrips damage. The scanning electron microscopic study confirmed that the wax crystals occurred as filaments, rods, platelets, tubes and complex dendritic structures, and that they were densely arranged in resistant or moderately resistant entries. Studies on the biochemical basis of resistance confirmed that there was a significant negative relationship between total phenol content and thrips damage. Similarly, the relationship between total foliar amino acids or total sugars and thrips damage was inversely correlated and non-significant. Hence, entries VI038552 and VI038512 could be promising candidates for breeding programmes aimed at developing onion varieties that are resistant to thrips and that are high yielding, which will help to enhance the productivity of onions in sub-Saharan Africa.

Euwallacea spp. (Coleoptera: Scolytidae) are polyphagous globally distributed invasive ambrosia beetles. One of the species was recently detected attacking Ricinus communis growing in Coffea canephora gardens in Uganda. This study was undertaken to: (a) determine the distribution, incidence, and relative abundance of Euwallacea sp. on R. communis in Uganda; (b) determine the influence of the presence of C. canephora on the incidence and abundance of Euwallacea sp. on R. communis; and (c) identify ambrosia fungus of Euwallacea sp. on R. communis. Five C. canephora farms with R. communis and five others with R. communis but without C. canephora were sampled in each of the six districts surveyed. Incidence of Euwallacea sp. on R. communis was measured, by inspecting the host trees in each farm for the presence or absence of the pest. Abundance of Euwallacea sp. on R. communis was estimated, by counting holes of Euwallacea sp. at the lower 1.7 m of R. communis stems. A fungus was isolated from galleries of Euwallacea sp. on R. communis and identified. Results show that Euwallacea sp. was present on R. communis in all districts surveyed, with 30–70% of the farms infested in each district and 5–28 holes of Euwallacea sp. found on each sampled stem of R. communis. Coffea canephora appeared to facilitate the infestation of R. communis by Euwallacea sp., although it did not seem to influence the multiplication of the insect inside the host. Cunninghamella echinulata appeared to be the ambrosia fungus associated with Euwallacea sp. Therefore, Euwallacea sp. is a threat to many economically important plants in Uganda that are known to be hosts of this pest.

Thrips, Frankliniella occidentalis (Pergande), is a major invasive pest that causes extensive yield losses in French bean and tomato in Kenya. Thrips management is based on the application of pesticides. In addition to increased environmental risks associated with pesticides, frequent use of these chemicals increases production costs and pesticide resistance. Furthermore, exports are restricted due to non-compliance to maximum residue levels in important consumer export markets, especially the European Union (EU). This study was conducted to estimate the potential benefits of the effectiveness of the icipe-developed strategy for control of western flower thrips before dissemination of the technology in Kenya, using the economic surplus model. We calculated the benefit–cost ratio, the Net Present Value (NPV) and the Internal Rate of Return (IRR) using Cost–Benefit Analysis (CBA). Assuming a maximum conservative adoption rate of 1% and a 10% discount rate for the base deterministic scenario, the NPV of the research was estimated at US$2.2 million, with an IRR of 23% and a BCR of 2.46. Sensitivity analyses indicated that the NPV, IRR and BCR increased at an increasing rate as adoption rates increased. However, as elasticities of supply and demand increased, the NPV, IRR and BCR increased at a decreasing rate. The findings demonstrate that farmers from developing countries can gain when they obtain access to suitable pest management innovations such as integrated pest management technologies. Consequently, investment in IPM technologies for suppression of western flower thrips should be enhanced.

The population density of the diamondback moth (DBM), Plutella xylostella (L.), the species diversity of its predators, parasitism on eggs, larvae and pupae, and associated yield of canola were evaluated in experimental plots where spring canola was grown either as a monoculture or strip-intercropped with annual alfalfa in the ratio of 3C:3A, 6C:3A and 9C:3A over a 2-year period. The egg density was significantly higher in monoculture than in intercrops. The highest and lowest densities of larvae and pupae of DBM were recorded in monoculture (2.9–3.2 larvae per plant and 1.14–1.20 pupae per plant) and intercrop 3C:3A (0.7–0.6 larvae per plant and 0.34–0.29 pupae per plant), respectively. Shannon diversity index (H') for species composition of the predators of DBM immature stages was lower in monoculture than in intercrops, and was similar amongst the three intercrops. Moreover, the percent parasitism for eggs, larvae and pupae was higher in intercrops than in monoculture. The dry seed weight loss was higher in monocrop (37.6–40.1%) compared to 3C:3A (7.9–8.6%), 6C:3A (19.5–21.4%) and 9C:3A (21.6–25.4%). Our results indicate that intercropping canola with annual alfalfa, especially in the ratio 3C:3A, can increase the species diversity, parasitism rates of DBM immature stages, and enhance the yield of canola. The implications of these findings, in relation to integrated pest management (IPM) in canola cropping systems, are discussed.