No abstract

Solanum viarum has been proposed as a potential dead-end trap crop for the management of Helicoverpa armigera because of its unsuitability for larval growth and survival despite being overwhelmingly preferred for oviposition. This study delved into the different S. viarum accessions for ovipositional preference and non-suitability for larval growth and survival of H. armigera. Besides, foliage trichomes, acylsugars, and phenolic content of S. viarum plants were assessed and compared with tomato. Since there is no significant variation in the ovipositional preference and larval performance of H. armigera, our result revealed that all those evaluated accessions of S. viarum have the potential to be used as a dead-end trap crop for the management of H. armigera. However, significant variation among the S. viarum accessions in terms of H. armigera oviposition was also evident in a no-choice experiment. Because of high-density glandular trichomes, acylsugars, and phenolic content, S. viarum significantly impaired H. armigera larval growth and survival compared to the tomato. Hence, our study elucidated that the S. viarum plant fits with the criteria for dead-end trap crop, and has the potential as a dead-end trap crop for the H. armigera, which needs to be tested under large, open-field conditions.

In natural habitats, there is a strong evolutionary selection pressure on herbivorous insects to avoid danger and choose suitable host plants. Similar selection pressures may drive movement and choices of oviposition hosts by herbivorous insects living in agricultural cropping systems, in which insecticides are often used. In this study, we quantified movement responses and nymph emergence (collectively referred to as bio-responses) of western-tarnished plant bug (Lygus hesperus Knight (Hemiptera: Miridae)) individuals when exposed to environments associated with a perceived “risk” (experimental insecticide treatments and their corresponding controls). We introduce a novel analytical approach in which treatments (risk environments) are ranked in ascending order based on bio-responses (movement or nymph emergence). Consequently, linear regression coefficients were generated and used to interpret bio-responses of Lygus individuals in different life stages to risk environments. Initially, we predicted movement by Lygus individuals to be positively associated with environmental risk and nymph emergence to be negatively associated with environmental risk. Overall, based on a comprehensive combination of no- and two-choice bioassays, we found that: (1) In no-choice bioassays, movement parameters (both total distance moved and movement percentage) by all three life stages were lowest in low-risk environments and highest when Lygus individuals were exposed to either malathion or Grandevo. Accordingly, environments involving malathion or Grandevo were considered high-risk. (2) No-choice movement bioassays also revealed that Lygus males moved significantly more (based on comparison of regression intercepts) than other life stages, and that they responded significantly more (based on comparison of regression slopes) than conspecific females and nymphs. (3) In two-choice movement bioassays, neem elicited the most consistent movement responses by Lygus individuals, and adult life stages showed the strongest response. Two-choice movement bioassays also revealed that Lygus adults, compared to nymphs, were more likely to spend time in low-risk areas of the test arenas. (4) Nymph emergence was markedly lower in no-choice compared to two-choice bioassays, and in two-choice bioassays, Grandevo and malathion elicited especially biased nymph emergence from low-risk beans. To our knowledge, this is the first study in which movement bioassays have been used to quantify and characterize behavioral responses by Lygus life stages to environments associated with varying degrees of risk. The novel analytical approach presented in this study provides a high degree of complementarity to more traditional performance-testing methods used to evaluate responses to insecticides. Furthermore, we believe that this analytical approach can be of considerable relevance to studies of animal phenomics and behavioral studies of animals more broadly, in which adaptation and fitness parameters are examined in response to environmental risk and heterogeneity.

Malnutrition, hunger, and rural poverty in Nepal are prevalent issues that have been exacerbated by the negative impacts of climate change on crop production. To create a more sustainable and resilient food system, it is crucial to explore alternative options beyond the small number of input-intensive crops that the country currently relies on. In this study, we conducted a comprehensive investigation of six underutilized food crops—amaranth, buckwheat, finger millet, foxtail millet, naked barley, and proso millet—in four mountainous districts of the Karnali province, Nepal. Using several approaches that included a literature review, key informant surveys, focus group discussions, and direct observations, we explored the production and utilization aspects of these crops, as well as their potential for improving nutrition and food security. Our findings indicate that these underutilized crops continue to be a vital element of the diets of people residing in Karnali and play an important role in their livelihoods. This study also highlights the diversity and potential of these underutilized crop landraces, and their significance in addressing nutrition and food insecurity, as well as in improving livelihoods in regions with marginal lands and inadequate food supply. Thus, promoting the cultivation and consumption of underutilized crops can create a more sustainable and diverse food system that is resilient to climate change. However, further investigation is needed to fully understand the socioeconomic importance and other potential benefits of these crops.