It ain't what you do, it's what drives why you do it: how the basis of growers' decision making affects the effectiveness of disease control

While the spread of plant disease depends strongly on biological factors controlling transmission, epidemics clearly also have a human dimension. Disease control depends on decisions made by individual growers, who are in turn influenced by a broad range of factors. Despite this, human behaviour has rarely been included in plant epidemic models. Considering Cassava Brown Streak Disease, we model how the perceived benefit of disease control influences participation in clean seed systems (CSS). Our models are rooted in game theory, with growers making strategic decisions based on the expected profitability of different control strategies. We find that both the information used by growers to assess profitability and the perception of economic and epidemiological parameters influence long-term participation in the CSS. Over-estimation of infection risk leads to lower participation in the CSS, as growers perceive that paying for the CSS will be futile. Additionally, though the CSS can reduce the burden of disease, and allow a scenario in which all growers control, disease is not eliminated from the system. These results are robust to stochastic and spatial effects. Our work highlights the importance of including human behaviour in plant disease models, but also the significance of how that behaviour is included.

Anguina tritici (wheat seed gall nematode).

Anguina tritici, commonly referred to as wheat seed gall nematode, is the cause of ear-cockle disease. It was the first plant-parasitic nematode to be described in the scientific literature in 1743. Its host range includes wheat, triticale, rye, and related grasses; the primary host is wheat. Ear cockle in the past was reported in all major wheat growing areas. However, physical and mechanical methods for separating infected galls from seed have eradicated the nematode from the western hemisphere. It remains a problem in several countries in the Near and Middle East, the Asian Subcontinent and Eastern Europe, most likely due to poor awareness and lack of campaigns for establishing clean seed. A. tritici is on the U.S. Pests of Economic and Environmental Importance List, and on the 'Harmful Organism Lists' for Argentina, Brazil, Chile, Colombia, Ecuador, Egypt, Guatemala, Indonesia, Israel, Madagascar, Namibia, Nepal, New Zealand, Paraguay, Peru, South Africa, Taiwan, Thailand, Timor-Leste and Uruguay.

Anguina tritici (wheat seed gall nematode).

Anguina tritici, commonly referred to as wheat seed gall nematode, is the cause of ear-cockle disease. It was the first plant-parasitic nematode to be described in the scientific literature in 1743. Its host range includes wheat, triticale, rye, and related grasses; the primary host is wheat. Ear cockle in the past was reported in all major wheat growing areas. However, physical and mechanical methods for separating infected galls from seed have eradicated the nematode from the western hemisphere. It remains a problem in several countries in the Near and Middle East, the Asian Subcontinent and Eastern Europe, most likely due to poor awareness and lack of campaigns for establishing clean seed. A. tritici is on the U.S. Pests of Economic and Environmental Importance List, and on the 'Harmful Organism Lists' for Argentina, Brazil, Chile, Colombia, Ecuador, Egypt, Guatemala, Indonesia, Israel, Madagascar, Namibia, Nepal, New Zealand, Paraguay, Peru, South Africa, Taiwan, Thailand, Timor-Leste and Uruguay.

Incidence and distribution of Sweetpotato viruses and their implication on sweetpotato seed system in Malawi

A survey was carried out in 19 districts to investigate the prevalence and distribution of sweetpotato virus disease (SPVD) and its implication on the sustainability of clean seed system in Malawi. A total of 166 leaf samples were collected and tested for the presence of 8 viruses using nitrocellulose membrane enzyme-linked immunosorbent assay (NCM-ELISA). SPVD foliar symptoms were observed in 68.42% of the surveyed districts. There were significant variations in disease incidence and severity (p < 0.001) among districts, with the highest incidence in Mulanje (28.34%). Average SPVD severity score was 3.05. NCM-ELISA detected sweet potato feathery mottle virus (SPFMV, 30.54%), sweet potato mild mottle virus (SPMMV, 31.14%), sweet potato mild speckling virus (SPMSV, 16.17%), sweet potato C-6 virus (SPC6V, 13.77%), sweet potato chlorotic stunt virus (SPCSV, 22.16%), sweet potato collusive virus (SPCV, 30.54%), sweet potato virus G (SPVG, 11.38%), cucumber mosaic virus (CMV, 7.78%) either in single or mixed infections. Data from this study indicate a significant SPVD occurrence in the country, and the consequence implications towards national sweetpotato seed system.

Claviceps fusiformis (pearl millet ergot).

C. fusiformis is widespread in Africa and India, where the host crop, pearl millet (Pennisetum glaucum), has been grown for thousands of years. The ergot disease it causes became a major yield constraint in India with the introduction of open-pollinated hybrid lines (Thukar and Rai, 2003). Conidia are spread from plant to plant by wind, rain-splash, and insects. Wild Pennisetum spp. are alternative hosts that may serve as reservoirs of inoculum. Ergot infection can have a significant impact on yields, with up to 70% loss in susceptible varieties (Natarajan et al., 1974). There are reports of the pathogen in the western hemisphere (San Martin et al., 1997; Velásquez-Valle et al., 1998). If the fungus has been introduced, then the use of clean seed and cultivation under particular climate conditions may prevent ergot from appearing as a significant problem in the Americas.

Trichoconiella padwickii (stackburn disease).

T. padwickii, previously known as Alternaria padwickii, is an asexually reproducing fungus that infects seeds of rice [Oryza sativa]. It is one of several fungi responsible for seed discolouration, seed rot and seedling blight, but has also been detected as a sheath-rotting pathogen (Naeimi et al., 2003). It occurs in southern Asia and in countries on other continents worldwide, but its presence in mainland North America is not confirmed. Transport to and transmission in new areas may be prevented by use of tested clean seed. Where the pathogen is already present, application of seed treatments should reduce disease incidence, but the fungus has an undetermined ability to survive as sclerotia in plant debris and soil.

Role of networking capability, socio-economic and institutional characteristics on adoption tendencies of clean seed potato agri-enterprises in central Rift Valley, Kenya

Even though quality of seed is a major yield determinant in potato (Solanum tuberosum L.) production and global food security, inadequate availability of and access to high quality (certified) seed is a major challenge to potato producers in Sub-Saharan Africa. The objective of this study was to examine farmer’s adoption tendency towards decentralised clean seed potato multiplication agri-enterprise (CSPMAE) in Central Rift Valley, Kenya, which aids in implementation of stage matched entrepreneurial interventions. A cross-sectional survey was conducted using a semi-structured questionnaire on 54 seed potato producers and 192 non-seed potato producers, through multistage sampling. Ordered logistic regression analysis, based on the trans-theoretical model, revealed that household head, partner knowledge, gender, land size allocated for potato production, level of education, ownership of transport and/or storage facilities, frequency of interaction with certified seed potato producers and agricultural extension officers influenced adoption tendencies of CSPMAE, positively and significantly. Seed potato value chain stakeholder platforms, development workers and donors should prioritise their support for clean seed agri-enterprises to farmers with such traits. This is likely to lead to increased supply of access to clean seed, thereby improving potato yields in Kenya.

Factors influencing agripreneurs’ investment decision and level in clean seed potato enterprises in the highlands of Kenya

High quality seed potato (Solanum tuberosum L.) supply has failed to meet the growing demand estimated at 250,000 metric tonnes from 161,000 ha of ware potato for cultivation by 600,000-800,000 small-scale farmers in Kenya. Increased investments by private seed potato multipliers could alleviate the shortage of seed potato by enhancing availability and accessibility to quality seed, and bridging the supply that currently meets less than 5% of the demand. The objective of this study was to investigate factors that influence agripreneurs’ investment decisions and level of investment in clean seed potato enterprise in the highlands of the Rift Valley, Kenya. The study was conducted through a cross-sectional survey of 380 agripreneurs. The Double hurdle (Craggit) model analysis revealed that training, frequency of extension services, family history in seed potato business, years spent in school and selling price, significantly (P<.05) influenced the probability of agripreneurs’ decision to invest in clean seed potato enterprises in the highlands of Kenya. Initial land size put under seed potato production at the commencement of the enterprise, higher annual household income, number of cropping seasons, total land under seed potato and group membership fee also significantly (P <.05) influenced the decision and level of investment in clean seed potato enterprise.