Pathogen buildup in vegetative planting material, termed seed
degeneration, is a major problem in many low-income countries. When
smallholder farmers use seed produced on-farm or acquired outside
certified programs, it is often infected. We introduce a risk assessment
framework for seed degeneration, evaluating the relative performance of
individual and combined components of an integrated seed health strategy.
The frequency distribution of management performance outcomes was
evaluated for models incorporating biological and environmental heterogeneity,
with the following results. (1) On-farm seed selection can perform
as well as certified seed, if the rate of success in selecting healthy plants
for seed production is high; (2) when choosing among within-season
management strategies, external inoculum can determine the relative
usefulness of ‘incidence-altering management’ (affecting the proportion
of diseased plants/seeds) and ‘rate-altering management’ (affecting
the rate of disease transmission in the field); (3) under severe disease
scenarios, where it is difficult to implement management components
at high levels of effectiveness, combining management components
can be synergistic and keep seed degeneration below a threshold;
(4) combining management components can also close the yield gap
between average and worst-case scenarios. We also illustrate the
potential for expert elicitation to provide parameter estimates when
empirical data are unavailable.