Explaining Andean potato weevils in relation to local and landscape features: A facilitated ecoinformatics approach

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Abstract

Background: Pest impact on an agricultural field is jointly influenced by local and landscape features. Rarely, however, are these features studied together. The present study applies a "facilitated ecoinformatics" approach to jointly screen many local and landscape features of suspected importance to Andean potato weevils (Premnotrypes spp.), the most serious pests of potatoes in the high Andes. Methodology/Principal Findings: We generated a comprehensive list of predictors of weevil damage, including both local and landscape features deemed important by farmers and researchers. To test their importance, we assembled an observational dataset measuring these features across 138 randomly-selected potato fields in Huancavelica, Peru. Data for local features were generated primarily by participating farmers who were trained to maintain records of their management operations. An information theoretic approach to modeling the data resulted in 131,071 models, the best of which explained 40.2-46.4% of the observed variance in infestations. The best model considering both local and landscape features strongly outperformed the best models considering them in isolation. Multi-model inferences confirmed many, but not all of the expected patterns, and suggested gaps in local knowledge for Andean potato weevils. The most important predictors were the field's perimeter-to-area ratio, the number of nearby potato storage units, the amount of potatoes planted in close proximity to the field, and the number of insecticide treatments made early in the season. Conclusions/Significance: Results underscored the need to refine the timing of insecticide applications and to explore adjustments in potato hilling as potential control tactics for Andean weevils. We believe our study illustrates the potential of ecoinformatics research to help streamline IPM learning in agricultural learning collaboratives. © 2012 Parsa et al.

Figures

  • Figure 1. Heavy infestations by Andean potato weevils (Premnotrypes spp.) on improved potato cultivar Yungay (S. tuberosum). Photo credit: Soroush Parsa. doi:10.1371/journal.pone.0036533.g001
  • Figure 2. Landscape in the study area in Huancavelica, Peru.
  • Table 1. Local and landscape features of hypothesized to exert important influences on Andean potato weevil infestations (Premnotrypes spp.).
  • Figure 3. Community knowledge worker assisting farmers with record-keeping activities associated with their potato harvest.
  • Figure 4. Temporal decay in the efficacy of insecticide treatments against Andean potato weevils (Premnotrypes spp.), as applied by farmers. The x-axis shows the parameter estimate 6 SEM associated with the effect of a single insecticide application on the proportion of tubers infested with weevils (sqrttransformed). The y-axis shows the month of the insecticide treatment. doi:10.1371/journal.pone.0036533.g004
  • Figure 5. Forward stepwise development of the global (least parsimonious) statistical model explaining Andean potato weevil infestations. The x-axis shows the progressive addition of explanatory variables in order of their contributions to lowering AIC. The y-axis shows cumulative reductions in AIC from the AIC associated with using only the mean to estimate infestations. The first dashed line shows the point where the addition of variables started to penalize the AIC, whereas the second dashed line shows the point where this penalty started to exceed two AIC values. The global model included all variables before the second dashed line. doi:10.1371/journal.pone.0036533.g005
  • Table 2. Parameter estimates weight-averaged across the 51 ‘‘best’’ models predicting Andean potato weevil infestations (square root of proportion infested tubers).
  • Figure 6. Standardized predicted impacts of explanatory variables on Andean potato infestations. The model is initially set to predict infestations for a field with no pesticide applications and with mean (for continuous variables) or most common (for ordinal and categorical variables) values for all other explanatory variables. For continuous explanatory variables, bars reflect predicted changes in infestations in response to a one standard deviation increase in the explanatory variable. For ordinal explanatory variables, the bars reflect predicted changes in infestations in response to a single unit increase in the explanatory variable; except for the number of hillings, for which only a decrease could maintain predictions within observed bounds.To obtain multi-model predictions, parameter estimates were multiplied by their corresponding parameter weights. Hence, predicted effects are ‘‘attenuated’’ for explanatory variables with parameter weights smaller than 1. doi:10.1371/journal.pone.0036533.g006

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Parsa, S., Ccanto, R., Olivera, E., Scurrah, M., Alcázar, J., & Rosenheim, J. A. (2012). Explaining Andean potato weevils in relation to local and landscape features: A facilitated ecoinformatics approach. PLoS ONE, 7(5). https://doi.org/10.1371/journal.pone.0036533

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