Explaining Andean Potato Weevils in Relation to Local and Landscape Features: A Facilitated Ecoinformatics Approach

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

Maria Huanca, nueva variedad de papa resistente al nematodo de quiste de la papa (Globodera pallida)

Desde 1980 el Centro Internacional de la Papa (CIP) ha estado enviando clones de papa a varios investigadores del Programa Nacional de Papa del Perú adscrito al Instituto Nacional de Investigación Agraria y Agroindustrial (INIAA), para evaluar su comportamiento y resistencia al nemátodo quiste de la papa con el objeto de seleccionar variedades resistentes. En 1983, el CIPA IV del INIAA, en La Libertad (Sierra Norte del Perú), seleccionó un clon sobresaliente, identificado como 279142.12 ó G3. Después de varias pruebas, el clon fue liberado en 1987 con el nombre de María Huanca, y es la primera variedad resistente a las razas P4A y P5A de G. pallida en el Perú y Latinoamérica. Esta variedad proviene de un cruce entre S. tuberosum subsp. andigena y un híbrido de 5. tuberosum subsp. tuberosum x S. vernei. Los tubérculos son oblongos, de piel rojiza, la pulpa es blanca, ocasionalmente con estrías moradas. La planta es erecta y alcanza una altura de 80 cm con pequeños folíolos de color verde oscuro; tiene el fenotipo de andigena. Los rendimientos de las Estaciones Experimentales variaron entre 30 y 60 t/ha y en campos de agricultores de 20 a 30 t/ha. Además de su resistencia al nemátodo del quiste de la papa, esta variedad es también resistente a las razas 1 y 2 de la verruga (Synchitrium endobioticum), inmune a PVY e hipersensitiva a la raza común de PVY. Es tolerante a rancha (Phytophthora infestans) y al carbón de la papa (Tecaphora solani); susceptible a roña (Spongospora subterranea),rizoctoniasis (Rhizoctonia solani), oidium (Erysiphe cichoracearum) y a mancha foliar (Phoma andigena)

Enabling more regenerative agriculture, food, and nutrition in the Andes : The relational bio-power of "seeds"

This chapter examines agrobiodiversity as the product of an aesthetic order. In so doing, it seeks to explain the management of life in agriculture and food as part of a value achieving process laden with potential, in this case useful for addressing priority concerns over maternal and child nutrition in the highland Andes. In prioritizing concrete experience over abstract instrumental science, the authors seek to shed light on how three interventions based on the mobilization of agrobiodiversity in Bolivia, Perú, and Ecuador reveal a commonly neglected or under-utilized potential for enabling novel human-nonhuman interactions and resulting material effects (e.g., N-fixation, food, fiber, wealth, and health) and subjective affects (flavor, taste, identity, and fulfilment) for purposes of rural development. Each case led to re-orderings that, while not always predictable or manageable, when in the hands of situated and empowered users, arguably contributed to the possibility of more regenerative agriculture, food, and nutrition

Temporal decay in the efficacy of insecticide treatments against Andean potato weevils (<i>Premnotrypes</i> spp.), as applied by farmers.

<p>The x-axis shows the parameter estimate ± SEM associated with the effect of a single insecticide application on the proportion of tubers infested with weevils (sqrt-transformed). The y-axis shows the month of the insecticide treatment.</p

Community knowledge worker assisting farmers with record-keeping activities associated with their potato harvest.

<p>The individual pictured in this manuscript has given written informed consent (as outlined in the PLoS consent form) to appear in the published photo. Photo credit: Soroush Parsa.</p

Local and landscape features of hypothesized to exert important influences on Andean potato weevil infestations (<i>Premnotrypes</i> spp.).

a<p>Farmers apply a layer of ash directly below the potato seed at the time of planting; this practice is intended to kill potato weevils.</p>b<p>Fertilization can influence crop defenses against herbivores <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0036533#pone.0036533-Throop1" target="_blank">[17]</a>.</p>c<p>Many agronomists recommend hilling the plants (piling dirt up around the stem of the plant) higher to lengthen the distance weevil larvae must travel to find tubers.</p>d<p>Early harvest shortens the exposure of tubers to neonate larvae <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0036533#pone.0036533-Khne1" target="_blank">[18]</a>.</p>e<p>Larger fields have lower perimeter to area ratios and have been suggested to have lower infestations <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0036533#pone.0036533-Rios1" target="_blank">[19]</a>.</p>f<p>Early emerging plants may experience greater infestations <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0036533#pone.0036533-Calderon1" target="_blank">[20]</a>.</p>g<p>Planting density may influence the abundance of many insect pests <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0036533#pone.0036533-Speight1" target="_blank">[21]</a>.</p>h<p>Planting potatoes following a potato planting should lead to very high infestations <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0036533#pone.0036533-Rios1" target="_blank">[19]</a>, but implementing a single host free period should eliminate this risk. Rotation 2007 indicates if potatoes were sown in the field the previous season while Rotation 2006 indicates if potatoes were sown there two seasons before the study.</p>i<p>The study hypothesized that weeds may serve as refuges for adult weevils before potato plants emerge.</p>j<p>Weevils are poorly adapted to elevations above 3,700 meters <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0036533#pone.0036533-Khne1" target="_blank">[18]</a>.</p>k<p>The study hypothesized that greater soil erosion in steeper slopes may increase tuber exposure to weevils.</p>l<p>Modern cultivars like Yungay may be more susceptible to insect pests <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0036533#pone.0036533-Harris1" target="_blank">[22]</a>.</p>m<p>The study was interested in exploring any soil influences on weevil infestations without any strong <i>a priori</i> expectations.</p>n<p>A measure of potato fields sown the within 100 m of the focal potato field; these current fields dilute the effect of immigrating weevils <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0036533#pone.0036533-Parsa2" target="_blank">[15]</a>.</p>o<p>A measure of potato fields harvested the previous season that lie within 100 m of the focal potato field; these previous fields may be sources of overwintering weevils that immigrate into focal fields <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0036533#pone.0036533-Ortiz1" target="_blank">[14]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0036533#pone.0036533-Parsa2" target="_blank">[15]</a>.</p>p<p>Potato storage units are facilities adjacent to farmer houses and are known to concentrate high densities of overwintering weevils that may immigrate into focal fields <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0036533#pone.0036533-Ortiz1" target="_blank">[14]</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0036533#pone.0036533-Parsa2" target="_blank">[15]</a>.</p

Standardized predicted impacts of explanatory variables on Andean potato infestations.

<p>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.</p

Forward stepwise development of the global (least parsimonious) statistical model explaining Andean potato weevil infestations.

<p>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.</p

Parameter estimates ± SEM for the best models predicting Andean weevil infestations based on local factors only (i.e. Best local), landscape factors only (i.e. Best landscape) or both local and landscape factors together (i.e. Best combined).

<p><i>Notes</i>: Lower AIC values suggest better model performance. The Akaike weight, <i>w</i>_i, is interpreted as the relative probability that a given model is the best in the set. The models included control variables for observer effects (not presented in the table).</p>*<p><i>P</i>≤0.05.</p>**<p><i>P</i>≤0.01.</p