Mapping

Weevil / © Michael Pettigrew

The number of potential pest-crop combinations are large. CABI (2006) documented over 8,000 specific pests, diseases and weeds affecting the 2,191 of the plants in the CABI database. As a practical point of departure, but mindful of the possibilities of sample selection bias, HarvestChoice is consulting experts at the University of Minnesota, IRRI, CIMMYT, CIAT, CSIRO, Entomology Division, Australia, IPM-CRSP, USDA Cereals Disease Laboratoryand scrutinizing the literature to finalize the list of biotic stressors targeted for an initial round of assessment.

Pests, Weeds and Diseases Selected for the First Round
of HarvestChoice Biotic Constraints Assessments

Pest, Weed and Disease Distributed Expert Survey

To calibrate HarvestChoice efforts to model the spatial likelihood of occurrence for its initial targeted group of 62 pests and diseases, an on-line survey of their frequency of occurrence is being conducted in collaboration with a group of key collaborators. Information from a knowledgeable set of more than 100 respondents from around the world will be used to calibrate efforts jointly undertaken by HarvestChoice and its partners to estimate the likely spatial occurrence of the pests and diseases worldwide. The resulting survey data will be synthesized into a "consensus view" of the spatial occurrence of these pests and diseases and released as a version 1.0 map. These maps are subject to updating or revision as new or better data become available.

Midge / © Joseph Calev

CLIMEX Modeling

CLIMEX is a pest distribution model initially developed by a team of CSIROscientists led by Robert Sutherst and Gunter Maywald. The CLIMEX model derives a metric of the suitability of locations for specific pests based on the climatic needs of the species. Specifically, the model uses a variety of pest and location characteristics to derive indices related to potential population growth and stress (heat-, cold-, wet- and dry-stress). CLIMEX has been used extensively to predict the possible spread of invasive species, and to consider the effects of climate change on pest ranges. View a listing of the known studies to date. Often, the specific growth and stress responses of a pest to a particular climatic regime are not well-understood, making it difficult to calibrate the CLIMEX model. An alternative approach to "fitting" a CLIMEX simulation to a specific pest is to calibrate the model's ecoclimatic predictions on the known spatial distribution of the pest. Unfortunately, presently available data on the spatial distribution of pests and diseases are sparse or non existent. To address this problem, the HarvestChoice team is presently soliciting information from an international team of experts on the spatial distribution of pests and diseases using a new web enabled survey instrument (dubbed V-GET).

Virtual Georeferenced Elicitation Tool (V-GET™)

V-GET™ is a web-enabled survey tool developed by the HarvestChoice team at the University of Minnesota. The tool facilitates a web enabled elicitation of spatially explicit data on the location and frequency of occurrence of specific pests and diseases from geographically disperse respondents. V-GET™ is built around the Google Maps application programming interface (API) which allows for manipulation and distribution of map data via Google’s servers while overlaying a structured survey. Respondents can provide spatial data by clicking a displayed map using a natural interface. V-GET™ was designed with the HarvestChoice pest and disease assessment in mind, but is programmed in a way that allows it to be readily adapted to web-enabled surveys of many other spatially explicit data layers where available data are scarce, such a information on production systems, agricultural inputs, and technology adoption). V-GET™ allows for such complexities as multiple, geographically disperse survey administrators and eliciting information from each respondent on multiple sub-topics (e.g., different pests). Since V-GET™ is a global surveying instrument, special attention was given to addressing problems that might be faced by low bandwidth respondents, particularly by using asynchronous data transfers to achieve a more interactive experience.

Proof of Concept Results

A draft version of geo-referenced maps are displayed here:

• spotted stalk borer (Chilo partellus) – Africa
• maize stalk borer (Busseola fusca)
• tropical corn rust (Puccinia polysora) – Africa
• yellow rust
• Turcicum leaf blight – Africa
• Turcicum leaf blight – Asia

The maps were prepared to assess the feasibility of using the CLIMEX modeling approach to mapping the spatial extent and likelihood of occurrence of a range of pests and diseases in situations with limited field data or prior published evidence. Encouraged by the feedback received from a team of international pest and disease experts assembled at CIMMYT during a HarvestChoice technical consultation held in June 2007, we are proceeding to apply the CLIMEX approach, informed by new survey results and continued literature searches, to model and map the spatial occurrence of pests and diseases deemed, a priori, to incur significant economic losses. A suite of 62 peer-reviewed pest and disease maps are scheduled for release in Fall 2008, with more to follow.