Arthropod pests are poikilothermic or ectothermic organisms that cannot regulate their own temperature internally; hence their development depends on the temperature to which they are exposed in the environment. They require a certain amount of heat to develop from one stage in their life-cycle to another, e.g. from egg to larva. Because of yearly variations in weather, calendar dates are not a good basis for predicting pest population growth and outbreaks and making management decisions. However, measuring the amount of heat accumulated over time provides a valuable physiological time scale that is biologically highly accurate.
Phenology models help predict the time of events in an organisms' development, and phenology models for insect pests based on temperature are important analytical tools for predicting, evaluating and understanding the dynamics of pest populations in agroecosystems under a variety of environmental conditions. CIP has developed a temperature-driven phenology model for the potato tuber moth,Phthorimaea operculella (Zeller) (Lepidoptera: Gelechidae) that successfully predicts life-table parameters for different agroecological zones (Sporleder et al. 2004), validated through field and laboratory data (Keller 2003). It was used to predict the establishment risk and potential pest activity in specific agroecologies according to temperature records (Kroschel and Sporleder 2006). Linked with geographic information systems (GIS) and atmospheric temperature, the model allows for the simulation of these risk indices on a worldwide scale or can be used to predict future changes of these indices due to global warming (Sporleder et al. 2007, Sporleder et al. 2008). The approach used to develop and implement the P. operculella model can principally be used for other insect species. Hence, CIP developed Insect Life Cycle Modeling software (ILCYM - version 2.0) to facilitate the development of further pest insect phenology models and provide analytical tools for studying pest population ecology. ILCYM software consists of two main modules. One, the "model builder", facilitates the development of insect phenology models based on experimental temperature data of a specific pest. This module also provides tools to analyze an insect life-table and to validate developed models. The second module implements the phenology model in a GIS environment and allows for spatial - global or regional simulation of pest activities ("pest risk mapping"). In its present version the software uses the phenology model of the potato tuber moth as an example. The objective of ILCYM software is to provide an open-source computer aided tool that facilitates the development of phenology models for researchers and students using advanced modeling techniques. ILCYM interactively leads the user through the steps for developing a pest phenology odel, or for conducting spatial simulations with a developed pest model. We are aware that a single modeling approach will not fit to each pest species of interest and that it cannot meet each purpose for which a model needs to be developed. However, the approach presented here might be applicable to many pest species and many circumstances for which pest phenology models are needed. ILCYM was developed on the Udig platform, which is a geographic information system (GIS) application that contains basic tools for mapping and managing geographic information.