Analysis and decision making in conventional Integrated Pest Management (IPM) is based on the consideration of single crop plant- herbivore insect relationships. The necessity of integrating more components of the agrosystem, including agricultural and non-agricultural habitats in the landscape, has been advocated by several authors. Landscape dimension of IPM is an obvious consequence of two features of the biology of agricultural and forest pests and their antagonists: one is that most of them are capable to move between different habitats along their life by themselves or through a vector and the other is they need resources that often are not provided by a unique habitat. A deep comprehension of biotic relationships between plants, insect herbivores and their natural enemies should lead to the design of landscapes and cultural practices aimed to both enhance environmental resistance to insect pest population increase and favour insect pest natural enemies. The present research project tries to identify how ecological processes operating in a landscape that affect organism population dynamics at landscape scale operate in a mixed landscape composed of ephemeral and permanent crops and non-crop habitats. The study is focused on three main biotic interactions: phytophagous insect-crop plant, phytophagous prey-predator, and host plant- virus (of maize)-insect vector. The three crops selected for developing this project are among the most common ones in our area, western Catalonia (Lleida county) and a N-S strip in eastern Aragon (Huesca county): field crops (maize and alfalfa) and stone fruit orchards. In a second part of the project, relationships between maize plants and several lepidopteran herbivores will be particularly studied. Maize plants to be studied will be GM with expression of Bacillus thuringiensis (Bt) and overexpression of some vitamins in the endosperm. How these modifications may affect the biology of the maize Lepidoptera herbivores and if these two modifications may interact each other will be the focus of the project in this second part.