Intensive agricultural production requires constant control of an agroecosystem. One of the most important aspects of this control is plant protection through pest and weed management. Proper management should minimize economic losses from pests and weeds, while not forgetting environmental protection. The present paper describes a national system of pest and weed control which is in operation in the German Democratic Republic. At present, 87 types of pests, diseases, and weeds are monitored and controlled throughout the entire country. 

In the GDR, three national operational systems have been developed as parts of an overall system for control of agricultural production. These are: a system of pest and weed management, a system of irrigation control, and a system of fertilizer application. They are fine examples of applied systems analysis which lie within the range of interests of the Resources and Environment Task 3, "Environmental Problems of Agriculture". Therefore, the principal authors of the systems were asked to describe their work in a Collaborative Paper which could be distributed through IIASA's information network. 

Although emphasis in this paper is given to monitoring and forecasting issues, all stages of a management system, from monitoring through analysis of information, and forecast to a management decision, are described. The authors of the paper are affiliated with the Institute of Plants Protection in Eberswalde, GDR; the Institute is a part of the GDR Academy of Agricultural Sciences.