The highlands of Northern Thailand (elevation over 800 m) cover 70% of the land area of that region. They are populated mainly by the 'hill tribes" who have had a low state of agricultural development and were unable to produce sufficient rice and other food crops to meet their needs. Traditionally, opium poppy (Papaver somniferum) has been the main crop. For a number of reasons, including the requirements of national security and opium suppression or replacement, there have been intensive programs of agricultural and social development in the highlands for over fifteen years. Many new crops are being introduced or are already grown by the hill tribes, including cash crops (such as coffee and temperate fruit) and improved varieties of subsistence crops. The tendency for these new crops to suffer severely from pests and diseases is a major obstacle to economic yields and high quality and hence to successful adoption by the hill tribes. The prevalence of pest problems and other contributing factors have led to widespread pesticide use in highland agriculture, and several undesirable chemicals have been introduced.