Agriculture on Guam has changed dramatically during the period of American governance (1898 to 1941 and 1944 to present). The primary event affecting agriculture during this period was the transition to a cash based economy. Employment for monetary wages became widespread during the last years of World War II (WWII) and during the military build-up immediately afterwards. Prior to WWII, the economy of Guam was based on subsistence agriculture . In a historic sense, the crops on Guam can be divided into three categories: (1) those that have basically disappeared as commercial commodities because of complete replacement by imports, i.e. rice, arrowroot, sugarcane, field corn and tobacco; (2) those that were important before the introduction of the cash economy and have remained relatively important for cultural or economic reasons, i.e., coconut, taro, yam, sweet potato, banana, pineapple and papaya; and (3) those that have become important since the late 1950s, i.e. watermelon, cucumber, beans, eggplant, tomato and cantaloupe. Increased demand and erratic local supplies of fresh vegetables and fruits encourage the importation of many commodities. Sources of variation in local production of fruits and vegetables are: periodic typhoons and tropical storms; soil saturation during rainy season; physiological disorders due to high temperature, high relative humidity, water stress, imbalances of soil nutrients, and the occurrence of diseases and pests. The recent emergence of landscaping and ornamental markets as well as turf management business of golf courses has diversified the island's agriculture. Some issues on Guam's future agriculture addressed are development of environmentally sound and sustainable cropping systems, new crop development, mechanization, improvement of post harvest technology, development of profitable market system, and further expansion of the newly developed ornamental, landscape and turf industry.