Pests of Composite Crops: Lettuce

Abstract

The lettuce (Lactuca sativa L.) has been developed from the wild lettuce (Lactuca scariola L.), a wasteland plant originating in the Eastern Mediterranean region. It is the basis of all salads and is usually eaten uncooked. There are several types of lettuce with varying horticultural characteristics. Recent developments in plant breeding have resulted in novel cultivars with serrated, dissected or crinkled leaves or with red leaf coloration. The lettuce is a frost-sensitive annual plant that grows rosettes of leaves forming a more or less compact heart. When allowed to grow naturally, a central raceme of composite flowers and seeds is quickly produced, after which the plant dies. There is little nutrient value but the white sap is rich in iron and contains some vitamins. Lettuce crops are grown either under glass or as field vegetables. They are sold fresh for immediate use or their shelf-life may be increased by cold-chain distribution of, e.g., crisphead cultivars through supermarket outlets. Demand varies with changing weather conditions, the popularity of salads increasing in warm weather.