EFFECT OF PLANT-AGE AT TIME OF INFECTION BY TOMATO SPOTTED WILT TOSPOVIRUS ON THE YIELD OF FIELD-GROWN TOMATO

Naturally infected tomato plants that expressed tomato spotted wilt vi rus symptoms at 24, 38, 45, 60, 67, and 74 days after transplanting we re monitored for production in an experimental crop grown in the open from May to September in northeastern Spain. Plants were tagged, teste d for tomato spotted wilt virus infection by enzyme-linked immunosorbe nt assay, and data on symptom expression and yield were individually r ecorded. Plants that developed symptoms at 24, 38, or 45 days after tr ansplanting yielded significantly less and produced fewer and smaller tomatoes than those that developed symptoms at 60, 67, and 74 days aft er transplanting. These later infected plants showed similar patterns of production with maximum yields between 27 July and 17 August, when most fruit was harvested. Production components such as fruit number p er plant, yield of mature fruit per plant, or fruit weight increased t he older the plants were when first symptoms were exhibited. However, marketable fruit production was drastically decreased by tomato spotte d wilt virus infection, due to abnormal ripening of mature fruit in in fected plants. Little and no significantly different amounts of market able fruit were produced, irrespectively of plant age at time of sympt om expression. Implications for spotted wilt management in tomato are discussed.