THE PROPORTION OF VIRULIFEROUS INDIVIDUALS IN-FIELD POPULATIONS OF FRANKLINIELLA-OCCIDENTALIS - IMPLICATIONS FOR TOMATO SPOTTED WILT VIRUS EPIDEMICS IN TOMATO

Tomato spotted wilt tospovirus (TSWV) infected plants and western flow er thrips (Frankliniella occidentalis Perg., WFT) adult population den sities were monitored during 1993 and 1994 in field tomatoes in Northe astern Spain. The proportion of viruliferous WFT adults in field popul ations was quantified. A significant association has been found betwee n early population densities of WFT adult thrips and final TSWV incide nce for early transplanted tomato crops. In contrast, for late transpl anted tomato crops, whereas similar high final disease incidences of T SWV could be attained, very low WFT adult population densities were al ways detected. The significantly higher infectious potential of WFT po pulations collected during the early growth stages of late transplante d tomatoes could be relevant for the TSWV incidences attained in spite of the low thrips numbers detected.