Pcj. Vanrijn et al., COMPARATIVE LIFE-HISTORY STUDIES OF FRANKLINIELLA-OCCIDENTALIS AND THRIPS TABACI (THYSANOPTERA, THRIPIDAE) ON CUCUMBER, Bulletin of entomological research, 85(2), 1995, pp. 285-297
Shortly after its invasion into Europe, the western flower thrips, Fra
nkliniella occidentalis (Pergande), became a more severe pest of green
house crops than the onion thrips, Thrips tabaci Lindeman. To test whe
ther this differential pest status was due to a larger capacity of pop
ulation increase, a comparative life history study was carried out on
cucumber (Cucumis sativus cv. Corona). Experiments at 25 degrees C sho
wed that the egg-to-egg period of F. occidentalis was shorter, but its
peak ovipositional rate was lower and its offspring sex ratio more ma
le biased. These differences resulted in a slightly lower intrinsic ra
te of population increase (r(m)) for F. occidentalis than for T. tabac
i (0.166 vs. 0.176/day). It was shown experimentally that between 15 a
nd 28 degrees C, developmental rate of F. occidentalis is linearly rel
ated to temperature, with a theoretical threshold temperature similar
to the value reported for T. tabaci (10.9 vs. 11.5 degrees C). It is a
rgued that the r(m)-value of F. occidentalis will not be higher than t
hat of T. tabaci for any temperature within this range. Alternative ex
planations for the difference in pest status between the two thrips sp
ecies are discussed.