Abstract:
Onion thrips (Thrips tabaci) (Thysanoptera:
Thripidae) is a serious pest of onion and other crops in Sudan.
Nevertheless, information about T. tabaci pertinent to different
habitats in the country is incomplete, especially with regard to
agro-ecological aspects. This research aimed to investigate the
seasonality of T. tabaci and its main associated predators at
Shendi area. These were fulfilled through field surveys on
three major host plants (onion, rocket and tomato) during
2011/12 season at three locations, besides a field experiment on
onion crop during 2012/13 season to validate surveys results.
Moreover, the populations of T. tabaci adult and nymphs
recorded from the field experiment were compared at monthly
and seasonal levels. Accordingly, T. tabaci showed its peak
levels on all crops (54-80% infested plants) during March,
coinciding with an increase in temperature and a decrease in
relative humidity at the end of winter season. Onion and rocket
crops showed significantly higher percentages of infested
plants than tomato. Adult thrips were significantly higher than
nymphs equally at the first month (November) and through the
second half (February-April) of the season. This proved that
the peak reproduction period of the pest is highly confined to
the succulent early stage of onion growth between November
and January. Concerning predators, the green lacewing
(Chrysoperla carnea) was the most abundant species, followed
by the 11-spotted ladybird (Coccinella undecimpunctata). They
peaked late in winter season (March-April), synchronizing with
that of onion thrips. Further studies are needed on cultural
practices to escape T. tabaci attack, particularly during the first
half of crop growth, and to enhance natural control of thrips.
Keywords: Onion thrips, seasonality, host plants, natural
enemies.
