Population Abundance of Thrips tabaci Lindeman and its Associated Predators on Some Crops at Shendi, River Nile State, Sudan

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.