Studies on Thrips Species and Their Associated Predators in Shendi Area,River Nile State, Sudan

Abstract

This study was conducted during November 2011 to February 2013 in Shendi, a promising agricultural area in the River Nile State, Sudan. It aimed to recognize the important thrips species, their host plants, and associated predators via field surveys. Preliminary laboratory investigations were also carried out, regarding life cycle (durations of pre-imaginal stages) of two key species of thrips as well as of two dominant predators, in addition to feeding capacity test for such predators when provided with adults of onion thrips (Thrips tabaci). The results revealed two thrips species, viz., onion thrips and cotton leaf thrips (Caliothrips sudanensis), with the former species reflected a wider host range (in terms of plant family and species) than the latter one. In addition, four predatory insects were detected, among which the green lacewing (Chrysoperla carnea) and the 11-spotted ladybird (Coccinella undecimpunctata) were predominant. The average total durations of immature stages of T. tabaci and C. sudanensis, during January-February 2013 in winter (av. 25°C and 35.8%R.H.), were 10.66±0.08 and 13.33±0.30 days, respectively. The shorter developmental period of T. tabaci and its threat to several host crops suggested its major pest status. On the other hand, the average durations of immature stages of C. carnea and C. undecimpunctata, during OctoberNovember 2013 of pre-winter time (av. 34°C and 42%R.H.), were 24.98±1.02 and 21.67±0.49 days, respectively. The results of feeding rates reflected that the larvae of C. carnea devoured insignificantly larger number of T. tabaci (76.45±1.66 adults) than those of C. undecimpunctata (74.00±3.88), during their lifetimes. However, such relative inferiority of the latter predator, regarding larval duration and feeding rate, seemed to be compensated by predation in adult stage. Therefore, both predators look important in regulating thrips populations, and this awaits further studies. Keywords: Thripidae, Thrips tabaci, Caliothrips, Chrysoperla, life cycle, feeding.