Natural Abundance and Biocontrol Efficiency of the Ectoparasitoid Diglyphus isaea Walker on the Serpentine Leafminer Liriomyza trifolii (Burgess) in Tomato Greenhouses in Alzawia Region Libya

Abstract

Aims: The present study aimed to evaluate the role of natural abundance of the ectoparasitoid D. isaea as biological control agent. Place and Duration: Alzawia region, Libya from March to June 2014. Methodology: Fifty tomato leaflets infested with L. trifolii Burgess were taken from each greenhouse. Samples were kept in plastic bags and examined in the laboratory. Number of living L. trifolii Burgess larvae, immature stages of the D. isaea walker and number of killed larvae according to feeding (no ovipositon) were counted and recorded. Results: D. isaea walker recorded two peaks of abundance in all studied greenhouses, the highest peaks recorded 23, 41, 32 and 33 individuals/ 50 infested leaflets in greenhouses 1,2,3 and 4, respectively. The highest average numbers occurred in April in all greenhouses recording 17.3±4.5, 26.4±11.5, 23.8±6.4 and 21.3±8.8 individuals/ 50 infested leaflets in greenhouses 1,2,3 and 4, respectively. On the other hand the percentage of parasitism ranged between 26.4±8.2 and 52.4±6.7% recording its highest numbers in June in greenhouses 1,2 and 3 recording  (49.4±11.9%, 50.6±5.5, 52.4±6.7) respectively and 40.3±5.2% in green house 4 in May. The percentage of killed larvae according to host-feeding recorded its highest monthly average numbers in May in greenhouses 1 and 2 recording (44.6±18.9 and, 38.2±2.5), in April in greenhouse 3 recording (29.4±3.3) and in may in greenhouse 4 recording 26.6± 20.5%. Conclusion: The parasitoid showed low populations in March then, developed good populations that kept the populations of the serpentine leaf miner L. trifolii Burgess at low densities till the end of the season in all studied greenhouses. So no chemical control measurements against L. trifolii Burgess should be applied at the high populations of this parasitoid.