Parasitization capability of four trichogrammatid species against the tomato leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) under different releasing regimes.
Tomato leaf miner (TLM), Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is an invasive pest causing significant loss to tomato production in Egypt. The success of biological control programs against this serious threat in tomato fields using trichogrammatid species release is a challenge, and depends basically on the number of released parasitoids and spacing among release points. In this study, cage and greenhouse experiments were conducted to evaluate the effect of release density and distance from releasing point on the parasitization capability of four trichogrammatid species (Trichogramma cacoeciae, T. evanescens, T. pretiosum and Trichogrammatoidea bactrae) against TLM. Results indicated that T. bactrae was the most effective parasitoid as indicated by higher percentages of parasitism, followed by T. evanescens, T. cacoeciae and T. pretiosum. In cage experiment, percentage of parasitism increased gradually with the increase of releasing density and reached its maximum at 256 parasitoid females/cage. T. bactrae showed the greatest overall average across all releasing densities at 51.82%, followed by T. cacoeciae, T. evanescens and T. pretiosum with 34.32, 32.58 and 12.45%, respectively. In greenhouse experiment, the percentages of parasitism decreased with increasing distance from the releasing point. T. bactrae was also superior in parasitization compared to the other species at all tested distances, where the percentages of parasitism by T. bactrae were 77.08, 65.00, 40.00 and 38.58% at the distances of 1.5, 3, 4.5 and 6 m from releasing point, respectively.