Influence of egg traits on parasitism by Trichogramma chilonis Ishii, 1941 and Telenomus remus Nixon, 1937 against Spodoptera frugiperda (J.E. Smith, 1797)

Trichogramma chilonis Ishii, 1941 and Telenomus remus Nixon, 1937 are the most common egg parasitoids of fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith, 1797) in maize growing areas. FAW lays single to multilayered egg which are covered with degrees of scale thickness. Here, we assessed the parasitism of both parasitoids over different FAW egg densities (single layered), egg mass scale coverage (multilayered), and the egg ages. Two laboratory experiments were conducted from May to November 2022 under controlled conditions (24.3 ± 0.8 °C, 69.3 ± 2.2% RH). The first experiment, using a three-factor complete randomized design (CRD), involved two egg parasitoid species, single-layered eggs at three densities (20, 43, and 60 eggs), and three egg age groups (less than 12 hours, 24–36 hours, and 48–60 hours), each replicated three times. The second experiment involved two parasitoid species, multilayered eggs with three levels of egg scale coverage (fully covered, partially covered, uncovered), and three egg age groups, each replicated three times. T. remus exhibited significantly higher parasitism rates than T. chilonis in both single and multilayered egg masses. T. remus parasitized all egg groups uniformly, while T. chilonis struggled with fully covered egg masses. Parasitism percentage decreased with the age of the host eggs in both parasitoid species. T. remus showed a higher adult emergence percentage, regardless of egg scale covering but declined with increasing host egg age. The percentage of female progeny and development period were similar for both parasitoid species but decreased as egg density and egg age increased.