Age and Suitability of Amorbia cuneana (Lepidoptera: Tortricidae) and Sabulodes aegrotata (Lepidoptera: Geometridae) Eggs for Trichogramma platneri (Hymenoptera: Trichogrammatidae)

The relationship between different ages of Amorbia cuneana (Lepidoptera: Tortricidae) Walsingham and Sabulodes aegrotata (Gueneé) (Lepidoptera: Geometridae) eggs and parasitism by Trichogramma platneri Nagarkatti platneri (Hymenoptera: Trichogrammatidae) was studied in the laboratory. T. platneri manifested low rates of larval mortality, high numbers of emerging adults per egg mass, and highly female-biased sex ratios, when T. platneri parasitized A. cuneana egg masses that were 1, 5, or 7 days old. No parasitoid larvae emerged when T. platneri parasitized 9-day-old egg masses. When T. platneri parasitized S. aegrotata eggs in an egg cluster, it had low rates of larval mortality and a highly female-biased sex ratio, but it only parasitized a few of the eggs in a 1- or 3-day-old egg cluster. No parasitoids emerged from the eggs in a 5-day-old egg cluster. In both species, embryos in the oldest eggs tested had well-developed head capsules. A few parasitoids emerged from singly laid, 9-day-old A. cuneana eggs, but those that emerged were smaller and less fecund than their counterparts from 1-, 5-, and 7-day-old egg masses. Acceptance of S. aegrotata eggs also depended on their physical properties. The thick chorion of S. aegrotata eggs and the sticky coating on recently laid eggs leads to fewer of the eggs being parasitized. These factors when coupled with the shorter developmental time of S. aegrotata eggs appear to explain the less frequent parasitism of S. aegrotata eggs when compared to those of A. cuneana. Acceptance of these eggs as hosts was also reflected in the percentage of the parasitoidʹs egg load retained after exposure to the hosts. Using this criterion, A. cuneana eggs were more readily accepted than those of S. aegrotata.