Age and suitability of Amorbia cuneana (Lepidoptera : Tortricidae) and Sabulodes aegrotata (Lepidoptera : Geometridae) eggs for Trichogramma platneri(Hymenoptera : Trichogrammatidae)
Jy. Honda et Rf. Luck, Age and suitability of Amorbia cuneana (Lepidoptera : Tortricidae) and Sabulodes aegrotata (Lepidoptera : Geometridae) eggs for Trichogramma platneri(Hymenoptera : Trichogrammatidae), BIOL CONTRO, 18(1), 2000, pp. 79-85
The relationship between different ages of Amorbia cuneana (Lepidoptera: To
rtricidae) Walsingham and Sabulodes aegrotata (Guenee) (Lepidoptera: Geomet
ridae) eggs and parasitism by Trichogramma platneri Nagarkatti platneri (Hy
menoptera: Trichogrammatidae) was studied in the laboratory. T. platneri ma
nifested 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 e
merged when T platneri parasitized 9-day-old egg masses. When T. platneri p
arasitized 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 f
ew of the eggs in a 1- or 3-day-old egg cluster. No parasitoids emerged fro
m the eggs in a 5-day-old egg cluster. In both species, embryos in the olde
st 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 sm
aller and less fecund than their counterparts from 1-, 5-, and 7-day-old eg
g masses. Acceptance of S. aegrotata eggs also depended on their physical p
roperties. The thick chorion of S. aegrotata eggs and the sticky coating on
recently laid eggs leads to fewer of the eggs being parasitized. These fac
tors when coupled with the shorter developmental time of S. aegrotata eggs
appear to explain the less frequent parasitism of S. aegrotata eggs when co
mpared to those of A cuneana. Acceptance of these eggs as hosts was also re
flected in the percentage of the parasitoid's egg load retained after expos
ure to the hosts. Using this criterion, A cuneana eggs were more readily ac
cepted than those of S. aegrotata. (C) 2000 Academic Press.