Effect of the Ages of Parasitoid and Host Eggs on Telenomus podisi (Hymenoptera: Platygastridae) Parasitism.

This study investigates the influence of parasitoid age and egg age of the hosts Euschistus heros (Fabricius) and Dichelops melacanthus (Dallas) on parasitism of Telenomus podisi Ashmead. Six separate bioassays were conducted: parasitism on eggs of E. heros (bioassay 1) and D. melacanthus (bioassay 2) by T. podisi females of different age (1, 5, and 10 days old); parasitism by T. podisi on eggs of different age (1, 2, 3, 4, and 5 days of embryonic development) of the hosts E. heros (bioassay 3) and D. melacanthus (bioassay 4); preference of T. podisi females for eggs at different embryonic developmental stages (eggs of 1, 2, 3, 4, and 5 days) of the hosts E. heros (bioassay 5) and D. melacanthus (bioassay 6). The age of T. podisi females and their hosts affected parasitism on both E. heros and D. melacanthus eggs. Overall, the parasitism rate was higher in older than younger parasitoids, independent of the tested host species, and host eggs between 1 and 3 days old were similarly parasitized. Thus, in T. podisi mass rearing facilities, it is recommended to use older adults (5 to 10 days old) as mother wasps to increase parasitism on the offered eggs. In addition, when hosts are completely absent in the field, or climatic conditions are unfavorable for release, mass-reared adults can be kept in the laboratory (25°C) for up to 10 days for later release in the field without any impairment of their subsequent parasitism performance.

Host Preferences of Telenomus podisi (Hymenoptera: Scelionidae): Parasitism on Eggs of Dichelops melacanthus, Euschistus heros, and Podisus nigrispinus (Hemiptera: Pentatomidae).

Successful biological control requires detailed knowledge about host preferences of the released parasitoid, because the presence of alternative hosts may affect the control of the target pest. The objective of this work was therefore to evaluate host preferences of Telenomus podisi Ashmead among the eggs of three stink bug species: Dichelops melacanthus Dallas, Euschistus heros Fabricius, and Podisus nigrispinus Dallas (Heteroptera: Pentatomidae). Three independent experiments were carried out to study host preferences among the following: (1) E. heros, D. melacanthus dallas, and P. nigrispinus (bioassay 1); (2) E. heros and D. melacanthus (bioassay 2); and (3) D. melacanthus and P. nigrispinus (bioassay 3). A single bioassay (bioassay 4) was carried out to evaluate the egg size of E. heros, D. melacanthus, and P. nigrispinus. Two more bioassays were carried out: bioassay 5 to study the biological characteristics of T. podisi reared on E. heros, D. melacanthus, and P. nigrispinus eggs, and bioassay 6 to study the morphological characters of T. podisi reared on those different host eggs. Overall, T. podisi consistently preferred eggs of D. melacanthus to those of the other studied hosts, due to probably their better nutritional value; hypothesis that is supported by the fast T. podisi development and bigger parasitoids when reared on D. melacanthus and P. nigrispinus eggs. This allows suggesting that neither pre-imaginal conditioning nor associative learning nor α-conditioning are relevant to T. podisi parasitism. Thus, E. heros eggs could be successfully used for mass rearing of this parasitoid for successive generations since it would not affect its parasitism on other species of the Pentatomidae family in the field.

Quality control of Telenomus remus (Hymenoptera: Platygastridae) reared on the factitious host Corcyra cephalonica (Lepidoptera: Pyralidae) for successive generations.

Egg parasitoid rearing on factitious hosts is an important step to reduce costs and increase availability of the biocontrol agent but it requires quality control to achieve success in field conditions. To this end, this study evaluated the quality of Telenomus remus (Hymenoptera: Platygastridae) reared on Corcyra cephalonica (Lepidoptera: Pyralidae) for until 45 generations. In the first bioassay, we evaluated the body size of the laboratory-produced parasitoids. In the second bioassay, flight activity was examined, measuring the percentage of 'flyers', 'walkers' and 'deformed' parasitoids. The third bioassay assessed parasitism on Spodoptera frugiperda (Lepidoptera: Noctuidae) eggs. Our data indicate that the laboratory-reared parasitoid neither lost its ability to fly nor to parasitize S. frugiperda eggs. In conclusion, quality did not decrease significantly during 45 generations, and therefore rearing of T. remus on C. cephalonica as factitious host promises to be successful.

Low Temperature Storage of Telenomus remus (Nixon) (Hymenoptera: Platygastridae) and its Factitious Host Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae).

We conducted three bioassays to evaluate the effect of low-temperature storage of eggs (host) and pupae and adults (parasitoid) on the biology and parasitism capacity of the egg parasitoid Telenomus remus (Nixon) (Hymenoptera: Platygastridae). Viable stored Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae) eggs were parasitized to the same degree or even higher than fresh eggs when stored until 14 days at 5°C or until 21 days at 10°C. In contrast, the percentage of parasitized sterilized eggs was equal to the control only when stored for 7 and 14 days. Survival of T. remus pupae declined with storage time at both studied temperatures (5 and 10°C). However, after 7 days of storage, survival of pupae was still 86.3 and 64.9% at 10 and 5°C, respectively. The number of adult male survivors remained similar until the fourth storage day at both 5 and 10°C. In contrast, female survival did not differ until day 8 at 10°C or day 6 at 5°C. Parasitism capacity of stored adults was not altered by storage compared with the control. Therefore, we conclude that the maximal storage time at 10°C is 21 days for viable C. cephalonica eggs and 7 days for T. remus pupae, while parasitoid adults should not be stored for more than 4 days at either 5 or 10°C.