Assessment of frozen larvae of Callosobruchus maculatus as hosts for rearing Pteromalus cerealellae (Ashmead) (Hymenoptera: Pteromalidae)

a b s t r a c t The suitability of frozen host larvae for rearing Pteromalus cerealellae (Ashmead) (Hymenoptera: Pteromalidae), an ectoparasitoid of Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae) and other stored-product insects was investigated. The reproductive potential (number and sex ratio of progeny) of female P. cerealellae was compared on live (fresh) C. maculatus larvae (concealed within cowpea seeds) versus frozen larvae (obtained by freezing infested cowpea seeds at À20°C for 48 h) which were subsequently thawed and held at ambient conditions ($25 ± 1°C, 50 ± 5% RH) for 4, 24, 48, 72, 96, and 120 h before exposure to female parasitoids. No significant differences were recorded in the numbers and sex ratios of the progeny produced by female P. cerealellae on live larvae compared to frozen host larvae that were thawed and held at ambient conditions for up to 96 h, suggesting that live and frozen larvae of C. maculatus are equally suitable for rearing P. cerealellae. However, the data showed that progeny production on frozen hosts gradually declined with thawing duration and was significantly reduced at the thawing duration of 120 h. When live and frozen host larvae were simultaneously presented together to female P. cerealellae at different exposure periods, relatively greater progeny production was recorded on live hosts than on frozen hosts at 12, 24, and 48 h of exposure. This may suggest preference of female P. cerealellae for live versus frozen host larvae. These results are discussed in relation to the life history strategy and host location behavior of P. cerealellae, and may have practical implications in the development of efficient mass rearing systems for the parasitoid

Behavioral Response of Plum Curculio, Conotrachelus nenuphar

Plum curculio, Conotrachelus nenuphar Herbst (Coleoptera: Curculionidae), is a key pest of stone and pome fruits in North America. The behavioral response of adults of different physiological states (sex, age, diet, and mating status) to three commercially available synthetic lures, benzaldehyde (BZ) and plum essence (PE), the male-produced aggregation pheromone, grandisoic acid (GA), or their combinations, was studied in the laboratory. Four choice olfactometer bioassays demonstrated significant attraction of both sexes to PE lure. Both BZ and GA lures were not attractive to plum curculio when tested as commercially formulated. PE had higher release rate (1.51 mg/hr) than BZ (0.36 mg/hr) and GA (ca. 0.04 mg/hr), suggesting that the higher attractiveness of PE may be due to its relatively higher release rates. Tests with combined lures showed a neutral effect of combining GA with PE and an inhibitory effect of combining BZ with PE. The physiological conditions of the weevils had no significant effect on their response to the lures. Olfactometer tests with pure 1,2,4-trichlorobenzene (TCB) confirmed that this compound was inhibitory to plum curculio. These results are discussed in relation to the contrasting field reports which implicated BZ + GA as an effective attractant for plum curculio

Effects of Food Source Availability, Host Egg:Parasitoid Ratios, and Host Exposure Times on the Developmental Biology of <i>Megacopta cribraria</i> Egg Parasitoids

Parasitoids forage for hosts in dynamic ecosystems and generally have a short period of time to access hosts. The current study examined the optimal reproductive attributes of two egg parasitoids, Paratelenomus saccharalis Dodd (Hymenoptera: Platygastridae) and Ooencyrtus nezarae Ishii (Hymenoptera: Encyrtidae), of the kudzu bug, Megacopta cribraria Fabricius (Hemiptera: Plataspidae). The proportion of O. nezarae and P. saccharalis adult offspring that emerged from M. cribraria eggs and the sex ratio of the parasitoid offspring were compared among treatments for the effects of different adult parasitoid food sources, host egg-to-adult parasitoid ratios, and host exposure times. Our results suggest that honey solution as a food source, a 21:7 host-to-parasitoid ratio, and three-to-five days of exposure time optimized the production of female O. nezarae offspring. For P. saccharalis, honey solution as a food source, a 21:7 host-to-parasitoid ratio, and one day were optimal for maximizing female offspring production. These findings provide new information about the biology of these egg parasitoids

Direct and Indirect Competitive Interactions between <i>Ooencyrtus nezarae</i> and <i>Paratelenomus saccharalis</i> Parasitizing <i>Megacopta cribraria</i> Egg Patches

The present study investigated egg parasitoid interspecific interactions between a generalist, Ooencyrtus nezarae Ishii (Hymenoptera: Encyrtidae) and a specialist, Paratelenomus saccharalis Dodd (Hymenoptera: Platygastridae) in a laboratory setting using kudzu bug (Megacopta cribraria Fabricius, (Hemiptera: Plataspidae)) eggs as their shared host. Three experiments were conducted to evaluate the emergence of wasps from parasitized hosts after the simultaneous and sequential release of wasps, monitor aggressive behavior of P. saccharalis, and quantify intraguild predation of O. nezarae larvae on heterospecific P. saccharalis larvae. Results showed that total host egg parasitism was higher when both wasps were released simultaneously than if wasps were released sequentially. Ooencyrtus nezarae produced more total offspring than P. saccharalis in all sequential/simultaneous treatments but produced male offspring in most cases. In the aggressive behavioral experiment, specialist, P. saccharalis used head butting to fight O. nezarae, but no other aggressions were observed. In an experiment examining intraguild predation, O. nezarae was able to develop in host eggs parasitized by P. saccharalis four days earlier, acting as a superior larval competitor. These findings shed light on the potential interspecific interactions between O. nezarae and P. saccharalis, which may determine their relative abundance and influence their compatibility in kudzu bug biological control programs