Session 3 Abstracts

Blackberry skeletonizer , Schreckensteinia festaliella: natural distribution and egg parasitism on six Rubus species in tropical Hawaiian rainforest Mohsen M. Ramadan State of Hawaii Department of Agriculture, Division of Plant Industry, Plant Pest Control Branch, 1428 South King Street, Honolulu, Hawaii 96814, USA. [email protected]

Several naturalized Rubus species (Rosaceae) are invasive weeds in pastures, displace native plants, and block passage in moist to wet Hawaiian rain forests. The blackberry skeletonizer, Schreckensteinia festaliella (: ), was introduced from California into Hawaii in 1963 to aid in biological control of the prickly Florida blackberry, Rubus argutus. The moth became established on four major islands, with partial success in suppressing the weed throughout the range of blackberry. Neither field efficacy nor possible non-target effects of the moth have been adequately evaluated in forested areas since its introduction. Relative oviposition activity of S. festaliella on four exotic Rubus species and two endemic Hawaiian species (akala raspberry, Rubus hawaiensis and Rubus macraei), sampled simultaneously at shaded (664±101 lux) and open canopy (45000 ±12449 lux) micro-habitats, and rates of egg parasitism, were assessed during the ’ peak population in the Olaa rainforest, Hawaii Volcanoes National Park, Hawaii Island. Female moths deposited eggs more frequently on Rubus hosts at deeply-shaded sites than at exposed open-canopy sites (mean number of eggs: 71.7 compared to 23.1) and more larvae were recorded at the shaded sites (mean number of larvae per 50 cm cane tips: 13.0 compared to 2.3). In shaded and open-canopy sites, the moths showed preference for Andean raspberry, Rubus glaucus, compared to the target host, Rubus argutus and to yellow Himalayan raspberry, Rubus ellipticus. The moths showed the lowest preference for the endemic Hawaiian akala raspberry, and for thimbleberry, Rubus rosaifolius, causing minimal damage to these plants regardless of host habitats. Rates of parasitism by the dominant egg parasitoid, Trichogramma chilonis (Hymenoptera: Trichogrammatidae), were not significantly affected by host-plant species or by habitat. Mean egg parasitism on S. festaliella ranged from 7-55% (mean 27.8%). Micro- habitat and egg parasitism were the most important factors influencing population numbers of S. festaliella in Hawaiian rain forests.

Does parasitism reduce the efficacy of Ceutorhynchus constrictus, a potential biological control agent for garlic mustard, Alliaria petiolata? Danielle Fife1, Tim Haye2 and Esther Gerber*2, 1Acadia University, Biology Department, 33 Westwood Drive, Wolfville, Nova Scotia, B4P 2R6, Canada. 2CABI, Rue des Grillons 1, 2800 Delémont, Switzerland. [email protected]

Biological weed control agents that escape attack from parasitoids present in the introduced range are more likely to establish and to successfully suppress populations of the target weed. In the case of Ceutorhynchus constrictus (Coleoptera: Curculionidae), a seed-feeding weevil currently investigated for the biological control of garlic mustard, Alliaria petiolata (Brassicaceae), in North America, attack by at least one parasitoid species is likely to occur in parts of its potential future range of introduction. Trichomalus perfectus (Chalcidoidea: Pteromalidae) was accidentally introduced from Europe into North America and its distribution range (Quebec and Ontario) overlaps with the distribution of A. petiolata. Trichomalus perfectus is mainly recorded from the cabbage seed-pod weevil, Ceutorhynchus obstrictus, but has also been found attacking larvae of C. constrictus at field sites in Europe. Using an experimental approach, we studied the impact of T. perfectus on C. constrictus development and seed consumption, and inversely, the effect of C. constrictus on T. perfectus fitness. The number of viable seeds produced on plants attacked by C. constrictus was not significantly different when the parasitoids, T. perfectus, were added. Trichomalus perfectus tended to reduce the number of C. constrictus larvae that developed in pods, but differences between treatments were not significant. A lower proportion of female parasitoids developed on larvae of C. constrictus (10%) than known from larvae of the larger host, C. obstrictus (48%). The body size of T. perfectus females and males reared on C. constrictus was significantly reduced compared to those reared on C. obstrictus. In conclusion, our results did not give rise to concerns that attack by T. perfectus could significantly reduce the effectiveness of C. constrictus as a biological control agent against garlic mustard if it were released in North America.

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