In New Zealand, unmanaged bees species can be important crop pollinators, but their abundance and distribution is poorly known within hybrid carrot seed crops. Standardised counts of bees visiting flowering carrot umbels (1350 umbels observed/field) across 19 commercial hybrid fields were conducted between 1000 h and 1500 h. Despite honey bees being observed in all fields, abundance varied greatly between fields (mean=98.1; maximum=330, minimum=1). Other bees observed visiting umbels were Lasioglossum sordidum (17 fields; mean=14; maximum=65); Leioproctus sp. (12 fields; mean=2.0; maximum=19); Hylaeus sp. (one field; maximum= 1) and Bombus terrestris (six fields; mean=2.0; maximum=11). The number of individual bees (all species together) counted/ umbel on male fertile umbels was significantly higher than on male sterile umbels, a factor that could contribute to sub-optimal pollen flow between umbel lines by bees. Examination of their movements between male fertile and sterile lines is required to verify their efficiency as pollinators.

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Interactions between biocontrol agents of crop pests can lead to neutral, detrimental, or improved outcomes for pest control. We investigated the existence and the nature of the additive interactions between a parasitoid, Diadegma semiclausum (Hellén) (Hymenoptera: Ichneumonidae), and two hemipteran predators, Oechalia schellenbergii Guérin-Méneville (Pentatomidae) and Nabis kinbergii Reuter (Nabidae), of the diamondback moth (DBM), Plutella xylostella (L.) (Lepidoptera: Plutellidae), under laboratory conditions. In the presence of the parasitoid, both O. schellenbergii and N. kinbergii increased predation by 56 and 66%, respectively. The escape response of the prey to avoid being parasitized (moving backwards and sometimes spinning down from the leaf on a silk thread, becoming less cryptic to the predators), may be at the basis of the enhanced predation by these predatory bugs; however, further studies are necessary to test this hypothesis. As the predators did not preferentially consume either parasitised or unparasitised larvae, coincidental intraguild predation should not affect this positive outcome in relation to DBM suppression. The findings highlight the potential utility of combining these natural enemies and may have important implications for the management of DBM in brassica crops in Australia and other multispecies systems.

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