Suitability of two root-mining weevils for the biological control of scentless chamomile, Tripleurospermum perforatum, with special regard to potential non-target effects

Adult Postabdomen, Immature Stages and Biology of Euryommatus mariae Roger, 1856 (Coleoptera: Curculionidae: Conoderinae), a Legendary Weevil in Europe

The larva and pupa of the saproxylic Euryommatus mariae Roger, 1857, the weevil species extremely rare in Europe, are described from Poland. It was reared from galleries in dead branches of a fallen spruce Picea abies. The larval morphology is compared with available larval descriptions of other genera of the supertribe Conoderitae, namely, the Palaearctic Coryssomerus, and the Nearctic Cylindrocopturus and Eulechriopus. The specific characters of the male and female postabdomen are described and illustrated, expressing the peculiar structure of endophallus and spermathecal duct, not seen in any other weevil species. A hypothesis regarding the mechanics of mating in this species is proposed. Euryommatus mariae is recorded for the first time to occur in China.

Root-feeding insects and their interactions with organisms in the rhizosphere

Root-feeding insects are an increasingly studied group of herbivores whose impacts on plant productivity and ecosystem processes are widely recognized. Their belowground habitat has hitherto hindered our understanding of how they interact with other organisms that share the rhizosphere. A surge in research in this area has now shed light on these interactions. We review key interactions between root-feeding insects and other rhizospheric organisms, including beneficial plant microbes (mycorrhizal fungi, nitrogen-fixing bacteria), antagonists/pathogens of root herbivores (arthropod predators, entomopathogenic nematodes/fungi, and bacterial pathogens), competitors, symbiotic microbes, and detritivores. Patterns for these interactions are emerging. The negative impacts of mycorrhizal fungi on root herbivores, for instance, raise the intriguing prospect that these fungi could be used for pest management. Moreover, a better understanding of symbiotic microbes in root herbivores, especially those underpinning digestion, could prove useful in industries such as biofuel production.

Two shoot-miners, Ceutorhynchus alliariae and Ceutorhynchus roberti, sharing the same fundamental niche on garlic mustard

A combination of observational and experimental methods, in both the laboratory and field, were used to assess niche partitioning between Ceutorhynchus alliariae Brisout and C. roberti Gyllenhal (Coleoptera: Curculionidae), two coexisting shoot-boring weevils on garlic mustard, Alliaria petiolata (M. Bieb.) Cavara and Grande (Brassicaceae). We compared their morphology, oviposition behavior, larval development, distribution, abundance, and attack rates in their sympatric range, and of C. alliariae when found alone and in sympatry with C. roberti. Results indicate only very small differences in the fundamental niches of the two species. Comparison of C. alliariae in the range it occurs alone with the range where it co-occurs with C. roberti revealed some evidence for competition between the two species, i.e., attack levels of C. alliariae were reduced in areas where it co-occurred with C. roberti. However, the study showed no character displacement in regard to adult size or shoot choice of C. alliariae and we found no indication for superiority of either of the two species. Clearly, manipulative experiments would be necessary to unambiguously test for competition between the two species. Our results, based on a subset of niche dimensions known to be important in other systems, suggest that C. alliariae and C. roberti may present one of the rare cases, in which niche differentiation is not the main mechanism underlying coexistence.

Belowground herbivory by insects: influence on plants and aboveground herbivores

Investigations of plant-herbivore interactions continue to be popular; however, a bias neglecting root feeders may limit our ability to understand how herbivores shape plant life histories. Root feeders can cause dramatic plant population declines, often associated with secondary stress factors such as drought or grazing. These severe impacts resulted in substantial interest in root feeders as agricultural pests and increasingly as biological weed control agents, particularly in North America. Despite logistical difficulties, establishment rates in biocontrol programs are equal or exceed those of aboveground herbivores (67.2% for aboveground herbivores, 77.5% for belowground herbivores) and root feeders are more likely to contribute to control (53.7% versus 33.6%). Models predicting root feeders would be negatively affected by competitively superior aboveground herbivores may be limited to early successional habitats or generalist root feeders attacking annual plants. In later successional habitats, root feeders become more abundant and appear to be the more potent force in driving plant performance and plant community composition. Aboveground herbivores, even at high population levels, were unable to prevent buildup of root herbivore populations and the resulting population collapse of their host plants. Significant information gaps exist about the impact of root feeders on plant physiology and secondary chemistry and their importance in natural areas, particularly in the tropics.