Higher Ant Diversity in Native Vegetation Than in Stands of the Invasive Arundo, Arundo donax L., Along the Rio Grande Basin in Texas, USA

Integrative Alternative Tactics for Ixodid Control

Simple Summary

Hard ticks are important for economic and health reasons, and control has mainly relied upon use of synthetic acaricides. Contemporary development of resistance and concerns relating to health and environmental safety have elicited exploration into alternative tactics for hard tick management. Some examples of alternative tactics involve biological control, desiccant dusts, growth regulators, vaccines, cultural methods, and ingested medications.

Abstract

Ixodids (hard ticks), ectoparasitic arthropods that vector the causal agents of many serious diseases of humans, domestic animals, and wildlife, have become increasingly difficult to control because of the development of resistance against commonly applied synthetic chemical-based acaricides. Resistance has prompted searches for alternative, nonconventional control tactics that can be used as part of integrated ixodid management strategies and for mitigating resistance to conventional acaricides. The quest for alternative control tactics has involved research on various techniques, each influenced by many factors, that have achieved different degrees of success. Alternative approaches include cultural practices, ingested and injected medications, biological control, animal- and plant-based substances, growth regulators, and inert desiccant dusts. Research on biological control of ixodids has mainly focused on predators, parasitoid wasps, infective nematodes, and pathogenic bacteria and fungi. Studies on animal-based substances have been relatively limited, but research on botanicals has been extensive, including whole plant, extract, and essential oil effects on ixodid mortality, behavior, and reproduction. The inert dusts kaolin, silica gel, perlite, and diatomaceous earth are lethal to ixodids, and they are impervious to environmental degradation, unlike chemical-based toxins, remaining effective until physically removed.

Genetic Improvement of Arundo donax L.: Opportunities and Challenges

Arundo donax L., the giant reed-being a long-duration, low-cost, non-food energy crop able to grow in marginal lands-has emerged as a potential alternative to produce biomass for both energy production, with low carbon emissions, and industrial bioproducts. In recent years, pioneering efforts have been made to genetically improve this very promising energy crop. This review analyses the recent advances and challenges encountered in using clonal selection, mutagenesis/somaclonal variation and transgenesis/genome editing. Attempts to improve crop yield, in vitro propagation efficiency, salt and heavy metal tolerance by clonal selection were carried out, although limited by the species' low genetic diversity and availability of mutants. Mutagenesis and somaclonal variation have also been attempted on this species; however, since Arundo donax is polyploid, it is very difficult to induce and select promising mutations. In more recent years, genomics and transcriptomics data are becoming available in Arundo, closing the gap to make possible the genetic manipulation of this energy crop in the near future. The challenge will regard the functional characterization of the genes/sequences generated by genomic sequencing and transcriptomic analysis in a complex polyploid genome.

Metastriate Ixodid Life Stages Protected from Predatory Ants in Texas

Multiple predatory ant species, including the red imported fire ant, Solenopsis invicta (Buren) (Hymenoptera: Formicidae), have been reported to attack ixodids (Ixodida: Ixodidae), but evidence has largely been circumstantial. When living lone star tick, Amblyomma americanum (L.) (Acarina: Ixodidae), eggs, and unfed and blood-engorged larvae, nymphs, and adults were deployed on bait transects with hot dog slices and dead house flies, Musca domestica L., in West, Central, and South Texas. The various ixodid life stages were not attacked while ants were strongly recruited to the hot dog and M. domestica baits. Similarly, when the same ixodid life stages and other baits were placed adjacent to colonies of two ant species (red harvester ant, Pogonomyrmex barbatus (Smith) and the red imported fire ant, Solenopsis invicta Buren) the ixodids were not preyed upon while hot dog slices and dead M. domestica were immediately attacked. Some ant species dragged blood-engorged adult ixodids and eggs away from the colony entrance, where they were originally placed, and discarded them. Evidence and mechanisms for allomone-based ant deterrence in the genera Amblyomma, Dermacentor, and Rhipicephalus (metastriate ixodids) are discussed. Protection of ixodids from predatory ants helps to explain why metastriate ixodids remain problematic worldwide despite the presence of predaceous ants.