Efficacy of Novaluron + Pyriproxyfen (Tekko Pro) Insect Growth Regulators Against Amblyomma americanum (Acari: Ixodidae), Rhipicephalus (Boophilus) annulatus, Rhipicephalus (Boophilus) microplus, and Rhipicephalus sanguineus

Lethal Effects of Imergard WP, a Perlite-based Dust, on Amblyomma americanum (Ixodida: Ixodidae) Larvae and Nymphs

As resistance in economically and medically important ixodids (hard ticks, Ixodida: Ixodidae) to conventional synthetic toxin-based acaricides has become increasingly widespread, research efforts to identify alternative control tactics have intensified. Laboratory bioassays on the lone star tick, Amblyomma americanum (L.), as a model for other ixodid species, were conducted to assess the efficiency of Imergard WP perlite-based dust versus CimeXa, a silica gel-based insecticidal product that is highly effective against ixodid larvae and nymphs. Each of the two inert desiccant dusts immobilized A. americanum larvae and nymphs within 4-6 h, and killed 100% of the ixodids by 24 h after contact by brief immersion in dry dusts, and after they crawled ≈7.3 cm across a filter paper disc treated with the dusts. Contact by crawling on a dried aqueous film of the dusts, however, did not immobilize and kill the ixodids by 24 h. Similar to silica gel-based desiccant dust, dry perlite-based Imergard WP dust might prophylactically protect cattle and other animals from medically and agriculturally important ixodid pests. Perlite can potentially be stored indefinitely, it can retain its lethal properties for as long as adequate amounts remain on a substrate, and it might be acceptable for limited application in environmentally sensitive habitats.

Desiccant Dusts, With and Without Bioactive Botanicals, Lethal to Rhipicephalus (Boophilus) microplus Canestrini (Ixodida: Ixodidae) in the Laboratory and on Cattle

The exotic southern cattle fever tick, Rhipicephalus (Boophilus) microplus (Canestrini) (Ixodida: Ixodidae), since its eradication from the United States in 1943, made a strong incursion into Texas, beginning 2016. The pest is arguably the most economically detrimental ectoparasite of cattle, Bos taurus L., worldwide. Current R. (B.) microplus control mostly relies on conventional synthetic acaricides to which the ixodid has been developing resistance. Our study demonstrates that commercially available desiccant dust products, with and without bioactive botanical additives, are strongly lethal, when applied dry, against larval R. (B.) microplus in the laboratory, and after being released on dust-treated cattle. Deadzone (renamed Celite 610, a diatomaceous earth product), Drione (silica gel + pyrethrins + piperonyl butoxide synergist), and EcoVia (silica gel + thyme oil), each prophylactically prevented larval R. (B.) microplus from attaching to and feeding on stanchioned calves. Desiccant dust-based products are less likely than conventional synthetic acaricides to decline in terms of efficacy as a result of ixodid resistance, and other desiccant dust advantages, including extended residual, flexibility in terms of application methods, environmental, animal, and human safety, and possible compatibility with organic, or 'green', production systems, are discussed. We anticipate that the desiccant dusts we evaluated, and others not included in this study (e.g., kaolin, perlite, and silica gel) will be effective when used with other control tactics in integrated pest management approaches for controlling R. (B.) microplus (and other ixodid species).

Field applications of granular and liquid pyrethroids, carbaryl, and IGRs to control the asian longhorned tick (Haemaphysalis longicornis) and impacts on nontarget invertebrates

Few documented control strategies exist for the invasive tick, Haemaphysalis longicornis, despite its potential to reach extremely high numbers and vector human and animal pathogens. In 2020, we evaluated the effects of single applications of five granular and liquid acaricides on H. longicornis in a public park in northern New Jersey. Acaricides tested included pyrethroids (lambda-cyhalothrin, bifenthrin), a carbamate (carbaryl), and the insect growth regulators (IGRs) pyriproxyfen and novaluron. We also monitored the impact of each treatment on non-target soil and above-ground invertebrate species using pitfall and sticky traps, respectively. We recorded over 70,000 H. longicornis ticks in the study area from July to October 2020. An average of 99% control was achieved with lambda-cyhalothrin spray and 95% with granular bifenthrin. In contrast, granular carbaryl did not significantly reduce any life stages of H. longicornis. The IGR (pyriproxyfen/novaluron) resulted in a significant 45% reduction of the larval stage following treatments in July. No other stages were significantly impacted by pyriproxyfen alone or in combination with novaluron. Analysis of non-target species revealed that the community composition of soil-dwelling arthropods was strongly impacted by pyrethroid treatments and, to a lesser extent, by the carbamate treatment. The granular pyrethroid bifenthrin had more pronounced effects and impacted a broader range of non-target groups in the pitfall traps than the liquid pyrethroid lambda-cyhalothrin. Arthropod groups that were negatively impacted included Isopoda, Formicidae, Coleoptera, Araneae, Acari, and Grylloidea. Collembola numbers, however, were elevated in both pyrethroid treatments. The community composition of arthropods collected on the above-ground sticky traps was strongly impacted only in the liquid lambda-cyhalothrin treatment. The primary groups impacted in the sticky trap analysis were Collembola and Hemiptera. Community composition in traps remained distinct in the pyrethroid treatments through the entire survey period up to 62 days post-treatment. The results of this study indicate that pyrethroid acaricides were highly effective at controlling H. longicornis, while other compounds, including carbaryl and IGRs, did not achieve consistent levels of control. Further research is needed to find effective and environmentally sustainable alternatives. Integrated management programs can include the judicious use of pyrethroids to control H. longicornis.

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.

Biosurveillance and Research Needs Involving Area-Wide Systematic Active Sampling to Enhance Integrated Cattle Fever Tick (Ixodida: Ixodidae) Eradication

The one-host cattle fever tick, Rhipicephalus (Boophilus) annulatus (Say), and southern cattle fever tick, Rhipicephalus (Boophilus) microplus (Canestrini), are important ectoparasitic pests of cattle, Bos taurus L., mostly for transmitting the causal agents of bovine babesiosis. Bovine babesiosis inflicted substantial cattle production losses in the United States before the vectors were eliminated by 1943, with the exception of a Permanent Quarantine Zone in South Texas, a buffer along the Mexico border where the invasive ixodids remain. As suitable hosts, infested white-tailed deer and nilgai antelope populations disperse R. annulatus and R. microplus, which increases the risk for emergence of bovine babesiosis in the United States. A R. microplus incursion first detected in 2016 on the South Texas coastal plain wildlife corridor involved infestations on cattle, nilgai antelope, white-tailed deer, and vegetation. Efforts at passive sampling of Rhipicephalus (Boophilus) spp. on hosts are concentrated in the Permanent Quarantine Zone. Hence, a knowledge gap exists on the full extent of the recent incursions. Area-wide, systematic, active sampling and supportive research, involving the Permanent Quarantine Zone, Temporary Quarantine Zone, most of the coastal plain, and other parts of Texas outside of the quarantine zones, are needed to bridge the knowledge gap. Herein, we provide research perspectives and rationale to develop and implement systematic active sampling that will provide an increasingly accurate assessment of Rhipicephalus (Boophilus) spp. distribution in Texas. We suggest that this is essential to advance integrated vector-borne animal disease eradication approaches for keeping cattle free of bovine babesiosis.

Lethal Effects of a Commercial Diatomaceous Earth Dust Product on Amblyomma americanum (Ixodida: Ixodidae) Larvae and Nymphs

With increasing development of resistance to conventional synthetic acaricides in economically and medically important ixodid species, interest in finding alternative control tactics has intensified. Laboratory bioassays were conducted, using the lone star tick, Amblyomma americanum (L.), as a model species, to assess the efficacy of a diatomaceous earth-based product, Deadzone, in comparison with a silica gel-based product, CimeXa. CimeXa is already known to be highly lethal against A. americanum larvae and nymphs. The two dust treatments were 100% effective against larvae and nymphs within 24 h after contact occurred by immersion in dry dusts and after crawling across a surface treated with the dry dusts. Contact by crawling on a dried aqueous film of the dusts, even at a concentration of 10%, was not as effective as exposure to the dusts in dry powder form. As has been demonstrated with CimeXa, it is likely that Deadzone will be capable of providing prophylactic protection of cattle from economically important one-host ixodids, such as the southern cattle fever tick, Rhipicephalus microplus (Canestrini), which vectors the causal agents of babesiosis. Diatomaceous earth can be stored indefinitely, will remain efficacious for as long as sufficient quantities remain on the substrate, it is a natural (organic) substance, and it might be amenable for limited use in environmentally protected habitats.