Evaluation of Barricade® to enhance survival of entomopathogenic nematodes on cowhide.

Entomopathogenic nematodes (EPNs), Steinernema riobrave and Heterorhabditis floridensis are under evaluation for eradication of the southern cattle fever tick, Rhipicephalus microplus infesting nilgai antelope, in South Texas. Cattle fever ticks are a significant threat to the U.S. livestock industry. Although they have been eradicated in the U.S. they frequently re-invade along the Texas-Mexico border. Remotely operated field sprayers have been developed to directly treat nilgai antelope with EPNs as they transit fence crossings and as they contact wetted foliage and soil from the surrounding area. EPNs are known to be susceptible to mortality from ultraviolet light (UV) and desiccation. A sprayable fire gel, Barricade®, has been reported to protect EPNs from UV and desiccation but has not been tested on animal hides. Barricade® at 1 and 2 percent rates was mixed with the water solution of S. riobrave and H. floridensis and applied to cowhides (to mimic direct treatment of nilgai) and filter paper and then these substrates were placed out of doors in 0, 30, 60 or 120 min of sunlight. Wax moth larvae, Galleria mellonella, were exposed to the cowhides and filter paper to determine efficacy of the EPNs. Efficacy of S. riobrave with 1 and 2% Barricade® gel applied to cowhides was significantly improved at 30 and 60 min as compared to the control. At 120 min mortality of the wax moth larvae was near zero for both the control and the treatments. Similar results were found with the filter paper test. In contrast, efficacy of H. floridensis with Barricade® applied to cowhides or filter paper was not significantly improved at 30, 60 or 120 min as compared to the water only control. Barricade® has the potential to improve the efficacy of S. riobrave and other EPNs by reducing mortality and desiccation, especially when used in the remotely operated sprayer developed for treatment of cattle fever tick infested nilgai.

Evolutionary changes in symbiont community structure in ticks.

Ecological specialization to restricted diet niches is driven by obligate, and often maternally inherited, symbionts in many arthropod lineages. These heritable symbionts typically form evolutionarily stable associations with arthropods that can last for millions of years. Ticks were recently found to harbour such an obligate symbiont, Coxiella-LE, that synthesizes B vitamins and cofactors not obtained in sufficient quantities from blood diet. In this study, the examination of 81 tick species shows that some Coxiella-LE symbioses are evolutionarily stable with an ancient acquisition followed by codiversification as observed in ticks belonging to the Rhipicephalus genus. However, many other Coxiella-LE symbioses are characterized by low evolutionary stability with frequent host shifts and extinction events. Further examination revealed the presence of nine other genera of maternally inherited bacteria in ticks. Although these nine symbionts were primarily thought to be facultative, their distribution among tick species rather suggests that at least four may have independently replaced Coxiella-LE and likely represent alternative obligate symbionts. Phylogenetic evidence otherwise indicates that cocladogenesis is globally rare in these symbioses as most originate via horizontal transfer of an existing symbiont between unrelated tick species. As a result, the structure of these symbiont communities is not fixed and stable across the tick phylogeny. Most importantly, the symbiont communities commonly reach high levels of diversity with up to six unrelated maternally inherited bacteria coexisting within host species. We further conjecture that interactions among coexisting symbionts are pivotal drivers of community structure both among and within tick species.

Exploring origins, invasion history and genetic diversity of Imperata cylindrica (L.) P. Beauv. (Cogongrass) in the United States using genotyping by sequencing.

Imperata cylindrica (Cogongrass, Speargrass) is a diploid C4 grass that is a noxious weed in 73 countries and constitutes a significant threat to global biodiversity and sustainable agriculture. We used a cost-effective genotyping-by-sequencing (GBS) approach to identify the reproductive system, genetic diversity and geographic origins of invasions in the south-eastern United States. In this work, we demonstrated the advantage of employing the closely related, fully sequenced crop species Sorghum bicolor (L.) Moench as a proxy reference genome to identify a set of 2320 informative single nucleotide and insertion-deletion polymorphisms. Genetic analyses identified four clonal lineages of cogongrass and one clonal lineage of Imperata brasiliensis Trin. in the United States. Each lineage was highly homogeneous, and we found no evidence of hybridization among the different lineages, despite geographical overlap. We found evidence that at least three of these lineages showed clonal reproduction prior to introduction to the United States. These results indicate that cogongrass has limited evolutionary potential to adapt to novel environments and further suggest that upon arrival to its invaded range, this species did not require local adaptation through hybridization/introgression or selection of favourable alleles from a broad genetic base. Thus, cogongrass presents a clear case of broad invasive success, across a diversity of environments, in a clonal organism with limited genetic diversity.

Animal use of fence crossings in southwestern rangelands.

Net-wire fencing built to confine livestock is common on rangelands in the Southwestern USA, yet the impacts of livestock fencing on wildlife are largely unknown. Many wildlife species cross beneath fences at defined crossing locations because they prefer to crawl underneath rather than jump over fences. Animals occasionally become entangled jumping or climbing over fences, leading to injury or death. More commonly, repeated crossings under net-wire fencing by large animals lead to fence damage, though the damage is often tolerated by landowners until the openings affect the ability to enclose livestock. The usage, placement, characteristics, and passage rates of fence crossings beneath net-wire fencing are poorly understood. We monitored 20 randomly selected fence crossings on net-wire livestock fencing across two study sites on rangelands in South Texas, USA, from April 2018 to March 2019. We assessed the characteristics of fence-crossing locations (openings beneath the fence created by animals to aid in crossing) and quantified crossing rates and the probability of crossing by all species of animals via trail cameras. We documented 10,889 attempted crossing events, with 58% (n = 6271) successful. Overall, 15 species of medium- and large-size mammals and turkey (Meleagris gallopavo) contributed to crossing events. Crossing locations received 3-4 crossing attempts per day on average, but the number of attempts and probability of successful crossing varied by location and fence condition. The probability of crossing attempts was most consistently influenced by the opening size of the crossing and season; as crossing size (opening) increased, the probability of successful crossing significantly increased for all species. Peaks in crossing activity corresponded with species' daily and seasonal movements and activity. The density and size of fence-crossing locations were dependent on fence maintenance and not associated with vegetation communities or habitat variables. However, crossing locations were often re-established in the same locations after fence repairs. This is one of the few studies to monitor how all animal species present interacted with net-wire livestock fencing in rangelands. Our results will help land managers understand the impact of net-wire livestock fencing on animal movement.

A decision-support tool to predict spray deposition of insecticides in commercial potato fields and its implications for their performance.

Approximately US $1.3 billion is spent each year on insecticide applications in major row crops. Despite this significant economic importance, there are currently no widely established decision-support tools available to assess suitability of spray application conditions or of the predicted quality or performance of a given commercial insecticide applications. We conducted a field study, involving 14 commercial spray applications with either fixed wing airplane (N=8) or ground rig (N=6), and we used environmental variables as regression fits to obtained spray deposition (coverage in percentage). We showed that (1) ground rig applications provided higher spray deposition than aerial applications, (2) spray deposition was lowest in the bottom portion of the canopy, (3) increase in plant height reduced spray deposition, (4) wind speed increased spray deposition, and (5) higher ambient temperatures and dew point increased spray deposition. Potato psyllid, Bactericera cockerelli (Sulc) (Hemiptera: Triozidae), mortality increased asymptotically to approximately 60% in response to abamectin spray depositions exceeding around 20%, whereas mortality of psyllid adults reached an asymptotic response approximately 40% when lambda-cyhalothrin/thiamethoxam spray deposition exceeded 30%. A spray deposition support tool was developed (http://pilcc.tamu.edu/) that may be used to make decisions regarding (1) when is the best time of day to conduct spray applications and (2) selecting which insecticide to spray based on expected spray deposition. The main conclusion from this analysis is that optimization of insecticide spray deposition should be considered a fundamental pillar of successful integrated pest management programs to increase efficiency of sprays (and therefore reduce production costs) and to reduce risk of resistance development in target pest populations.

Biology of an Adventive Population of the Armored Scale Rhizaspidiotus donacis, a Biological Control Agent of Arundo donax in California.

Arundo donax (giant reed) is invasive in Mediterranean, sub-, and tropical riparian systems worldwide. The armored scale Rhizaspidiotus donacis is approved for biocontrol in North America, but an adventive population was recently discovered in southern California. We documented this population's distribution, phylogeny, phenology, potential host spillover to Phragmites spp., and potential for parasitism by a common biocontrol parasitoid of citrus scale. The adventive scale was found within a single watershed and is genetically closest to Iberian scale genotypes. Rhizaspidiotus donacis developed on Phragmites haplotypes but at much lower densities than Arundo. The adventive population is univoltine, producing crawlers from March-June. Aphytis melinus parasitoids exhibited sustained interest in R. donacis during choice and no-choice trials and oviposition resulted in a small second generation. Rhizaspidiotus donacis appears limited in distribution by its univoltinism and sessile adult females. This presents challenges for broad biocontrol implementation but allows for targeted application. The genetic differentiation between imported biocontrol samples and adventive populations presents an opportunity for exploring benefits of hybrids and/or alternative genotypes where establishment has been difficult. While unlikely to occur in situ, spillover to vulnerable endemic Phragmites or deleterious parasitoid effects on scale biocontrol agents warrants consideration when planning use of R. donacis.

In-vitro efficacy of a botanical acaricide and its active ingredients against larvae of susceptible and acaricide-resistant strains of Rhipicephalus (Boophilus) microplus Canestrini (Acari: Ixodidae).

Ticks and tick-borne diseases are a major constraint for a sustainable cattle industry in the tropical and subtropical regions of the world. The development of resistance to most of the commonly used acaricides has led to an assessment of herbal products for acaricidal activity as an eco-friendly tick control alternative. A botanical product, Essentria® IC-3 insect concentrate containing rosemary oil (10%), geraniol (5%) and peppermint oil (2%), acts on target pests by blocking octopamine. Essentria® IC-3 and its active components were evaluated for larvicidal activity against several susceptible and acaricide-resistant strains of the cattle fever tick, Rhipicephalus (Boophilus) microplus Canestrini by Larval Packet test using 14-21 d old unfed larvae. The efficacy was assessed by measuring percent larval mortality and estimating lethal concentrations at 50% (LC50) and 95% (LC95) with 95% confidence limits (CL) using probit analysis. The LC50 and LC95 (95% CL) values for Essentria® IC-3 against the susceptible strain were estimated as 0.647% (0.59-0.69) and 1.033% (0.94-1.19), respectively, whereas, LC50 and LC95 values for other strains were variable, ranging from 0.597-1.674% and 0.927-2.236%, respectively. Among the various active ingredients, the larvicidal property of Essentria® IC-3 seem to be attributable mainly to geraniol and the LC50 and LC95 (95% CL) values for geraniol against the susceptible Deutch strain were estimated as 0.656% (0.61-0.69) and 1.114% (1.03-1.25), respectively. The comparison of LC50 and LC95 values of acaricide-resistant strains showed susceptibility comparable to Deutch against geraniol except for the Las Palmas strain. We report a low level of resistance in some of the acaricide-resistant strains against the herbal acaricide in the cattle tick for the first time, possibly due to cross-resistance to chemical acaricides.

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

Our hypothesis was that there will be greater ant biodiversity in heterogeneous native vegetation compared with Arundo stands. Changes in ant biodiversity due to Arundo invasion may be one of the ecological changes in the landscape that facilitates the invasion of cattle fever ticks from Mexico where they are endemic. Ants collected in pitfall traps were identified and compared between native vegetation and stands of Arundo, Arundo donax L., monthly for a year at 10 locations. A total of 82 752 ants representing 28 genera and 76 species were collected. More ants were collected in the native vegetation which also had greater species richness and biological diversity than ants collected from Arundo stands. It is suggested that the greater heterogeneous nature of native vegetation provided greater and more predictable nourishment in the form of nectars and more abundant arthropod prey when compared with Arundo stands.

Comparison of natural and artificial odor lures for nilgai (Boselaphus tragocamelus) and white-tailed deer (Odocoileus virginianus) in South Texas: Developing treatment for cattle fever tick eradication.

Cattle fever ticks (CFT), vectors of bovine babesiosis and anaplasmosis, were eradicated from the United States by 1943, but are frequently reintroduced from neighboring border states of Mexico via stray cattle and wildlife hosts including white-tailed deer (Odocoileus virginianus) (WTD) and nilgai antelope (Boselaphus tragocamelus). Nilgai antelope are exotic bovids from India that are hosts of CFT, have large home ranges as compared to WTD, thus have the potential to spread CFT through the landscape. Currently, there are no methods to control CFT on nilgai. Odor lures were evaluated to determine if nilgai could be attracted to a central point for development of control methods. Four treatments, nilgai offal a natural odor lure was used as the positive control; and compared to three artificial odors; screw worm lure, volatile fatty acids, citronella oil. Studies were conducted on a free-ranging population of nilgai at the East Foundation's Santa Rosa Ranch (Kenedy Co., near Riviera, Texas, USA). Game cameras were used to document visitation to the lures. In the ten randomly placed transects, 110 nilgai and 104 WTD were photographed. Offal had significantly more visits by nilgai (71% of total visits) than screwworm (15%), VFA (11%), and citronella (4%). For WTD, there was no significant difference in visitation at the lure treatments.

Movement patterns of nilgai antelope in South Texas: Implications for cattle fever tick management.

Wildlife, both native and introduced, can harbor and spread diseases of importance to the livestock industry. Describing movement patterns of such wildlife is essential to formulate effective disease management strategies. Nilgai antelope (Boselaphus tragocamelus) are a free-ranging, introduced ungulate in southern Texas known to carry cattle fever ticks (CFT, Rhipicephalus (Boophilus) microplus, R. (B.) annulatus). CFT are the vector for the etiological agent of bovine babesiosis, a lethal disease causing high mortality in susceptible Bos taurus populations and severely affecting the beef cattle industry. Efforts to eradicate CFT from the United States have been successful. However, a permanent quarantine area is maintained between Texas and Mexico to check its entry from infested areas of neighboring Mexico states on wildlife and stray cattle. In recent years, there has been an increase in CFT infestations outside of the permanent quarantine area in Texas. Nilgai are of interest in understanding how CFT may be spread through the landscape. Thirty nilgai of both sexes were captured and fitted with satellite radio collars in South Texas to gain information about movement patterns, response to disturbances, and movement barriers. Median annual home range sizes were highly variable in males (4665ha, range=571-20,809) and females (1606ha, range=848-29,909). Female movement patterns appeared to be seasonal with peaks during June-August; these peaks appeared to be a function of break-ups in female social groups rather than environmental conditions. Nilgai, which reportedly are sensitive to disturbance, were more likely to relocate into new areas immediately after being captured versus four other types of helicopter activities. Nilgai did not cross 1.25m high cattle fences parallel to paved highways but did cross other fence types. Results indicate that females have a higher chance of spreading CFT through the landscape than males, but spread of CFT may be mitigated via maintenance of cattle fences running parallel with paved highways. Our results highlight the importance of documenting species-specific behavior in wildlife-livestock interfaces that can be used to develop effective disease management strategies in the United States and worldwide.

Shoot transcriptome of the giant reed, Arundo donax.

The giant reed, Arundo donax, is a perennial grass species that has become an invasive plant in many countries. Expansive stands of A. donax have significant negative impacts on available water resources and efforts are underway to identify biological control agents against this species. The giant reed grows under adverse environmental conditions, displaying insensitivity to drought stress, flooding, heavy metals, salinity and herbaceous competition, thus hampering control programs. To establish a foundational molecular dataset, we used an llumina Hi-Seq protocol to sequence the transcriptome of actively growing shoots from an invasive genotype collected along the Rio Grande River, bordering Texas and Mexico. We report the assembly of 27,491 high confidence transcripts (≥200 bp) with at least 70% coverage of known genes in other Poaceae species. Of these 13,080 (47.58%), 6165 (22.43%) and 8246 (30.0%) transcripts have sequence similarity to known, domain-containing and conserved hypothetical proteins, respectively. We also report 75,590 low confidence transcripts supported by both trans-ABBySS and Velvet-Oases de novo assembly pipelines. Within the low confidence subset of transcripts we identified partial hits to known (19,021; 25.16%), domain-containing (7093; 9.38%) and conserved hypothetical (16,647; 22.02%) proteins. Additionally 32,829 (43.43%) transcripts encode putative hypothetical proteins unique to A. donax. Functional annotation resulted in 5,550 and 6,070 transcripts with assigned Gene Ontology and KEGG pathway information, respectively. The most abundant KEGG pathways are spliceosome, ribosome, ubiquitin mediated proteolysis, plant-pathogen interaction, RNA degradation and oxidative phosphorylation metabolic pathway. Furthermore, we also found 12, 9, and 4 transcripts annotated as stress-related, heat stress, and water stress proteins, respectively. We envisage that these resources will promote and facilitate studies of the abiotic stress capabilities of this exotic plant species, which facilitates its invasive capacity.

Biological control of weeds: research by the United States Department of Agriculture-Agricultural Research Service: selected case studies.

Research by the USDA-Agricultural Research Service (ARS) on biological control of weeds has been practiced for many years because of its inherent ecological and economic advantages. Today, it is further driven by ARS adherence to Presidential Executive Order 13112 (3 February 1999) on invasive species and to USDA-ARS policy toward developing technology in support of sustainable agriculture with reduced dependence on non-renewable petrochemical resources. This paper reports examples or case studies selected to demonstrate the traditional or classical approach for biological control programs using Old World arthropods against Tamarix spp, Melaleuca quinquenervia (Cav) ST Blake and Galium spurium L/G aparine L, and the augmentative approach with a native plant pathogen against Pueraria lobata Ohwi = P montana. The examples illustrated various conflicts of interest with endangered species and ecological complexities of arthropods with associated microbes such as nematodes.

Pathogenic Landscape of Transboundary Zoonotic Diseases in the Mexico-US Border Along the Rio Grande.

Transboundary zoonotic diseases, several of which are vector borne, can maintain a dynamic focus and have pathogens circulating in geographic regions encircling multiple geopolitical boundaries. Global change is intensifying transboundary problems, including the spatial variation of the risk and incidence of zoonotic diseases. The complexity of these challenges can be greater in areas where rivers delineate international boundaries and encompass transitions between ecozones. The Rio Grande serves as a natural border between the US State of Texas and the Mexican States of Chihuahua, Coahuila, Nuevo León, and Tamaulipas. Not only do millions of people live in this transboundary region, but also a substantial amount of goods and people pass through it everyday. Moreover, it occurs over a region that functions as a corridor for animal migrations, and thus links the Neotropic and Nearctic biogeographic zones, with the latter being a known foci of zoonotic diseases. However, the pathogenic landscape of important zoonotic diseases in the south Texas-Mexico transboundary region remains to be fully understood. An international perspective on the interplay between disease systems, ecosystem processes, land use, and human behaviors is applied here to analyze landscape and spatial features of Venezuelan equine encephalitis, Hantavirus disease, Lyme Borreliosis, Leptospirosis, Bartonellosis, Chagas disease, human Babesiosis, and Leishmaniasis. Surveillance systems following the One Health approach with a regional perspective will help identifying opportunities to mitigate the health burden of those diseases on human and animal populations. It is proposed that the Mexico-US border along the Rio Grande region be viewed as a continuum landscape where zoonotic pathogens circulate regardless of national borders.

Matching the origin of an invasive weed for selection of a herbivore haplotype for a biological control programme.

The Florida Everglades have been invaded by an exotic weed fern, Lygodium microphyllum. Across its native distribution in the Old World tropics from Africa to Australasia it was found to have multiple location-specific haplotypes. Within this distribution, the climbing fern is attacked by a phytophagous mite, Floracarus perrepae, also with multiple haplotypes. The genetic relationship between mite and fern haplotypes was matched by an overarching geographical relationship between the two. Further, mites that occur in the same location as a particular fern haplotype were better able to utilize the fern than mites from more distant locations. From a biological control context, we are able to show that the weed fern in the Everglades most likely originated in northern Queensland, Australia/Papua New Guinea and that the mite from northern Queensland offers the greatest prospect for control.

Biology and phenology of the eriophyid mite, Floracarus perrepae, on its native host in Australia, Old World climbing fern, Lygodium microphyllum.

The biology and phenology of the eriophyid mite, Floracarus perrepae Knihinicki and Boczek, a potential biological control agent of Lygoditon microphyllun (Cav.) R. Br., was studied in its native range--Queensland, Australia. F. perrepae forms leaf roll galls on the subpinnae of L. mnicrophyllum. It has a simple biology, with females and males produced throughout the year. The population was female biased at 10.5 to 1. The immature development time was 8.9 +/- 0.1 and 7.0 +/- 0.1 days; adult longevity was 30.6 +/- 1.6 and 19.4 +/- 1.2 days and mean fecundity per female was 54.5 +/- 3.2 and 38.5 +/- 1.6 eggs at 21 and 26 degrees C, all respectively. Field studies showed that the mite was active year round, with populations peaking when temperatures were cool and soil moisture levels were highest. Two species of predatory mites, Tarsonemus sp. and a species of Tydeidae, along with the pathogen Hirsutella thompsonii, had significant effects on all life stages of F. perrepae. Despite high levels of predators and the pathogen, F. perrepae caused consistent damage to L. microphyllum at all the field sites over the entire 2 years of the study.