Highest Infestation Rate Research Articles

Host fish status of native and invasive species for the freshwater mussel Anodonta anatina (Linnaeus, 1758)

The worldwide extinction of species especially affects freshwater ecosystems. Even widespread species like the European freshwater duck mussel Anodonta anatina face population declines in many countries and regions. Due to an obligate parasitic phase in its life cycle, knowledge on host fish use is essential for effective conservation of A. anatina. Therefore, in this study host suitability of ten different fish species (native and invasive to Europe) from four different fish families was tested by simultaneously infesting them with the glochidia of A. anatina. Nine out of ten fish species were identified as suitable hosts, but infestation rates, duration of metamorphosis phase as well as duration and rate of juvenile mussel excystment differed significantly between all host species. The bitterling (Rhodeus amarus) was the only fish species with no juvenile mussel excystment. Surprisingly, one of the tested invasive fish (Ctenopharyngodon idella) turned out to be the second best host for the larvae of A. anatina, suggesting that the general assumption that non-native fishes would be a threat to native mussel populations no longer holds true. Compared to the second native Anodonta species in Europe (Anodonta cygnea), this study revealed that A. anatina had higher infestation rates and rates of juvenile mussels excystment as well as a different host compatibility than A. cygnea. These findings illustrate that species-specific assessments of host suitability form an urgent basis for evidence-based conservation and restoration of freshwater mussel populations and the ecosystem services they provide.

Measuring biological age to assess colony demographics in honeybees.

Honeybee colonies are increasingly exposed to environmental stress factors, which can lead to their decline or failure. However, there are major gaps in stressor risk assessment due to the difficulty of assessing the honeybee colony state and detecting abnormal events. Since stress factors usually induce a demographic disturbance in the colony (e.g. loss of foragers, early transition from nurse to forager state), we suggest that disturbances could be revealed indirectly by measuring the age- and task-related physiological state of bees, which can be referred to as biological age (an indicator of the changes in physiological state that occur throughout an individual lifespan). We therefore estimated the biological age of bees from the relationship between age and biomarkers of task specialization (vitellogenin and the adipokinetic hormone receptor). This relationship was determined from a calibrated sample set of known-age bees and mathematically modelled for biological age prediction. Then, we determined throughout the foraging season the evolution of the biological age of bees from colonies with low (conventional apiary) or high Varroa destructor infestation rates (organic apiary). We found that the biological age of bees from the conventional apiary progressively decreased from the spring (17 days) to the fall (6 days). However, in colonies from the organic apiary, the population aged from spring (13 days) to summer (18.5 days) and then rejuvenated in the fall (13 days) after Varroa treatment. Biological age was positively correlated with the amount of brood (open and closed cells) in the apiary with low Varroa pressure, and negatively correlated with Varroa infestation level in the apiary with high Varroa pressure. Altogether, these results show that the estimation of biological age is a useful and effective method for assessing colony demographic state and likely detrimental effects of stress factors.

BIOCHEMICAL IMPACTS OF DIFFERENT SORGHUM AND MAIZE CULTIVARS ON THE CORN APHID, RHOPALOSIPHUM MAIDIS (HEMIPTERA: APHIDIDAE)

Aphids cause serious damage to cereal crops worldwide leading to great economic loss. In this work, we addressed the correlation between the infestation rate of Rhopalosiphum maidis (Hemiptera: Aphididae) and the changes in some biochemical parameters after feeding on three cultivars of both sorghum (local, dorado, and sphinx) and maize (local, unique 6 and triple 310) plants cultivated at Assiut University farm in Egypt. Local variety of sorghum showed lower infestation rate by R. maidis than dorado and sphinx varieties, as well as it led to significant enhancement of total antioxidant, carbohydrates, and lipids, and activity of amylase and lipase. On the other hand, local strain of maize showed higher infestation rate by R. maidis than unique 6 and triple 310 varieties. The higher infestation rate to local variety of maize was associated with significant increase in total antioxidants, carbohydrate, and lipid content, and activity of amylase and lipase. This research suggests that there was no correlation between the infestation rate of R. maidis fed on different cultivars of sorghum and maize and the total content of antioxidants, carbohydrate and lipid content, as well as their catabolic pathways.

Influence of ecological factors on the presence of a triatomine species associated with the arboreal habitat of a host of Trypanosoma cruzi

BackgroundThe white-naped squirrel, Simosciurus nebouxii (previously known as Sciurus stramineus), has recently been identified as an important natural host for Trypanosoma cruzi in Ecuador. The nests of this species have been reported as having high infestation rates with the triatomine vector Rhodnius ecuadoriensis. The present study aims to determine the levels of nest infestation with R. ecuadoriensis, the ecological variables that are influencing the nest site selection, and the relationship between R. ecuadoriensis infestation and trypanosome infection.ResultsThe study was carried out in transects in forest patches near two rural communities in southern Ecuador. We recorded ecological information of the trees that harbored squirrel nests and the trees within a 10 m radius. Manual examinations of each nest determined infestation with triatomines. We recorded 498 trees (n = 52 with nests and n = 446 without nests). Rhodnius ecuadoriensis was present in 59.5% of the nests and 60% presented infestation with nymphs (colonization). Moreover, we detected T. cruzi in 46% of the triatomines analyzed.ConclusionsWe observed that tree height influences nest site selection, which is consistent with previous observations of squirrel species. Factors such as the diameter at breast height and the interaction between tree height and tree species were not sufficient to explain squirrel nest presence or absence. However, the nest occupancy and tree richness around the nest were significant predictors of the abundance of triatomines. Nevertheless, the variables of colonization and infection were not significant, and the data observed could be expected because of chance alone (under the null hypothesis). This study ratifies the hypothesis that the ecological features of the forest patches around rural communities in southern Ecuador favor the presence of nesting areas for S. nebouxii and an increase of the chances of having triatomines that maintain T. cruzi populations circulating in areas near human dwellings. Additionally, these results highlight the importance of including ecological studies to understand the dynamics of T. cruzi transmission due to the existence of similar ecological and land use features along the distribution of the dry forest of southern Ecuador and northern Peru, which implies similar challenges for Chagas disease control.

Residents Attitudes and Home Sanitation Predict Presence of German Cockroaches (Blattodea: Ectobiidae) in Apartments for Low-Income Senior Residents.

The German cockroach, Blattella germanica (L.), is a common pest found in apartment buildings. Prevalence of cockroach infestations is affected by both environmental conditions and building occupant behavior, but their relationships are not well studied. The objective of this study was to analyze the presence of German cockroaches in relation to environmental conditions, resident demographics, and residents' tolerance of cockroaches. We conducted resident interviews, placed sticky traps to detect the presence of German cockroaches, and assessed apartment conditions. A total of 388 apartments from seven low-income apartment buildings, occupied by senior citizens in New Jersey, United States, were included. Among the 344 apartments where trap count data were obtained, 30% had German cockroaches. Among interviewed residents whose apartments had existing cockroach infestations, 36% were unaware of the presence of cockroaches. The odds of having cockroaches in apartments with a 'poor' sanitation rating in kitchens and bathrooms was 2.7 times greater than that in apartments with better sanitation conditions. Residents' tolerance to cockroaches is significantly associated with presence of cockroaches and cockroach population size. The median cockroach count when residents were bothered by cockroaches was ≥3, based on deployment of 4 sticky traps per apartment, over a 2-wk period. Assessing and reducing cockroach tolerance thresholds and improving housekeeping through resident education and assistance from community and housing management should be incorporated in future cockroach management programs in order to reduce high cockroach infestation rates found in similar communities.

Epidemiological survey and economic significance of bovine hypodermosis on the Kars Plateau in the Northeast Anatolia Region of Turkey

The aim of this study was to determine the prevalence and seroprevalence of hypodermosis and to calculate the economic loss associated with hide damage in the cattle on the Kars Plateau, Turkey. A total of 6563 randomly selected cattle were examined by skin palpation from 1 April to 31 May 2014. A subset of 465 serum samples was collected from October to November in 2014 and analyzed using a commercial ELISA kit. The overall prevalence of hypodermosis was 16.9% in the cattle examined by skin palpation. In respect of each of the risk factors assessed, the highest prevalence rates were recorded in 2-year-old (26.4%), Brown Swiss crossbred (17.9%), female (18.1%), and dark-colored (49.7%) cattle. A total of 15,349 warble larvae were detected under the skin of 1114 cattle. The larval count per animal ranged from 1 to 91, with a mean count of 13.8. Seroprevalence was found to be 73.8% (343/465), with the highest rates of infestation in 2-year-old (87.7%), dark-colored (81.1%), female (80.4%), and Brown Swiss crossbred (87.7%) cattle. The highest seroprevalence rate was 96.8% and the lowest was 49.5%. The economic loss caused by the disease was calculated as 18,615 Turkish lira in the survey areas.

Occurrence of Orientia tsutsugamushi, the Etiological Agent of Scrub Typhus in Animal Hosts and Mite Vectors in Areas Reporting Human Cases of Acute Encephalitis Syndrome in the Gorakhpur Region of Uttar Pradesh, India.

Outbreaks of acute encephalitis syndrome (AES) with high fatality and disability, are reported every year in the Gorakhpur region of Uttar Pradesh, India, with the etiology of >60% of the cases being attributed to scrub typhus. In the present study, the prevalence of Orientia tsutsugamushi, the etiological agent of scrub typhus, was investigated among animal hosts and their ectoparasitic trombiculid mites prevalent in AES-reported areas of Gorakhpur. A total of 154 rodents/shrews were collected using 777 Sherman traps set in 12 study villages, and the overall trap rate was 19.8%. In total, 2726 trombiculid mites belonging to 12 species were collected from 154 rodents/shrews trapped. The shrew mouse Suncus murinus was the predominant animal species (78.6%) collected. The principal vector mite Leptotrombidium deliense was the predominant species (82.7%), and its index was 14.6 per animal. Of 114 rodent/shrew sera samples screened through the Weil-Felix test, 57% were positive for antibodies against O. tsutsugamushi. Of 128 blood samples tested by polymerase chain reaction (PCR), one rodent sample was positive for the gene encoding 56 kDa protein and 25 for 60 kDa. Among 2726 mite samples tested as 315 pools through nested PCR, seven pools were positive for 56 kDa gene. Phylogenetic analysis confirmed circulation of Gilliam, Karp, and TA678 serotypes of O. tsutsugamushi in Gorakhpur. The study clearly demonstrated natural infection of O. tsutsugamushi in both small-animal hosts and vector mites in the AES-reporting villages of Gorakhpur, which confirms transmission of the scrub typhus pathogen in this region. The high infestation rate of L. deliense with O. tsutsugamushi infection indicates that the people living in the rural villages of Gorakhpur are at risk of infection with scrub typhus, which might lead to AES.

Indicadores socioambientais de focos do Aedes aegypti no extremo sul de Santa Catarina

Esta pesquisa analisou a distribuição espacial de focos do Aedes aegypti encontrados em 2016 na área de abrangência da Associação de Munícipios do Extremo Sul Catarinense (AMESC) e comparou com indicadores socioambientais (precipitação, temperatura, saneamento básico e população). Todos os dados são secundários, disponibilizados por diferentes órgãos governamentais. Foram observados 44 focos distribuídos em 6 municípios, sendo que o município Passo de Torres concentrou 61% desses focos. Esta cidade faz fronteira com o Estado do Rio Grande do Sul, região afetada, e, assim como os demais municípios com alto índice de infestação, é atravessada longitudinalmente pela BR-101. Isto pode indicar que a BR-101 é o principal meio de dispersão do vetor. Há maior ocorrência do vetor nas estações mais quentes (verão e outono), entretanto, não foi observada correlação com a precipitação, ainda que em 2016 esta superou a média histórica da região. Apesar da boa cobertura do abastecimento de água, não há dados sobre resíduos, tampouco sobre o esgotamento na região. Assim, a indisponibilidade de dados específicos de saneamento prejudicou uma análise detalhada de aspectos relacionados a esse indicador. Embora estas informações possam ser utilizadas pelos gestores públicos para definição de diretrizes de combate ao mosquito, são necessárias maiores complementações em nível local.

Canker and decline diseases caused by soil- and airborne Phytophthora species in forests and woodlands.

Most members of the oomycete genus Phytophthora are primary plant pathogens. Both soil- and airborne Phytophthora species are able to survive adverse environmental conditions with enduring resting structures, mainly sexual oospores, vegetative chlamydospores and hyphal aggregations. Soilborne Phytophthora species infect fine roots and the bark of suberized roots and the collar region with motile biflagellate zoospores released from sporangia during wet soil conditions. Airborne Phytophthora species infect leaves, shoots, fruits and bark of branches and stems with caducous sporangia produced during humid conditions on infected plant tissues and dispersed by rain and wind splash. During the past six decades, the number of previously unknown Phytophthora declines and diebacks of natural and semi-natural forests and woodlands has increased exponentially, and the vast majority of them are driven by introduced invasive Phytophthora species. Nurseries in Europe, North America and Australia show high infestation rates with a wide range of mostly exotic Phytophthora species. Planting of infested nursery stock has proven to be the main pathway of Phytophthora species between and within continents. This review provides insights into the history, distribution, aetiology, symptomatology, dynamics and impact of the most important canker, decline and dieback diseases caused by soil- and airborne Phytophthora species in forests and natural ecosystems of Europe, Australia and the Americas.

Bilateral Congenital Ectropion Uveae, Anterior Segment Dysgenesis and Aniridia with Microspherophakic Congenital Cataracts and RubeosisIridis

In recent times, multiple eye diseases have been seen associated with an increase in the rate of Demodex infestation as a possible cause, but in the particular case of dry eye syndrome in patients treated with platelet-rich plasma, this increase in mite may be relevant to guide a more adequate treatment focusing on the elimination of the mite in conjunction with the recovery of the ocular ecology. The demodex mite is a commensal parasite that lives in hair follicles, sebaceous glands and meibomian, which in a high rate of infestation can generate alterations in the ocular area. Performing an adequate diagnosis for the detection of the mite and treatment for its eradication can be effective for the recovery of the normal physiology of the tear film that constitutes a cause of dry eye.

Urastoma cyprinae, NO MEXILHÃO Perna perna CULTIVADO NO SUL DO BRASIL

Urastoma cyprinae (Platyhelminthes: Urastomidae) foi coletado entre os filamentos branquiais do mexilhão cultivado Perna perna de três localidades do estado de Santa Catarina no sul do Brasil. Amostras de P. perna foram coletadas mensalmente de julho de 2010 a junho de 2011. O diagnóstico de U. cyprinae em P. perna mostrou-se mais eficiente por observações ao microscópio estereoscópico do que por histopatologia, onde menor prevalência e taxa de infestação foram registradas. A temperatura do mar e a salinidade durante o perí­­odo de pesquisa não afetaram a prevalência de U. cyprinae em P. perna. A análise no microscópio estereoscópico apresentou maior prevalência (54,2%) de U. cyprinae nos mexilhões da localidade do norte estudada (Penha - 26º46’S). Além disso, os mexilhões da localidade do sul (Palhoça - 27º45’S) apresentaram a maior taxa de infestação (7,4). Apesar de apresentar alta prevalência e taxa de infestação durante o perí­­odo de estudo, não há evidências de que este turbelário esteja causando danos histopatológicos ao hospedeiro. Mesmo sendo tratado como um parasita de moluscos bivalves, neste estudo observou-se que a relação entre U. cyprinae e P. perna não é de parasitismo sensu stricto.

Domestic honeybees affect the performance of pre-dispersal seed predators in an alpine meadow.

Flowering plants interact simultaneously with mutualistic pollinators and antagonistic herbivores such that plant-mediated interactions between pollinators and herbivores must exist. Although the effects of herbivores on pollinator behavior have been investigated extensively, the effect of pollinators on herbivore performance has seldom been explored. We hypothesized that insect pollinators could improve the survival and growth of pre-dispersal seed predators by increasing seed production. We tested this hypothesis along three transects radiating from well-established apiaries in an alpine meadow by supplementing pollination in sites close to and distant from apiaries and subsequently examining seed production of the dominant nectariferous plant species Saussurea nigrescens (Asteraceae) and the performance of three dominant pre-dispersal seed predators (tephritid fly species). Pollen supplementation (1) significantly increased seed set and mass of developed seed per capitulum (i.e., flowerhead) in the distant but not the close sites, (2) did not change the survival and growth rates of the smaller-bodied species (Tephritis femoralis and Campiglossa nigricauda) at either site, but (3) improved the performance of the larger-bodied seed predator (Terellia megalopyge) at distant sites but not close sites. In addition, the larger-bodied tephritid fly showed higher infestation rates and relative abundance in the close sites than in the distant sites, whereas the smaller-bodied species had lower relative abundances in the close sites and similar infestation rates in both site types. These observations demonstrate contrasting effects of plant mutualists on the performance of antagonists with potential consequences for population sizes of insect herbivores.

First description of epizoic ciliates (Sessilida Stein, 1933) on Bathyporeia Lindström, 1855 (Peracarida, Amphipoda) and infestation patterns in brackish and marine waters

During a re-examination of macrozoobenthic samples from a long-term monitoring programme in the Dutch Oosterschelde and Westerschelde, the abundant presence of peritrich ciliates on specimens ofBathyporeiaLindström, 1855, was discovered. Out of the more than 3500Bathyporeiaspecimens investigated, 44% contained ciliates. AlthoughBathyporeia sarsiWatkin, 1938 was significantly more often infested thanBathyporeia pilosaLindström, 1855, these differences in infestation rates were largely due to differences between water bodies with higher infestation rates in the polyhaline than in the mesohaline reach. Observation of additionally collected living specimens and freshly preserved material showed that at least two, and likely three, species of ciliates are present of which two might be undescribed so far. One of the observed species matchesZoothamnium nanumKahl, 1933. A second species belongs to the genusEpistylisEhrenberg, 1830, but does not seem to match a so far known species. This also accounts for a possible third species belonging to the genusZoothamniumBory de St. Vincent, 1826, deviating fromZ. nanumamongst others in the habitus of the stalk. The front part ofBathyporeiaspp. and the antennae in particular, significantly more often harboured ciliates than the remainder of the body, where additional ciliates were only found on the ventral side. This shows that the peritrich ciliates benefit from the water currents induced by the basibiont, providing food items, but might also indicate thatBathyporeiaspp. benefits from the presence of the epibionts as they are most prevalent on the body parts that are easiest to clean. Analyses of densities and distributions of epibiont and basibiont species gave first indications of the ecological niche of the peritrich ciliate communities.

Studies on Prevailing Parasitic Trematodiasis Affecting Some Cultured Marine Fishes in Ismailia Governorate

This study was carried out to detect the trematodes affecting some marine fishes. Fish species collected were 100 Dicentrarchus labrax and 100 Dicentrarchus punctatus from private farms at Ismailia provinces. There were no pathognomonic signs in infested fishes except marbling of gills in fishes with gill monogenean infestations. Other signs and P. M. lesions were haemorrhages, abrasions on skin, sluggish movement, abdominal distension and emaciation, pale liver, congesion intestine with entritis in some cases. The higher infestation rate was in D. punctatus (52%) followed by D. labrax (35%). The isolated parasites in D. labrax and D. punctatus were monogenetic trematodes (Diplectanum bocqueti) and Digenetic trematodes (Acanthostomum sp.and Allostomachicolina secundus). Detection of Acanthostomum sp. using molecular biology (PCR) was recorded. Seasonal prevalence in relation to fish sex, body weight, body length and infestation, statistical analysis and histopathological picture was also recorded.

Head lice infestation among local and displaced secondary school girls and its effect on some haematological parameters in Kirkuk city.

Background: Head lice infestation is one of the most important health problems throughout of the world. The species which cause pediculosis in humanus beings is Pediculus humanus capities. Objectives: The aim of the current study is to estimate the distribution of head lice among local and displaced secondary school girls to assess haemoglobin and packed cell volume in Kirkuk city. Methods: The hair of all students was examined by researchers and blood samples were drawn from each student for determination of haemoglobin concentration and PCV percentage. A questionnaire form was filled for each student including personal and family information. The student t-test was used to show significant difference of PCV and Hb between lice infested and non infested students. Results: The overall rate of head lice infestation among secondary students girls was 34.7% (displaced 42.7% and local 26.7%). The highest rate of infestation was among 16-18 years and lowest was among 13-15 years. The highest rate in displaced students was among middle educated status, while in local students among low educated status. The PCV and Hb values in infested girls were lower than non- infested ones

Infection of Anaplasma phagocytophilum and Ehrlichia spp. in Opossums and Dogs in Campeche, Mexico: The Role of Tick Infestation

In recent years, some tick-borne diseases such as anaplasmosis and ehrlichiosis became widespread worldwide, threatening the health of humans, domestic animals and wildlife. The aims of this study were to determine the presence of Anaplasma phagocytophilum, Ehrlichia canis and Ehrlichia chaffeensis in 102 opossums (Didelphis spp.) and 44 owned free-ranging dogs in southeastern Mexico using a specific polymerase chain reaction (PCR). Anaplasma phagocytophilum was detected in opossums and dogs with a prevalence of 3 and 27 %, respectively. E. canis was only present in 7 % of dogs, while we didn’t detect E. chaffeensis in any host. We report the first evidence of infections of Anaplasma phagocytophilum in Didelphis virginiana and D. marsupialis in Mexico. The infection rates and patterns we found of A. phagocytophilum suggest that dogs are more directly involved in the ecology of this pathogen than opossums. Despite the small prevalence found, our results are of public health concern because of the zoonotic capabilities of A. phagocytophilum, the high tick infestation rates found and because both opossums and free-ranging dogs can achieve high population densities in the region.

CAPIVARAS (Hydrochoerus hydrochaeris) E A PRESENÇA DO CARRAPATO (Amblyomma sculptum) NO CAMPUS DA UFSCAR-ARARAS, SÃO PAULO

Resumo Capivaras são territoriais e vivem em grupos sociais, ocorrendo comumente em áreas antropizadas. Em algumas regiões do Brasil, estes animais apresentam infestação por carrapatos do gênero Amblyomma, que por sua vez são considerados como principal vetor biológico e reservatório natural da bactéria Rickettsia rickettsii, agente causador da Febre Maculosa Brasileira. Na UFSCar campus Araras, a interação entre capivaras, carrapatos e comunidade acadêmica é frequente, ocorrendo principalmente durante a estação seca. Este estudo teve como objetivo realizar um censo populacional das capivaras que ocupam o campus, identificando sua área de uso e se estes roedores se encontravam infestados por carrapatos. Realizou-se observação direta das capivaras, captura-marcação e recaptura com uso de um brete, e também coleta dos carrapatos nas capivaras e no ambiente. Registrou-se um total de 56 capivaras, com densidade de 1,50 ind./ha. Foram capturados 24 animais, sendo 25% machos e 75% fêmeas, dos quais 25% eram adultos, 45,8% jovens e 29,2% filhotes. A espécie de carrapato amplamente encontrada infestando tanto os animais como o ambiente foi A. sculptum. Conclui-se que o grupo de capivaras apresentou um número elevado de indivíduos por causa da abundância de recursos e ausência de predadores, e também com grande infestação por carrapatos.

Impact of Neem Extracts, Azadirachta indica A. Juss Induced against Red Palm Weevil, Rhynchophorus ferrugineus (Olivier) Attacking Date Palm Orchards in Egypt

Red palm weevil (RPW), Rhynchophorusferrugineus (Olivier) (Coleoptera: Curculionidae) is considered to be themost devastating boring pest attacking the date palm trees, Phoenix dactyliferaL. (Arecales: Arecaceae). During this study the date palm orchards wereinvestigated at Ismailia governorate in Egypt to throughout 2015-2016 andresults revealed the wide distribution of RPW with high infestation rates atthe visited localities. Rates and degrees of infestation were detected throughthe attacked spots showing a direct proportional rate with the total planteddate palm trees in each location recording a highest infestation rate of 91.6%and a maximum infestation degree was 3.4 hole/ tree. Least average infestationlevels were 14.9% and 1.19 hole/ tree. Extracts of neem seeds, Azadirachta indica A. Juss(Sapindales: Meliaceae)were tested in the laboratory against the RPW stages using organic solvents inaddition to the commercial Nemazal brand as a comparison treatment. Laboratoryexperiments revealed a potential effect of the used titers againstboth adult and larval R. ferrugineus stagesresulting in high mortality rates reached 85.4 and 79.5%on average for larval and adult stages, respectively. Consequent field trialswith such agents were conducted on both remedial and protective scalesrevealing a considerable reduction of infestation was 60.8% and 53.1% repellencyon average for all applied treatments. Field trials proved the possibility ofthose treatments usage in the control programs of that borer in Egypt.

Optimal Inspection of Imports to Prevent Invasive Pest Introduction.

The United States imports more than 1 billion live plants annually-an important and growing pathway for introduction of damaging nonnative invertebrates and pathogens. Inspection of imports is one safeguard for reducing pest introductions, but capacity constraints limit inspection effort. We develop an optimal sampling strategy to minimize the costs of pest introductions from trade by posing inspection as an acceptance sampling problem that incorporates key features of the decision context, including (i) simultaneous inspection of many heterogeneous lots, (ii) a lot-specific sampling effort, (iii) a budget constraint that limits total inspection effort, (iv) inspection error, and (v) an objective of minimizing cost from accepted defective units. We derive a formula for expected number of accepted infested units (expected slippage) given lot size, sample size, infestation rate, and detection rate, and we formulate and analyze the inspector's optimization problem of allocating a sampling budget among incoming lots to minimize the cost of slippage. We conduct an empirical analysis of live plant inspection, including estimation of plant infestation rates from historical data, and find that inspections optimally target the largest lots with the highest plant infestation rates, leaving some lots unsampled. We also consider that USDA-APHIS, which administers inspections, may want to continue inspecting all lots at a baseline level; we find that allocating any additional capacity, beyond a comprehensive baseline inspection, to the largest lots with the highest infestation rates allows inspectors to meet the dual goals of minimizing the costs of slippage and maintaining baseline sampling without substantial compromise.

STATUS OF THE INVASION OF A POACEAE SPECIES IN TROPICAL SEMIARID RESERVOIRS

ABSTRACT The species of the Urochloa genus, exotic and infesting in Brazilian waters, are known to be invasive and dominant, occupying from humid, shallow areas, and irrigation canals to margins of deep reservoirs. This paper hypothesis that less depth reservoirs have higher infestation rate and higher biomass of U. arrecta. The objectives were to measure the percentage of occurrence of exotic macrophyte U. arrecta in 40 ecosystems from the Mamanguape basin (Paraíba, Brazil) and determine the infestation of the species in two reservoirs. The acquired data were geo-referenced with the ArcGIS software (v. 9.3). A covariance analysis was performed using the R program (The R project is Statistical Computing). The results showed large spatial distribution of the species, indicating that reservoirs may act as steppingstones in the landscape, in a regional scale. The hypothesis of biotic acceptance is seen as a relevant factor in explaining the presence of the species with low percentage of occurrence in 37 out of the 40 sampled ecosystems, being observed only in areas prone to the colonization of native and naturalized macrophytes, in banks and points of lower declivity, in both spatial scales studied. Thus, factors such as environmental instability (promoted by intermittent or prolonged desiccation of the habitat), shadowing and declivity of the reservoirs synergistically acted on exotic and native species.