Sweep Net Sampling Research Articles

Vectors and alternative hosts of Tobacco yellow dwarf virus in southeastern Australia

Factors that determine the epidemiology of Tobacco yellow dwarf virus (TbYDV), including alternative host plants and insect vector(s), were assessed over three consecutive growing seasons at four field sites in Northeastern Victoria in commercial tobacco growing properties. In addition, these factors were assessed for one growing season at three bean growing properties. Overall, 23 leafhopper species were identified at the 7 sites, with Orosius orientalis as the predominant leafhopper. Of the leafhoppers collected, only O. orientalis and Anzygina zealandica tested positive for TbYDV by polymerase chain reaction (PCR). The population dynamics of O. orientalis was assessed using sweep net sampling over three growing seasons and a trimodal distribution was observed. Despite large numbers of O. orientalis occurring early in the growing season (September–October), TbYDV was only detected in these leafhoppers between late November and end of January. The peaks in the detection of TbYDV in O. orientalis correlated with the observation of disease symptoms in tobacco and bean and were associated with warmer temperatures and lower rainfall. Spatial and temporal distribution of vegetation at selected sites was determined using quadrat sampling. Of the 40 plant species identified, TbYDV was detected only in four dicotyledonous species, Amaranthus retroflexus, Phaseolus vulgaris, Nicotiana tabacum and Raphanus raphanistrum. The proportion of host and non‐host availability for leafhoppers was associated with climatic conditions.

Comparison of Three Insect Sampling Methods in Sweetpotato Foliage in Mississippi

Three sampling methods—sweep-net, hand-vacuum modified from a leaf vacuum/blower, and a wheeled, blower-vacuum designed to blow insects from the foliage into the vacuum port of a leaf vacuum—were compared as methods for sampling insects in sweetpotatoes, Ipomoea batatas L. Results of the 4-yr study at 2 locations in Mississippi showed that the number of insects collected by the blower-vacuum method was lower than the number collected by the other 2 methods. Although results differed with different insect species, the numbers of insects collected in hand-vacuum samples were usually greater than or equal to those collected in sweep-net samples during the first few weeks after planting, but less than those in sweep-net samples late in the season. Based upon these results, sweep-nets are the preferred method for season-long sampling of insects in sweetpotatoes.

Temperature sensitivity of gamogenesis in littoral cladocerans and its ecological implications

Temperature sensitivity of chydorid (Cladocera, Chydoridae) gamogenesis in southern Finland was examined. Chydorid sweep net samples and littoral surface water temperature measurements of seven lakes were taken weekly. Percentage abundances of gamogenetic females were used to estimate the temperature optima and tolerances for gamogenesis of individual chydorid species. The estimations were carried out using a weighted averaging (WA) technique. The results indicated that the optimum temperature of gamogenesis ranged between 7.0 and 9.7 °C and the total tolerances were between 2.0 and 4.7 °C suggesting a species-specific response for gamogenesis. Alonella nana and Chydorus sphaericus s.l. had the lowest optima, which was possibly due to their ubiquitous ecological preference and wide geographical distribution. Camptocercus rectirostris, Alonella excisa and Grabtoleberis testudinaria had high optima for their gamogenesis. These estimations provide first numerical autecological data on gamogenesis of natural and contemporary chydorid populations. Furthermore, the results provide species-specific estimations of the effect of the present climate warming on chydorid reproduction patterns. This information can be useful background data in global change assessments regarding freshwater lakes.

Arthropods of a semi-natural grassland in an urban environment: the John F. Kennedy International Airport, New York

Semi-natural grassland habitat fragments, such as those found on airports, might be important for arthropod conservation and biodiversity in urban ecosystems. The objectives of this study were to: (1) describe the arthropod communities present within the grasslands on the John F. Kennedy International Airport and (2) assess spatial and temporal variation in those arthropod communities. We collected arthropods using a vacuum sampler during 2003 and using sweep-net collection methods during 2003 and 2004. During 2003, a total of 1,467 arthropods, representing 17 orders and 68 families were found in vacuum samples. A total of 3,784 arthropods, representing 12 orders and 94 families were collected in sweep-net samples during 2003. In 2004, a total of 3,281 arthropods, representing 12 orders and 85 families were collected in sweep-net samples. Hemiptera, Orthoptera, and Diptera were the most abundant taxa, accounting for 47, 18, and 14% of all arthropods captured, respectively. We found evidence of spatial and temporal variation in arthropod abundance, in particular as noted by fluctuations in Orthoptera: Acrididae and Hemiptera: Auchenorrhyncha. Hemipteran family diversity was also influenced by habitat type. Grassland habitats on airfields, although influenced by anthropogenic factors (e.g., mowing), have the potential to provide abundant and diverse arthropod communities and might serve as a refugium for such species within urban ecosystems.

Insect Diversity in Switchgrass Grown for Biofuel in South Carolina

Switchgrass (Panicum virgatum L.) has tremendous potential as a biomass and stock crop for cellulosic ethanol production or combustion as a solid fuel. A three-year study was conducted to assess insect and weed diversity in a perennial switchgrass crop in Florence, SC. Insects were sampled from 2007 to 2009, using pitfall traps and sweep-nets. Collected specimens were identified to family and classified by trophic groups, and the predominant species were identified. The diversity and density of weeds in the field during the establishment year (2007) were greater than the following years. The ratio of dry weight of switchgrass to weeds increased from 2.4 in January 2008 to 15.3 in January 2009. Insect diversity at the family level varied significantly across sampling dates only for sweep-net samples, with diversity peaks in May of each year. Diversity at the trophic-group level showed significant differences for predators in pitfall traps and for predators and herbivores in sweep-net samples across dates. Diversity of herbivores in pitfall traps tended to decrease over time. Draeculacephala sp., Melanoplus sp., and a species of Tettigoniidae were the predominant herbivores, while Solenopsis invicta Buren was the predominant predator. Assessing arthropod diversity in switchgrass is a first step in identifying potential pest and beneficial insects in this crop.

Regional Assemblages of Lygus (Heteroptera: Miridae) in Montana Canola Fields

Abstract Sweep net sampling of canola (Brassica napus L.) was conducted in 2002 and 2003 to determine Lygus (Heteroptera: Miridae) species composition and parasitism levels in four regions of Montana. Regardless of region or seasonal change, Lygus elisus (Van Duzee) was the dominant species in all canola fields sampled, averaging 60–99% of the total adult populations. Lygus borealis (Kelton), Lygus keltoni (Schwartz) and Lygus lineolaris (Palisot) were detected at much lower levels. Total lygus population density was greatest in the southwest and central regions. The northeast and southwest regions had the greatest lygus species diversity. The proportion of L. elisus increased from early to late crop maturity stages in the southwest and central regions while there was no change in northeast and southwest canola production regions. Nymphal stages III–V were dissected to detect parasitism in 2003 only. Parasitism was found to be negligible in the dissection of 1,230 nymphs. Lygus population densities in can...

Tarnished Plant Bug (Hemiptera: Miridae) Thresholds and Sampling Comparisons for Flowering Cotton in the Midsouthern United States

The tarnished plant bug, Lygus lineolaris (Palisot de Beauvois) (Hemiptera: Miridae), has become the primary target of foliar insecticides in cotton, Gossypium hirsutum L., throughout the Midsouth over the past several years. This prompted a reevaluation of existing action thresholds for flowering cotton under current production practices and economics. A trial was conducted at 19 locations throughout the Midsouth during 2006 and 2007. Threshold treatments ranged from a weekly automatic insecticide application to a very high threshold of 10 tarnished plant bugs per 1.5 row-m on a black drop cloth. Individually, all locations reached the lowest threshold, and eight locations had a significant yield loss from tarnished plant bugs. Across all locations, lint yield decreased 0.85 to 1.72% for each threshold increase of one tarnished plant bug per 1.5 row-m. Yield loss was most closely correlated to pest density during the latter half of the flowering period. The relationship between plant bug density or damage and yield was similar for drop cloth, sweep net, and dirty square sampling methods, but the correlations among these sampling methods were not high. Incorporating actual insecticide application data from the trial and average production and economic factors for Midsouth cotton, the economic threshold, if monitoring once per week, should be between 1.6 and 2.6 tarnished plant bugs per 1.5 row-m during the flowering period. More frequent monitoring or situations where insecticide applications are more efficacious may alter this threshold.

Aggregation Behavior of Western Spotted Cucumber Beetle (Coleoptera: Chrysomelidae) in Vegetable Cropping Systems

Aggregation behavior of adult western spotted cucumber beetles (Diabrotica undecimpunctata undecimpunctata Mannerheim) (Coleoptera: Chrysomelidae) was examined in six snap bean (Phaseolus vulgaris) fields adjacent to corn fields in western Oregon in 2004-2006. In the 2004 and 2005 studies, sweep net sampling was used to estimate beetle numbers along transect lines running perpendicular to the edges of the bean fields next to sweet corn fields. Beetles were collected from the fields and dissected to determine sex and egg development. Beetles were highly aggregated along the edge of the snap bean field next to the sweet corn, with the highest number of beetles occurring within the first meter next to the edge. Beetles in the aggregation areas were mostly females (average female to male ratio of 8.4 to 1), whereas beetles in the field section away from the edges were mostly male (female to male ratio of 0.6 to 1). Of the females collected in the aggregation areas, an average of 53% contained developing or fully developed eggs. In the 2006 study, beetle densities in the field edges were compared with densities within the fields in 40 bean fields with adjacent corn fields. Linear regression analysis showed that, across fields, nearly two times as many beetles were found in the field borders as in the rest of the field. These data suggest modifying traditional field scouting protocol to include field margins when a bean field is adjacent to or near a sweet corn field. A pest management strategy of only spraying the edges of bean fields containing beetle aggregations shows potential for significant pesticide reduction, as well as reducing risk of economic loss from crops harvested from the highly aggregated areas.

Seasonal dynamics of Urophora quadrifasciata on spotted knapweed in the Arkansas Ozarks

AbstractPeriodic sweep-net sampling and capitula sampling were conducted between April and October 2007 to determine the seasonal phenology of Urophora quadrifasciata (Meigen) (Diptera: Tephritidae) on spotted knapweed, Centaurea stoebe subsp. micranthos (Gugler) Hayek (Asteraceae), in the Arkansas Ozarks of the United States of America. Urophora quadrifasciata produces up to three generations in Arkansas, rather than being bivoltine as in the northern United States of America. The first, second, and third generations of U. quadrifasciata reached peak adult numbers around 26 May, 29 June, and 27 July, respectively. Males tended to emerge earlier than females but the female:male ratio was approximately 1:1 for most of the season. The majority of the offspring of the three generations emerged between June and October, while approximately 38% entered diapause and emerged as adults in April-June of the following year; 3.4 ± 0.1 (mean ± SE) (range 1–12) flies emerged from each infested capitulum. The absence of other, competing knapweed biological control agents as well as very low rates of parasitism, mild weather conditions, and a longer knapweed growing season likely contributed to the adaptation and establishment of U. quadrifasciata on spotted knapweed in Arkansas.

Leafhoppers (Homoptera: Cicadellidae) Associated with Potatoes in Alaska: Species Composition, Seasonal Abundance, and Potential Phytoplasma Vectors

Leafhopper transmitted phytoplasma diseases are an emerging problem for potato and vegetable producers in the conterminous US. Due to its geographical isolation and climatic constraints, Alaska is considered relatively free of diseases and insect pests; therefore growers in the state are exploring the potential of producing seed potato for export. However, the biology of agricultural insect pests in the circumpolar region is lacking or poorly understood. Research conducted from 2004 to 2006 in the main potato (Solanum tuberosum L.) production areas of Alaska resulted in the identification of 41 leafhopper species associated with agricultural settings. Twenty species were identified from sweep net samples and adhesive cards in association with potato. Two species, Davisonia snowi (Dorst) and Macrosteles fascifrons (Stal), made up approximately 60% of the total number of individuals collected, representing 34 and 26%, respectively. Both species, M. fascifrons and D. snowi generally arrived in fields by late May to early June and numbers peaked by late June to July, but in all years M. fascifrons populations peaked earlier than D. snowi. Twenty-three percent of the specimens were immature or could not be identified. Three of the species collected [Balclutha punctata (Fabricius), M. fascifrons, and Scaphytopius acutus (Say)] are known vectors of phytoplasmas of potatoes and other agricultural crops or have the potential to cause mechanical damage to potatoes. This report represents the first extensive study of cicadellids from potatoes in Alaska.

Observations on phenology and overwintering of spiders associated with apple and pear orchards in south-central Washington

Beating tray and sweep net samples from apple and pear orchards in south-central Washington State were used to obtain information on life history and phenology of orchard-associated spiders. Cardboard shelters placed in the orchards in the fall and collected during the winter yielded information on spider overwintering. Data were obtained for 43 species in 28 genera and 12 families. The eight most abundant species were Pelegrina aeneola (Curtis 1892), Meioneta fillmorana (Chamberlin 1919), Oxyopes scalaris Hentz 1845, Theridion neomexicanum Banks 1901, Misumenops lepidus (Thorell 1877), Xysticus cunctator Thorell 1877, Philodromus cespitum (Walckenaer 1802), and Sassacus papenhoei Peckham & Peckham 1895. Each was represented by more than 690 specimens. Salticidae, Philodromidae, and Linyphiidae were represented by the largest number of species. Most species appear to have univoltine life cycles in the study area. Species matured at different times during the season between spring and fall. Twenty-seven species utilized cardboard shelters for overwintering, but some common spiders failed to do so and apparently use alternative locations. Some species overwintered in a broad range of developmental stages, whereas other species overwintered in only one or two instars.

Are Sweep Net Sampling and Pitfall Trapping Compatible with Molecular Analysis of Predation?

Molecular analysis of predation enables accurate and reliable elucidation of trophic linkages in complex food webs, but identifying the strength of such interactions can be subject to error. Currently two techniques dominate: monoclonal antibody-based enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR). Although the optimization and characterization of these systems ensures their sensitivity and specificity, predator collection protocols such as sweep-netting and vacuum sampling could overestimate feeding rates because of surface-level contamination, yielding positive reactivity or predation within the sampling device. Therefore, two sampling techniques (sweep-net sampling and hand collection) were compared within an alfalfa agroecosystem using a monoclonal antibody-based ELISA to test the hypothesis that cross-contamination is a source of error, i.e., significantly more predators (linyphiid spiders) would test positive for prey (Diptera) proteins. A concurrent study examining the viability of trapping predators into saline solution was also undertaken. No significant differences were found between the proportions of spiders screening positive for Diptera when collected by sweep-net versus hand collection, rejecting the hypothesis that sweep-netting predators for subsequent molecular gut content analysis overestimates predation frequency. ELISA was also capable of detecting prey proteins in predator guts from pitfall traps containing phosphate-buffered saline, indicating the suitability of this approach for the collection and analysis of epigeal predators. Although these results indicate that sweep netting and pitfall trapping into solution is appropriate in this predator-prey and ELISA analysis system, caution should be exercised with other interactions and PCR-based analysis. The likelihood for false-positive reactivity should therefore be considered on a case-by-case basis.

Are Sweep Net Sampling and Pitfall Trapping Compatible with Molecular Analysis of Predation?

Are Sweep Net Sampling and Pitfall Trapping Compatible with Molecular Analysis of Predation?

Insecticidal control of late-season plant bug (Hemiptera: Miridae) infestations in Manitoba has no effect on alfalfa seed quantity and quality

In Manitoba, plant bugs (Lygus spp. and Adelphocoris spp.) can be numerous in seed alfalfa crops in late August and September and are often the target of insecticide applications. From 2002 to 2004 in field plots in commercial fields, one or two insecticide applications in late August and September were made to reduce plant bug numbers relative to those in untreated check plots. Despite significant reductions in plant bug numbers in sweep net samples in sprayed plots, there were no significant effects of treatments on total seed yield per unit area, seed weight, percentage germination or percentage of hard seed. Relative to the check plots, reductions in plant bug numbers in insecticide-treated plots were not associated with increases in seed yield. Also, seed yield increases in insecticide-treated plots were not correlated with numbers of plant bugs immediately before insecticide application, and so it was not possible to estimate an economic injury level. The practice of applying an insecticide in August to control late-season plant bugs is economically unjustified within the range of plant bug numbers encountered in this study. Key words: Plant bugs, alfalfa seed, Lygus, Adelphocoris, economic impact

EFFECTS OF HAY CROPPING ON INVERTEBRATE BIOMASS AND THE BREEDING ECOLOGY OF SAVANNAH SPARROWS (PASSERCULUS SANDWICHENSIS)

Abstract In hay fields in the northeastern United States, Savannah Sparrows (Passerculus sandwichensis) whose first nests fail as a result of the harvesting of hay renest in the same field in a dramatically altered habitat. We evaluated availability of invertebrate prey in two treatments (harvested and unharvested hay fields) in Vermont's Champlain Valley and assessed potential effects of food resources on clutch size, food provisioning by adults, and growth of nestling Savannah Sparrows. A relative measure of invertebrate biomass (sweep-net samples) showed a 36–82% decline after harvesting, compared with continual increases throughout the nesting season on unharvested fields. Clutch sizes were not significantly different between treatments. Nestling provisioning rates obtained through video observations differed between treatments, with birds on unharvested fields delivering 73% more food than those on harvested fields (P = 0.02). However, food provisioning differences did not translate into differences ...

Timing of Prescribed Burns Affects Abundance and Composition of Arthropods in the Texas Hill Country

Prior research has demonstrated that fire can be an important structuring force for plant communities in prairies and grasslands. However, investigations of land-management techniques, such as prescribed fire, often overlook responses of local fauna, particularly the arthropods. In this study, we examined a previously unappreciated, although potentially important, component of fire ecology by asking, does the timing of prescribed burns alter community structure of arthropods? At a site in the Texas Hill Country, we used sweep-net sampling to collected arthropods from experimental plots that had been treated with a summer-burn or winter-burn regime. Summer-burn plots supported >170% more individual arthropods than winter burns. Although overall diversity of arthropods did not significantly differ between treatments, there were significantly more carnivorous arthropods and marginally more herbivorous arthropods after fire in summer relative to fire in winter. Effects of timing were particularly strong for Cicadellidae (leaf hoppers) and Tetragnathidae (long-jawed spiders). Our results demonstrate that timing of prescribed fire can substantially alter composition of resident communities of arthropods. Furthermore, these data highlight the importance of examining composition of the community, in addition to diversity indices, when assessing response of arthropods to land-management techniques.

Effects of Single and Multiple Applications of Mosquito Insecticides on Nontarget Arthropods

Mosquito management plans have been implemented in the United States and globally to manage mosquito vectors of West Nile virus and many other diseases. However, there is public concern about ecological risks from using insecticides to manage mosquitoes. Two studies were conducted during the late summers of 2004 through 2006 at Benton Lake National Wildlife Refuge near Great Falls, MT. The first experiment was conducted in 2004 and 2005 to assess acute impacts of mosquito adulticides (permethrin and d-phenothrin) and larvicides (Bacillus thuringiensis israelensis and methoprene) on nontarget aquatic and terrestrial arthropods after a single application. The second experiment was conducted in 2005 and 2006 to assess longer-term impacts of permethrin on nontarget terrestrial arthropods after multiple repeated applications. For aquatic samples, in the first study, no overall treatment effects were observed despite a potentially deleterious effect on amphipods on sample date 1 in 2004. During the same study, 1 of 54 responses had a significant overall treatment effect for sticky-card samples. Many of the responses for sticky-card samples suggested significant time effects and time x treatment effects. Three response variables were associated with fewer individuals present in the insecticide-treated plots in a multivariate analysis. For the multiple-spray study conducted in 2005 and 2006, 6 of the response variables collected via sticky cards exhibited significant overall treatment effects, but none was associated with fewer individuals in the insecticide-treated plots. None of the responses collected using sweep-net sampling suggested overall treatment effects. Time and time x treatment effects were prevalent in 2005, but no discernable pattern was evident. In general, nearly all of the responses evaluated for either study indicated few, if any, deleterious effects from insecticide application.

Aphidophagous Predators in Iowa Soybean: A Community Comparison across Multiple Years and Sampling Methods

Abstract There is increasing evidence that Aphis glycines Matsumara (Hemiptera: Aphididae) populations are negatively impacted by endemic natural enemies within North America. In Iowa, surveys of natural enemies in soybean, Glycine max (L.) Merr., conducted before the arrival of A. glycines revealed a number of species that may contribute to their mortality. We used several sampling methods to determine the diversity of the natural enemy community in Iowa soybean since the arrival of A. glycines. Natural enemies were collected using field-counts (in situ sampling), destructive counts, sweep-net sampling, and yellow-sticky cards. When predaceous arthropods were combined across all sampling methods, six orders were identified, including nine families and 13 genera. In comparison with a similar study conducted 26 yr ago, we observed fewer native coccinellids with the most abundant being the exotics Harmonia axyridis (Pallas) and Coccinella septempunctata L. (Coleoptera: Coccinellidae). Combining all foliar-b...

Short-distance dispersal behavior and establishment of the parasitoid Gonatocerus ashmeadi (Hymenoptera: Mymaridae) in Tahiti: Implications for its use as a biological control agent against Homalodisca vitripennis (Hemiptera: Cicadellidae)

The egg parasitoid Gonatocerus ashmeadi Girault (Hymenoptera: Mymaridae), was introduced into French Polynesia as a biological control agent to control the invasive plant feeding pest Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae). The short-distance dispersal of G. ashmeadi was monitored as part of the biological control program. G. ashmeadi showed exponential dispersal capacity with 47 m/day being a minimum estimate of its natural rate of spread at high host densities (>150 nymphs per minute of sweep net sampling) in urbanized areas at sea level, which were characterized by a high diversity of exotic ornamental plants. This rate of spread contrasted starkly with almost nonexistent establishment and dispersal where host densities were very low (<2 nymphs per minute of sweep net sampling) at high elevation (800 m) with relatively undisturbed native vegetation. Survey results across different altitudes revealed an effect of vegetative diversity and host density on the measurable mobility and establishment of G. ashmeadi. In contrast, no significant influence of wind direction was found on G. ashmeadi dispersal rate or direction. Survey results for G. ashmeadi from French Polynesia suggest that the best release establishment strategies for classical biological control of H. vitripennis are: (1) many small releases where host density is high, or (2) larger and fewer releases where host densities are low.

Determination of Oebalus pugnax (Hemiptera: Pentatomidae) Spatial Pattern in Rice and Development of Visual Sampling Methods and Population Sampling Plans

Commercial rice, Oryza sativa L., fields in southeastern Texas were sampled during 2003 and 2004, and visual samples were compared with sweep net samples. Fields were sampled at different stages of panicle development, times of day, and by different operators. Significant differences were found between perimeter and within field sweep net samples, indicating that samples taken 9 m from the field margin overestimate within field Oebalus pugnax (F.) (Hemiptera: Pentatomidae) populations. Time of day did not significantly affect the number of O. pugnax caught with the sweep net; however, there was a trend to capture more insects during morning than afternoon. For all sampling methods evaluated during this study, O. pugnax was found to have an aggregated spatial pattern at most densities. When comparing sweep net with visual sampling methods, one sweep of the “long stick” and two sweeps of the “sweep stick” correlated well with the sweep net (r2 = 0.639 and r2 = 0.815, respectively). This relationship was not affected by time of day of sampling, stage of panicle development, type of planting or operator. Relative cost-reliability, which incorporates probability of adoption, indicates the visual methods are more cost-reliable than the sweep net for sampling O. pugnax.