Comparison of economic and plant phenology-based thresholds for management of Lygus lineolaris (Hemiptera: Miridae) in Minnesota strawberries

Field studies were conducted in southeastern Minnesota, 2000-2002, to assess damage potential and management options for adult Lygus lineolaris (Palisot de Beauvois) in June-bearing strawberries (Fragaria x ananassa). The first study was designed to assess the efficacy of a published economic threshold for L. lineolaris nymphs compared with a plant phenology-based threshold management program, targeted at L. lineolaris adults. L. lineolaris nymphs were sampled using the standard white pan beat method; adults were sampled using yellow sticky traps. In the second study, during 2001-2002, caged strawberries were artificially infested with adult L. lineolaris at specific plant growth stages (i.e., vegetative, green bud, white bud, first blossom, peak blossom, first green fruit, and first ripe fruit) to determine the most susceptible growth stages of strawberry. The phenology-based thresholds proved to be more effective in managing L. lineolaris than the current economic threshold based on nymphs. Results from the infestation timing study indicate that early-growth stages (i.e., green and white bud) are most susceptible to adult L. lineolaris feeding damage. During the early-growth stages, only L. lineolaris adults were present; infestations of nymphs occurred primarily from first blossom to green berry. Results from both studies indicate that (1) management of adult L. lineolaris during the early strawberry growth stages is recommended for maximizing marketable yield and (2) the use of plant phenology-based thresholds, when adults are present, will significantly improve insecticide spray timing, and thus minimize the number of insecticide sprays.     

Circadian activity of Lygus lineolaris (Hemiptera: Miridae) and effectiveness of sampling techniques in strawberry fields

Mobility and distribution of adult tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), was studied on a day-neutral strawberry cultivar ('Selva') in 1991 and 1992 at L'Acadie, Quebec, Canada. On cage-covered plants, individuals were located mainly on reproductive parts. Study of the flight activity with sticky posts revealed that most captures were obtained < 1 m from ground level and that the time of the day at which the maximum counts occur varied among seasons. Three pest-sampling methods (white sticky trap, tapping of flower clusters, and D-Vac) were evaluated over continuous 24-h periods. Maximum captures of adults with white sticky traps were made at midday (1000-1400 hours), whereas the two other methods proved more effective at the beginning (0600-0800 hours) or the end of the day (2000-2200 hours) or during night time. For nymphs, maximum catches were obtained during the day with tapping and D-Vac; white sticky traps were ineffective. Because the D-Vac captures individuals present on all parts of the plant, these counts were used to monitor the effectiveness of the two other sampling techniques. The data suggest that tapping flower clusters throughout the day is a very effective sampling method to estimate nymphal tarnished plant bug populations in strawberries. However, sampling of populations with a high proportion of adults should take into account the bias caused by their flight activity, and sampling should be conducted early in the morning or at the end of the day.     

Field evaluation of efficacy and persistence of an insect vacuum device against the tarnished plant bug (Hemiptera: Miridae) in a day-neutral strawberry field

The efficacy of a vacuuming device to reduce Lygus lineolaris (Palisot de Beauvois) populations was evaluated over 3 yr in a day-neutral strawberry field. Immediately after treatments, a significant reduction of population estimates (by tapping of flower clusters) was observed for adults (75% of the time) and nymphs (50% of the time). Under the same conditions, control (i.e., vacuum turbine off) treatments significantly reduced adult population estimates 25% of the time. Lygus lineolaris tapping samples taken from strawberry plants adjacent to the treated zone did not show significant variations over sampling time, suggesting that no escape behavior occurred. This was supported by adult catches on sticky traps located in zones adjacent to the treated one. Our results suggest that vacuuming had inconsistent effect on tarnished plant bug populations and that L. lineolaris mobility plays a marginal role in the use of this control method.     

Effects of ground cover treatments and insecticide use on population density and damage caused by Lygus lineolaris (Heteroptera: Miridae) in apple orchards

We conducted a 2-yr study in commercial apple orchards in Nova Scotia to assess the effects of ground cover treatments and insecticides on population density and fruit injury caused by tarnished plant bug, Lygus lineolaris (Palisot de Beauvois). The design was a split-plot with insecticides applied to whole orchard blocks and ground cover treatments applied to plots nested within orchard blocks. Ground cover treatments were 1) standard herbicide use, 2) enhanced weed control in tree rows, and 3) treatment two plus use of a selective herbicide in laneways. Treatments had few significant effects on vegetation in the tree row, but in laneways, known dicot hosts of L. lineolaris were suppressed and nonhost grasses promoted with treatment 3. Ground cover treatments did not affect cumulative captures of adult tarnished plant bugs on white sticky traps located in the plots but did affect captures in sweep nets. Split-plot ANOVA indicated no significant effect of insecticides on injury in either year, but ground cover treatments were significant in 2001. The lowest ranking rates of injury in both years were in orchards treated before bloom with a pyrethroid insecticide, either cyhalothrin-lambda or cypermethrin. The highest ranking rate of injury occurred in an orchard where insecticide was not applied until after bloom despite a high prebloom capture of L. lineolaris adults on orchard perimeter sticky traps. Fruit injury values for the ground cover treatment 3 were 63.3% (n.s.) and 50.0% (P < 0.05), respectively, of those in the standard treatment in 2000 and 2001.     

Effect of trap color and orientation on the capture of Aphelinus mali (Hymenoptera: Aphelinidae), a parasitoid of woolly apple aphid (Hemiptera: Aphididae)

The factors affecting trap capture of adult Aphelinus mali (Haldeman) (Hymenoptera: Aphelinidae) were studied in 2010-2011 in eastern Washington apple (Malus spp.) orchards infested with its host woolly apple aphid, Eriosoma lanigerum (Hausmann) (Hemiptera: Aphididae). The initial study of white sticky cards indicated that traps stapled to the trunk in a vertical orientation had the highest capture. A factorial experiment of three colors (clear, white, and yellow) by three orientations (trunk, scaffold, and hanging) indicated that yellow traps and traps on trunks caught higher numbers ofA. mali. For this reason, the recommended trap for this natural enemy is a yellow trap stapled to the trunk. Having a readily available and effective sampling method for this species may be helpful in implementing biological control programs and assessing the impact of different spray regimes.     

Comparison of sampling methods for determining relative densities of Homalodisca vitripennis (Hemiptera: Cicadellidae) on citrus

Four sampling methods that included A-Vac, D-Vac, pole-bucket, and beat-net devices were evaluated for estimating relative densities of glassy-winged sharpshooter, Homalodisca vitri-pennis (Germar) (Hemiptera: Cicadellidae) nymphs and adults on citrus (Citrus spp.) trees. All four methods produced similar temporal and spatial distribution profiles, although significant differences in quantities of H. vitripennis adults and nymphs caught by each device were observed. The four sampling methods also showed a consistent male bias in adult populations across a range of densities, suggesting that previously reported male-biased sex ratios in H. vitripennis adult populations are real and not a product of sampling bias. A strong relationship (R2 = 0.95) between the monitoring methods we evaluated and yellow sticky trap catches of female H. vitripennis adults suggest that yellow sticky trap catches may provide a good relative index of infestation levels in citrus trees. Based on quantitative analyses examining precision and cost, the pole bucket was the most efficient method for sampling nymphs, and it was as efficient as the beat-net method for sampling adults and both stages combined. In addition to these analyses, consideration of other sampling characteristics such as added flexibility in sampling and higher sensitivity in detecting infestations within individual trees helped to fortify the conclusion that the pole bucket was the best overall sampling method of those tested.     

Population ecology and phenology of Diaphorina citri (Hemiptera: Psyllidae) in two Florida citrus groves

Studies were conducted to assess population densities and phenology of the psyllid Diaphorina citri Kuwayama at two citrus groves in east-central Florida. One grove contained young, irrigated grapefruit trees and the other contained mature, nonirrigated orange trees. The two groves were sampled weekly for eggs, nymphs, and adults on flush shoots; for adults on mature leaves; and for adults captured on yellow sticky card traps. Because infestations of immature D. citri develop strictly on young flush, the abundance of flush was assessed weekly. Overall means of 26.5, 16.8, and 0.27 eggs, nymphs, and adults per flush shoot, respectively, were observed in the young grapefruit trees. In the grove of mature orange trees, overall means of 16.0, 12.7, and 0.31 eggs, nymphs, and adults per flush shoot were observed, respectively. Flush abundance was an inconsistent indicator of the mean density of D. citri per flush shoot. Mean density per shoot by itself was an inconsistent indicator of overall population levels of D. citri at each study site because few shoots were sometimes present when mean densities per shoot were high. May, June, and July were periods of time when immature D. citri were consistently present and most abundant at each study site, but the study indicated large infestations could occur at any time of the year depending on environmental factors and flush availability. Yellow sticky traps were effective for both male and female D. citri and useful for gauging adult population trends.     

Economic injury levels for western flower thrips (Thysanoptera: Thripidae) on greenhouse cucumber

Low, medium and high densities of western flower thrips, Frankliniella occidentalis (Pergande), were established in three greenhouses at the Greenhouse and Processing Crops Research Centre, Ontario, Canada, in 1996 and 1998 to develop economic injury levels for thrips on greenhouse cucumber. Thrips densities were monitored weekly using yellow sticky traps and flower counts. Fruit was harvested twice a week, graded for size, weighed, and rated for thrips damage using three damage categories. Significant yield reduction was detected 4 wk after severe fruit damage was observed in the high and medium thrips density treatments in 1996 and 7 wk in 1998. Percentage of severe damaged fruit (P(F3)) has significant linear relationships with the adult thrips density (x) that was sampled by sticky traps 1 wk before harvest (P(F3) = -0.2533 + 0.0828x) and that was sampled by flower counts 2 wk before harvest (P(F3) = -0.2025 + 0.5490x). Based on the regression equations, economic injury levels, expressed as adult thrips per sticky trap per day or adult thrips per flower, were calculated for various combinations of control costs, yield potential and fruit prices. The economic injury levels for F. occidentalis ranged from 20 to 50 adults per sticky trap per day or 3 to 7.5 per flower as determined under average greenhouse production conditions in Ontario, Canada.     

Sampling and distribution pattern of Trioza erytreae Del Guercio, 1918 (Hemiptera: Triozidae) in citrus orchard

Developing efficient sampling protocols is essential to monitor crop pests. One vector of the citrus disease HLB, the African citrus psyllid Trioza erytreae Del Guercio, 1918 (Hemiptera: Triozidae), currently threatens the lemon industry throughout the Mediterranean region. In this work, a pool of sampling methods devoted to monitoring the population of T. erytreae was compared, its spatial distribution in the orchard was assessed, and the minimum sampling effort for the best sampling method was estimated. Three lemon orchards in North-western Portugal were sampled for one year using two types of yellow sticky traps (standard yellow and fluorescent Saturn yellow), B-vac sampling and sweep net sampling. The method that best performed, in terms of cost-efficiency, was the yellow sticky traps. The two colours of the sticky traps tested did not yield a significantly different number of catches. The spatial distribution throughout the orchards was found to be aggregated towards the borders. A minimum of three sticky traps per hectare was found to be enough to estimate the population at 90% accuracy for the mean during the outbreak. These results should help to monitor and anticipate outbreaks that may even colonize neighbour orchards. Studies on the local dispersion patterns of T. erytreae throughout the orchard are mandatory to further refine and optimize efficient monitoring protocols.     

Sampling method affects estimates of population density and reproductive maturity of summer‐form pistachio psyllids

Abstract

In this study, the effects of using three different sampling methods (yellow sticky traps, beating tray, organdy bags) on estimating the distribution through the canopy of the summer‐form adults of the pistachio psyllid (Agonoscena targionii (Licht.)) was investigated throughout the vegetative period. The traps or bags were hung at two heights in the tree canopy, 3.5 m above ground and 2 m above ground. Psyllids were counted weekly, and their sex determined. Adult abundance varied during the study, but all three sampling methods indicated that densities were higher in the upper canopy than the lower canopy. The percentage of females having mature eggs was lowest in late May, and highest in June and September. Sex ratios were highly variable among sampling dates and among sampling methods, at both canopy heights. Sex ratios in bags tended to be more female‐biased in the lower canopy than in the upper canopy. Sticky trap counts were significantly male biased, more so in the upper canopy than in the lower canopy. Mean sex ratios differed significantly between bag and sticky trap samples at both heights, but did not differ significantly between tray and bag samples at either height. In addition, for a given tray or bag count, sticky trap catch of males was larger than catch of females, and was larger in the upper canopy than in the lower canopy. Bag counts (psyllids per leaflet) strongly increased with tray count.

Of the three sampling methods described here, the bag samples provided direct estimates of psyllid numbers per leaflet, but this method is extremely time consuming. Bag counts (psyllids per leaflet) increased with tray count, suggesting that beat trays can be used to estimate absolute densities.     

An alternative sampling technique for cucumber beetles (Coleoptera: Chrysomelidae) and diurnal beetle activity on muskmelon

Field studies were conducted to investigate the effectiveness of yellow sticky traps as an alternative sampling technique for striped, Acalymma vittatum (F.), and spotted, Diabrotica undecimpunctata howardi Barber, cucumber beetles (Coleoptera: Chrysomelidae) and the diurnal beetle activity on muskmelon, Cucumis melo L., near Vincennes, IN, in 2003 and 2004. The experimental design included six replications of seven 20-m-long rows each of muskmelon with 1.5 m between rows. On each sampling date, two yellow sticky traps were placed randomly between rows in each replication. One sticky trap was placed vertically with the lower edge even with the top of the canopy, whereas the other trap was placed horizontally, even with the top of the canopy. After traps were placed in the field, number of beetles on plants was counted in situ from 0800 to 1600 hours at 2-h intervals the next day. After 48 h in the field, the number of cucumber beetles adhering on traps was counted. Analyses of variance and Tukey's multiple comparison procedure were used to compare the densities of beetles among sampling times, and regression analyses were applied to correlate the numbers of beetles on traps and the numbers of in situ counts. Results show that both species of cucumber beetles were most active from 1200 to 1400 hours, and 20 beetles on the vertically positioned sticky trap were equivalent to one beetle per plant in the field. The application of the sampling technique and scouting time for cucumber beetle management are discussed.     

Evaluation of yellow sticky traps for monitoring the population of thrips (Thysanoptera) in a mango orchard

Populations of several thrips species were estimated using yellow sticky traps in an orchard planted with mango, Mangifera indica L. during the dry and wet seasons beginning in late 2008-2009 on Penang Island, Malaysia. To determine the efficacy of using sticky traps to monitor thrips populations, we compared weekly population estimates on yellow sticky traps with thrips population sizes that were determined (using a CO(2) method) directly from mango panicles. Dispersal distance and direction of thrips movement out of the orchard also were studied using yellow sticky traps placed at three distances from the edge of the orchard in four cardinal directions facing into the orchard. The number of thrips associated with the mango panicles was found to be correlated with the number of thrips collected using the sticky trap method. The number of thrips captured by the traps decreased with increasing distance from the mango orchard in all directions. Density of thrips leaving the orchard was related to the surrounding vegetation. Our results demonstrate that sticky traps have the potential to satisfactorily estimate thrips populations in mango orchards and thus they can be effectively employed as a useful tactic for sampling thrips.     

Distribution and phenology of Dasineura oxycoccana (Diptera: Cecidomyiidae) in Michigan blueberries

The blueberry gall midge, Dasineura oxycoccana Johnson, is a serious pest of rabbiteye blueberries in Florida, Georgia, and Mississippi, and a potential pest of southern and northern highbush blueberries. Its damage has been observed with increasing frequency in highbush blueberry plantings in the Great Lakes region, including in Wisconsin and in Michigan. Unlike in rabbiteye blueberry plantings, where blueberry gall midge primarily damages flowering buds, it is found to damage only the vegetative shoots of northern highbush blueberry. In this study, farms throughout Michigan were surveyed for the presence of blueberry gall midge and it was found in 43 of 46 sampled farms in 11 counties. From 2009-2011, several monitoring techniques, including yellow sticky traps, emergence traps, observational sampling, and vegetative shoot dissections were used to determine the ecology of this species in blueberry fields in southwest Michigan. Emergence traps were most useful in early detection of blueberry gall midge in April, and observational sampling for damage symptoms and vegetative shoot dissections revealed multiple population peaks throughout July and August. Infestation was detected in vegetative shoot tips in all parts of the bushes, with initial infestation greatest at the base of bushes. Degree day accumulations until first midge detection and peak infestation suggest some potential for predicting key events in the pest's phenology. This information about the distribution and timing of infestation will be useful in developing management strategies for blueberry gall midge infestation.     

Visual Responses of Adult Asian Citrus Psyllid (Hemiptera: Liviidae) to Colored Sticky Traps on Citrus Trees

The effects of five differently-colored sticky traps in capturing adult Diaphorina citri were evaluated in citrus orchards. Trap catches of D. citri were monitored fortnightly on blue, green, red, white and yellow sticky cards placed on three citrus varieties during D. citri active flight period from April to July in south Texas. Evaluation of mean trap catches of each color by repeated measures analysis of variance produced three separate groups: yellow traps caught significantly more D. citri adults than the other four traps; red and green traps caught significantly more D. citri than blue and white traps, which were not significantly different. Although the number of adult psyllid captured on all trap types significantly increased with time during the trapping period, the performance of traps did not change with time. Trap catches were also significantly influenced by the citrus species; traps placed on lemon trees captured more D. citri than those placed on sweet orange and grapefruit, suggesting that plant preference exhibited by D. citri may influence the performance of traps. The ratio of trap reflectance between the 680 to 700 nm and the 450 nm was significantly correlated with total trap catches in all host species studied. Thus, this index was a good indicator of the attractiveness of adult D. citri to colored traps. Additionally, we compared the reflectance values of young versus mature flush shoots of the three host plants used in this study as related to densities of D. citri recorded in colored traps. We discussed the importance of visual cues in the host finding behavior of adult D. citri.     

6种颜色粘虫板对春季菜地昆虫的诱集效应

为筛选对春季蔬菜害虫具有较好诱集效果的粘虫板,促进蔬菜害虫绿色防控技术的研究与推广,采用红色、黄色、绿色、蓝色、白色和黑色6种颜色的市售粘虫板对菜地昆虫进行诱集试验.结果显示,粘虫板诱集的害虫以尖眼蕈蚊Bradysia minpleuroti、小菜蛾Plutella xylostella、端大蓟马Megalurothrips distalis和黄蓟马Thrips flavus为优势种;黄曲条跳甲Phyllotreta striolata、南美斑潜蝇Liriomyza huidobrensis、灰地种蝇Delia platura、棉蚜Aphis gossypii、小绿叶蝉Empoasca flavescens、菜粉蝶Pieris rapae为常见种.试验中蓝色粘虫板诱集的灰地种蝇的数量显著高于其它处理组(P<0.05);黄色粘虫板诱集的南美斑潜蝇、棉蚜、小绿叶蝉的数量显著高于其它处理组(P<0.05);蓝色和白色粘虫板诱集的端大蓟马、黄蓟马的数量显著高于其它处理组(P<0.05);蓝色粘虫板诱集到的尖眼蕈蚊的数量显著低于其它处理组(P<0.05).各种颜色粘虫板诱集昆虫的益害比较低,诱集益虫总数仅占诱集昆虫总数的1.64％,表明该时段使用粘虫板防治菜地害虫,对益虫伤害较小,对保护利用天敌昆虫具有重要意义.本研究结果为科学使用粘虫板防治菜地害虫提供理论依据.     

Evaluation of sampling methodology for determining the population dynamics of onion thrips (Thysanoptera: Thripidae) in Ontario onion fields

Onion thrips, Thrips tabaci Lindeman, are an economic pest of alliums worldwide. In Ontario onion-growing regions, seasonal abundance and population trends of onion thrips are not well known. The objectives of this research were to investigate onion thrips population dynamics by using both white sticky traps and plant counts, to gain insight into flight height, and to determine the genus and sex of thrips fauna present in monitored fields. Adult thrips were captured on white sticky traps placed in two commercial onion fields in the Thedford-Grand Bend Marsh region as early as mid-May in 2001, 2002, and 2003. Thrips were not recorded on onion plants in these fields until late June and early July. A comparison of sticky trap captures to plant counts revealed a strong, positive correlation, indicating that sticky traps, which consistently detected thrips earlier than plant counts, could be used instead of plant counts early in the season to monitor onion thrips populations. Pole traps placed in onion and an adjacent soybean, Glycine max (L.) Merr., field revealed that regardless of crop type, most thrips were captured 0.7-0.95 m above the soil surface. During this study, 70% of 137,000 thrips captured on sticky traps and 89% of 1,482 thrips captured in pan traps were female onion thrips. No male onion thrips were identified in this study: most of the remaining thrips were Frankliniella spp.     

Host plants of the tarnished plant bug (Heteroptera: Miridae) in Central Texas

The tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), has taken on added importance as a pest of cotton in the Cotton Belt after successful eradication efforts for the boll weevil (Anthonomus grandis grandis Boheman). Because the Southern Blacklands region of Central Texas is in advanced stages of boll weevil eradication, blooming weeds and selected row crops were sampled during a 3-yr study to determine lygus species composition and associated temporal host plants. L. lineolaris was the sole lygus species in the region. Thirteen previously unreported host plants were identified for L. lineolaris, of which 69% supported reproduction. Rapistrum rugosum L. Allioni and Ratibida columnifera (Nuttall) Wooton and Standley were primary weed hosts during the early season (17 March to 31 May). Conyza canadensis L. Cronquist variety canadensis and Ambrosia trifida L. were primary weed hosts during the midseason (1 June to 14 August) and late-season (15 August to 30 November), respectively. Sisymbrium irio L. and Lamium amplexicaule L. sustained L. lineolaris populations during the overwintering period (1 December to 16 March). The proportion of females and numbers of nymphs found in R. rugosum, C. canadensis, A. trifida, and S. irio suggests these weeds supported reproductive adults during the early, mid-, and late season and overwintering period, respectively. Medicago sativa L. was the leading crop host for L. lineolaris; Glycine max L. Merrill did not yield L. lineolaris. Few L. lineolaris were collected in Gossypium hirsutum L. These results provide a more comprehensive assessment of host plants contributing to L. lineolaris populations in central Texas.     

Novel visual-cue-based sticky traps for monitoring of emerald ash borers, Agrilus planipennis (Col., Buprestidae)

We examined various methods of trapping emerald ash borers (EAB), Agrilus planipennis Fairmaire, using solely visual cues based on previous work that has documented the importance of visual cues in EAB mate location. Here, we give the results of two of these methods, coloured sticky cards (yellow or blue), or live ash leaves covered with spray-on adhesive to which dead male EAB visual lures had been pinned. Feral male beetles were captured effectively on the sticky traps made from dead male EAB on ash leaves. These sticky-leaf-traps captured more male EAB when deployed in high-population density areas than low-density areas, but did capture EAB even at lower population densities. More feral males were captured on these traps when they were placed higher in the trees, regardless of the population density of EAB. Very few feral female EAB were captured using the sticky-leaf-traps. This novel method of EAB trapping may allow 'real-time' population detection and monitoring of EAB adults during the active flight period rather than locating larval galleries during the autumn and winter after adult flight and attack. Feral male beetles were also captured using standard yellow- or blue-coloured sticky cards to which male EAB had been affixed with adhesive; however, this type of trap was much less effective overall than using the sticky-leaf-traps. Furthermore, Agrilus cyanescens , a species similar in colour to EAB but smaller in size, showed a strong response to blue-coloured sticky traps to which dead male EAB had been affixed with adhesive, suggesting a general use of visual cues in the mating systems of some of the other Buprestidae as well.     

Phenology and demography of Homalodisca coagulata (Hemiptera: Cicadellidae) in southern California citrus and implications for management

Populations of Homalodisca coagulata (Say) were sampled from citrus orchards in southern California, USA to characterize and quantify seasonal occurrences of nymphs and adults with the goal of identifying management opportunities through well-timed treatments and/or natural enemy releases. Higher densities of H. coagulata in 2001 contributed to a complete seasonal profile that began in early spring with the emergence of first instar nymphs and their progression through five nymphal instars lasting until mid-August. Adult emergence began in mid-June with peak adult densities attained from mid to late August followed by a gradual decline through autumn. A persistent and significant male bias was observed in the adult sex ratio from the time of first emergence through mid-October in oranges; the same trend was present in lemons, but with more variability. Adult densities gradually declined through the winter months into the following spring before rapidly increasing again in June as the 2002 spring generation of nymphs began emerging as adults. The seasonal timing of nymphs and adults in 2002 was nearly identical to that observed the previous year. Phenology data from both years were incorporated into a stochastic, temperature-dependent model that predicts the occurrences of H. coagulata stages through time. Applications of imidacloprid early in the spring generation of nymphs proved very effective at reducing nymphs and sustaining lower densities of adults through summer.     

A labor-saving marking and sampling technique for mark-release-recapture research

A marking and recapture sampling method was developed that shows promise for studying the dispersal behavior of small and delicate arthropods. Adult sweetpotato whiteflies, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), were externally marked with a liquid fluorophore that glows brightly under ultraviolet (UV) light. Then, a series of simulated recapture tests on fluorophore-marked whiteflies using yellow sticky cards were conducted. The marked whiteflies captured on the sticky cards were detected by direct visual inspection of photographs taken of the cards under white light and UV light. Whitefly counts taken under white and UV light were almost identical, implying high marking efficacy and visual distinctiveness. These results suggest that this fluorophore marking and sampling method could eliminate the tedious task of removing specimens from sticky cards and examining them individually for the presence of a mark.