Phenology of Lygus lineolaris (Hemiptera: Miridae) in Minnesota June-bearing strawberries: comparison of sampling methods and habitats

Field studies were conducted in southeastern Minnesota from 2000 to 2002 to determine the phenology of Lygus lineolaris in various habitats and to compare yellow and white sticky traps as a sampling method for adult L. lineolaris. Strawberry fields were sampled for L. lineolaris adults using yellow sticky traps, and nymphs were sampled using the standard white pan beat method. Adult L. lineolaris abundance in alfalfa, an adjacent fence-row, and a wooded habitat were also compared. The nonlinear relationship between cumulative trap catch and cumulative degree-days was modeled with a two-parameter cumulative Weibull function to predict early-season adult capture using yellow sticky traps. Adult L. lineolaris were detected in bearing-year strawberries at the onset of vegetative growth in all years. Yellow sticky traps caught significantly higher densities of adult L. lineolaris than white sticky traps. The Weibull model predicted 50% capture at 10 DD (>12.4 degrees C), which corresponds to the vegetative strawberry growth stage. L. lineolaris nymphs were not detected until the blossom stage. Alfalfa harbored significantly higher densities of L. lineolaris than other habitats during early-season sampling (i.e., March-June). Late-season sampling (July-September) revealed significantly higher densities in bearing-year strawberries. These results suggest that monitoring at the onset of vegetative growth, using yellow sticky traps, will be an efficient method for detecting early L. lineolaris adult activity.     

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.     

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.     

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.     

Monitoring spruce web-spinning sawflies Cephalcia spp.: the correlation between trap catches and soil sampling

The web-spinning sawflies of the genus Cephalcia Panzer (Hymenoptera, Pamphiliidae) are usually monitored by sampling prepupae in soil and by catching adults with visual traps, including yellow sticky traps. However, adult catches have never been compared with the actual density of prepupae. In this paper, a relationship is presented between the catches of Cephalcia arvensis Panzer adults (mostly males) and the number of prepupae ready to emerge (pronymphs) in an outbreak area of spruce forest (Picea abies Karsten) in the Southern Alps (Asiago, Italy). A significant linear relationship between the logarithmic estimates of the two variables was found. The model includes a spatial autoregressive parameter because adult catches were spatially correlated. The relationship allows to know whether or not the defoliation threshold of 20 pronymphs/m2 in spring samples is being exceeded, based on the number of adults caught on yellow sticky traps (defoliation threshold of 14.26 adults/trap). The variance not explained by the model is probably due to the flight behaviour of adult males, to the low precision of the estimated pronymph density at low population levels, and to the attraction of males by few females that are trapped and remain alive. The model was validated in a large monitoring programme of undamaged alpine spruce forests and allowed detection of two newly infested stands out of six that were considered at risk of defoliation, because of adult catch exceeded the threshold. Low adult catches were always associated with absence of defoliation. Our conclusion is that trapping of adult sawflies is a cheaper and easier monitoring method than prepupae sampling in the soil. This makes earlier detection of outbreaks possible, and consequently more efficient control.     

Economic Thresholds of Western Flower Thrips (Thysanoptera: Thripidae) for Unripe Red Pepper in Greenhouse

This study was conducted to develop economic thresholds of western flower thrips (Frankliniella occidentalis Pergande) for unripe red pepper in greenhouses. To investigate the relationship between the density of thrips and resulting damages, experimental plots with five treatments (0, 4, 16, 48, 96 adults per plot) as initial release densities were established at the National Institute of Agricultural Science and Technology, Suwon, Korea, in 2004. Western flower thrips density was monitored using flower samplings and yellow sticky trap (8×13 cm) counts. Western flower thrips density was directly related to increased numbers of damaged fruits and reduced fruit yield. The number of marketable fruits produced decreased as the thrips densities increased. The major damage to pepper fruits caused by thrips was cosmetic scars that resulted from immature feeding. When flower samples or yellow trap caches were used to determine the density of thrips, which were collected on a previous sampling date, thrips densities were determined to be related to the percentage of fruits that were damaged, and a significant relationship was found for the flower samples (y = 0.3219x + 1.0792, r² = 0.8640 and for trap catches (y = 11.9209 log(x) −2.158, r² = 0.8306). The economically-tolerable ratio of damaged fruits based on control cost and market values under current greenhouse cultivation was estimated as 3.4 to 8.0%. Economic thresholds of western flower thrips ranged from 0.7 to 2.1 adults or nymphs per flower, and 2.3 to 5.7 adults per four-day sticky card count.     

Evaluation of sampling methods and development of sample plans for estimating predator densities in cotton

The cost-reliability of five sampling methods (visual search, drop cloth, beat bucket, shake bucket, and sweep net) was determined for four groups of predatory arthropods on cotton plants in Texas. The beat bucket sample method was the most cost-reliable sampling method for Orius adults, and the beat bucket and drop cloth were the most cost-reliable methods for Orius nymphs. The drop cloth and beat bucket were the most cost-reliable methods for sampling spiders. For sampling adult Coccinellidae, the sweep net and the beat bucket were the most cost-reliable. The visual sample method was the least cost-reliable method for Orius adults and nymphs and spiders. No one sampling method was identified as the optimum method for all four predator groups. However, the relative cost-reliability of the beat bucket method ranked first or second among the five sampling methods and this method was chosen for further evaluation in field studies in Texas and Arizona. The relative cost-reliability of 1-, 3-, 5-, and 10-plants per beat bucket sample varied with predator group, but multiple plant sample units were equal to or more cost-reliable than the one plant sample unit. Fixed sample plans for the beat bucket method were developed for Orius adults, Orius nymphs, spiders, and adult Coccinellidae, and the sum of these groups using the 3-, 5-, and 10-plant sample unit sizes. The greater cost-reliability of the beat bucket sampling method and its ease of use is of particular advantage in assessing predator densities in a commercial cotton field monitoring program.     

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.     

Development of a novel sticky trap for container-breeding mosquitoes and evaluation of its sampling properties to monitor urban populations of Aedes albopictus

Collection methods currently used for large-scale sampling of adult Stegomyia mosquitoes (Diptera: Culicidae) present several operational limitations, which constitute major drawbacks to the epidemiological surveillance of arboviruses, the evaluation of the impact of control strategies, and the surveillance of the spreading of allochthonous species into non-endemic regions. Here, we describe a new sticky trap designed to capture adult container-breeding mosquitoes and to monitor their population dynamics. We tested the sampling properties of the sticky trap in Rome, Italy, where Aedes (Stegomyia) albopictus is common. The results of our observations, and the comparison between sticky trap catches and catches made with the standard oviposition trap, are presented. The sticky trap collected significantly larger numbers of Ae. albopictus females than any other Culicidae species representing >90% of the total catches. A maximum of 83 An. albopictus females was collected in a single week. A high correlation (Pearson correlation coefficient r= 0.96) was found between the number of females and the number of eggs collected by the traps. The functional relationship between the number of eggs and the number of adult females was assessed by major axis regression fitted to log(1 +x)-transformed trap counts as y= 0.065 + 1.695x. Trap samples significantly departed from a random distribution; Taylor's power law was fitted to the trap samples to quantify the degree of aggregation in the catches, returning the equations s(2)= 2.401 m(1.325) for the sticky trap and s(2)= 13.068 m(1.441) for the ovitrap, with s(2) and m denoting the weekly catch variance and mean, respectively, indicating that eggs were significantly more aggregated than mosquitoes (P < 0.0001). Taylor's power law parameters were used to estimate the minimum number of sample units necessary to obtain sample estimates with a fixed degree of precision and sensitivity. For the range of densities encountered in our study area during the Ae. albopictus breeding season, the sticky trap was more precise and sensitive than the ovitrap. At low population densities (c. < 0.1 mosquito/trap), however, the ovitrap was more sensitive at detecting the presence of this species. Overall, our results indicate that our new model of sticky trap can be used to sample Ae. albopictus females in urban environments, and, possibly, other container-breeding Stegomyia mosquitoes (e.g. Aedes aegypti). The technical properties of the new trap are discussed with respect to its possible application in monitoring the population dynamics of container-breeding mosquitoes, in studying their bionomics, and in vector surveillance and, possibly, control.     

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.     

Dispersion patterns and sampling plans for Diaphorina citri (Hemiptera: Psyllidae) in citrus

The abundance and spatial dispersion of Diaphorina citri Kuwayama (Hemiptera: Psyllidae) were studied in 34 grapefruit (Citrus paradisi Macfad.) and six sweet orange [Citrus sinensis (L.) Osbeck] orchards from March to August 2006 when the pest is more abundant in southern Texas. Although flush shoot infestation levels did not vary with host plant species, densities of D. citri eggs, nymphs, and adults were significantly higher on sweet orange than on grapefruit. D. citri immatures also were found in significantly higher numbers in the southeastern quadrant of trees than other parts of the canopy. The spatial distribution of D. citri nymphs and adults was analyzed using Iowa's patchiness regression and Taylor's power law. Taylor's power law fitted the data better than Iowa's model. Based on both regression models, the field dispersion patterns of D. citri nymphs and adults were aggregated among flush shoots in individual trees as indicated by the regression slopes that were significantly >1. For the average density of each life stage obtained during our surveys, the minimum number of flush shoots per tree needed to estimate D. citri densities varied from eight for eggs to four flush shoots for adults. Projections indicated that a sampling plan consisting of 10 trees and eight flush shoots per tree would provide density estimates of the three developmental stages of D. citri acceptable enough for population studies and management decisions. A presence-absence sampling plan with a fixed precision level was developed and can be used to provide a quick estimation of D. citri populations in citrus orchards.     

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.     

Seasonal abundance and spatio-temporal distribution of dominant xylem fluid-feeding hemiptera in vineyards of central Texas and surrounding habitats

A survey of xylem fluid-feeding insects (Hemiptera) exhibiting potential for transmission of Xylella fastidiosa, the bacterium causing Pierce's disease of grapevine, was conducted from 2004 to 2006 in the Hill Country grape growing region of central Texas. Nineteen insect species were collected from yellow sticky traps. Among these, two leafhoppers and one spittlebug comprised 94.57% of the xylem specialists caught in this region. Homalodisca vitripennis (Germar), Graphocephala versuta (Say), and Clastoptera xanthocephala Germar trap catches varied significantly over time, with greatest counts usually recorded between May or June and August and among localities. A comparison of insect counts from traps placed inside and outside vineyards indicated that G. versuta is always more likely captured on the vegetation adjacent to the vineyard. C. xanthocephala was caught inside the vineyard during the summer. Between October and December, the natural habitat offers more suitable host plants, and insects were absent from the vineyards after the first freezes. H. vitripennis was caught in higher numbers inside the vineyards throughout the grape vegetative season. However, insects were also caught in the habitat near the affected crop throughout the year, and residual populations overwintering near vineyards were also recorded. This study shed new light on the fauna of xylem fluid-feeding insects of Texas. These results also provide critical information to vineyard managers for timely applications of insecticides before insect feeding and vectoring to susceptible grapevines.     

Effects of a particle film on biology and behavior of Diaphorina citri (Hemiptera: Psyllidae) and its infestations in citrus

Studies were conducted to investigate the effects of a kaolin-based hydrophilic particle film, Surround WP, on the biology and behavior of the psyllid Diaphorina citri Kuwayama (Hemiptera: Psyllidae) and to assess population densities of D. citri in citrus subjected to monthly applications of Surround WP. Laboratory investigations indicated a 3% (wt:vol) suspension of Surround WP in water applied directly was not acutely toxic to eggs, older nymphs or adults. Presence of the dried particle film on leaves interfered with the ability of adults to grasp and walk on citrus leaves. During a 30-s period, adults spent an average of 5 s moving on leaves with particle film compared with 16 s on leaves without particle film. When leaves were inverted, a significantly higher percentage of adults fell or flew from treated leaves (53%) than untreated leaves (16%). In a 12-mo study investigating infestations of D. citri on citrus treated monthly with Surround WP, cumulative reductions of 78% in adult numbers on mature leaves and of 60% in adult numbers on flush shoots (immature leaves) were observed in treated trees compared with untreated trees. Numbers of eggs and nymphs per flush shoot were reduced by 85 and 78%, respectively, in trees treated with particle film. Reductions in infestation levels of D. citri in treated trees were attributed to the negative effects of the particle film on the ability of adults to grasp, move, and oviposit. The suppressive effects of a Surround treatment against adult psyllids were degraded by rain.     

Sticky trap monitoring of a pest–predator system in glasshouse tomato crops: are available trap colours sufficient?

Monitoring of pest presence and population development in the crop during the season is essential for integrated pest management. Although many tools, for instance coloured sticky traps, have been developed, the full advantage of available information is rarely taken into account in decision‐making. The reasons behind include high workload in practice but also the poorly studied relationships between trap catches and populations in the crop. Here, we investigate whether commercially available coloured sticky traps can be used as tool to monitor population densities of a pest–predator system in glasshouse tomato. The response of Macrolophus pygmaeus (Rambur) (Hemiptera, Miridae) to blue and yellow sticky traps was tested in laboratory and glasshouse experiments. The results indicate that M. pygmaeus can be monitored equally well with both trap colours. The number of trapped insects showed good correlation with the population densities on the crop. Under growing conditions, more M. pygmaeus were trapped on blue compared with yellow sticky traps. However, due to the known preference of Trialeurodes vaporariorum (Westwood) (Hemiptera, Aleyrodidae), yellow traps should be used for a combined pest–predator monitoring.     

Cross-correlation analysis of fluctuations in local populations of pear psyllids and anthocorid bugs

1. To test whether predatory anthocorids migrate into pear orchards when populations of pear psyllids are building up, a cross-correlation analysis was carried out on their population numbers. Predator and prey population sizes were assessed weekly in 3 consecutive years (1991–93) by sampling pear leaves for eggs and nymphs of psyllids and pear tree branches for adult psyllids, as well as adults and nymphs of predatory anthocorids. The time-series consisted of numbers (per leaf or branch) averaged over preselected pear trees in an orchard and, in addition, over other trees selected along the hedgerows flanking the orchard. 2. The fluctuations in populations of adult and juvenile anthocorids showed strong cross-correlations with those of the eggs and nymphs of pear psyllids, but less correlation with adults of pear psyllids, as expected based on their increased ability to escape from predation. The psyllids always appeared first on the pear trees, resulting in positive phase shifts. The first peak of adult anthocorids on pear trees was always later than the first peak in the hedgerows, and the first peak of nymphal anthocorids on pear trees was always later than the first peak of adults on these pear trees. In each of the 3 years, anthocorids were rarely observed in the pear orchard during the first part of the growing season (April–June), but during the second half of the growing season (July–August) there was a strong numerical response of the anthocorid populations to increasing population densities of pear psyllids. 3. These results provide support for the hypothesis that the numerical response of the predators to prey density is caused initially by migration of anthocorids into the pear orchard and then by a reproductive response. The migrants originate from the hedgerows and other trees elsewhere, where they feed on aphids during the first part of the growing season.     

Spatial and temporal dynamics of overwintering Homalodisca coagulata (Hemiptera: Cicadellidae)

A 4-yr landscape-scale study was conducted to investigate spatial and temporal dynamics of overwintering Homalodisca coagulata (Say) (Hemiptera: Cicadellidae) in the lower San Joaquin Valley, California. Spatial structures of H. coagulata distributions were characterized with Moran's I index, and spatial associations between H. coagulata and the surrounding environment were investigated with a geographic information system. H. coagulata was caught consistently with sticky traps throughout the winter, and trap catches formed a distinctive peak in December or January, indicating active flight of H. coagulata during the winter. In 2000-2001, the mean +/-SE trap count was 4.8 +/- 1.21 per trap per wk, and H. coagulata trap catches were spatially autocorrelated within approximately 1.3 km. Approximately 49% of H. coagulata were caught in citrus, 23% in stone fruit, and 11% in grape. After a control program began in spring 2001, the mean trap count was considerably lower (0.041 +/- 0.0004 per trap per wk), and no spatial autocorrelations were detected in 2001-2004. H. coagulata trap catch-crop associations also changed after initiation of the control program. Between 25 and 38% of H. coagulata trap catches were from citrus, between 8 and 20% were from stone fruit, and between 11 and 25% were from grape. Potential for winter-season spread and management of Xylella fastidiosa Wells et al., a pathogen causing Pierce's disease, are discussed.     

Monitoring methods for Diaphorina citri Kuwayama (Hemiptera: Liviidae) on citrus groves with different insecticide application programmes

The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), is a major citrus pest that transmits the bacteria Candidatus Liberibacter asiaticus and Ca. L. americanus associated with huanglongbing (HLB) disease. Diaphorina citri population densities can affect the effectiveness of its monitoring and sampling methods. Thus, we compared different methods for adult D. citri monitoring in groves with and without insecticide application programmes. Four short‐term experiments were carried out, each one lasting four consecutive weeks. In these experiments, sticky cards with different colours (yellow, light green, green and dark green), sweep net, two suction device models, visual inspection and stem tap sampling were assessed. Two long‐term experiments were conducted for 4.5 and 5 years, in which only yellow sticky card and visual inspection for D. citri monitoring were assessed. For the short‐term experiments, psyllids were detected by all monitoring methods during all sampling periods in areas without chemical control. However, in areas with psyllid control via fortnightly and monthly applications of insecticides, only sticky cards, regardless of their colour, were able to detect the presence of D. citri. Similarly, for the long‐term experiments, yellow sticky cards were more effective than visual inspection for detecting and quantifying D. citri in all areas with or without insecticide application. Therefore, in areas where HLB is present and chemical control of psyllid is required, sticky cards are the most reliable option for monitoring D. citri.     

Diurnal Patterns of Flight Activity and Effects of Light on Host Finding Behavior of the Asian Citrus Psyllid

The Asian citrus psyllid, Diaphorina citri (Hemiptera: Psyllidae), is an invasive pest of citrus in the United States. The psyllid feeds and reproduces primarily on new flush growth of citrus and other rutaceous plants. Because it vectors the bacterial causal agents of the deadly citrus greening disease, D. citri is potentially a pest of economic importance in all citrus growing areas where it occurs together with the disease. We investigated the diurnal patterns of its flight activity in the field and the effects of light on its host selection and egg laying behaviors. The numbers of adult psyllids caught on yellow sticky traps were 3 to 4-fold higher during daytime than nighttime. Daytime flight activity of D. citri adults also varied with time of the day with peak catches occurring at midday from 1200 to 1500 h. Illumination of the traps at night increased their attractiveness to adult psyllids by 5-fold. Similarly, light significantly increased plant colonization by adults and female egg deposition on potted plants in the laboratory. These results showed that the flight activity and host selection behavior of adult psyllids are regulated by light and circadian rhythms. Thus, adult psyllids utilize light as visual cues in their host-plant selection process.     

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.