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.     

Determining the spatial autocorrelation of dengue vector populations: influences of mosquito sampling method,covariables, and vector control

We investigated spatial autocorrelation of female Aedes aegypti L. mosquito abundance from BG‐Sentinel trap and sticky ovitrap collections in Cairns, north Queensland, Australia. BG‐Sentinel trap collections in 2010 show a significant spatial autocorrelation across the study site and over a smaller spatial extent, while sticky ovitrap collections only indicate a non‐significant, weak spatial autocorrelation. The BG‐Sentinel trap collections were suitable for spatial interpolation using ordinary kriging and cokriging techniques. The uses of Premise Condition Index and potential breeding container data have helped improve our prediction of vector abundance. Semiovariograms and prediction maps indicate that the spatial autocorrelation of mosquito abundance determined by BG‐Sentinel traps extends farther compared to sticky ovitrap collections. Based on our data, fewer BG‐Sentinel traps are required to represent vector abundance at a series of houses compared to sticky ovitraps. A lack of spatial structure was observed following vector control treatment in the area. This finding has implications for the design and costs of dengue vector surveillance programs.     

Kairomone attractant for the leafmining fly, Liriomyza bryoniae (Diptera, Agromyzidae)

A field test carried out in an industrial greenhouse in Lithuania revealed the attractiveness of synthetic methyl salicylate (MeSa) towards an economically important leafmining tomato pest, Liriomyza bryoniae (Kaltenbach) (Diptera, Agromyzidae). The behavioural reaction of the flies depended very much on the simultaneous presence of both olfactory and visual stimuli. The attractiveness depended on the colour of a sticky trap: MeSa attracted significantly more flies (ca. 2.2 times) when placed in yellow traps than in aluminium foil colour ones, when catches in such traps were compared to a corresponding control. L. bryoniae is the first species within the Agromyzidae family attracted by MeSa. The attractant was attributed to kairomones, as the compound is known as a plant-produced volatile. MeSa can be an effective extra-tool for increasing the attractiveness of traps. It should be evaluated in future whether such trap/bait combination is effective for the mass trapping of L. bryoniae leafminers in greenhouses (closed area).     

A new Y-tube olfactometer for mosquitoes to measure the attractiveness of host odours

The behavioural responses of flying western flower thrips (Frankliniella occidentalis Pergande) (Thysanoptera: Thripidae) to the colour yellow and the odour anisaldehyde were examined. In a wind tunnel, upwind flight by female thrips was common in an airflow of 0.11 m s^–1 but was impeded at 0.22 m s^–1. In the absence of anisaldehyde, flying female thrips exhibited an oriented response towards a yellow cue in the wind tunnel at a wind speed of 0.11 m s^–1. The main response of females to anisaldehyde in the wind tunnel was flight inhibition. There was no evidence of an odour-induced visual response, an odour-induced anemotactic response or chemotaxis by female thrips to anisaldehyde in wind tunnel bioassays, but chemokinesis was implicated. With a matrix of yellow or black water traps with and without anisaldehyde in a greenhouse sweet pepper crop, yellow traps with anisaldehyde caught more thrips adults than yellow traps without anisaldehyde, black traps with anisaldehyde and black traps without anisaldehyde (1.3, 28 and 721 times for males respectively and 2.4, 9 and 117 times for females, respectively). Differences between respective traps were statistically significant in almost all cases. Trapping experiments using a centre-baited trap design to reduce the interaction of anisaldehyde between baited and unbaited traps were undertaken in tomato and sweet pepper greenhouse crops. When the spatial distribution of the thrips adult population within the greenhouse was taken into account, yellow water traps with anisaldehyde caught between 11 and 15 times more female and 3 and 20 times more male F. occidentalis adults than yellow traps without anisaldehyde.     

Population suppression of Bemisia tabaci (Hemiptera: Aleyrodidae) using yellow sticky traps and Eretmocerus nr. rajasthanicus (Hymenoptera: Aphelinidae) on tomato plants in greenhouses

We conducted three experiments for management of Bemisia tabaci (Gennadius) biotype ‘B’ on tomatoes under greenhouse conditions: (i) vertically placing yellow sticky cards either parallel or perpendicular to tomato rows at a rate of 1 per 3‐m row; (ii) releasing Eretmocerus sp. nr. rajasthanicus once at 30 adults/m² in the high whitefly density greenhouses (> 10 adults/plant), or twice at 15 adults/m² at a 5‐day interval in the low whitefly density greenhouses (< 10 adults/plant); and (iii) using combinations of yellow sticky cards that were placed vertically parallel to tomato rows and parasitoids released once at 30/m² in high whitefly density greenhouses or twice at 15/m² at a 5‐day interval in low whitefly density greenhouses. Our data show that yellow sticky cards trapped B. tabaci adults and significantly reduced whitefly populations on tomato. The yellow sticky cards that were placed parallel to tomato rows caught significantly more whitefly adults than those placed perpendicular to tomato rows on every sampling date. In the treatment where parasitoids were released once at 30/m² in high whitefly density greenhouses, the number of live whitefly nymphs were reduced from 4.6/leaf to 2.9/leaf in 40 days as compared with those on untreated plants on which live whitefly nymphs increased from 4.4/leaf to 8.9/leaf. In the treatment where parasitoids were released twice at 15/m² in low whitefly density greenhouses, the numbers of live nymphs of B. tabaci on tomato leaves were reduced from 2.1/leaf to 1.7/leaf in 20 days as compared with those on untreated plants on which numbers of live nymphs of B. tabaci increased from 2.2/leaf to 4.5/leaf. In the treatment of yellow sticky cards and parasitoid release once at 30/m² in high whitefly density greenhouses, the numbers of live nymphs of B. tabaci on tomato leaves were reduced from 7.2/leaf to 1.9/leaf, and in the treatment of yellow sticky cards and parasitoid release twice at 15/m² at a 5‐day interval at low whitefly density, the numbers of live nymphs of B. tabaci on tomato leaves were reduced from 2.5/leaf to 0.8/leaf; whereas the numbers of live nymphs of B. tabaci on untreated plants increased from 4.4/leaf to 8.9/leaf. An integrated program for management of B. tabaci on greenhouse vegetables by using yellow sticky cards, parasitoids and biorational insecticides is discussed.     

Attraction of Trialeurodes vaporariorum and Bemisia argentifolii to eggplant, and its potential as a trap crop for whitefly management on greenhouse poinsettia

Trap cropping, though promising, has had little evaluation in greenhouses. This study evaluated eggplant, Solanum melongena L. (Solanaceae), as a trap crop for two whitefly species, Trialeurodes vaporariorum (Westwood) and Bemisia argentifolii Bellows & Perring (both Hemiptera: Aleyrodidae), on greenhouse poinsettia, Euphorbia pulcherrima Willd. ex Koltz (Euphorbiaceae). Because the two whitefly species co‐occur in greenhouses, a common trap crop for both whiteflies is desirable. When adults were provided a choice between eggplant and poinsettia in a cage, 60% of B. argentifolii and 98% of T. vaporariorum were observed on eggplant after 3 days. However, when adults were given eggplant after first settling on poinsettia, only 38% of B. argentifolii were later found on eggplant, whereas 95% of T. vaporariorum moved to eggplant. In a greenhouse experiment, eggplant did not affect either the spatial distribution or density of adult B. argentifolii on poinsettias. In contrast, eggplant changed the spatial distribution of T. vaporariorum within 3 days by attracting and retaining the adults. However, the attractiveness of eggplant did not result in a reduced number of T. vaporariorum on poinsettias compared with poinsettias in monoculture. Adult T. vaporariorum mortality was high on poinsettias and this likely caused adult density on poinsettias in monoculture to decrease as fast as that under trap cropping. A simulation model was developed to examine how adult whitefly mortality on poinsettia influences trap cropping effectiveness. When whitefly mortality was high, simulated densities were similar to the experimental data. This reveals an unexpected factor, pest mortality on the main crop, that can influence the relative effectiveness of trap cropping. Our results indicate that eggplant will not work unilaterally as a trap crop for B. argentifolii. For T. vaporariorum, attraction to eggplant might be useful as a trap crop system when whitefly mortality on the main crop is not high.     

Effect of microclimate heterogeneity and ventilation system on entomopathogenic hyphomycete infection of Trialeurodes vaporariorum (Homoptera: Aleyrodidae) in Mediterranean greenhouse tomato

Collaborative research was conducted in the south of France to assess constraints related to both climate heterogeneity and ventilation systems on the control potential of a Lecanicillium muscarium-based formulation against whiteflies in Mediterranean greenhouses. Four series of small-scale greenhouse trials were performed in 2001 and 2002. Two applications at 4–5 day intervals of Mycotal were conducted on young larvae of the greenhouse whitefly, Trialeurodes vaporariorum, at the rate recommended by the manufacturer (ca. 10¹⁰ viable spores per liter of water suspension). The climatic heterogeneity was taken into account by comparing the fungus-induced mortality of nymphs located on lateral row plants to that of nymphs on center row plants. In spite of significant differences in air flows (0.7–1.2 and 0.3 ms⁻¹, respectively) there was no effect on fungus efficacy (53–76% mortality). When comparing the influence of greenhouse equipment (sophisticated glasshouse vs. polyethylene-covered greenhouse), the fungus was not affected (89–96% mortality) in spite of significant differences in ventilation rates. The results confirmed that entomopathogenic Hyphomycetes have a strong potential for microbial control of whitefly larvae infesting tomato crops at moderate ambient humidity in Mediterranean greenhouses in spite of windy periods. These investigations confirmed that microclimatic conditions prevailing in the targeted insect habitat (under-leaf surface boundary layer) are greatly disconnected from that of both outside and inside the greenhouse. In northern Mediterranean greenhouses, non-stressed tomato crops provide unexpected favorable conditions for mycoinsecticide use against a phyllophagous insect.     

Spatial distribution of Oncometopiafacialis (Signoret) (Hemiptera: Cicadellidae) in citrus orchard

The spatial distribution of Oncometopia facialis (Signoret) was studied in sweet orange to elaborate sampling plans and decision-making procedure for the control of this sharpshooter in the field. The samplings were carried out fortnightly in a grid design disposition of 100 points (plants) in citrus orchard, with yellow sticky traps. The average number of O. facialis ranged from 0.35 to 1.17 insects/trap, with the I index varying from 0.89 to 1.82. The fit tests to negative binomial, Poisson distribution, I index and Morisita index indicated aggregated distribution of this insect. The b result of Taylor's power law was 1.6382 (t = 2.71; d.f. = 11; P < 0.05). Sampling plans were elaborated with a precision level of 10, 20 and 25% of error in the mean estimation.     

Effect of environmental factors on the flight activity of Trialeurodes vaporariorum (Westwood) under greenhouse conditions

The flight activity of the greenhouse whitefly Trialeurodes vaporariorum (Westwood) was monitored over a 3‐year period in greenhouses containing tomato and zucchini crops. The environmental factors affecting its flight activity and dispersal were analyzed. Among the climatic variables, temperature had a positive impact on T. vaporariorum flight, whereas relative humidity had only a weak effect. More flights were made during the morning and afternoon, with fewer flights occurring when the temperature was above 25°C in greenhouses containing zucchini or above 30°C in those containing tomato; no flights were recorded when the temperature was 12.30°C in either setting. Flight typology, classified as short, long or dispersal, and covering a few centimeters to more than 2–3 m, was influenced by the vegetative condition of the plants. As the plants aged and declined in condition, the number of short flights decreased, whereas the number of long and dispersal flights increased. Based on these results, we can conclude that the dispersal of T. vaporariorum in greenhouses containing either tomato or zucchini crops is generally influenced by environmental factors, which also affect the type of flight, with a trade‐off between short and long dispersal flights. However, adult dispersal is driven not only by temperature, but also by other factors, such as conspecific density and time of the day. Therefore, producers must consider such factors when aiming to reduce the dispersal of pest insects within greenhouses and, thus, to maintain the productivity of their crops.     

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.     

Preferences by Rhagoletis indifferens (Diptera,Tephritidae) for rectangles of various yellow colours and fluorescence

Sticky rectangle traps of various yellow colours and fluorescence made of cardboard were field tested against western cherry fruit fly, Rhagoletis indifferens Curran, in paired trap preference experiments in Washington state. In a first experiment that involved comparisons of Alpha Scents (proprietary paint), Fluorescent Yellow (aerosol paint), Saffron Thread and Neon Light (semi‐gloss enamel paints) traps at two sites, the best performing trap was the Saffron Thread trap. In a second experiment comparing Citrus Splash (semi‐gloss enamel paint) with Alpha Scents and with Macaw and Lemon Zest (both semi‐gloss enamel paints) traps at a third site, the Citrus Splash trap outperformed the Alpha Scents trap. The Citrus Splash trap did not differ statistically from Saffron Thread and Lemon Zest traps, even though it caught 51% more flies than the Lemon Zest trap. The Alpha Scents trap caught significantly more non‐target Diptera than Fluorescent Yellow, Neon Light and Citrus Splash traps at two of three trap sites where non‐target Diptera populations were relatively high and overall it appeared less selective than the Citrus Splash trap. Results suggest that sticky rectangle traps painted semi‐gloss enamel Saffron Thread or Citrus Splash with low fluorescence could be highly useful for detecting R. indifferens.     

Evaluation of yellow rectangle traps coated with hot melt pressure sensitive adhesive and sticky gel against Rhagoletis indifferens (Diptera: Tephritidae)

Sticky yellow rectangle traps have been used for many years to capture Rhagoletis (Diptera: Tephritidae) fruit flies. Traditional sticky yellow traps are coated with a sticky gel (SG) that can leave residues on the hands of users. An alternative to SG on traps are hot melt pressure sensitive adhesives (HMPSAs), which are less messy. The main objective here was to evaluate two rectangle traps of two yellow colors, the Alpha Scents Yellow Card coated with HMPSA (Alpha Scents, West Linn, OR), and the Pherocon AM trap coated with SG (Pherocon; Trécé, Adair, OK), for capturing western cherry fruit fly, Rhagoletis indifferens Curran. Flies captured on both traps and held in the laboratory and field did not escape their surfaces. Flies caught on HMPSA were damaged when removed from traps without citrus solvent, whereas flies caught on SG could be removed intact without solvent. In field tests, Alpha Scents traps baited with an ammonium bicarbonate lure captured 1.4-2.2 times more R. indifferens than Pherocon traps baited with the same lure. Results of an experiment that eliminated differences in surface sticky material type, overall size, and surface sticky area between Alpha Scents and Pherocon traps suggested, although did not show conclusively, that more flies were caught on the Alpha Scents than Pherocon traps because of their different yellow color and/or lower fluorescence and not the HMPSA. Overall, the Alpha Scents trap is a viable alternative to the Pherocon trap for detecting R. indifferens.     

Greenhouse whitefly control through the combined use of the colour attraction system with the parasite waspEncarsia formosa [Hym.: Aphelinidae]

The combined use of colour attraction (yellow sticky plates) andEncarsia formosa (Gahan) parasites reduced the greenhouse whiteflyTrialeurodes vaporariorum (Westwood) population in a spring tomato crop to an extremely low level. Whiteflies were strongly attracted to yellow sticky plates while the parasite,E. formosa, was not attracted so long as suitable and sufficient hosts were present. As the numbers of whiteflies declined, parasites were increasingly trapped by the plates. The percent parasitization increased continuously during the experiment, reaching about 90%, indicating the complete compatibility of colour attraction and biological control.     

Control of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) in greenhouse tomato crops using the mating disruption technique

The effectiveness of mating disruption to control the tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), in greenhouse tomato crops was evaluated in four trials carried out in winter–spring and summer–winter growing seasons in Southwestern Sardinia (Italy). Pheromone dispensers loaded with 60 mg of the natural blend of the major and minor sex pheromone component (rate 90 : 10) were applied in disrupted greenhouses at a rate of 1000/ha (60 g of active ingredient/ha). Male captures in monitoring pheromone traps, percentage of tomato plants infested by T. absoluta and damage on leaves and fruits were monitored weekly and compared in disrupted and untreated (control) greenhouses. In greenhouses disrupted with 1000 dispensers/ha, a reduction of 93–97% in male trap captures was observed, compared with control. Leaf damage was significantly lower in greenhouses disrupted with 1000 dispensers/ha than in control ones, with a reduction of infestation throughout the growing season ranging from 57% to 85%. Pheromone dispensers applied at the density of 1000/ha significantly reduced the percentage of damaged fruits by 62–89%. In control greenhouses, the highest damage on leaves and fruits was generally observed in edge plants, while leaf and fruit infestation was uniformly distributed in pheromone‐treated greenhouses, indicating an even distribution of the pheromone cloud inside the greenhouse. Mating disruption showed to be an efficient strategy to control in greenhouse the tomato leafminer and can be included in the overall tomato integrated pest management programs.     

Light emitting diode(LED)‐based trapping of the greenhouse whitefly (Trialeurodes vaporariorum)

Visual traps like yellow sticky card traps are used for monitoring and control of the greenhouse whitefly (Trialeurodes vaporariorum). However, reflected intensity (brightness) and hence, attractiveness depend on the ambient light conditions, and the colour (wavelength) might not fit with the sensitivity of whitefly photoreceptors. The use of light emitting diodes (LEDs) is a promising approach to increase the attractiveness, specificity and adaptability of visual traps. We constructed LED‐based visual traps equipped with blue and green high‐power LEDs and ultraviolet (UV) standard LEDs according to the putative spectral sensitivities of the insects' photoreceptors. In a series of small‐scale choice and no‐choice recapture experiments, the factors time of day as well as light intensity and light quality (colour) of LED traps were studied in terms of attractiveness compared to yellow traps without LEDs. Green LED traps (517 nm peak wavelength) were comparably attractive in no‐choice experiments but clearly preferred over yellow traps in all choice experiments. The time of day had a clear effect on the flight activity of the whiteflies and thereby on the trapping success. Blue LEDs (474 nm) suppressed the attractiveness of the light traps when combined with green LEDs suggesting that a yet undetected photoreceptor, sensitive for blue light, and an inhibiting interaction with the green receptor, might exist in T. vaporariorum. In choice experiments between LED traps emitting green light only or in combination with UV (368 nm), the green‐UV combination was preferred. In no‐choice night‐time experiments, UV LEDs considerably increased whitefly flight activity and efficacy of trapping. Most likely, the reason for the modifying effect of UV is the stimulating influence on flight activity. In conclusion, it seems that the use of green LEDs alone or in combination with UV LEDs could be an innovative option for improving attractiveness of visual traps.     

Reduction of sooty mold damage through biocontrol of the greenhouse whitefly <Emphasis Type="Italic">Trialeurodes vaporariorum</Emphasis> (Hemiptera: Aleyrodidae) using selective insecticides in tomato cultivation greenhouses

The proliferation of sooty mold on tomato fruit, Solanum lycopersicum L.—as caused by the secretion of honeydew on the fruit by greenhouse whitefly, Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae)—has recently become a serious problem in estivo-autumnal greenhouse tomato cultivation in Japan. It is becoming increasingly difficult to control T. vaporariorum using insecticides because whiteflies have developed resistance to a variety of insecticides. As the first step towards integrated pest management, we examined whether the use of selective insecticides could prompt a cascade process in which an increase in parasitoids is followed by a decrease in whitefly occurrence and then a reduction in sooty mold damage. We compared greenhouses in which nonselective insecticides effective against T. vaporariorum and its parasitoids were used (hereafter denoted “nonselective insecticide greenhouses”) with greenhouses in which selective insecticides for T. vaporariorum were used (hereafter denoted “selective insecticide greenhouses”) in terms of the density and level of parasitism of T. vaporariorum as well as the degree of damage from sooty mold. The number of parasitized whiteflies increased with the number of whiteflies in the selective insecticide greenhouses, whereas it remained at low levels regardless of the number of whiteflies in the nonselective insecticide greenhouses. Furthermore, the selective insecticide greenhouses showed significantly higher parasitism levels, fewer whiteflies, and reduced sooty mold damage compared to the nonselective insecticide greenhouses. These results suggest that the use of selective insecticides causes an increase in parasitism, which in turn suppresses the number of greenhouse whiteflies and, eventually, sooty mold.     

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.     

Seasonal activity and abundance of Orosius orientalis (Hemiptera: Cicadellidae) at agricultural sites in Southeastern Australia

Orosius orientalis is a leafhopper vector of several viruses and phytoplasmas affecting a broad range of agricultural crops. Sweep net, yellow pan trap and yellow sticky trap collection techniques were evaluated. Seasonal distribution of O. orientalis was surveyed over two successive growing seasons around the borders of commercially grown tobacco crops. Orosius orientalis seasonal activity as assessed using pan and sticky traps was characterised by a trimodal peak and relative abundance as assessed using sweep nets differed between field sites with peak activity occurring in spring and summer months. Yellow pan traps consistently trapped a higher number of O. orientalis than yellow sticky traps.     

Protocol for semi‐automatic identification of whiteflies Bemisia tabaci and Trialeurodes vaporariorum on yellow sticky traps

Yellow sticky traps (YSTs) are commonly used in greenhouse crops to monitor flying pest species. Whiteflies like Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae) and Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) are typically monitored using YSTs in tomato and sweet pepper crops. By counting the whiteflies on a YST, growers get an idea of the pests density in space and time in the greenhouse and can take pest control measurements accordingly. The downside is that manual counting of whiteflies on a YST is very time‐consuming and thus costly. A protocol to semi‐automate counting and identification of whiteflies on YSTs using image analysis software was developed to speed up the monitoring process. Bemisia tabaci is on average smaller than T. vaporariorum and by discriminating by size based on the amount of pixels in digital images, ratios of both species in a mixed population on YSTs could be estimated accurately. At low densities, the countings of different YSTs should be pooled till a 200 density threshold is reached in order to get accurate ratio estimates of both species. This study provides a protocol to reliably count and identify whiteflies semi‐automatically on standardized pictures. More research is required to develop alternative techniques to make standardized pictures in the field (e.g., with smartphone).     

Visual orientation of the black fungus gnat,Bradysia difformis,explored using LEDs

Fungus gnats occur worldwide with more than 1 700 described species. They can cause serious damages on ornamentals, crop plants, and edible mushrooms, and are considered to be a serious pest in the last years. Bradysia difformisFrey (Diptera: Sciaridae) represents a common species in Europe. Usually, yellow sticky traps are used for monitoring and control in greenhouses and fluorescent tube‐based light traps are additionally applied for control in mushroom cultivation. The importance of such visual trapping measures for efficient monitoring or alternative control increases in biological and integrated plant protection. However, detailed color preferences of fungus gnats are mostly unknown. We studied the visual orientation of B. difformis with light‐emitting diodes (LEDs) in a broad range of peak wavelengths from 371 nm (ultraviolet, UV) to 619 nm (amber). We determined attractive wavelengths in consecutive choice experiments in daylight and darkness. Highest numbers of adult B. difformis were attracted to UV radiation (382 nm) followed by green‐yellow light (532–592 nm). The responses to UV and the green‐yellow range were relatively unspecific and mostly independent from intensity. Combination of UV and yellow LEDs improved trapping efficacy compared to a single UV or yellow LED trap, as well as compared to a common yellow sticky trap. When both wavelengths were compared to a black surface to increase contrasts, the black surface was preferred over yellow, but was less attractive than UV. Thus, B. difformis displays two, probably wavelength‐specific, behaviors to UV radiation and green‐yellow light, with UV being the most attractive stimulus. These behaviors might be directly related to underlying photoreceptors, suggesting dichromatic vision in B. difformis.