Effect of soybean canopy closure on landing rates of aphids with implications for restricting spread of soybean mosaic virus

Alate Aphis citricola and Myzocallis punctatus were caught more abundantly on horizontal ermine-lime canopy-level sticky traps in a closed soybean canopy than on similar traps in an open canopy. This is the first reported case in which more alate aphids were collected on traps in fields with relatively more ground cover. Capitophorus elaeagni were caught more abundantly on traps in relatively more open canopy, and Lipaphis erysimi, Rhopalosiphum maidis and Schizaphis graminum were collected in statistically similar numbers in open and closed canopies. Our trapping technique was designed in an attempt to collect only those aphids which would otherwise have landed on the soybean canopy. Landing rates differed among species; therefore, the efficacy of using ground cover manipulation to reduce spread of soybean mosaic virus would depend upon seasonal occurrence of the important local vector species.     

THE COMPARISON OF YELLOW CYLINDRICAL, FLAT AND WATER TRAPS, AND OF JOHNSON SUCTION TRAPS, FOR SAMPLING APHIDS

Different traps were compared to find the type most suitable for studying aphid vectors of plant viruses quantitatively.
A Moericke water trap caught more aphids than a flat sticky trap of equal area. A flat sticky trap (930 sq. cm.) caught half as many aphids as a cylindrical trap (945 sq. cm.), which caught about one-third as many as a water trap (1200 sq. cm.) or a Johnson suction trap (9 in. fan) when operated at between 2 and 3 ft. over bare soil.
Yellow traps caught proportionally more Tuberculoides annulatus , and in summer more Capitophorus species than a suction trap, but significantly fewer Anoecia corni, Sitobium spp. and Pemphigus bursarius. Traps with a level surface caught proportionally more Brevicoryne brassicae, Aphis fabae and Myzus persicae , but fewer Anoecia corni and Drepanosiphum plantanoides than vertical cylindical traps. Attraction by colour influences the catch on horizontal traps more than on cylindrical traps because there is less impaction by the wind.
Only suction traps indicate the number of aphids per unit volume of air and are non-selective, but they are expensive and require an electric power supply. Water traps effectively catch those aphids that are attracted to yellow, but they require frequent attention. Sticky traps catch fewer aphids than either suction or water traps, but they can be left unattended for about 2 weeks. Flat sticky traps catch aphids likely to land on a crop, and cylindrical traps show when aphids are in the air, but not if those aphids are able or wanting to land. For routine work cylindrical sticky traps have other advantages; they are cheap and do not require skilled handling, and their catches of alate Myzus persicae have been correlated with the spread of some plant viruses.     

Response of Trichogramma egg parasitoids to colored sticky traps

The response of Trichogramma spp. egg parasitoids to colored sticky traps was evaluated in the field during two seasons (1995/1996, 1996/1997). Traps consisted of a glass tube coated with Bird-Tanglefoot® into which colored paper was inserted or clear traps without paper. Colors tested were white, green, blue, yellow and red in the first season and white, green, yellow and black in the second season. The proportion of both female and male parasitoids caught on the sticky traps was significantly different among colors, indicating that the parasitoids actively move between plants and are not solely carried along passively by wind. White was the color most preferred by female parasitoids, followed by clear and green traps. Yellow was preferred over black but was less attractive than green. Visual cues may be used by Trichogramma spp. during the habitat location process. The color preference of male Trichogramma spp. differed significantly from females with yellow and green being more attractive than white. For all colors, more female Trichogramma spp. were caught on the sticky traps (>85% of all wasps caught), indicating a lower activity level and/or shorter lifespan for males. The use of white cylindrical sticky traps for monitoring Trichogramma spp. populations in the field is recommended.     

Response of alate aphids to green targets on coloured backgrounds

To study the effect of background colour on aphid landing on green targets (water pan traps), two field experiments were set up in Hessen, Germany, in 2003. Traps were put onto coloured plastic sheets (13 colours, straw mulch, transparent foil, and uncovered soil, Experiment 1). In Experiment 2, green water pans were again put on coloured plastic sheets (red, white, green, and yellow), and the sheets were either sprayed with insect glue or not. Backgrounds and traps were spectrally characterised with a field radiometer (320–950 nm). Aphid catches were highest in the traps on the uncovered background, and lowest in the traps on white or silver backgrounds. For Brevicoryne brassicae, Myzus persicae (Homoptera: Aphididae, Macrosiphini) and five further aphid species, there was a significant negative correlation between UV‐reflectance (320–400 nm) and log(N + 1)‐transformed number of individuals. However, the effect of straw mulch (reduced aphid catches with straw compared to the uncovered background), could not be attributed to differences in UV‐reflectance, as UV was almost identical in soil and straw. High numbers of alate aphids were caught in traps with dark backgrounds (e.g. black, dark green), a result which was attributed to the high contrast between the background and target. The substantially higher aphid numbers from targets with bare soil than from targets with spectrally similar black backgrounds were thought to be caused by the structure of the background surface: for alate aphids, landing close to the target on smooth surfaces may induce probing, and the lack of appropriate substrate will result in take‐off, whereas soil will not induce probing, and aphids will continue to move towards the green targets.     

Effects of population density on alienicolae of Aphis fabae Scop.: V. Variations in size, relative wing length and numbers of antennal sensorla of field alatae

Size, relative wing length and numbers of antennal sensoria of alate Aphis fabae caught in a suction trap 12.2 m above ground and of migrants, flyers and non-flyers among alate A. fabae from field infestations on beans and beet are compared. The size of aphids in successive samples decreased throughout the period of colonization but, on average, beet aphids were bigger and broad bean aphids were smaller than field bean aphids. There were very few migrant alatae among the very large or the very small aphids from any of the crops, neither were aphids of these extreme sizes caught in the suction trap. Non-flyers and beet aphids generally had relatively shorter wings than migrants and bean aphids respectively. The numbers of antennal sensoria differed more between aphids from the three crops than between classes of alatae from the same crop, although trap aphids, presumed to be migrating from field beans had more sensoria than alatae taken from that crop. The mean dry mass of flyers was usually less than that of migrants of a similar size, although if the mass of nymphs deposited before flight is added, it is apparent that a flyer would be heavier than a migrant of the same size at maturity. This additional mass is thought to be due to increased development of the embryos in the ovarioles of flyers at this time and indicative of their greater adaptation for reproduction.     

Design and selection of trap color for capture of the tea leafhopper,Empoasca vitis,by orthogonal optimization

The tea leafhopper, Empoasca vitis (Göthe) (Hemiptera: Cicadellidae), is a major pest of the tea plant, Camellia sinensis (L.) O. Kuntze (Theaceae). In this study, the RGB color model was used to describe the colors of sticky traps. The most effective color for attraction of E. vitis was investigated by orthogonal optimization. The selected color was verified in tea gardens and the most effective height for positioning of color sticky traps for capturing tea leafhoppers was investigated. After the determination of the effect of the three color parameters and their interactions by orthogonal optimization, the color gold (RGB: 255, 215, 0) was selected as the most effective color to trap tea leafhoppers. In tea gardens, more leafhoppers were captured using gold sticky traps (RGB: 226, 204, 4) than using commercially available yellow sticky traps. The most effective height of gold sticky traps for trapping leafhoppers was 40–60 cm above the tea canopy. Few lady beetles were captured at this height. We conclude that the orthogonal optimization method is a convenient and efficient method to screen digitally generated colors for attracting and trapping of pests.     

不同颜色粘虫板对多毛小蠹和皱小蠹的诱集效果

试验对比了红、黄、蓝、绿、黑、白六种颜色粘虫板对新疆吐鲁番地区杏树上多毛小蠹(Scolytus seulensis)和皱小蠹(Scolytus rugulosus)的引诱效果,结果表明红色和黑色粘虫板对多毛小蠹的引诱效果明显高于其他颜色;其中黑色粘虫板对皱小蠹的引诱效果最强,平均每块黑板诱捕到(11.8±5.0)头皱小蠹,红色次之,其他颜色对两种小蠹均无明显的引诱效果;红色粘虫板对多毛小蠹的引诱效果最强,平均每块红板诱捕到(16.±3.0)头多毛小蠹,黑色次之,其他颜色对两种小蠹均无明显的引诱效果.通过色板引诱虫量的变化体现出两种小蠹的不同扬飞高峰期,多毛小蠹的扬飞高峰期应在六月初,而皱小蠹的扬飞高峰出现在六月中旬.     

黑龙江省哈尔滨地区吸虫塔有翅蚜种群动态

【目的】明确吸虫塔对作物蚜虫防控的指导意义,明确中国黑龙江省哈尔滨地区有翅蚜(和大豆蚜)的种群动态,为大豆蚜虫防控提供预警信息。【方法】2009至2012年通过吸虫塔监测哈尔滨地区有翅蚜及有翅大豆蚜动态结合当年田间大豆蚜动态调查。【结果】哈尔滨吸虫塔全年收集有翅蚜量为0.6~1.7万头不等。具1~3个高峰(不同年份有翅蚜发生高峰数量不同),高峰期时间1个月左右,位于7月中旬至10月中旬之间。周有翅蚜量达200头时预示着有翅蚜高峰期的到来,高峰期有翅蚜量可占年有翅蚜量的90%以上。同一地区不同年份有翅蚜高峰期时间不同。吸虫塔有翅大豆蚜亦具1~3个高峰期,时间位于当年有翅蚜的高峰期时间内,为短短的1周或几周,高峰期蚜量占全年采集有翅大豆蚜量的80%~95%。田间大豆蚜只存在一个高峰,2009、2010、2012年田间大豆蚜高峰期均与吸虫塔收集的大豆蚜高峰期相重叠,且峰值日期一致。【结论】吸虫塔可以很好地反应当年田间大豆蚜的种群动态,表现在高峰期及高峰点的预测,可为大豆蚜的预测预报提供预警信息。     

Vertical distribution of codling moth adults in pheromone-treated and untreated plots

The vertical distribution of codling moth,Cydia pomonella (L.) within pheromone-treated and untreated apple and pear orchard canopies was determined using tethered virgin females, unbaited sticky traps, and blacklight observation of released moths. Mating of virgin females tethered at various heights in untreated orchard canopies increased with placement height from 1–4 m. Application of pheromone dispensers for mating disruption at 2 and 4 m above the ground greatly decreased mating. Greatest capture of males and females on unbaited sticky traps occurred at mid- and upper-canopy heights. Total capture of males and females in pheromone-treated plots was not statistically different than in untreated plots. The percentage of mated females captured on sticky traps did not vary with trap height or pheromone treatment. Released moths marked with flourescent powder and observed at dark with a blacklight indicated that moths are primarily distributed high in the canopy. However, males shifted to a position lower in the canopy when pheromone dispensers were placed 2.1 m above the ground. Results suggest that pheromone dispensers be placed in the upper canopy for optimal disruption of codling moth mating.     

Effect of trap type, trap position, time of year, and beetle density on captures of the redbay ambrosia beetle (Coleoptera: Curculionidae: Scolytinae)

The exotic redbay ambrosia beetle, Xyleborus glabratus Eichhoff (Coleoptera: Curculionidae: Scolytinae), and its fungal symbiont Raffaellea lauricola Harrington, Fraedrich, and Aghayeva are responsible for widespread redbay, Persea borbonia (L.) Spreng., mortality in the southern United States. Effective traps and lures are needed to monitor spread of the beetle and for early detection at ports-of-entry, so we conducted a series of experiments to find the best trap design, color, lure, and trap position for detection of X. glabratus. The best trap and lure combination was then tested at seven sites varying in beetle abundance and at one site throughout the year to see how season and beetle population affected performance. Manuka oil proved to be the most effective lure tested, particularly when considering cost and availability. Traps baited with manuka oil lures releasing 5 mg/d caught as many beetles as those baited with lures releasing 200 mg/d. Distributing manuka oil lures from the top to the bottom of eight-unit funnel traps resulted in similar numbers of X. glabratus as a single lure in the middle. Trap color had little effect on captures in sticky traps or cross-vane traps. Funnel traps caught twice as many beetles as cross-vane traps and three times as many as sticky traps but mean catch per trap was not significantly different. When comparing height, traps 1.5 m above the ground captured 85% of the beetles collected but a few were caught at each height up to 15 m. Funnel trap captures exhibited a strong linear relationship (r2 = 0.79) with X. glabratus attack density and they performed well throughout the year. Catching beetles at low densities is important to port of entry monitoring programs where early detection of infestations is essential. Our trials show that multiple funnel traps baited with a single manuka oil lure were effective for capturing X. glabratus even when no infested trees were visible in the area.     

Evaluation of double-decker traps for emerald ash borer (Coleoptera: Buprestidae)

Improved detection tools are needed for the emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), an invasive forest insect from Asia that has killed millions of ash (Fraxinus spp.) trees in North America since its discovery in Michigan in 2002. We evaluated attraction of adult A. planipennis to artificial traps incorporating visual (e.g., height, color, silhouette) and olfactory cues (e.g., host volatiles) at field sites in Michigan. We developed a double-decker trap consisting of a 3-m-tall polyvinyl pipe with two purple prisms attached near the top. In 2006, we compared A. planipennis attraction to double-decker traps baited with various combinations of manuka oil (containing sesquiterpenes present in ash bark), a blend of four ash leaf volatiles (leaf blend), and a rough texture to simulate bark. Significantly more A. planipennis were captured per trap when traps without the rough texture were baited with the leaf blend and manuka oil lures than on traps with texture and manuka oil but no leaf blend. In 2007, we also tested single prism traps set 1.5 m above ground and tower traps, similar to double-decker traps but 6 m tall. Double-decker traps baited with the leaf blend and manuka oil, with or without the addition of ash leaf and bark extracts, captured significantly more A. planipennis than similarly baited single prism traps, tower traps, or unbaited double-decker traps. A baited double-decker trap captured A. planipennis at a field site that was not previously known to be infested, representing the first detection event using artificial traps and lures. In 2008, we compared purple or green double-decker traps, single prisms suspended 3-5 m above ground in the ash canopy (canopy traps), and large flat purple traps (billboard traps). Significantly more A. planipennis were captured in purple versus green traps, baited traps versus unbaited traps, and double-decker versus canopy traps, whereas billboard traps were intermediate. At sites with very low A. planipennis densities, more A. planipennis were captured on baited double-decker traps than on other traps and a higher percentage of the baited double-decker traps captured beetles than any other trap design. In all 3 yr, peak A. planipennis activity occurred during late June to mid-July, corresponding to 800-1200 growing degree-days base 10 degrees C (DD10). Nearly all (95%) beetles were captured by the end of July at approximately 1400 DD10.     

Barley yellow dwarf virus in aphids caught in suction traps, 1969-73

Suction traps operating at low level (1 5 m) were used to catch live alate Rhopalosiphum padi, Macrosiphum (Sitobion) avenae and Metopolophium dirhodum which were tested for transmission of barley yellow dwarf virus (BYDV). The first species caught and infective was R. padi, followed by M. (S.) avenae infective some 2–3 wk later and M. dirhodum 3–4 wk later still. Never more than 11-5% of the annual catch of any species transmitted BYDV and the proportion fluctuated from week to week and between seasons in different years. The relative abundance of infective vectors of ths three species varied; annual numbers of infective M. (S.) avenae and M. dirhodum varied inversely with infective R. padi, the latter also usually transmitted severer virus. The results of the infectivity tests have been compared with the catches of these aphids by the Rothamsted Insect Survey and show that numbers of alate aphids do not necessarily indicate the likely incidence of BYDV.     

Yellow Traps Can Be Used to Monitor Populations of Coccinella transversalis (F.) and Adalia bipunctata (L.) (Coleoptera: Coccinellidae) in Cotton Crops

During 1992–4, square (30 times 30 cm) sticky traps of various colours were used on a commercial cotton farm to trap adults of Coccinella transversalis and Adalia bipunctata which are both major predators of Helicoverpa spp. Both insects were attracted most to yellow traps which also reflected the most visible light between 500 nmand 600 nm(where green foliage reflects most light). When yellow was diluted with white to produce yellow-white hues, the light reflected between 500 nm and 600 nm was reduced and the numbers of C. transversalis and A. bipunctata adults caught on these traps were also significantly reduced. This suggests that C. transversalis and A. bipunctata adults can discriminate foliage-like hues (500–580 nm) from non-foliage-like hues (<500 nm and >580 nm) and are attracted to colours that suggest the foliage of host plants that may harbour their prey. Yellow sticky traps placed 25–50 cm above ground caught significantly more C. transversalis and A. bipunctata adults than those placed at 75–150 cm and are the most appropriate traps to monitor populations of C. transversalis and A. bipunctata adults in cotton farms.     

Interannual dynamics of aerial and arboreal green spruce aphid populations

Partial defoliation of spruce by the green spruce aphid Elatobium abietinum (Walker) is a recurrent event in European and, increasingly, North American forests. The patterns of insect abundance on trees have never been satisfactorily described by a numerical model despite considerable knowledge of endogenous and exogenous factors in the population dynamics of the species. Long-term field population estimates of the aphid on foliage provided the opportunity to evaluate such a model. Unlike comparable models for tree-dwelling aphids, this was also applicable to almost completely independent aphid field data derived from the Rothamsted Insect Survey’s nationwide network of suction traps. Although based on relatively few parameters, the model was robust in its predictions of alate aphids geographically remote from the forest in which the original population was estimated. The population maximum, which causes the greatest forest damage, is reached in early summer and can be predicted from knowledge of winter temperature (chill bouts), spring temperature (thermal sum), and interannual negative feedback (density dependence). The model provides confirmation that alate populations of spruce aphids, upon which a number of other extensive studies have been based, are ultimately influenced by similar endogenous and climatic factors and that they are a reasonable proxy for aphids on trees.     

Differential response of male and female emerald ash borers (Col., Buprestidae) to (Z)‐3‐hexenol and manuka oil

We conducted two trapping experiments in green ash plantations in Ontario, Canada to compare the response of the emerald ash borer (EAB), Agrilus planipennis, to (Z)‐3‐hexenol (Z3‐6:OH) and manuka oil. In the first experiment, Z3‐6:OH (7.6 mg/day) in purple prism traps hung 1.5 m above ground caught significantly more EAB than the unbaited controls, with male catches significantly greater than female catches at two locations. Manuka oil (50 mg/day) attracted equal numbers of males and females but they were significantly greater than the controls at only one location. Adding (Z)‐3‐hexenal or (Z)‐3‐hexenyl acetate in binary or ternary combinations with Z3‐6:OH did not enhance trap catch. In the second experiment, Z3‐6:OH released at two rates (7.6 or 80 mg/day) in light green prism traps placed in the ash canopy also caught significantly more males than females and more males than the unbaited controls or manuka oil‐baited traps. Manuka oil had no significant effect on catches relative to the controls. Combining Z3‐6:OH with manuka oil did not enhance catches of EAB. We conclude that there was a strong male‐biased EAB response to Z3‐6:OH lures, whereas manuka oil, when effective, attracted both sexes equally. Z3‐6:OH in light green prism traps in the canopy is an effective lure for EAB, particularly for males.     

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.     

A reappraisal of flight regulation in the green spruce aphid, Elatobium abietinum

Alate formation and its importance in the population dynamics of Elatobium abietinum is examined. It is concluded that alate formation is related to high soluble nitrogen levels in Sitka spruce needles. In N.E. Scotland the proportion of the population developing as alatae was related to aphid density. The apparently differing status of alatae in S. England may be related to differences in the physiology of the host caused by heat input. In Scotland alate formation may cause a decline in spruce aphid populations when densities are very high but, at the densities normally encountered in Scotland and Germany only small proportions of the populations become alate. In these areas the population collapses in late June or early July occur in response to low soluble nitrogen levels in the spruce needles. The role of alate adults in the formation of new colonies following migration to uncolonised hosts is discussed.     

Observations on different methods of aphid trapping

Cylindrical and horizontal sticky traps painted in a range of spectral colours were used to determine the flight and landing behaviour of aphids. Data are also presented on aphid catches in suction traps at two heights and in light traps. Apart from colour sensitivity (yellow versus white) there was apparently a separate response to colour which in some species varied with season. Within yellow-sensitive species there was also a differential response to colour. With the experimental methods used, it was not possible to define mathematically the active and passive landing components on cylindrical traps. Though the active landing component was large it varied between aphid species. Most species caught on horizontal traps at ground level had been flying above 1 m. In some species the response of males to colour and their landing behaviour differed from that of viviparae and oviparae. Four years data from suction traps suggest that aphid species can be divided into three categories on the basis of the height at which they normally fly. One group, mostly tree-feeders, always show the greatest density at a high level (12.2 m) throughout the season. The second group always have the highest density at a low level (1 m) whilst a third group of species change at a specific date each autumn from a maximum density at 1–12.2 m. Attraction to light (moth trap) appeared to be linked with the grouping of species by height of flight. The interpretation of catch data is discussed in the light of these observations.     

Flight orientation behavior of Ooencyrtus nezarae (Hymenoptera: Encyrtidae), an egg parasitoid of phytophagous bugs in soybean

We conducted field experiments to examine flight orientation behavior of Ooencyrtus nezarae Ishii, an egg parasitoid of soybean feeding bugs, using sticky traps with synthetic aggregation pheromones of the host, Riptortus clavatus (Thunberg). Experiments were conducted in plots either containing a soybean field or not containing one. When the traps were suspended at heights of 0.5, 1.5 and 3.0 m above a soybean field in Kobe, O. nezarae females were most frequently caught in the 0.5 m traps. In an open field on the same campus where the vegetation was predominantly tall goldenrod, females were more frequently trapped at 1.5 or 3.0 m. In a soybean field in Kumamoto, females were most frequently trapped in the 0.8 m traps, compared to traps placed at 2.0, 4.0 and 6.0 m. In an oat field in the same area, females were trapped most frequently at heights of 0.8 and 2.0 m. Unlike females, only a small number of males were trapped in the fields in both areas. The result that O. nezarae females were caught in traps at higher positions in non‐host habitats than in soybean fields probably reflects differences in host searching behavior in or movement between the habitats. In host habitats, females mainly walk on the plants or fly within the plant canopy to search for hosts. In non‐host habitats, females may not intensively search for hosts within the plants, and directly respond to host pheromones in the traps at heights equal to or a little higher than the plant canopy.     

Host selection, development, survival, and reproduction of turnip aphid (Homoptera: Aphididae) on green and red cabbage varieties

Host selection, development, survival, and reproduction of the turnip aphid, Lipaphis erysimi (Kaltenbach), on selected green and red cabbage varieties, Brassicae oleracea L. variety capitata, were studied in the laboratory. Although numbers of alate L. erysimi on different varieties varied generally, more alate adults and nymphs were observed on green than on red varieties on day 3; whereas, these differences were not so significant on day 15. There were no significant differences in alate adults on all six varieties on day 15. Numbers of nymphs and apterous adults of L. erysimi varied among the varieties. When mean numbers of those aphids on green varieties were compared with those on red varieties, the green varieties had more nymphs and apterous adults than those on the red varieties. Developmental durations of L. erysimi nymphs also varied among all varieties, and the nymphs fed on green varieties developed longer than those fed on red varieties. Adult longevities on these cabbage varieties were not significantly different; whereas, the adult fecundities were. Survival rates of L. erysimi varied greatly among all varieties, but there are no significant differences between the green and red varieties. Factors that might affect aphid host selection, growth, longevity, fecundity, and survivorship were discussed.