Blending of pheromone lures for two exotic European pest elaterid beetles

Two exotic European click beetle species, Agriotes obscurus and Agriotes lineatus, were introduced into the lower Fraser valley of British Columbia over a century ago, and are now predominant pests of a number of arable crops. A semiochemical-based method of monitoring both species has been developed as a part of an integrated pest management plan, and there is interest in mass trapping with pheromones as a management tool. A. obscurus females produce primarily geranyl octanoate (G8) and geranyl hexanoate (G6), while A. lineatus females produce both G8 and geranyl butanoate (G4). The current studies examined the possibility of using a blend of G8, G6, and G4 components in a single lure to trap both species simultaneously. A blended G8, G6 and G4 lure in a 1:1:1 ratio was, on average, 1.42 times more attractive to A. lineatus males than standard A. lineatus pheromone lures, but caught only 0.24 times the number of A. obscurus in standard A. obscurus traps. Blended traps, therefore, are effective for monitoring and mass trapping of A. lineatus, but only for detection of A. obscurus.     

Occurrence of Agriotes wireworms in Austrian agricultural land

Agriotes wireworms (Coleoptera: Elateridae) are abundant soil-dwelling herbivores which can inflict considerable damage to field crops. In Europe up to 40 species occur, differing in their ecology and pest status. Their distribution in the larval stage, however, has rarely been assessed because of the considerable effort in collecting wireworms and the difficulties in identifying them to species-level. Here, we examined the occurrence of Agriotes wireworms in Austrian agricultural land with regard to their association with climatic and soil parameters. Using a molecular identification system, 1348 field-collected larvae from 85 sites were identified to species-level. Three species, Agriotes obscurus, Agriotes brevis, Agriotes ustulatus, and two that could not be discerned molecularly (Agriotes lineatus and Agriotes proximus), were assigned to two ecological groups: (i) A. brevis/A. ustulatus, found in areas with a warmer, drier climate and alkaline soils, and (ii) A. obscurus/A. lineatus/proximus which occur mainly at higher altitude characterised by lower temperatures, higher precipitation and acidic, humus-rich soils. Agriotes sputator was abundant throughout Austria, confirming its euryoecious nature. Only one larva of Agriotes litigiosus was found, prohibiting further analysis. These data contribute to a characterisation of species-specific traits in Agriotes larvae in agricultural land, an important prerequisite to develop efficient control strategies for these wireworms.     

Physical exclusion of adult click beetles from wheat with an exclusion trench

Click beetles, the adult stage of wireworms, will enter fields of their preferred hosts (i.e., grasses, pasture, and cereals) from various reservoir habitats, and lay eggs which give rise to wireworm problems in subsequent years. To prevent click beetles, Agriotes obscurus, from immigrating into fields, a portable trench barrier composed of an extruded, PVC plastic trough was evaluated in 2001 in Agassiz, British Columbia, Canada. Plots of wheat or bare ground that were surrounded by trenches had significantly lower numbers of males in pheromone traps and females in pitfall traps relative to non-trenched plots. Exclusion was more pronounced in the first part of the study (about 75 % reduction) than later in the study (30–42 %), likely due to gradual within plot emergence of overwintered beetles and/or flight activity. The potential for use of exclusion devices for click beetle control and future directions for research are discussed.     

Comparison of lure-baited insecticide-treated tripod trap logs and lure-baited traps for control of Ips duplicatus (Coleoptera: Curculionidae)

Two methods were compared for capturing the bark beetle Ips duplicatus Sahlberg (Coleoptera: Curculionidae, Scolytinae): lure-baited, insecticide-treated tripod trap logs (TRIPODs) versus Theysohn pheromone traps (TPTs). In 2008 and 2011 and at each of three clearcuts, five TPTs and five TRIPODs baited with ID Ecolure pheromone evaporators were installed with 10 m spacing. The pheromone evaporators were renewed every 8 weeks. The TRIPODs were treated with the insecticide Vaztak 10 EC in mid-April and then every 5 weeks thereafter. Trap logs and traps were inspected weekly during the entire period of I. duplicatus flight activity (April–September). Two to three times more beetles were trapped by the TPTs than by the TRIPODs. The TPTs captured more females than males, while TRIPODs captured equivalent numbers of males and females or more males than females on some dates. The TPTs and TRIPODs trapped approximately the same numbers of males, but the TPTs captured more females than the TRIPODs. Both traps captured more adults in spring than in summer. The higher numbers of entomophagous arthropods, including the predacious beetles Thanasimus formicarius L. and T. femoralis, were captured in the TRIPODs than in the TPTs.     

Zur Wirkung von Aasgeruch auf die Fangleistung von Buchdruckerfallen

The effect of carrion smell on the catching-efficiency of pheromone baited flight barriere traps for the spruce bark beetleIps typographus L. was studied from June to September 1989 in a spruce forest near Göttingen. We compared the number of spruce bark beetles and carrion beetles catched with 6 pairs of Theysohn-Slit-Traps, baited with Pheroprax^®. The first trap of each pair controlled in regular time intervals of 14 days. The second controlled singulary at the end of the study. If the traps aren't controlled at regular intervals, the catching-efficiency of the traps decreases caused by the dead beetles in the trap. Contemporarily the number of carrion beetles in the traps increases. During the flight of the second generation ofIps typographus controll intervals of 14 days lead to an increased impact of carrion beetles in the traps.     

Factors affecting field performance of pheromone traps for tobacco beetle, <Emphasis Type="Italic">Lasioderma serricorne</Emphasis>, and tobacco moth, <Emphasis Type="Italic">Ephestia elutella</Emphasis>

Tobacco beetle, Lasioderma serricorne (F.) (Coleoptera: Anobiidae), is one of the most serious insect pests of stored tobacco, and traps baited with the female-produced sex pheromone, serricornin, are used for monitoring the pest. In two trapping experiments carried out in tobacco warehouses in Greece, two commercially available trap and lure systems for L. serricorne were found to be equally effective in terms of the numbers of beetles trapped. In contrast to previous reports, anhydroserricornin was unattractive and lures containing serricornin and anhydroserricornin were less attractive than lures containing serricornin only. The sex pheromone of the other main insect pest of tobacco, Ephestia elutella (Hübner) (Lepidoptera: Pyralidae), could be added to the lures without affecting the attractiveness of either pheromone to their respective species. Lures remained attractive for at least 4 weeks under field conditions, and, in laboratory tests, release of pheromone could still be detected after 30 days at 27 °C. The stereoisomeric composition of the serricornin in the two commercial lures was similar with high proportions of the attractive (4S,6S,7S)-isomer. The proportion of the (4S,6S,7R)-isomer was low, and this is known to reduce the attractiveness.     

Non-target beetles (Coleoptera) in Trypodendron pheromone traps in Finland

Non-target beetles were surveyed in Trypodendron pheromone traps in 3 localities in Finland. Two window traps baited with Trypolure, containing lineatin dissolved in ethanol, and one control trap without attractant were used in each locality. A total of 1648 specimens belonging to 223 non-target species were recorded. The species were divided into five ecological groups to be treated separately. Hylurgops palliatus and Hylastes cunicularius were abundant in baited traps, whereas other scolytids as a group did not show clear attraction. Other species living in recently dead trees, including bark- and wood-boring species and associated species (predators, scavengers, fungivores, etc.), were clearly attracted by Trypolure. The most abundant ones were Hylecoetes flabellicornis, Thanasimus formicarius, Rhizophagus dispar, and Rhizophagus nitidulus. Although numerous in the samples, saproxylic species inhabiting more decayed wood and non-saproxylic species did not seem to be attracted. Grouping of species into ecological groups was helpful in the search for attraction patterns among species that usually are scarce in pheromone traps.     

Preliminary investigations into the use of trap crops to control Agriotes spp. (Coleoptera: Elateridae) in potato crops

A field trial was conducted to investigate the use of peas (Pisum sativum cv. Valverde), wheat (Triticum aestivum cv. Capo) and oilseed radish (Raphanus sativus var. oleiformis cv. Adagio) as trap crops to control wireworm in potato fields. We investigated the efficacy of trap crops and distance of attraction by counting larvae in both potato and trap crop rows. Wireworms of the genera Agriotes, Adrastus and Hemicrepidius were observed. In the plots planted with peas as a trap crop, significantly more wireworms were observed than in the other treatments, which was clearly due to the influence of the trap crop pea. The potato rows 0.75 m away from the peas showed 2.4 times more larvae than the potato rows 1.5 m away. This may be due to a decrease of the peas’ attractiveness over time (Miles and Petherbridge 1927), with wireworms that were initially attracted to the peas moving back to the nearby potatoes. In the plots planted with wheat, oilseed radish and the control (bare soil instead of a trap crop), there was no significant difference in numbers of larvae between the potato rows. In the control plots, significantly more larvae were found in the potato rows than in the bare soil. We assessed the damage to potato tubers by weighing them and counting the wireworm holes. Our results indicate that peas are more attractive to wireworms than potatoes and might be an effective trap crop if the right timing and spacing relative to the potatoes is found.     

Fängigkeit von differenziert bestückten Borkenkäferpheromonfallen in einem niedersächsischen Forstgebiet bei Hannover während der Jahre 1992 und 1993

In the years 1992 and 1993 blackTheysohn slit-traps were set up in a forest area near Hanover, Germany. The traps were baited with combinations of the synthetic bark beetle pheromones Pheroprax^®, Chalcoprax^®, Linoprax^®, and Cembrax^®. Their captivity was tested in comparison to singly baited and control traps without pheromone. Additionally, combinations of Pheroprax+Cembrax and Linoprax+Cembrax were tested. The captivity numbers obtained fromIps typographus, Pityogenes chalcographus, Xyloterus lineatus andX. domesticus were discussed in relation to the differently baited traps. In the latter three species, females and males were separated. The periods of flight activity of the four Scolytidae baited were ascertained for both years. Concerning the singly baited traps, Pheroprax captured the highest amount ofIps typographus per trap, its population increased 9% in 1993 related to that of 1992. ForP. chalcographus, the combination of the four pheromones resulted in a little higher number of individuals than in singly baited traps.Xyloterus lineatus preferred the four-pheromone combination, in which Linoprax was present showing a synergistic effect of baiting. In contrary, the baiting ofX. domesticus was lower by the combined pheromones than by Linoprax alone. The latter was found in lower numbers thanX. lineatus. The trapped amounts of both Xyloterus species were continuously reduced throughout the years 1989 to 1993. The Coleoptera species, not specially trapped, amounted yearly to 0.6–0.7% of the collected individuals.P. chalcographus was collected to 85–87%, andIps typographus to 11–14% of the total amount of Coleoptera trapped.     

Ribosomal RNA phylogeny of bacterial and fungal pathogens of Agriotes wireworms

Wireworms, the polyphagous larvae of click beetles belonging to the genus Agriotes (Coleoptera: Elateridae), are severe and widespread agricultural pests affecting numerous crops. Biological control agents and methods for this general pest are highly solicited. In a screening for microbial Agriotes pathogens, an intracellular bacterium and a mitosporic fungus were isolated. Phylogenetic analysis based on ribosomal RNA operon sequences of both micro-organisms corroborated their previous morphology-based taxonomic classification. The bacterial pathogen has been assigned to the taxonomic genus Rickettsiella (Gammaproteobacteria) wherein it represents a new pathotype, ‘Rickettsiella agriotidis’, that appears most closely related to subjective synonyms of the nomenclatural type species, Rickettsiella popillae. The fungal pathogen has been shown to belong to the form-species Beauveria bassiana, i.e., an obligate anamorph related to the genus Cordyceps (Ascomycota: Hypocreales). Furthermore, the B. bassiana strain from Agriotes has been shown to be potentially susceptible to identification by gIi-diagnosis, i.e., a diagnostic method making use of the strain-specific presence of self-splicing group-I introns within the ribosomal RNA operons of certain hyphomycetous fungi.     

Die Lufttemperatur als limitierender Faktor für die Schwärmaktivität zweier rindenbrütender Fichtenborkenkäferarten,lps typographus L. undPityogenes chalcographus L. (Col., Scolytidae)

Single catches of bark beetles in pheromone baited traps were registered by the aid of a new instrument. It consists of an electronical weather station in connection with a pheromone trap with infrared sensors as additional equipment. So it was possible also to register weather data at the moment of every catching event. It could be shown that the flight behaviour of both species of bark beetles was influenced by air temperature.I. typographus did not fly beneath a minimum temperature of 16.5°C. There was also an upper limit of 30°C for flight activity of this species.P. chalcographus has a threshold of temperatures about 16.8–17°C, for activity. No upper limit of temperature could be observed up to 35°C. Both of them,I.typ. andP. chalc., reacted very sensitive and spontaneous to these temperature thresholds.     

IPM thresholds for Agriotes wireworm species in maize in Southern Europe

Currently, integrated pest management (IPM) of wireworms is not widespread in Europe. Therefore, to estimate the densities of three major wireworm species in southern Europe (Agriotes brevis Candeze, A. sordidus Illiger, and A. ustulatus Schäller), bait traps were deployed pre-seeding in maize fields in north-eastern Italy between 1993 and 2011. Research discovered that there was a significant correlation between all three wireworm species caught in the bait traps and damage to maize plants, but damage symptoms varied. Wherever A. ustulatus was the main species caught, there was no significant damage to maize plants, but seeds were damaged. Most of the symptoms caused by A. brevis and A. sordidus were to the central leaf/leaves, which wilted because of feeding on the collar. A. brevis was the most harmful species; when more than one A. brevis wireworm was caught per trap, plant damage sometimes resulted in reduced yield. Five A. ustulatus larvae per trap caused the same damage to maize as one A. brevis. A. sordidus came second (threshold two larvae/trap). These thresholds are reliable for: (1) bare soil in which there are no alternative food sources; (2) average soil temperature 10 cm beneath the surface of above 8 °C for 10 days; (3) soil humidity near to field water capacity, but days of flooding have not been considered. The implementation of the practical method described herein may lead to effective IPM of wireworms in maize and to a significant reduction in the number of fields treated with soil insecticides.     

Pheromone-based decision support tools for management of <Emphasis Type="Italic">Halyomorpha halys</Emphasis> in apple orchards: development of a trap-based treatment threshold

The invasive brown marmorated stink bug, Halyomorpha halys (Stål), has become a serious pest in mid-Atlantic apple orchards. Because no decision support tools exist for H. halys management, calendar-based insecticide applications have been the only successful technique for mitigating H. halys injury in orchards. Following the identification of the two-component aggregation pheromone of H. halys, we conducted a study to determine whether biological information generated by traps baited with this pheromone and pheromone synergist could be used to make management decisions. In this study, experimental apple orchards were treated with a H. halys-targeted insecticide only when a predetermined cumulative threshold of either 1, 10, or 20 adults per trap was reached. Once threshold was reached, two alternate row middle sprays 1 week apart were triggered and the threshold was reset. For comparison, some orchards were also subjected to a weekly alternate row middle spray or left untreated as controls. At harvest, significantly less fruit injury was observed when treated weekly or using a threshold of 1 or 10 H. halys adults per trap to trigger insecticide applications. Orchards treated using a cumulative threshold of 20 adults per trap or when left unsprayed had significantly higher fruit injury. In addition, insecticide applications were reduced by 40% using a threshold of 10 adults per trap. Our results suggest that baited pheromone traps can be used as decision support tools to trigger insecticide applications when needed to mitigate risk and effectively manage H. halys in apple orchards.     

A survey of microbial antagonists of Agriotes wireworms from Germany and Italy

Wireworms of the genus Agriotes (Coleoptera: Elateridae) are severe and widespread agricultural pests affecting numerous crops throughout the world and causing damage of economic importance. Between 2008 and 2011, a survey of the occurrence of natural microbial antagonists of wireworms was conducted. Altogether, 3,420 wireworms and two dead beetles from agricultural habitats and grassland of various parts of Germany and 700 lab-reared wireworms from Italy were screened for the presence of disease. Of these, 283 selected dead and moribund Agriotes specimens were diagnosed by light and electron microscopy for insect pathogens; 66 wireworms contained unspecified bacterial infections; and 86 specimens displayed fungal growth with 25 infected by the entomopathogenic taxa Beauveria bassiana, Metarhizium anisopliae, Isaria fumosorosea, Isaria spp. and Lecanicillium sp. Nematodes were observed in 29 dead individuals, and 141 individuals showed no distinguishable pathogens. In one dead Agriotes larva, an intracellular bacterium was identified as a new Rickettsiella pathotype named ‘Rickettsiella agriotidis’. The survey resulted in a natural infection rate of 0.66 %. The possible use of these pathogens as biocontrol agents is discussed.     

Seasonal variability of sex-ratio in<Emphasis Type="Italic"> Ips typographus</Emphasis> (L.) pheromone traps in a multivoltine population in the Southern Alps

The aim of the study was to monitor the seasonal variation in the sex-specific responses of Ips typographus to a commercial pheromone in relation to the two generations per year occurring in the Southern Alps. The study was carried out over 2 years (2000–2001). Each year, 15 Theysohn traps were baited with Pheroprax. Traps were emptied weekly and the number of beetles determined. In the same forest each year, three spruce logs were set up at the beginning of spring for natural colonisation by Ips typographus and then put in breeding boxes. All adults emerging from the logs or found in the traps were counted and a subsample sexed by genital extraction. Spring captures were always higher than summer captures (second generation). Similarly, the proportion of trapped males was always higher in spring than in summer. Except in the first and second week, the number of females was higher than males. During the first 3 weeks of monitoring, the number of trapped males dropped from above 50 to about 30%. Thereafter, the sex ratio was constant over time, about 33% males. In contrast to trap catches, about 50% of adults emerging from the breeding logs were males. The low proportion of males in traps depends both on discrimination (they avoid strong sources of male pheromone) and on differential mortality of the sex over time. As the pioneer beetles in I. typographus are males, their number is highest in the first part of the flight period when they search for suitable host trees. Such a search can be lethal for several males, decreasing the sex ratio.     

Categorization and numerical assessment of wireworm mobility over time following exposure to bifenthrin

We discuss the effect of the pyrethroid insecticide bifenthrin incorporated into soil at 100, 200, and 300 g AI/ha on late-instar larvae of the dusky wireworm, Agriotes obscurus (Coleoptera: Elateridae), and present a method of assessing wireworm health and mobility over time. Wireworms became moribund within 1 h of placement in soil amended with bifenthrin at all rates. After 2 weeks of morbidity in amended soils, wireworms recovered within 7 days of being placed in clean soil. A considerable proportion (0.13–0.93) of wireworms placed in amended soil moved to the soil surface and remained there for 2 weeks or more in a moribund state; wireworms transferred to clean soil no longer moved to the soil surface. Eight distinct mobility categories were observed and are described, and a new method for assessing wireworm health and mobility over time is discussed.     

Ein Beitrag zum Verhalten des BuchdruckersIps typographus L. während der Flugphase

In the open air newly emerged beetles showed a very different flight capability. The initial flight was directed by optical structures next to the starting place. The number of caught beetles in pheromone baited traps showed that in the endemic phase the summergeneration ofIps typographus extended the dispersal flight to decidous stands. Relative high numbers of beetles were counted in traps on the southern edge of a beechstand at a distance of at least 400m from the next potential breeding place. Within the beechstand beetles were caught too but in a significant smaller number as on the edge.     

Distribution of a bark beetle and its predator within and outside old growth forest reserves: No increase of hazard near reserves

To test the hypothesis that reserves create a hazard because pest insects are more abundant in unmanaged forest reserves than in managed forests, pheromone trapping of lps typographus was done within and outside two small old growth forest reserves (Tallet and Nyteboda) in southern Sweden. Initially, two 2 km perpendicular transects centered in the Tallet reserve did not show higher abundance of insects in the reserve in 1986 and 1987. A second hypothesis, that more predators existed in the diverse ecosystem in the reserves (giving fewer bark beetles) was tested. An important predator of bark beetles, Thanasimus formkarius, was monitored with kairomone traps inside and outside reserves, together with the prey in 1989. The catches of the prey (Ips) showed the same pattern as earlier. The predator was caught in small numbers, but in a pattern opposite to the predictions of the hypothesis of higher catches inside the reserves.     

Vergleich der Attraktivität von 3 Pheromonfallentypen auf die Mehlmotte,Ephestia kühniella Zeller

In the laboratory three types of pheromone traps for the Mediterranean Flour Moth,Ephestia kühniella were tested. The trap of the Albany International Corp. was compared with the Detia Mottenindikator and a trap of the Institute for Pesticide Research in Wageningen. In separated series of trials with paired traps, all six possible combinations between traps and lures were tested. The direct comparison between Detia Mottenindikator and the Albany trap revealed no significant difference in moth catch. But the shape of the Detia trap is better than the Albany one, whereas for the lures the reverse holds true. The best combination is therefore Detia trap/Albany lure. Significant fewer moths were caught with the trap of the Institute for Pesticide Research than with the Albany trap.     

Vergleich zwischen sechs verschiedenen Pheromonfallen bezüglich ihrer Fangleistung auf die Mehlmotte,Ephestia kühniella Zeller

Six different pheromone traps were tested in the laboratory to catch the Mediterranean Flour Moth,Ephestia kühniella. In 15 sets of experiments 2 traps were compared by pairs. The best results were achieved with the Detia Mottenindikator (Detia-Degesch GmbH, Laudenbach, Germany) and the Trappit Funnel trap (Biological Control-Systems Limited, England). The other 4 traps were: A-Trap Combi (Ciba-Geigy A. G., Switzerland), Trappit-Delta-Trap (Biological Control-Systems Limited, UK), Traptest^® (Istituto G. Donegani, Italy) and Mastrap^® (Istituto G. Donegani, Italy).