Several Agriotes click beetle species are important pests of vegetables and field crops. Monitoring for beetles is generally done with pheromone-baited traps maintained in permanent locations. Since ...dispersal is mostly by walking, such traps may deplete populations around them, leading to underestimations of populations relative to nontrapped areas, and of concomitant risk of wireworm damage to nearby crops. We placed sets of five pitfall traps in field headland areas in 2015–2017, of which two were baited with Agriotes obscurus (L) or Agriotes lineatus (L) (Coleoptera: Elateridae) pheromone. Of these, one was maintained in a permanent location, while the other moved among the remaining positions. Traps were checked weekly over the emergence period. For A. obscurus, fixed and moving traps initially collected similar numbers, but the latter collected significantly more later in the season, indicating depletion around fixed traps. Depletion was most pronounced after a period of cold weather, and around the peak swarming period. Depletion observed for A. lineatus was not statistically significant.This indicates pheromone-baited traps used for walking insects can underestimate populations, but depletion rates vary with species and temperature and should be accounted for when traps are used to develop action thresholds or time control strategies.
New pest management solutions are needed to control soil invertebrates (insects, nematodes, mollusks) in order to implement the goals of the European Green Deal. Natural volatile organic compounds ...(VOCs) such as 1-octen-3-ol and 3-octanone, emitted by the entomopathogenic fungus Metarhizium brunneum could be part of the solution. Three major crop pests, Agriotes lineatus (wireworm), Diabrotica virgifera virgifera (corn rootworm) and Phyllopertha horticola (garden chafer), were susceptible to fumigation with 1-octen-3-ol and 3-octanone. The toxicity of the VOCs was tested in soil-free arenas and in soils which differed in moisture content and porosity. The mortality rates were dependent on the interaction between the VOC treatment, dose and pest species. The insects differed in their sensitivity to these VOCs. A dose of 1.25 µl of 1-octen-3-ol applied in a closed glass tube was sufficient to kill D. v. virgifera and P. horticola in soil trials whereas 5 µl was needed to kill A. lineatus. The highest dose (20 µl) was highly toxic to all insects. Soil moisture content slightly influenced mortality rates whereas porosity had no obvious impact. The mode of action of the VOCs is unknown but the compounds are likely to cause tissue damage and loss of body fluids. This may explain the shrivelled appearance of corn rootworm and garden chafer and melanisation in wireworm. Both 1-octen-3-ol and 3-octanone show promise as biofumigants.
The predatory wireworm Hemicrepidius niger (L.) is newly reported from North America (Canada: Ontario and New Brunswick). The agricultural pest species Athous haemorrhoidalis (Fabricius) is newly ...recorded from North America (Canada: Ontario and USA: Massachusetts). New provincial and state records are reported for the Palaearctic agricultural pest species Agriotes lineatus (L.) (USA: Massachusetts and Canada: Prince Edward Island) and Agriotes obscurus (L.) (Canada: Prince Edward Island). New national, provincial or state records are listed for 14 native North American species.
1. Feeding by insect herbivores can affect plant growth and the concentration of defense compounds in plant tissues. Since plants provide resources for soil organisms, herbivory can also influence ...the composition of the soil community via its effects on the plant. Soil organisms, in turn, are important for plant growth. We tested whether insect herbivores, via their effects on the soil microbial community, can influence plant-soil feedbacks. 2. We first examined the effects of above-ground (AG) and below-ground (B) insect herbivory on the composition of pyrrolizidine alkaloids (PAs) in roots and on soil fungi in roots and rhizosphere soil of ragwort (Jacobaea vulgaris). The composition of fungal communities in roots and rhizosphere soil was affected by both AG and BG herbivory, but fungal composition also differed considerably between roots and rhizosphere soil. The composition of PAs in roots was affected only by BG herbivory. 3. Thirteen different fungal species were detected in roots and rhizosphere soil. The presence of the potentially pathogenic fungus Fusarium oxysporum decreased and that of Phoma exigua increased in presence of BG herbivory, but only in soil samples. 4. We then grew new plants in the soils conditioned by plants exposed to the herbivore treatments and in unconditioned soil. A subset of the new plants was exposed to foliar insect herbivory. Plantsoil feedback was strongly negative, but the feedback effect was least negative in soil conditioned by plants that had been exposed to BG herbivory. There was a negative direct effect of foliar herbivory on plant biomass during the feedback phase, but this effect was far less strong when the soil was conditioned by plants exposed to AG herbivory. AG herbivory during the conditioning phase also caused a soil feedback effect on the PA concentration in the foliage of ragwort. 5. Synthesis. Our results illustrate how insect herbivory can affect interactions between plants and soil organisms, and via these effects how herbivory can alter the performance of late-growing plants. Plant-soil feedback is emerging as an important theme in ecology and these results highlight that plant-soil feedback should be considered from a multitrophic AG and BG perspective.
The volatile organic compounds (VOCs) 1-octen-3-ol and 3-octanone produced by the entomopathogenic fungus
Metarhizium brunneum
are known to have pesticidal properties at high doses against a range of ...invertebrate pests. Very little is known about their behavior-modifying (semiochemical) properties. This study focused on investigating the behavioral responses of three subterranean crop pests, wireworm (
Agriotes lineatus
)
,
western corn rootworm (
Diabrotica virgifera virgifera
), and garden chafer (
Phyllopertha horticola
), to relatively low doses of 1-octen-3-ol and 3-octanone. The behavior of wireworms and corn rootworms were slightly influenced by the VOCs, yet not significantly. Western corn rootworms appeared to be slightly attracted by 100 µl and 200 µl 1-octen-3-ol and 100 µl dose of 3-octanone, respectively but slightly repelled by the higher dose of 3-octanone. Wireworms appeared to be slightly repelled by 1-octen-3-ol and high dose 3-octanone, but slightly attracted by the 100 µl dose of 3-octanone. The VOCs had no significant impact on garden chafer. In silico studies showed that corn rootworm odorant binding proteins (OBPs) had a strong binding affinity of 1-octen-3-ol and high dose 3-octanone, indicating that these VOCs can be detected and recognized by corn rootworm. OBPs are well conserved between species; thus, wireworm and garden chafer OBPs should also be able to bind with the VOCs. Further trials will be done to confirm that VOCs could be used as semiochemicals. Appropriate formulation of the VOCs should increase their efficacy and prevent rapid dissipation of the VOCs.
Conservation Agriculture (CA), which combines three principles, (1) limitation of soil disturbance, (2) its permanent cover and (3) crop diversification, is growing worldwide as a low-input system. ...By limiting soil disturbance, this farming system provides favourable conditions for the development of soil-dwelling organisms including insect pests. Despite potentially high wireworm densities in CA systems, economic damage to maize crop is rarely observed. In this study, we investigated the long-term influence of three tillage practices of decreasing intensity (mouldboard ploughing, surface tillage and no tillage) on wireworm density to confirm that reducing tillage intensity does increase wireworm density. In addition, we hypothesised that the presence of crop residues can limit damage caused by wireworms by diverting them from the main crop and altering their feeding behaviour. Accordingly, we examined whether covering the soil with a mulch at sowing date or leaving below-ground residues of a cover crop grown before maize sowing can limit wireworm damage on maize compared to leaving the soil bare. This study, using CA systems as a case study, improves our understanding of how cover crop management can help reducing wireworm damage for the following crop and illustrates the interest of manipulating pest feeding behaviour to design promising strategies of Integrated Pest Management.
Mark–release–recapture was used to investigate the dispersal of click beetles in spring wheat or fallow fields using edge or centre field releases. Three types of pitfalls were used: gutter traps ...near field margins, as well as conventional pitfall traps or cross‐traps consisting of four gutter trap arms leading to a central pitfall. Capture of naturally occuring beetles was concurrently recorded.
In total, 6952 marked Agriotes obscurus (males and females) and Agriotes lineatus (males) were released and 14.74% were recaptured at some time during the present study. Recovery rates ranged from 3.54% to 28.5%.
Agriotes obscurus dominated wild populations, with 4011 males and 1672 females trapped compared with 17 males and three females for A. lineatus. Males dominated early in the period, although the sex ratio tended towards equality as the season progressed.
Generally, captures of A. obscurus males released in equal numbers at field edges followed a uniform distribution. There were differences for wild beetles caught in the same traps.
Spatial trapping patterns of wild and marked beetles across the fields were similar. Within 19 h of release at the field edges A. obscurus males were captured >30 m away.
The crop type had a significant interspecific effect on trap counts for males and an intraspecific effect on A. obscurus females, reinforcing the need for caution when using trapping systems to monitor adult stages of these pests.
The results of the present study demonstrate that uncropped field margins comprise sources of click beetles. We also conclude that click beetles disperse much further than reported previously.
Plants are often simultaneously or sequentially attacked by multiple herbivores and changes in host plants induced by one herbivore can influence the performance of other herbivores. We examined how ...sequential feeding on the plant Plantago lanceolata by the aboveground herbivore Spodoptera exigua and the belowground herbivore Agriotes lineatus influences plant defense and the performance of both insects. Belowground herbivory caused a reduction in the food consumption by the aboveground herbivore independent of whether it was initiated before, at the same time, or after that of the aboveground herbivore. By contrast, aboveground herbivory did not significantly affect belowground herbivore performance, but significantly reduced the performance of later arriving aboveground conspecifics. Interestingly, belowground herbivores negated negative effects of aboveground herbivores on consumption efficiency of their later arriving conspecifics, but only if the belowground herbivores were introduced simultaneously with the early arriving aboveground herbivores. Aboveground–belowground interactions could only partly be explained by induced changes in an important class of defense compounds, iridoid glycosides (IGs). Belowground herbivory caused a reduction in IGs in roots without affecting shoot levels, while aboveground herbivory increased IG levels in roots in the short term (4 days) but only in the shoots in the longer term (17 days). We conclude that the sequence of aboveground and belowground herbivory is important in interactions between aboveground and belowground herbivores and that knowledge on the timing of exposure is essential to predict outcomes of aboveground–belowground interactions.
Reactions of plants to insect pests include the activation of a local and systemic defence response. This response is based on transcriptional changes that are mainly controlled and coordinated by ...phytohormones. The above‐ and belowground part of plants can be challenged by different insects and therefore, the defence response to one attacker can influence other insects. The study of plant‐mediated interaction between pests that are physically or temporally separated yielded a variety of outcomes, with positive, negative, and neutral effects described in the literature. In this study, we examined possible plant‐mediated interactions between above‐ and belowground insect pests with different feeding guilds in tomato, Solanum lycopersicum L. (Solanaceae). Root feeding by Agriotes lineatus (L.) (Coleoptera: Elateridae) larvae caused a decrease in the development rate, fertility, and weight in Myzus persicae (Sulzer) (Hemiptera: Aphididae). To gain insights into the plant systemic signalling mechanisms, we also performed a time‐course expression analysis of defence‐related phytohormone marker genes. The result indicated a dynamic systemic response in leaves following root herbivory, which comprises the activation of genes dependent on different molecular pathways involved in plant stress response. Our work demonstrated that root herbivory increased aphid resistance in tomato and that a combination of signals enables the communication between below‐ and aboveground pests with different feeding guilds.
The aims of this work were: (i) to determine the distribution and abundance of
Agriotes lineatus
, (ii) correlate the abundance with the prevailing climatic conditions to establish how temperature ...and rainfall are influencing the dominance, and (iii) to determine the activity characteristics of the adults. Investigations were conducted in 17 fields grouped in four regions characterized by different climatic conditions. Using sex pheromone traps the most important Agriotes species (
A. lineatus
L.,
A. sputator
L.,
A. obscurus
L.,
A. brevis
Cand. and
A. ustulatus
Schall.) were collected. The monitoring period for
A. brevis
,
A. sputator
,
A. lineatus
and
A. obscurus
was from the 18th to the 32nd, and for
A. ustulatus
from the 23rd to the 32nd week of the year. A total of 61,247 individuals Agriotes were captured, of which 24,916 individuals were
A. lineatus
. Abundance and dominance of
A. lineatus
were significantly higher in the region of Zagreb compared to other regions. Moving east, rainfall decreased and temperatures increased and associated with that the abundance and dominance indices were lower. It was determined that the abundance of
A. lineatus
was negatively correlated with average air temperature (
r
= −0.5201;
p
< 0.0001). Compared to earlier data from the region of Zagreb the dominance index decreased. This might be a result of climate change as established average yearly temperature in these regions increased for 1.04 °C compared to the average data for the period 1961–1990. Other potentially damaging Agriotes species (
A. brevis
and
A. ustulatus
) were also present in high abundances in some micro-regions.
PDF
