Wireworms, the larvae of click beetle species
Agriotes lineatus, A
.
obscurus
and
A
.
sputator
are serious pests for several field crops. They are considered severe pests of potato tubers and the ...damages caused by them can be resulted a significant loss especially in organic crop production. Since synthetic insecticides are prohibited in Organic Farming; biological control methods have to be used in organic crop production. In the current study naturalis
Beauveria bassianaa
strain ATCC 74040 was used both under laboratory and field conditions using wheat and potato crops as a food source respectively. Fungus showed a significant mortality in high number of wireworms boxes (50%) compared to low number of wireworms (17%) and untreated boxes (13%) respectively. However, seed germination showed no effect in all three categories. Field data have shown mixed results when
B. bassiana
has been applied in a variety of application methods. Maximum infestation (3.99%) was recorded in untreated plots; while significantly lower damage (1.11%) was recorded in whole surface treated plots. During first year all the treatments were significantly different from each other; however, no significant differences were noted between furrows and whole surface applications but were different from control treatment during second year of experimentation. The results showed that the biological control of wireworms by using entomopathogenic fungi, such as
B
.
bassiana
is a promising target specific option without disturbing the other communities in the soil.
The importance of root herbivory is increasingly recognized in ecological studies, and the effects of root herbivory on plant growth, chemistry, and performance of aboveground herbivores have been ...relatively well studied. However, how belowground herbivory by root feeding insects affects aboveground parasitoid development is largely unknown. In this study, we examined the effects of root herbivory by wireworms (
Agriotes lineatus
) on the expression of primary and secondary compounds in the leaves and roots of ragwort (
Jacobaea vulgaris
). We also studied the effects of root herbivory on the performance of a generalist aboveground herbivore,
Mamestra brassicae
and its parasitoid
Microplitis mediator
. In contrast to what most other studies have reported, root herbivory in
J
.
vulgaris
had a strong negative effect on the total concentration of pyrrolizidine alkaloids (PAs) in shoot tissues. The composition of PAs in the shoots also changed after root herbivory. In particular, the concentration of less toxic
N
-oxide PAs decreased. There was no significant effect of root herbivory on PA composition and concentration in the roots. Although the concentration of PA in the leaves decreased,
M
.
brassicae
tended to grow slower on the plants exposed to root herbivory. Parasitoid performance was not affected by root herbivory, but parasitoids developed faster when the concentration of jacobine-type PAs in the foliage was higher. These results point at a putative role of individual PAs in multitrophic interactions and emphasize that generalizations about aboveground-belowground effects should be made with great caution.
Plants are simultaneously attacked by a multitude of herbivores that affect plant responses and plant-mediated interactions in a variety of ways. So far, studies on indirect interactions between ...below- and aboveground herbivores have almost exclusively focused on interactions between only one root and one shoot herbivore species at the same time. Since these studies show a variety of outcomes, we test the hypothesis that root herbivore identity matters in below-/aboveground interactions. We studied the combined effects root-feeding nematodes (
Pratylenchus penetrans) and wireworms (
Agriotes lineatus larvae) on
Plantago lanceolata and on the performance of aboveground phloem-feeding aphids (
Myzus persicae) and chewing caterpillars (
Chrysodeixis chalcites larvae). Since root herbivores may also affect resource availability and the microbial community in the rhizosphere, we examined resource utilization by soil microorganisms using BIOLOG EcoPlates™.
Wireworms decreased root biomass by 13%, but led to compensatory shoot growth. Nematodes and the aboveground herbivores did not affect the biomass of
Plantago lanceolata. Feeding by
C. chalcites larvae enhanced the concentration of aucubin in leaves, which might explain the high mortality of the caterpillars. Aphids and the belowground herbivores did not change iridoid glycoside levels in the leaves. However, the number of aphid offspring was reduced by 44% when nematodes had been added to the soil, whereas wireworms had no effect. We observed higher utilization of BIOLOG carbon sources by the soil microorganisms only in the presence of
Pratylenchus penetrans. Our results suggest that the outcome of below–aboveground interactions highly depends on herbivore identity.
Pflanzen werden gleichzeitig von vielen Herbivoren attackiert, was sowohl die Reaktionen der Pflanze als auch ihre Interaktionen auf vielfältige Weise beeinflusst. Untersuchungen zu indirekten Interaktionen zwischen unter- und oberirdischen Herbivoren haben sich bis jetzt fast ausschließlich auf Interaktionen zwischen einem Wurzel- und einem Sprossherbivor zur selben Zeit beschränkt. Weil diese Untersuchungen unterschiedliche Ergebnisse aufweisen, wird hier die Hypothese getestet, dass die Identität des Wurzelherbivores in Interaktionen zwischen unter- und oberirdischen Herbivoren eine Rolle spielt. Wir untersuchten die Effekte von phytophagen Nematoden (
Pratylenchus penetrans) und Drahtwürmern (
Agriotes lineatus Larven) auf Spitzwegerich (
Plantago lanceolata) und oberirdisch saugende (
Myzus persicae) und kauende (
Chrysodeixis chalcites Raupen) Herbivore. Da Wurzelherbivore die Verfügbarkeit von Ressourcen und die mikrobielle Gemeinschaft in der Rhizosphäre beeinflussen können, wurde die Ressourcennutzung von Mikroorganismen mit BIOLOG EcoPlates™ getestet. Drahtwürmer reduzierten die Wurzelbiomasse um 13%, führten aber zu einem kompensatorischen Sprosswachstum. Nematoden und die oberirdischen Herbivore hatten keinen Einfluss auf die Biomasse von
Plantago lanceolata. Der Fraß der
C. chalcites Raupen erhöhte die Konzentration von Aucubin in den Blättern, was die hohe Mortalität der Raupen erklären könnte. Blattläuse und die unterirdischen Herbivore beeinflussten die Konzentration der iridoiden Glykoside in den Blättern nicht. Die Anzahl an Blattlausnachkommen war jedoch um 44% reduziert, wenn Nematoden zum Boden zugefügt worden waren, wohingegen Drahtwürmer keinen Effekt hatten. Wir beobachteten gesteigerte Nutzung der BIOLOG™-Kohlenstoffquellen durch die Mikroorganismengemeinschaft, wenn sich
Pratylenchus penetrans in der Rhizosphäre befand. Unsere Resultate weisen darauf hin, dass Ergebnisse von Interaktionen zwischen unter- und oberirdischen Herbivoren stark von der Identität der Herbivore abhängen.
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.
1 Previous work had suggested that adult male click beetles (Agriotes spp.) show differential responses to species specific pheromone traps. This hypothesis was tested using mark-release-recapture ...methods to estimate the maximum sampling range and the effective sampling area of traps for three species. 2 Captured beetles of the species Agriotes lineatus, Agriotes obscurus and Agriotes sputator were marked to show the direction of release, the distance of the release point from the trap and the replicate. Analysis of variance showed that there were significant differences in recapture rates between species and release distances. There were no significant differences between release direction and replicates. 3 Calculated linear speeds suggested differences in movement rates in the order: A. lineatus > A. obscurus > A. sputator. There were also substantial differences between the species in the maximum sampling ranges and effective sampling areas of the traps. These placed the species in the same order. 4 The results are used to estimate the minimum cost of mass trapping programmes to prevent males from mating, giving values of Euro Sign165/ha/year (A. lineatus), Euro Sign247.5/ha/year (A. obscurus) and Euro Sign2343/ha/year (A. sputator). 5 Implications for the use of pheromone traps in wireworm pest management are discussed. It is concluded that current U.K. recommendations based on the cumulative total catch of the three species over a sampling season can be improved by considering the spatial relationships between the adult trapping system and larval distribution. The current constraint to this is the general inability to separate wireworms into species.
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.
The landscape scale distributions of adult male click beetles of the species Agriotes lineatus, A. obscurus and A. sputator, and the cranefly Tipula paludosa were studied using traps along transects ...over 2 years. The transects (0.7–1.7 km with either sex pheromone (Agriotes) or water (T. paludosa) traps at 100 m spacings) were in an area of mixed organic land use. Agriotes lineatus was the most numerous click beetle caught even though its larvae were absent from these fields. Greater trap counts were found for all taxa except A. obscurus in grassland. The number of click beetles were influenced by the sampling year, crop type and the species, and interactions of other variables, suggesting that sex pheromone trap counts exhibit variability because of the complexity of the environment. Trap catches were spatially clustered with the exception of A. lineatus in 2005 which had a random distribution. Only A. sputator showed a significant, positive relationship between counts in 2005 and 2006. Variation in catch count of crane flies was largely determined by crop type. We conclude that Agriotes spp. disperse widely and may be recruited from outside the field which makes the interpretation of sex pheromone trap counts scientifically challenging.
1. Understanding the spatiotemporal ecology of invertebrates in agricultural ecosystems is important for developing management strategies to enhance biodiversity and reduce pesticide use. There is ...increasing recognition that studies need to be undertaken at scales larger than the field but the ability to do this is often resource limited. Pheromone traps, developed for pest management, can provide a relatively cheap means of collecting data across wide geographical scales. In this study we used such traps to examine the spatial stability of two species of agrioted beetles in non-farmed habitats over a period of 3 years. 2. The spatial distributions of adult male Agriotes lineatus and Agriotes obscurus were sampled from April until July at a number of sites across 950 ha on Westham Island, British Columbia, Canada. Data were assembled as spatially referenced cumulative trap counts by species and year, and analysed for evidence of aggregation and clustering using spatial analysis by distance indices (SADIE) methodology. Both intraspecific and interspecific association analyses were then carried out. A further set of analyses considered the spatial associations between different sampling dates in 2004. 3. Agriotes lineatus was clustered into patches and gaps at the landscape scale in all 3 years, and A. obscurus showed similar spatial structure in 2002 and 2003. For both species, spatiotemporal stability at the landscape scale was evident. There was also a positive association between the two species in 2 out of the 3 years, suggesting that they were responding in a similar manner to the landscape environment. 4. Synthesis and applications. This study showed that there was substantial temporal stability in the spatial structures of A. lineatus and A. obscurus in non-farmed habitats, and that the two species respond in a broadly similar way to a heterogeneous agricultural landscape. This suggests that models to predict distributions within a landscape could be developed to guide decisions about where to grow vulnerable crops. Identification of the environmental factors that differentiate between clusters and gaps in their spatial distributions may also make it possible to manipulate populations and reduce their impact as pests without recourse to insecticides. Moreover, our results extend the spatial scales over which SADIE statistics have been used, and demonstrate the usefulness of pheromone trapping as a sampling method in addressing ecological questions at a landscape scale.
Indirect plant defences have largely been studied within the scope of above‐ground interactions. Here we provide novel evidence that root herbivory can induce an above‐ground indirect defence. Cotton ...plants (Gossypium herbaceum) exposed to root‐feeding wireworms (Agriotes lineatus) increased their foliar extrafloral nectar production ten‐fold in comparison to undamaged control plants. Mechanical root damage also yielded an increase in nectar production. In nature, extrafloral nectar production allows plants to recruit predators, which in turn protect the plant against above‐ground insect herbivores. Our results show that root‐feeding herbivores may alter such above‐ground defensive interactions.
Studies on induced defenses have predominantly focused on foliar induction by above-ground herbivores and pathogens. However, roots are attacked by as many if not more phytophages than shoots, so in ...reality plants are exposed to above- and below-ground attack. Here, we report effects of foliar and/or root damage on terpenoid aldehyde accumulation in cotton (Gossypium herbaceum). Using HPLC, we analyzed concentrations of individual terpenoid aldehydes in foliage and root tissue. In undamaged plants, terpenoid aldehydes were concentrated in young immature main leaves. Concentrations in side leaves, branching from the main leaves, did not differ among leaf position. Above-ground feeding by Spodoptera exigua larvae on a mature leaf enhanced terpenoid concentrations in immature leaves but not in the damaged leaf. In particular, concentrations of hemigossypolone and the heliocides 1 and 4 were enhanced following herbivory. Root herbivory by wireworms (Agriotes lineatus) also resulted in an increase in terpenoid levels in the foliage. In contrast with foliar herbivory, both immature and mature leaves were induced. However, the level of induction after root herbivory was much lower compared to foliar herbivory. Plants exposed to root herbivory also had significantly higher levels of terpenoid aldehydes in root tissue, while no such effect was found following foliar herbivory. Plants exposed to both root and foliar herbivory appeared to induce primarily above-ground at the cost of below-ground defense. The implications for above- and below-ground Mutitrophic interactions are discussed.
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