The spatial structure of agricultural landscapes can have a strong impact on the distribution and diversity of insects. Here we studied the effects of within-field position (edge or center) as well ...as adjacent habitats on the community structure of the natural enemies of cereal aphids. Twelve agricultural sites were included in the study, with two spring wheat fields selected for each site (one adjacent to an alfalfa field, the other adjacent to a corn field). We sampled two rows per field (1 and 20 m from the edge) using pitfall trapping for ground-dwelling predators, sweep netting for leaf-dwelling predators and hand collecting of aphid mummies for parasitoids. Adjacent alfalfa areas, as opposed to corn fields, can significantly increase the abundance and diversity of leaf-dwelling predators and parasitoids near the field edges. Abundance and diversity were found significantly higher near the edges than in the centers of fields adjacent to alfalfa areas. In contrast, no significant differences were found between edges and centers of fields adjacent to corn fields. Of the fifteen most abundant species, Aphidius avenae (Haliday), A. gifuensis (Ashmead), Hippodamia variegata (Goeze) and Chrysopa sinica (Tjeder) were significantly more abundant near the edge than in the center. Being adjacent to alfalfa habitats could enhance parasitism and predator/prey ratios of leaf-dwelling predators at the edges, but has no effects on ground-dwelling predators. In conclusion, the effect of within-field position and adjacent habitats on natural enemies of agricultural pests was species specific. This should be considered for designing efficient plans of biological control.
Essential oils of three mint species (Mentha aff. arvensis, Mentha aff. rotundifolia and a probably feral hybrid of Mentha spp.) were investigated for their antimicrobial properties against ...Paenibacillus larvae (White). The bioactivity of the oils was compared using the combination of in vitro techniques such as microdilution, agar dilution and bioautography. The chemical composition of the oils was analyzed by GC/MS. Using the bioautography assay, menthol, menthone, menthofuran and piperitone oxide were found to be responsible for the antimicrobial activity of these oils. A quantitative structure-activity relationship (QSAR) model was developed for four terpenoids with significant antimicrobial activity using Hyperchem 8.0 and Gaussian 03 software. The QSAR approach leads to a better understanding of the structural properties of these terpenoids which are responsible for bioactivity. The present work reports the first systematic study about the use of QSAR properties to correlate antimicrobial activity of natural substances against P. larvae.
ABSTRACT This study analyzed the predatory behavior of adult females of Nabis punctipennis Blanchard (Nabidae) towards Acyrthosiphon pisum Harris (Aphididae) in the laboratory in order to determine ...its functional response and potential as a biological control agent of this aphid. Both hemipterans are common in alfalfa, Medicago sativa L., in Chile. The females of N. punctipennis presented a type II functional response, with a handling time of 2.757 ± 0.1181 h prey-1 and a searching rate of 0.353 ± 0.3214 h-1.
An intronic single nucleotide polymorphism (SNP) in RICH2 (rs2072255; 255i), in complete linkage disequilibrium (LD) with an exonic SNP (rs2072254; 254e), has been identified in a genome wide ...association study to be associated with progression to AIDS in Caucasian individuals. RICH2 links tetherin to the cortical actin network and the RICH2/tetherin interaction has been shown to be important for the downstream activation of NF-κβ and the consequential promotion of proinflammatory responses. We investigated the role of these two SNPs in natural control of HIV-1 in black South Africans including healthy controls (HCs; N=102) and antiretroviral-naive HIV-1-infected controllers (HICs; N=52) and progressors (N=74). HICs were stratified as elite controllers (ECs; N=11), viraemic controllers (VCs; N=30), high viral load (VL) long term non-progressors (HVL LTNPs; N=11) and also according to VL<400RNA copies/ml (HICs VL<400; N=20) and VL>400RNA copies/ml (HICs VL>400; N=32). Results showed that in contrast to Caucasians who had very strong LD between these SNPs (r2=0.97), black populations exhibited low LD (r2=0.11–0.27), however a 254e minor allele was always present with a 255i minor allele but not vice versa. The SNPs did not show significant over- or underrepresentation in any particular group, however the combination of 254e major allele homozygosity and 255i heterozygosity (254eAA/255iGA) was underrepresented in HICs (OR=3.26; P=0.04) and VCs (OR=7.77; P=0.02) compared to HCs, and in HICs VL>400 compared to both HCs (P=0.002) and progressors (P=0.02). A lower CD4+ T-cell count was associated with 254eAA/255iGA and 255i (GA+AA) in the total HIV-1-infected group (P=0.043) and progressors (P=0.017), respectively. In silico analysis predicted loss of an exonic splice enhancer site with the 254e-G allele. We postulate that altered splicing of RICH2 will affect levels of RICH2 expression and consequently NF-κβ activation. These findings point to a role for RICH2 and tetherin in viraemic natural control of HIV-1.
•A combination genotype of two RICH2 SNPs is associated with natural HIV-1 control.•Genotype is deleterious with respect to control in the presence of detectable viraemia.•In silico analysis predicts loss of an ESE site (SRSF2) with rs2072254 minor allele.•Progressing individuals with RICH2 rs2072255 (GA+AA) have lower CD4+ T-cell counts.•Postulate altered RICH2 expression affecting tetherin's downstream NF-κβ activation.
The tiny size of eriophyoid mites is a key feature regarding their status as herbivorous pests. Many eriophyoid species are highly host specific and live in concealed sites (refuges) on their hosts, ...which are difficult to access by natural enemies. We explored the spatial refuge used by one of the most important coconut pests, the coconut mite
Aceria guerreronis Keifer (Eriophyidae). Based on the assumption that
A. guerreronis shifted its habitat under the perianth of coconut to avoid competition and/or escape from predation we investigated the fine scale spatial distribution of
A. guerreronis and associated competitors and predators. Coconut fruits were sectioned and discrete chambers identified under the perianth.
A. guerreronis was present on 92% of fruits and by far the most abundant mite under the perianth. It preferentially resided in the tightest chambers to the fruit surface. Another herbivore,
Steneotarsonemus furcatus De Leon (Tarsonemidae) was found on ∼30% of fruits most of which were simultaneously occupied by
A. guerreronis.
Neoseiulus baraki Athias-Henriot (Phytoseiidae) was the predominant predatory mite (∼35% of fruits) followed by
Proctolaelaps bickleyi Bram (Ascidae) (∼7% of fruits).
A. guerreronis,
S. furcatus and
N. baraki showed a slightly different but more similar repartition among chambers under the perianth than
P. bickleyi. Overall, our study suggests that refuge use by
A. guerreronis is a key issue for its natural and/or biological control. Potential control strategies are discussed.
Natural enemies suppress many aphid populations, and yet, population outbreaks sometimes occur. The reasons predation fails to suppress such outbreaks are not clearly understood. While manipulating ...predators to examine their role in soybean aphid population growth, a natural immigration of soybean aphids occurred that enabled us to compare the roles immigration and predation played in population growth. Using predator exclusion cages, we found that predation on the top of the plant accounted for 42.3 ± 11.4% (mean ± SE) reduction in aphid population growth rates. When 90–100% of the canopy was exposed, predation failed to reduce aphid population growth because winged immigrants colonized plants, with an observed 6‐fold increase in alates compared to plants completely covered or exposing only the top nodes (approximately 10% of the total canopy). We conclude that reproduction by immigrants contributed to population growth rates sufficiently to compensate for predation. These results demonstrate that immigration can counteract high levels of predation and lead to aphid population growth rates that could result in outbreak population densities.
The six major pests of winter rape in Europe: cabbage stem flea beetle (Psylliodes chrysocephala), cabbage stem weevil (Ceutorhynchus pallidactylus), rape stem weevil (C. napi), pollen beetle ...(Meligethes spp.), cabbage seed weevil (C. obstrictus) and brassica pod midge (Dasineura brassicae) are partly, sometimes fully, controlled by natural enemies. Crop management can either support or counteract this natural control. An objective of this European Union project No. QLK5-CT-2001-01447 was to design and test an Integrated Crop Management (ICM) system that aimed to be energy-efficient and high-yielding, giving a good economic net return yet with high natural control of pests and to compare it with a standard STaNdard (STN) farming system aimed to depict a modern way of growing rape. The two systems were compared in joint experiments in five countries. Non-inversion tillage was used to increase parasitisation of pollen beetle and seed weevil and activity-densities of ground beetles. Schedule spraying gave more control of stem weevil larvae than spraying to-control thresholds. Differences in yield between the two systems were generally small. Where control thresholds were used, pesticide use was more than halved. Cost of soil tillage and the seed yield achieved were the main factors determining net return. Embedded energy of nitrogen fertiliser was more important than energy used for soil tillage. In the ICM system, total production costs, total energy use, labour and fuel costs were lower despite the need for one additional herbicide treatment; however, energy efficiency and nitrogen utilisation was a little lower indicating a need to better adjust nitrogen supply to yield level. A fanning system based on the principles of ICM with non-inversion cultivation of soil can be recommended to farmers as a strategy to improve natural control of economically-important pests of winter oilseed rape, usually increase net return, decrease environmental impact and use less resources.
The ectoparasitic mite Podapolipus khorasanicus Hajiqanbar n. sp. (Acari: Heterostigmatina: Podapolipidae), detached from abdominal tergites of Opatroides punctubtus Brulle, 1832 (Coleoptera: ...Tenebrionidae) in northeastern Iran, is described and compared with related species. A key to world species of the coleopteran parasites of the genus Podapolipus Rovelli & Grassi (1888) is provided, and their distribution and host range are discussed.
It is important to understand how components of the agroecosystem interfere with the attack of a pest species and their seasonality in order to use these components in IPM programs. This study ...focused on the evaluation of the seasonality of natural control factors associated with the guava psyllid Triozoida limbata (Enderlein) in Brazil. Life-table data were collected from an experimental guava orchard during four periods that roughly represented four seasons. Natural mortality was monitored daily through the immature stages, and the relative importance of each natural mortality factor and its seasonality was determined. Significant statistical differences were observed in the mortality during the four periods (P < 0.05). Several factors contributed to the mortality of T. limbata, including rainfall, physiological disturbance, the parasitoid Psyllaephagus sp. (Hymenoptera: Encyrtidae) and specific predators: syrphids, predatory wasps and other generalist predators. Depending on the location of nymphs (exposed or inside galls), the relative importance of the different natural mortality factors changed. The principal component analysis (PCA) showed some trends in the relationship of natural control agents and weather conditions. For example, the occurrence of predatory wasps was positively correlated with temperature and occurrence of winds; the occurrence of syrphids and Psyllaephagus sp. were negatively correlated with temperature and winds; and the occurrence of other generalist predators were negatively correlated with the occurrence of rainfall and photoperiod. The results showed the importance of natural mortality factors for the management of T. limbata and their changes through the different seasons which should be considered when implementing IPM programs in guava orchards.
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