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Cawood, United Kingdom

McDaniel T.,Northumbria University | Tosh C.R.,Northumbria University | Gatehouse A.M.R.,Northumbria University | George D.,Stockbridge Technology Center | And 2 more authors.
Agronomy for Sustainable Development

The glasshouse whitefly, Trialeurodes vaporariorum, is an important pest of many crop plants including tomato, Solanum lycopersicum. Many wild tomato species exhibit a higher resistance to whiteflies. Therefore, locating the source of this enhanced resistance and breeding it into commercial tomato species is an important strategy to reduce the impact of pests on crops. Here, we assessed the pest resistance of Lycopersicon pimpinellifolium by comparing oviposition and feeding data from T. vaporariorum on this wild tomato species with data collected from a susceptible commercial tomato, S. lycopersicum var. ‘Elegance’. The location of resistance factors was examined by use of electrical penetration graph (EPG) studies on these tomato species. Results show that whiteflies preferentially settled on the commercial tomato more often in 80 % of the replicates when given free choice between the two tomato species and laid significantly fewer eggs on L. pimpinellifolium. Whiteflies exhibited a shorter duration of the second feeding bout, reduced pathway phase probing, longer salivation in the phloem and more non-probing activities in the early stages of the EPG on the wild tomato species compared to the commercial tomato. These findings evidence that a dual mode of resistance is present in this wild tomato against T. vaporariorum: a post-penetration, pre-phloem resistance mechanism and a phloem-located factor, which to the best of our knowledge is the first time that evidence for this has been presented. These findings can be used to inform future breeding strategies to increase the resistance of commercial tomato varieties against this important pest. © 2016, The Author(s). Source

Muir C.D.,Indiana University Bloomington | Muir C.D.,University of British Columbia | Muir C.D.,Stockbridge Technology Center | Hangarter R.P.,Indiana University Bloomington | And 2 more authors.
Plant, Cell and Environment

Natural selection on photosynthetic performance is a primary factor determining leaf phenotypes. The complex CO2 diffusion path from substomatal cavities to the chloroplasts - the mesophyll conductance (gm) - limits photosynthetic rate in many species and hence shapes variation in leaf morphology and anatomy. Among sclerophyllous and succulent taxa, structural investment in leaves, measured as the leaf dry mass per area (LMA), has been implicated in decreased gm. However, in herbaceous taxa with high gm, it is less certain how LMA impacts CO2 diffusion and whether it significantly affects photosynthetic performance. We addressed these questions in the context of understanding the ecophysiological significance of leaf trait variation in wild tomatoes, a closely related group of herbaceous perennials. Although gm was high in wild tomatoes, variation in gm significantly affected photosynthesis. Even in these tender-leaved herbaceous species, greater LMA led to reduced gm. This relationship between gm and LMA is partially mediated by cell packing and leaf thickness, although amphistomy (equal distribution of stomata on both sides of the leaf) mitigates the effect of leaf thickness. Understanding the costs of increased LMA will inform future work on the adaptive significance of leaf trait variation across ecological gradients in wild tomatoes and other systems. © 2013 John Wiley & Sons Ltd. Source

Mul M.F.,Wageningen UR Livestock Research | van Riel J.W.,Wageningen UR Livestock Research | Meerburg B.G.,Wageningen UR Livestock Research | Dicke M.,Wageningen University | And 4 more authors.
Experimental and Applied Acarology

For integrated pest management (IPM) programs to be maximally effective, monitoring of the growth and decline of the pest populations is essential. Here, we present the validation results of a new automated monitoring device for the poultry red mite (Dermanyssus gallinae), a serious pest in laying hen facilities world-wide. This monitoring device (called an “automated mite counter”) was validated in experimental laying hen cages with live birds and a growing population of D. gallinae. This validation study resulted in 17 data points of ‘number of mites counted’ by the automated mite counter and the ‘number of mites present’ in the experimental laying hen cages. The study demonstrated that the automated mite counter was able to track the D. gallinae population effectively. A wider evaluation showed that this automated mite counter can become a useful tool in IPM of D. gallinae in laying hen facilities. © 2015, The Author(s). Source

George D.R.,Stockbridge Technology Center | George D.R.,Northumbria University | Banfield-Zanin J.A.,Stockbridge Technology Center | Collier R.,Warwick Crop Center | And 4 more authors.

To inform current and future pesticide availability to glasshouse vegetable growers, the current project trialled more than twenty products, including existing industry standards, against four key pests of glasshouse tomatoes and bell peppers. These included experimental conventional chemical pesticides as well as alternative biopesticide and biorational products based on phytochemicals, microbials and physically-acting substances. The results suggest that certain biopesticide products, particularly botanicals, provide good levels of pest control, with the same being true of experimental conventional chemical pesticides not yet recommended for use against these pests on these crops. Efforts are on-going to ensure that results of the current project translate to industry benefit via new pesticide approvals. © 2015 by the authors; licensee MDPI, Basel, Switzerland. Source

George D.R.,Lancaster University | George D.R.,Northumbria University | King L.,Lancaster University | Donkin E.,University of York | And 3 more authors.
Biological Control

The aim of this study was to test the hypothesis that floral visitation and foraging by the hoverfly Episyrphus balteatus De Geer would have no effect on the attraction to, or use of, flowers by the parasitoid wasp Aphidius ervi Haliday. Results demonstrated that in two-way choice tests, air-streams emanating from live Fagopyrum esculentum Moench (buckwheat) flowers were significantly more attractive than clean air to both male and female wasps, by more than one and two orders of magnitude, respectively. When air-streams from flowers presented alone were compared to those from flowers presented with E. balteatus, or exposed to E. balteatus prior to use, no preferences were detected. Nevertheless, air that had passed through chambers containing only live E. balteatus was significantly repellent to female wasps, with individuals spending 18 times less in these air-streams than clean air. Conversely, air passed over E. balteatus was attractive to male A. ervi, with wasps spending more than six times longer in this vs. clean air. We argue that hoverfly floral visitation/use should have minimal impact on floral attractiveness to A. ervi based on these results, and that for male wasps greater benefits might be gained by responding positively to hoverfly volatiles in the absence of floral cues.In a separate experiment, a consistent trend for reduced fitness of female A. ervi on caged F. esculentum was observed under increasing competitive pressure from E. balteatus. High densities of hoverflies significantly reduced wasp longevity by more than 25%, though lower densities had no significant effect. Conversely, male A. ervi appeared to survive for longer where higher densities of hoverflies were present, though results were not as clear-cut statistically. We argue that antagonistic interactions seen between hoverflies and female A. ervi were the result of behavioural interference and would only be observed in the field under conditions of extreme competitive pressure. © 2013 Elsevier Inc. Source

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