Ground predator abundance affects prey removal in highbush blueberry (<Emphasis Type="BoldItalic">Vaccinium corymbosum</Emphasis>) fields and can be altered by aisle ground covers

Habitat management to conserve natural enemies has increased biological control of insect pests in various cropping systems [Annu. Rev. Entomol. 45: 175–201, 2000]. We wanted to determine if insect predation in highbush blueberry, Vaccinium corymbosum L. (Ericales: Ericaceae), is influenced by manipulation of edaphic arthropod community and whether management of ground cover in aisles between blueberry rows enhances this community. The first question was studied in blueberry plots bounded by trenches permitting selective movement into plots (ingress) or out of plots (egress), as well as unbounded control plots. We observed a significant effect of boundary type on the arthropod communities relative abundance as measured with pitfall traps, with relative abundance highest in ingress plots, intermediate in control plots and lowest in egress plots. Effects of ground arthropod abundance on predation rates were assessed with onion fly, Delia antiqua (Meigen) (Diptera: Anthomyiidae), pupae as sentinel prey. Pupa recovery was greatest in egress boundary plots, intermediate in control plots and lowest in ingress boundary plots. Regression analyses indicate pupal recovery rate decreased as a function of carabid abundance as well as the abundance of non-insect ground predators. To determine if ground cover management influenced natural enemy abundance, aisles were clean cultivated or planted with three ground covers (clover, ryegrass, or buckwheat). Increasing ground cover had a significant effect on the relative abundance of Harpalus pensylvanicus De Geer (Coleoptera: Carabidae). In addition to conserving natural enemies for control of blueberry insect pests, we discuss additional benefits of ground covers that may increase their utility for blueberry production.     

Nectar sugar composition and volumes of 47 species of Gentianales from a southern Ecuadorian montane forest

BACKGROUND AND AIMS: This study investigates 47 taxonomically related species (Gentianales), all native to a tropical montane forest in southern Ecuador, in terms of nectar chemistry and nectar volumes in relation to pollination biology. METHODS: Nectar volumes of covered (24-h production) and uncovered (standing crop) flowers were measured in the natural habitat. Sucrose, fructose and glucose were quantified in the nectar using high performance liquid chromatography. Flower visitors were observed. KEY RESULTS: Nectar sugar concentration did not differ significantly among the pollination syndromes. Regarding sugar composition, the only significant differences were found in chiropterophilous and myiophilous flowers, which had a significantly lower sugar ratio than sphingophilous flowers. A separation of chiropterophilous and myiophilous flowers from the other pollination syndromes is further substantiated by non-linear multidimensional scaling using the chord-normalized expected species shared index of dissimilarity based on nectar sugar compositions. The matrix test revealed no correlation of observed floral visitors to nectar concentrations; however, a weak significant correlation was found between floral visitors and nectar sugar compositions. The nectar volumes of covered and uncovered flowers are related to, and differ significantly among, pollination syndromes. Matrix tests revealed correlation between floral visitors and nectar volume of covered flowers and, to a lesser extent, of uncovered flowers. CONCLUSIONS: Sucrose is the predominant floral nectar sugar in the order Gentianales, suggesting that nectar sugar composition is a conservative characteristic. However, some degree of an adaptive convergence of floral nectar compositions to principal pollinator type within the constraints set by phylogenetic history is likely. The driving force to visitation appears to be the volume of nectar the visitor can expect to consume.     

Ground beetle species (Carabidae,Coleoptera) activity and richness in relation to crop type,fertility management and crop protection in a farm management comparison trial

Ground beetle activity and species richness was monitored using pitfall traps in a plot trial system on a farm in northern England where the effects of organic and conventional fertility and crop protection management were separated within different crop types between 2005 and 2008. As well as analyses on species activity the beetles were split into small, medium‐sized and large groups, and into groups of herbivores and specific Collembola feeders. Crop type had significant effects on the activity of the 20 most abundant species and all groups, generally with most in beans and winter barley and least in vegetables and spring barley. Most significant reactions to crop protection and fertility management were in cereals and grass/clover. Activity of small species was highest in conventionally crop‐protected cereals but not in vegetables, with more medium‐sized and herbivorous species in organic plots, but there was little influence of crop protection management on large and Collembola feeding species. However, large species were significantly more active in organically fertilised cereals and grass/clover, but not in vegetables, and there were more Collembola feeders in conventional cereals but not in grass/clover. Small species were more abundant in conventionally fertilised grass/clover but there were more in organic cereals and vegetables. These inconsistent activity reactions to management were also observed with individual species but most preferred organically managed plots. There were few significant crop protection : fertility management interactions. Species richness was also significantly affected by crop type and where management had an influence, more species were found in organically managed plots. Constrained ordination emphasised that ground beetle activity was influenced more by crops than by management. Given the diverse nature of organic crop rotations, crop type should be considered a major influence in any environmental manipulation aimed at increasing ground beetle activity for provision of ecosystem services.     

Bromelain, a cysteine protease from pineapple (Ananas comosus) stem, is an inhibitor of fungal plant pathogens

Aim: This study aimed to evaluate the effect of bromelain, a cysteine protease isolated from pineapple (Ananas comosus), on growth of several agronomically important fungal pathogens. Methods and Results: Purification of bromelain from pineapple stems was carried out by chromatography techniques, and its antimicrobial activity was tested against the fungal pathogens Fusarium verticillioides, Fusarium oxysporum and Fusarium proliferatum by broth microdilution assay. A concentration of 0·3 μmol l^?1 of bromelain was sufficient for 90% growth inhibition of F. verticillioides. The capability of bromelain to inhibit fungal growth is related to its proteolytic activity. Conclusions: The study demonstrates that stem bromelain exhibits a potent antifungal activity against phytopathogens and suggests its potential use as an effective agent for crop protection. Significance and Impact of the Study: The results support the use of a natural protease that accumulates at high levels in pineapple stems as alternative to the use of chemical fungicides for crop protection.     

Crossing the divide: gene flow produces intergeneric hybrid in feral transgenic creeping bentgrass population

Gene flow is the most frequently expressed public concern related to the deregulation of transgenic events ( Snow 2002 ; Ellstrand 2003 ). However, assessing the potential for transgene escape is complex because it depends on the opportunities for unintended gene flow, and establishment and persistence of the transgene in the environment ( Warwick et al. 2008 ). Creeping bentgrass (Agrostis stolonifera L.), a turfgrass species widely used on golf courses, has been genetically engineered to be resistant to glyphosate, a nonselective herbicide. Outcrossing species, such as creeping bentgrass (CB), which have several compatible species, have greater chances for gene escape and spontaneous hybridization (i.e. natural, unassisted sexual reproduction between taxa in the field), which challenges transgene containment. Several authors have emphasized the need for evidence of spontaneous hybridization to infer the potential for gene flow ( Armstrong et al. 2005 ). Here we report that a transgenic intergeneric hybrid has been produced as result of spontaneous hybridization of a feral‐regulated transgenic pollen receptor (CB) and a nontransgenic pollen donor (rabbitfoot grass, RF, Polypogon monspeliensis (L.) Desf.). We identified an off‐type transgenic seedling and confirmed it to be CB × RF intergeneric hybrid. This first report of a transgenic intergeneric hybrid produced in situ with a regulated transgenic event demonstrates the importance of considering all possible avenues for transgene spread at the landscape level before planting a regulated transgenic crop in the field. Spontaneous hybridization adds a level of complexity to transgene monitoring, containment, mitigation and remediation programmes.     

A biophysical model of Sugarcane growth

Scientists predict that global agricultural lands will expand over the next few decades due to increasing demands for food production and an exponential increase in crop‐based biofuel production. These changes in land use will greatly impact biogeochemical and biogeophysical cycles across the globe. It is therefore important to develop models that can accurately simulate the interactions between the atmosphere and important crops. In this study, we develop and validate a new process‐based sugarcane model (included as a module within the Agro‐IBIS dynamic agro‐ecosystem model) which can be applied at multiple spatial scales. At site level, the model systematically under/overestimated the daily sensible/latent heat flux (by ?10.5% and 14.8%, H and λE, respectively) when compared against the micrometeorological observations from southeast Brazil. The model underestimated ET (relative bias between ?10.1% and –12.5%) when compared against an agro‐meteorological field experiment from northeast Australia. At the regional level, the model accurately simulated average yield for the four largest mesoregions (clusters of municipalities) in the state of São Paulo, Brazil, over a period of 16 years, with a yield relative bias of ?0.68% to 1.08%. Finally, the simulated annual average sugarcane yield over 31 years for the state of Louisiana (US) had a low relative bias (?2.67%), but exhibited a lower interannual variability than the observed yields.     

Impacts of land use change due to biofuel crops on carbon balance,bioenergy production,and agricultural yield,in the conterminous United States

Growing concerns about energy and the environment have led to worldwide use of bioenergy. Switching from food crops to biofuel crops is an option to meet the fast‐growing need for biofuel feedstocks. This land use change consequently affects the ecosystem carbon balance. In this study, we used a biogeochemistry model, the Terrestrial Ecosystem Model, to evaluate the impacts of this change on the carbon balance, bioenergy production, and agricultural yield, assuming that several land use change scenarios from corn, soybean, and wheat to biofuel crops of switchgrass and Miscanthus will occur. We found that biofuel crops have much higher net primary production (NPP) than soybean and wheat crops. When food crops from current agricultural lands were changed to different biofuel crops, the national total NPP increased in all cases by a range of 0.14–0.88 Pg C yr^?1, except while switching from corn to switchgrass when a decrease of 14% was observed. Miscanthus is more productive than switchgrass, producing about 2.5 times the NPP of switchgrass. The net carbon loss ranges from 1.0 to 6.3 Tg C yr^?1 if food crops are changed to switchgrass, and from 0.4 to 6.7 Tg C yr^?1 if changed to Miscanthus. The largest loss was observed when soybean crops were replaced with biofuel crops. Soil organic carbon increased significantly when land use changed, reaching 100 Mg C ha^?1 in biofuel crop ecosystems. When switching from food crops to Miscanthus, the per unit area croplands produced a larger amount of ethanol than that of original food crops. In comparison, the land use change from wheat to Miscanthus produced more biomass and sequestrated more carbon. Our study suggests that Miscanthus could better serve as an energy crop than food crops or switchgrass, considering both economic and environmental benefits.     

Estimation of climatic factors relating to occurrence of the maize orange leafhopper, Cicadulina bipunctata

The maize orange leafhopper, Cicadulina bipunctata is a serious pest of forage maize in East and Southeast Asia. In temperate Japan, the occurrence of this leafhopper fluctuates widely among years. Here, we examined effects of climatic factors (temperature, precipitation and sunlight) on the occurrence of C. bipunctata. Seasonal occurrence of adult C. bipunctata in a census field from July to August, when forage maize was most susceptible to the pest, could be described by a simple exponential function with two parameter: estimated density of C. bipunctata on 1 July (N ₀) and intrinsic rate of natural increase (r) for each year. Forward stepwise multiple regression analysis using seasonal occurrence data from 2004 to 2009 detected positive contributions of average temperatures in the previous December and February and a negative contribution of total precipitation during the previous winter to N ₀. The analysis also indicated that average temperature in July of the current year and N ₀ contributed positively and negatively to r, respectively. These results indicated that high temperature and little precipitation during winter and high temperature in early summer induced high occurrence of C. bipunctata in summer. A prediction model based on these factors supported the actual seasonal occurrence in 2010, suggesting that this prediction model is applicable to C. bipunctata forecasting. The prediction model indicated that further global warming in the future is likely to cause further outbreaks of C. bipunctata.     

Protected raspberry production alters aphid–plant interactions but not aphid population size

• 1 Aphid population dynamics in crops are often driven by interactions with their host plants, which can be extensively influenced by environmental change. Protective environments (i.e. plastic tunnels) are now frequently used for soft fruit production, which may affect the localized climate and alter such interactions. This two year study on red raspberry (Rubus idaeus) addressed how protected environments affected two aphid species; the large raspberry aphid Amphorophora idaei (LRA) and the small raspberry aphid Aphis idaei (SRA).
• 2 Temperatures were higher (up to 7–10 °C) in tunnels compared with the field. Plants in tunnels grew approximately 1.4 cm/week faster and had lower (approximately 35%) foliar amino acid concentrations than plants in the field.
• 3 Aphids affected plant growth differently depending on growing environment; they promoted plant growth by 18–37% in tunnels, although they had no such effect in the field. Aphids reduced total and essential amino acid concentrations, with SRA causing greatest reductions (approximately 40% and 33%, respectively).
• 4 Aphid population sizes were similar in both environments, although individual LRA were smaller in tunnels (30% smaller in 2007) compared with those in the field. We suggest that faster aphid development rates inside warmer tunnels were not realized as a result of the variable effects of the growing environment on amino acid composition.
• 5 We conclude that the increasing use of protected environments in crop production will not necessarily cause predictable increases in aphid populations, although it may alter aphid–plant interactions in terms of aphid‐induced changes to plant growth.

     

Use of ryegrass strips to enhance biological control of aphids by ladybirds in wheat fields

Abstract Non‐crop habitats may play a vital role in conservation biological control. This study tested the effect of ryegrass (Lolium multiflorum L.) strips on aphid and ladybird populations in adjacent winter wheat fields. The field experiment was conducted in three ryegrass‐margin wheat plots and three control plots in 2010 in North China. In spring, the same aphid species, Sitobion miscanthi (Takahashi), was found in both the ryegrass strips and wheat plots. The population density of ladybirds in the ryegrass strips (3.5 ± 0.9/m²) was significantly higher than in the wheat plots (1.5 ± 0.5/m²). We cut the ryegrass, forcing the ladybirds to migrate to the wheat fields. Three and eight days after cutting the ryegrass, the aphid numbers in the ryegrass‐margin wheat plots decreased significantly: they were 19.9% and 53.6%, respectively, lower than in control plots. In the early period of ladybird population development, the percentage of larvae was greater in the ryegrass‐margin wheat plots than in controls, and the peak number of pupae in the ryegrass‐margin wheat plots occurred 5 days earlier than in the control plots. The results suggest that ryegrass strips may promote the development of ladybird populations. Cutting ryegrass can manipulate ladybirds to enhance biological aphid control in wheat fields. The efficiency of this management approach is discussed.