Olfactory response of Typhlodromus pyri (Acari: Phytoseiidae) to synthetic methyl salicylate in laboratory bioassays

The herbivore‐induced plant volatile (HIPV) methyl salicylate (MeSA) is widely present in the chemical profile of several plant species and is known to attract natural enemies, including predatory mites. In this study, the response of Typhlodromus pyri, a key predator of pest mites in west coast vineyards, to synthetically produced MeSA was tested using a Y‐tube olfactometer in laboratory bioassays. Six doses ranging from 0.002 to 200 μg of MeSA diluted in 0.1 ml hexane were tested. Significantly higher proportions of T. pyri preferred MeSA at doses 0.02, 0.2 and 20 μg. No differences in response to MeSA were detected at the highest (200 μg), intermediate (2 μg) and lowest (0.002 μg) doses. Mite response to MeSA was a function of dose when fitting polynomial and logistic regression models using dose and square of the log dose prediction factors. Results indicate that synthetic MeSA may be applied to attract predatory arthropod populations in vineyards to enhance biological control of pest mites.     

Parasitoids of obscure mealybug,Pseudococcus viburni (Hem.: Pseudococcidae) in California: establishment of Pseudaphycus flavidulus (Hym.: Encyrtidae) and discussion of related parasitoid species

To improve natural suppression of the obscure mealybug, Pseudococcus viburni (Signoret), the parasitoids Pseudaphycus flavidulus (Brèthes) and Leptomastix epona (Walker) (Hymenoptera: Encyrtidae) of Chilean origin were released in California's Central Coast vineyards from 1997 to 1999. A survey for parasitoids of P. viburni was conducted in the Edna Valley appellation wine grape region from 2005 to 2007, 6–8 years after classical biological control releases were discontinued. Two survey methods were used. First, field collections of obscure mealybugs from commercial vineyard blocks (2005–2007) and, second, placement of “sentinel mealybugs” on potted (1 L) grape vines (2006 only). From both survey methods, P. flavidulus was recovered, albeit levels of parasitism were low (less than 0.6%). We also placed longtailed mealybug, Pseudococcus longispinus (Targioni Tozzetti), on potted plants concurrent with placement of sentinel obscure mealybugs in the vineyard in order to measure parasitoid activity on this closely-related mealybug species. No P. flavidulus were recovered from P. longispinus. Other encyrtid parasitoids reared from either P. viburni or P. longispinus were Anagyrus pseudococci (Girault), Leptomastix dactylopii Howard, Leptomastidea abnormis (Girault), Coccidoxenoides perminutus Girault, and Tetracnemoidea peregrina (Compere). A hyperparasitoid, Chaetocerus sp., was also reared. The data are discussed with respect to biological control of vineyard mealybugs and newly developed controls for the Argentine ant, Linepithema humile (Mayr) (Hymenoptera: Formicidae). Because Pseudaphycus species reared from mealybugs are superficially very similar a taxonomic key and discussion of host relationships for selected Pseudaphycus species are provided.     

Transverse hydraulic redistribution by a grapevine

Root hydraulic redistribution has been shown to occur in numerous plant species under both field and laboratory conditions. To date, such water redistribution has been demonstrated in two fundamental ways, either lifting water from deep edaphic sources to dry surface soils or redistributing water downward (reverse flow) when inverted soil Ψ_s gradients exist. The importance of hydraulic redistribution is not well documented in agricultural ecosystems under field conditions, and would be important because water availability can be temporally and spatially constrained. Herein we report that a North American grapevine hybrid (Vitis riparia × V. berlandieri cv 420 A) growing in an agricultural ecosystem can redistribute water from a restricted zone of available water under a drip irrigation emitter, laterally across the high resistance pathways of the trunk and into roots and soils on the non-irrigated side. Deuterium-labelled water was used to demonstrate lateral movement across the vine's trunk and reverse flow into roots. Water redistribution from the zone of available water and into roots distant from the source occurred within a relatively short time frame of 36 h, although overnight deposition into rhizosphere soils around the roots was not detected. Deuterium was eventually detected in rhizosphere soils adjacent to roots on the non-irrigated side after 7 d. Application of identical amounts of water with the same deuterium enrichment level (2%) to soils without grapevine roots showed that physical transport of water through the vapour phase could not account for either downward or transverse movement of the label. These results confirmed that root presence facilitated the transport of label into soils distant from the wetted zone. When deuterium-labelled water was allowed to flow directly into the trunk above the root–trunk interface, reverse flow occurred and lateral movement across the trunk and into roots originating around the collar region did not encounter large disproportionate resistances. Rapid redistribution of water into the entire root system may have important implications for woody perennial cultivars growing where water availability is spatially heterogeneous. Under the predominantly dry soil conditions studied in this investigation, water redistributed into roots may extend root longevity and increase the vines water capacitance during periods of high transpiration demand. These benefits would be enhanced by diminished water loss from roots, and could be equally important to other cited benefits of hydraulic redistribution into soils such as enhancement of nutrient acquisition.     

Ground wētā in vines of the Awatere Valley,Marlborough: biology,density and distribution

The endemic New Zealand ground wētā (Hemiandrus sp. ‘promontorius’) has a Naturally Uncommon conservation status. This is because of the paucity of information on its density and distribution. Here, the biology, density and distribution of a population of this wētā found in and around vineyards in the Awatere Valley, Marlborough was studied. Wētā density was assessed in vineyards, paddocks and shrublands in this valley. Soil moisture, penetration resistance, pH and organic matter were recorded at locations with and without wētā. Wētā density in vineyards was significantly higher than in either paddocks or shrub habitats. In vineyards, the density of this insect was significantly higher under-vines than in the inter-rows. Higher numbers of this wētā were found in moist soils that required lower force to burrow. Females laid an average of 55 eggs between March and April, which hatched in September. These findings highlight the intersection between agriculture and conservation.     

Agroecological management of a soil‐dwelling orthopteran pest in vineyards

The efficacy of different combinations of undervine and inter‐row treatments for managing a soil‐dwelling orthopteran pest, weta (Hemiandrus sp.), in vineyards was investigated over 2 seasons. This insect damages vine buds, thus reducing subsequent grape yield. The undervine treatments comprised pea straw mulch, mussel shells, tick beans [Vicia faba Linn. var minor (Fab)], plastic sleeves on vine trunks (treated control) and control (no intervention), while inter‐rows contained either the existing vegetation or tick beans. Treatments were arranged in a randomized complete block design with 10 replicates. Data were collected on weta densities, damage to beans and components of yield. The latter were numbers of bud laid down per vine, shoots per bud, clusters per shoot, grape bunches per vine, bunch weight and yield. The undervine treatments significantly affected all variables except the number of shoots per bud. In contrast, none of the variables was significantly affected by the inter‐row treatments or their interaction with undervine treatments, apart from weta density. At the end of the experiment, weta density in the shell treatment was about 58% lower than in the control. As a result, there was about 39% significant yield increase in that treatment compared to the control. Although the undervine beans and sleeves treatments increased yield, there were no reductions in weta density. With undervine beans, the insect fed on the bean plants instead of vine buds. Thus, yield in that treatment was approximately 28% higher than in the control. These results demonstrate that simple agroecological management approaches can reduce above‐ground damage by soil‐dwelling insects.     

High incidence of arbuscular mycorrhizal fungi in rare and endangered wild grapevine

High levels of arbuscular mycorrhizal fungi colonisation of 90–100%, as well as high vesicular and arbuscular colonisation were found in the roots of the rare and endangered wild grapevine (Vitis vinifera subsp. sylvestris) along the Neretva River in southwestern Bosnia and Herzegovina, surpassing colonisation in region vineyads.     

Occurrence and Distribution of Grapevine Leafroll-associated Viruses 1, 2, 3 and 7 in Turkey

Grapevines in central Anatolia region of Turkey were surveyed for the prevalence of grapevine leafroll viruses. The field study and collection of samples were conducted in nine major grapevine‐growing areas. Samples collected from 622 vines were tested for Grapevine leafroll‐associated virus 1, 2, 3 and 7 (GLRaV‐1, ‐2, ‐3 and ‐7). According to diagnostic tests and surveys, 27 of 41 cultivars and 95 of 622 samples (15.27%) were found to be infected at least one virus. GLRaV‐1 (8.36%) was found to be the most frequently encountered virus associated with leafroll disease of grapes, followed by GLRaV‐3 (5.78%), GLRAV‐7 (3.86%) and GLRAV‐2 (2.41%).     

Contrasting land uses in Mediterranean agro-silvo-pastoral systems generated patchy diversity patterns of vascular plants and below-ground microorganisms

The aims of this paper were (i) to define how contrasting land uses affected plant biodiversity in Mediterranean agro-silvo-pastoral-systems across a gradient of disturbance regimes: cork oak forests, secondary grasslands, hay crops, grass covered vineyards, tilled vineyards; (ii) to determine whether these patterns mirrored those of below-ground microorganisms and whether the components of γ-diversity followed a similar model. The disturbance regimes affected plant assemblage composition. Species richness decreased with increasing land use intensity, the Shannon index showed the highest values in grasslands and hay crops. Plant assemblage composition patterns mirrored those of Basidiomycota and Ascomycota. Richness in Basidiomycota, denitrifying bacteria and microbial biomass showed the same trend as that observed for vascular plant richness. The Shannon index pattern of below-ground microorganisms was different from that of plants. The plant γ-diversity component model weakly mirrored those of Ascomycota. Patchy diversity patterns suggest that the maintenance of contrasting land uses associated with different productions typical of agro-silvo-pastoral-systems can guarantee the conservation of biodiversity.     

Isolation and identification of ochratoxin A-producing Aspergillus section Nigri strains from California raisins

Aims: To determine incidence and levels of ochratoxin A (OTA) in California raisins and to isolate and characterize OTA‐producing fungi from California raisin vineyard populations. Methods and Results: Forty raisin clusters sampled from four California vineyards in the San Joaquin Valley were analysed for OTA content using immunoaffinity and HPLC methods. OTA was detected in 93% of the samples, at levels from 0·06 to 11·4 ng g^?1. From these raisin samples, a total of 400 strains of Aspergillus were isolated and analysed for OTA production. Twelve isolates (3%), from five raisin samples, produced OTA. These isolates were identified as Aspergillus carbonarius, based on morphological characteristics and multilocus sequence analysis. Levels of OTA produced by these isolates on raisin agar ranged from 0·9 to 15 μg g^?1. Conclusions: OTA is a common contaminant of raisin vineyards, but average levels are much lower than EU regulatory limits for dried fruit. The primary species responsible for OTA contamination in California raisins is A. carbonarius. Significance and Impact of the Study: This study illustrates that low‐level OTA contamination of raisins occurs in California and that ecological studies of A. carbonarius within the Aspergillus section Nigri population on raisins are warranted to monitor ochratoxigenic potential of the crop.     

Linear landscape elements in an Austrian viticultural landscape have limited effects on spatial patterns of plant genetic diversity

Background: The Wachau region along the river Danube in eastern Austria represents one of central Europe's hotspots of plant and animal species diversity. One of the typical landscape elements is vineyards, mostly established as linear elements on terraces along the slopes, with a characteristic and species-rich flora and fauna on terrace slopes lying between the cultivated terraces.

Aims: We addressed the question of how the genetic variation of four plant species of open grassland vegetation types is distributed. We asked if levels and distribution of genetic diversity of the plant species Aster amellus, Gentianella aspera, Pulsatilla grandis, and Stachys recta were correlated with geographic distances along the terrace slopes.

Methods: The dominant inherited molecular marker system random amplified polymorphic DNA (RAPD ) was used to estimate and compare the distribution of genetic diversity of the four selected species.

Results: We found only low levels of correlation of the distribution of genetic variation with linear geographic patterns and obtained indirect evidence for high levels of gene flow between adjacent terrace slopes.

Conclusions: We found that genetic diversity parameters of the four target species did not mirror the pattern of linear landscape elements, indicating that gene flow acts efficiently against the linear distribution of genetic variation.