Residues of diflubenzuron on horse chestnut (Aesculus hippocastanum) leaves and their efficacy against the horse chestnut leafminer, Cameraria ohridella

Residues of the insect growth regulator diflubenzuron were quantified on horse chestnut (Aesculus hippocastanum L.) leaves treated with a diflubenzuron 480 g litre^?1 SC, Dimilin. To analyse the samples, an analytical procedure was developed involving a simple extraction step followed by high‐performance liquid chromatography on an octadecyl‐modified silica column with methanol + 0.01 M ammonium acetate mobile phase. The results showed diflubenzuron to be highly stable on horse chestnut leaves; more than 4 months (127 days) after application, 38% (on average) of the insecticide still remained on/in the leaves. The data confirmed biological observations showing diflubenzuron's long‐term efficacy against the horse chestnut leafminer, Cameraria ohridella Deschka & Dimi?, which is the most important pest of the horse chestnut in Europe. The hypothesis of possible penetration of diflubenzuron into the leaf mass is explored and discussed. Copyright © 2006 Society of Chemical Industry     

The control of Varroa destructor using oxalic acid

Twenty-four honeybee (Apis mellifera) colonies were used to monitor the efficacy of a solution of 2.9% oxalic acid (OA) and 31.9% sugar against the mite Varroa destructor. Mite mortality was established prior to and after OA treatments, which were conducted in August and September. The treatments resulted in 37% mite mortality as opposed to 1.11% in the controls. OA treatment conducted in September on previously untreated colonies resulted in 25% mite mortality. OA treatments in October and November resulted in approximately 97% mite mortality. These results suggest that OA is effective during the broodless period and less effective when applied to colonies with capped broods. The possible use of OA against the Varroa mite in honeybee colonies as an alternative to routine chemical treatments is discussed.     

Quantitative real-time PCR assay for rapid detection of Pseudomonas amygdali pv. lachrymans in cucumber leaf rinse

Journal of Plant Diseases and Protection - Pseudomonas amygdali pv. lachrymans (Pal) is a bacterium that causes angular leaf spot disease of cucumbers. There is no direct protection against this...     

Representation of wild Lactuca spp. (Asteraceae, Lactuceae) in world genebank collections

The spread of the genus Lactuca worldwide includes 16 species in Europe, 51 in Asia, 43 in Africa and 12 in America (mostly North American subcontinent). Natural distributions of Lactuca spp. are compared with the representation of wild Lactuca spp. in world genebank collections as recently summarized in the International Lactuca database (ILDB). A total of 27 wild Lactuca species are reported in world genebank collections in the ILDB, however, due to incorrect taxonomic determination the real number of species is lower. The substantial part (92%) of the collections is represented only by three species (L. serriola, L. saligna, L. virosa) and from a geographic viewpoint they are mostly European in origin. The autochthonous species originating from other continents (Asia, Africa, America), which form c. 83% of known Lactuca spp. richness, are very poorly represented in collections (only c. 3%). The majority of accessions originate from Europe (59%) and Asia (37%), nevertheless the whole area of natural distribution is not well covered. An extremely low number of accessions is available from Africa and America (2% each). Thus, the global biodiversity of Lactuca spp. germplasm is represented very poorly and is biased in genebank collections. For future studies of taxonomy, phytogeography, ecology, phylogenetic relationships, genetic diversity, inter- and intra-population structure, resistance research and practical breeding exploitation of wild Lactuca spp. germplasm, plant material from a wider ecogeographic distribution must be collected and introduced into genebank collections more intensively.     

Distribution of race-specific resistance against <Emphasis Type="Italic">Bremia lactucae</Emphasis> in natural populations of <Emphasis Type="Italic">Lactuca serriola</Emphasis>

A metapopulation approach was applied to population studies of a common weed, Lactuca serriola (prickly lettuce). Seedlings grown from seed samples collected from 752 individual L. serriola plants in 50 populations occurring along an east-to-west transect across four European countries (Czech Republic, Germany, Netherlands and United Kingdom) were screened for resistance to 10 common races of Bremia lactucae. Based on the recorded reaction patterns, host individuals were characterized into specific resistance (R-) phenotypes. Diversity of R-phenotypes, their variation and distribution among and within European populations, was evaluated at different spatial scales, i.e. from a metapopulation involving the entire European study area to individual plants occurring in local populations. Generally, European populations of L. serriola have been shown to be highly susceptible to B. lactucae. However, large variation in L. serriola resistance was found both among and within individual countries. There was a clear gradient of increasing uniformity of race-specificity moving from central to western Europe, as well as a slight decrease in the diversity of R-phenotypes. Populations in the United Kingdom were the most divergent in terms of resistance structure from other geographic regions, and also were the most homogeneous, most likely a consequence of the relatively greater degree of spatial isolation from other regions. Metapopulation, inter- and intra-population variation in host resistance is discussed from the viewpoint of occurrence of race-specific interactions in this wild plant pathosystem.     

Recent changes in landscape structure and function in a mediterranean region of SW Spain (1950–1984)

Recent economic development has altered landscape structure and function of a mediterranean region in Southwestern Spain. Intensive agricultural systems have concentrated in the more fertile areas, while marginal ones have been abandoned. As a result, landscape structure has changed. Consequences of this structural change on landscape processes are discussed.