1,720,964 research outputs found
Osservazioni preliminari sull’influenza degli ospiti Planococcus citri e Planococcus ficus su alcuni parametri demografici del parassitoide Leptomastix dactylopii
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Le principali avversità del nocciolo in Sardegna
No full textIn Sardegna il nocciolo è coltivato prevalentemente nell'areale della Barbagia di Belvì (Nu). Oltre alle varietà locali chiamate genericamente “nocciole sarde”, vengono coltivate anche cultivar importate come la Tonda Gentile Romana, la Tonda Gentile delle Langhe e la Trebisonda. Oggi molti noccioleti versano in uno stato di abbandono e in quelli produttivi gli interventi agronomici sono occasionali. Due anni di ricerca e di monitoraggio specifico dei principali insetti fitofagi hanno evidenziato una situazione piuttosto favorevole. Uno degli aspetti più interessanti è l'assenza del coleottero curculionide Curculio nucum (L.) considerato il fitofago chiave nel noccioleto in Europa e in Asia. Particolarmente evidente è il danno sui rametti apicali causato dalle larve del coleottero cerambicide Oberea linearis (L.). Fra gli spermofagi è stata rilevata la presenza di emitteri eterotteri agenti del cosiddetto “cimiciato”. Si segnala inoltre la presenza dell'acaro delle gemme Phytoptus avellanae Nal.
Fra le malattie batteriche è stata accertata la presenza di Pseudomonas syringae pv. syringae associato ad un parziale avvizzimento dei rametti e delle branche e di P. s. pv. coryli, agente dell'avvizzimento rameale, mentre il rinvenimento di Xanthomonas arboricola pv. corylicola è stato occasionale. Fra quelle fungine sono presenti il “mal dello stacco” causato da Cytospora corylicola, il “mal bianco” da Phyllactinia guttata e l'“antracnosi” da Gloeosporium coryli. I maggiori danni sono causati dalle due pathovar di Pseudomonas syringae e dalla Cytospora corylicola. Le cultivar Tonda Gentile delle Langhe e Tonda Gentile Romana sono risultate più suscettibili alle malattie batteriche mentre il “mal dello stacco” era particolarmente dannoso sulle varietà locali. Di queste malattie si riportano aspetti sintomatici e fenotipici e alcune considerazioni sui fattori predisponenti. Da questa prima indagine emerge una situazione sanitaria piuttosto confortante resa precaria dal fatto che, generalmente, non vengono adottate misure atte a prevenire la diffusione delle malattie presenti e l'introduzione di altri patogeni con il materiale di propagazione.In Sardinia, the hazelnut is cultivated in the area of Barbagia di Belvì (Nu). In the hazelnut orchards various imported cultivars (Tonda Gentile Romana, Tonda Gentile delle Langhe and Trebisonda) live alongside local varieties, generally called the “Sardinian Hazelnut”. Nowadays, many hazelnut orchards have been completely abandoned and even in the productive orchards agronomic management occurs occasionally. Two years of research and specific monitoring of the main pests have found a rather favourable situation. One of the most interesting findings is the complete absence of Curculio nucum (L.) (Coleoptera Curculionidae), which is considered to be the key hazelnut pest in Europe and Asia. On the other hand, there is particularly evident damage caused by Oberea linearis ( L . ) (Coleoptera Cerambicidae), whose larvae attack the apical twigs. Among the spermophagous insects, the presence of hazelnut bugs, agent of the spotted-kernel has been observed. In addition, the presence of the bud mite Phytoptus avellanae Nal. has been noted.
Among bacterial diseases, Pseudomonas syringae pv. syringae and P . s. pv. coryli have been observed. The former is associated with a partial wilting of the twigs and branches and the latter is the agent of bacterial twig dieback. By contrast, Xanthomonas arboricola pv. corylina, agent of the bacterial blight of hazelnut, was only occasionally found. The main fungi diseases found so far in Sardinia are: “mal dello stacco” caused by Cytospora corylicola; powdery mildew caused by Phyllactinia guttata; anthracnose caused by Gloeosporium coryli. It has been observed that most damage is caused by the P. syringae pathovars and C. corylicola. Tonda Gentile delle Langhe and Tonda Gentile Romana cultivars were found to be more susceptible to the bacterial diseases, while “mal dello stacco” is particularly harmful to the local varieties. The symptomatic aspects, main phenotypic characteristics and some predisposing factors of the diseases found in Sardinia are described. From this survey, a phytosanitary situation emerges which is rather encouraging. However, it is made precarious by the fact that preventive measures are not usually taken against the spreading of the diseases present or against the introduction of other pathogens from imported propagation materials
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Attività inibente del miele nei confronti di Bacillus subtilis e Bacillus stearothermophilus.
No full textInfluence of ant-exclusion on generalist predators in a citrus orchard
No full textAbstract: Formicids have been observed to protect honeydew-producing Homoptera from their natural enemies by disturbing or killing parasitoids and predators, thereby reducing natural enemy effectiveness. In field studies carried out over two growing seasons (1998-1999) in an organic citrus orchard in Sardinia, Italy, sticky trunk barriers were used to exclude ants from orange tree canopies in order to enhance the biological control of the mealybug Planococcus citri Risso. The influence of antexclusion on the abundance of four groups of generalist predators (spiders, true bugs, lacewings and ladybirds) was examined. Predators and ants were collected every ten days, on randomly selected fruits, for about five months per year. Four species of ants were found and Lasius niger (L.) was the most common species (> 80%). The total number of generalist predators was significantly higher in the ant-excluded plot relative to the undisturbed one (P < 0.000). The same result, with the only exclusion of Neuroptera (P = 0.1022), was obtained considering each predator group singularly
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