Pseudomonas savastanoi pv. savastanoi causes olive knot disease, which is present in most countries where olive trees are grown. Although the use of cultivars with low susceptibility may be one of the most appropriate methods of disease control, little information is available from inoculation assays, and cultivar susceptibility assessments have been limited to few cultivars. We have evaluated the effects of pathogen virulence, plant age, the dose/response relationship, and the induction of secondary tumors in olive inoculation assays. Most P. savastanoi pv. savastanoi strains evaluated were highly virulent to olive plants, but interactions between cultivars and strains were found. The severity of the disease in a given cultivar was strongly dependent of the pathogen dose applied at the wound sites. Secondary tumors developed in noninoculated wounds following inoculation at another position on the stem, suggesting the migration of the pathogen within olive plants. Proportion and weight of primary knots and the presence of secondary knots were evaluated in 29 olive cultivars inoculated with two pathogen strains at two inoculum doses, allowing us to rate most of the cultivars as having either high, medium, or low susceptibility to olive knot disease. None of the cultivars were immune to the disease.

Pseudomonas savastanoi pv. savastanoi (Psv) is the causal agent of olive knot disease. The bacterium survives epiphytically and gains ingress through new wounds where infections and colonization result in knot formation. The natural spread of the bacterium and the subsequent appearance of the disease in olive orchards is poorly understood. The aim of this study was to monitor Psv epiphytic populations in inoculated plants with knots versus non-inoculated healthy trees within the same orchard over four years. Additionally, disease severity was measured in both inoculated and non-inoculated control trees. Epiphytic Psv populations moved from inoculated to non-inoculated trees, although average Psv populations were higher in inoculated trees. Olive knot severity increased over the course of the study in all treatments and cultivars, with all plants reaching a high level of disease by the end of the study. However, the delay in the onset of disease was longer in non-inoculated than in inoculated trees. Molecular typing of Psv isolates recovered from non-inoculated control trees confirmed that they were similar to the inoculated strain. These data demonstrate that Psv can move over short distances in olive orchards through dissemination of epiphytic bacteria and suggest a relationship between the presence of epiphytic Psv and the number of knots on trees.

Soapberry, Paullinia clavigera Simpson (Sapindaceae) is used as a craft insecticide in Peruvian Amazon. The aim of the current research was to evaluate the toxicological effect of P. clavigera proceeding of Pucallpa, Peru, on Daphnia magna Strauss, 1820 (Crustacea: Daphniidae), and on two biological controls of agriculture pests: Copidosoma koehleri Blanchard, 1940 (Hymenoptera: Encyrtidae), and Chrysoperla externa (Hagen 1861) (Neuroptera: Chrysopidae). In D. magna (LC50 at 48 h exposure), the highest effects were found with leaves (LC50 = 237 mg L–1) and stem cortex (LC50 = 398 mg L–1) chlorophormic extracts. In C. koehleri (LC50 at 48 h exposure and emergence of adults), only hexanic extracts of leaves (LC50 = 145 mg L–1; 38.9%) and stem cortex (LC50 = 298.6 mg L–1; 16.8%) produced effects on mortality and emergency of adults, respectively. Toxicological effects of stem cortex chlorophormic botanic extracts on larvae of C. externa (at 96 h of exposure) were not found. Leaves and stem cortex ethanolic extracts had the most potential for use in an integrated pest management (IPM) because they were less toxic and selective to biological control and for D. magna in the freshwater environment.

Fifty-six tumorigenic Spanish grapevine strains of Agrobacterium spp. were tested for biovar classification, pathogenicity on several hosts, opine utilization, 16S rRNA gene sequencing and PCR amplifications using five primer sets targeting chromosomal and Ti plasmid genes. Fifty of them belonged to A. vitis (biovar 3), three to A. tumefaciens (biovar 1) and three to A. rhizogenes (biovar 2). All strains were tumorigenic on grapevines. Most A. vitis strains were also pathogenic on tomato and tobacco plants, while the three A. tumefaciens strains were only pathogenic on grapevine. Although most A. vitis strains used octopine, 12 utilized neither octopine nor nopaline. 16S rRNA gene sequencing clearly distinguished between strains belonging to the three species. Those of A. vitis could be further divided into three chromosomal backgrounds according to their 16S ribosomal RNA gene sequences. No universal primer pair was found for the detection of all three Agrobacterium species isolated from grapevine. DNA from all A. vitis strains was amplified with the chromosomally-encoded pehA primer pair. In both A. vitis and A. tumefaciens a correlation was observed between the amplifications obtained using the tmr and the virA Ti-plasmid-targeting primer pairs. Three types of Ti plasmid were found in A. vitis strains according to their PCR amplifications and opine utilization profiles. A given chromosomal background harboured only one type of Ti plasmid within the strains from each analysed sample, showing a strong association between chromosomal backgrounds and Ti plasmids in A. vitis .

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