Aim The most common pathway for the movement of plant pests across borders is the horticultural trade in live plants, especially potted ornamentals. Soilborne pathogens, possibly alien and potentially invasive, have a higher possibility of surviving transportation and becoming established at their destination if they are carried in potted plants. The European Union (EU) has an open‐door phytosanitary system, under which any plant that is not specifically regulated can be imported. Inspections are focussed on a small number of economically important plant pests and even then limited to visual examinations of the aerial parts of the plant. Inspections fail to detect regulated pests or others internal to the tissues, or in the soil, if plants appear asymptomatic, or if incipient symptoms are limited to the roots. Phytophthora, a soilborne pathogen universally infamous for its ruinous outbreaks, but poorly regulated in Europe, was chosen to illustrate the risk inherent in the nursery pathway. The aim of this study was to demonstrate the level of infestation by Phytophthora in ornamental plants largely traded to, from and within Europe. Location European Union. Methods As Phytophthora species are not easily isolated, a real‐time PCR assay was developed, based on a genus‐specific TaqMan MGB probe, to detect the pathogens in plant tissues or soil even when present at low concentrations, and before symptoms occurred. Phytophthora species were identified by isolation and sequencing of the ITS (internal transcribed spacer) region. Results Phytophthora was detected by qPCR in 87% of the tested pots and in 70% of the asymptomatic potted plants. Potted plants in soil carried several Phytophthora species without showing any external symptoms. Main conclusions The results of this study strongly support the case for more rigorous European legislation on the trade of live plants in pots. As eradication of soilborne organisms is difficult, if not impossible, an embargo on plant movements into the EU and between member states is the only advisable measure against the spread of these pathogens.

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Dasineura oleae (Angelini, 1831) (Diptera: Cecidomyiidae), the olive leaf gall midge, is a pest of olive crops that has never been problematic in Italy since 2016, when a massive infestation of this pest was reported in a small region of Central Italy. We selected infested olive orchards through farmers’ reports aiming at quantifying the pest infestation level and the parasitism rate in each site. Also, we aimed at exploring the landscape effect in both pest and parasitoids, using proportion of olive crops and semi-natural habitats, as well as the Shannon index as a measurement of the landscape diversity, estimated at four different scales (250m, 500m, 750m and 1000m buffers around the sampling points). Results showed different landscape effect depending on the organism and on the scale. We underlined a small-scale effect on the parasitism rate and a large-scale effect on the olive leaf midge mediated by the Shannon Index. Moreover, some preliminary results showed that the parasitism rate was high in sites where plants associated with D. oleae parasitoids were present in the adjacent semi-natural habitat. Further study should deepen and validate our findings on the effect of landscape and of the vegetation on natural enemies of D.oleae. These results should stimulate new approaches in the studying of the olive gall leaf midge as well as new suppression strategies.

BACKGROUND Dasineura oleae (Angelini 1831) (Diptera: Cecidomyiidae) was considered a minor pest in olive orchards, but in recent years severe outbreaks have been registered in several Mediterranean countries. Damage is caused by the feeding activity of larvae that induce gall formations and alters the physiological activity of the leaves. In Italy, this pest may be controlled by four Hymenoptera parasitoid species belonging to Platygaster and Mesopolobus genera such as Platygaster demades Walker 1835, Platygaster oleae Szelenyi 1940 (Hymenoptera: Platygastridae), Mesopolobus aspilus (Walker 1835) and Mesopolobus mediterraneus (Mayr 1903) (Hymenoptera: Pteromalidae), but parasitization becomes evident only after gall dissection. RESULTS In this study, we aim to: (i) design a primer for the detection of specimens belonging to Platygaster and Mesopolobus genera; (ii) develop a multiplex quantitative polymerase chain reaction (qPCR) protocol combined to a fast samples DNA extraction method; (iii) apply the developed protocol to field‐collected specimens and compare this method with traditional techniques based on visual estimation of parasitism rate on larvae. Primers were designed to anneal with cytochrome oxidase subunit I (COI) sequences of Platygaster and Mesopolobus genera while protocols were developed to be fast and capable to process several samples at the same time. Molecular analyses demonstrated to provide almost double of the parasitism rate assessed by visual inspection. Furthermore, on second instar larvae the PCR‐based method was able to detect ten‐fold times the parasitization rate estimated by visual inspection. CONCLUSION The application on a greater scale of this newly developed method could be fundamental in the determination of the biological control potential in olive orchards.