Natural enemies of the South American moth, Tuta absoluta, in Europe, North Africa and Middle East, and their potential use in pest control strategies

The South American tomato leafminer, Tuta absoluta Meyrick (Lepidoptera: Gelechiidae), is an invasive Neotropical pest. After its first detection in Europe, it rapidly invaded more than 30 Western Palaearctic countries becoming a serious agricultural threat to tomato production in both protected and open-field crops. Among the pest control tactics against exotic pests, biological control using indigenous natural enemies is one of the most promising. Here, available data on the Afro-Eurasian natural enemies of T. absoluta are compiled. Then, their potential for inclusion in sustainable pest control packages is discussed providing relevant examples. Collections were conducted in 12 countries, both in open-field and protected susceptible crops, as well as in wild flora and/or using infested sentinel plants. More than 70 arthropod species, 20 % predators and 80 % parasitoids, were recorded attacking the new pest so far. Among the recovered indigenous natural enemies, only few parasitoid species, namely, some eulophid and braconid wasps, and especially mirid predators, have promising potential to be included in effective and environmentally friendly management strategies for the pest in the newly invaded areas. Finally, a brief outlook of the future research and applications of indigenous T. absoluta biological control agents are provided.     

First detection of a virulent strain of Citrus tristeza virus (Closteroviridae) in a citrus orchard of Chlef Valley (Algeria)

A large‐scale survey of Citrus tristeza virus (CTV) was carried out from 2016 to 2018 in the Chlef Valley, one of the main citrus growing areas in Algeria. In this study a total of 1680 citrus trees from 93 commercial orchards were sampled. The collected samples were tested by direct tissue blot immunoassay analysis and by the double antibody sandwich enzyme‐linked immunosorbent assay technique, and 54 trees were identified as being infected with CTV. This result confirmed that 54 trees were infected by the virus, corresponding to an infection rate of 3.21% throughout the studied area. Five of these local CTV sources were chosen for further molecular investigations to determine the genotype associated with the CTV isolates now spreading in the Chlef area. Characterization with multiple molecular markers showed the presence of the T30 and VT genotypes. This result allowed confirmation of the presence of a virulent strain belonging to the VT genotype. The other CTV isolates were similar to those from the Mitidja region, which showed 99% nucleotide identity with the Spanish mild CTV isolate. This early finding of a strain belonging to the VT genotype is an issue for Algerian citrus producers and needs rapid actions to be taken by the National phytosanitary services, extending the surveillance to other citrus production regions and uprooting the infected trees.     

Diversity in Allium ampeloprasum: from small and wild to large and cultivated

Allium ampeloprasum evolved as a complex of different cyto- and morpho-types widely distributed either in the wild or domesticated range of the Mediterranean regions. The assessment of genetic and phylogenetic relationships between Tunisian A. ampeloprasum and specimens from different origins and with variable degree of domestication can promote conservation and breeding. Minisatellite M13, microsatellite (GTG)₅ and nucleotide sequence analysis of the internal transcribed spacer region (ITS) were used to assess DNA polymorphism and genetic diversity. M13 and (GTG)₅ molecular markers efficiently discriminated A. ampeloprasum gene-pool from A. sativum. Geographic genetic patterns of variation of the wild gene-pool were not detected. However, domesticated A. ampeloprasum (great headed garlic, kurrat and leek) clustered consistently within the ampeloprasum group. A. sativum was found to be closer to A. ampeloprasum than A. fistulosum and A. schoenoprasum. A high number of single point mutations (SNPs) was recorded over the ITS1-2 spacer sequence. Most of these SNPs were heterozygous only in great headed garlic. It is inferred that heterozygosity played the major role in promoting great headed garlic domestication. Thus, great headed garlic adaptation to horticultural conditions along with its yield trait sizes are mainly associated to heterozygosity rather than to polyploidy.     

First record of the mealybug Phenacoccus madeirensis Green, 1923 (Hemiptera: Coccomorpha: Pseudococcidae) in Algeria

The mealybug Phenacoccus madeirensis Green (Hemiptera: Coccomorpha: Pseudococcidae) is recorded from Algeria for the first time. This pest was first detected in the summer of 2018 in private gardens in Salamandre, on the coastal side of Mostaganem City in north‐western Algeria, feeding on three ornamental plants: Hibiscus rosa‐sinensis L., Hibiscus syriacus L. (Malvaceae) and Cestrum nocturnum L. (Solanaceae). In October 2018, it was also found on Aloysia citriodora Palàu (Verbenaceae) growing near Hibiscus. The first samples collected had been attacked by hymenopteran parasitoids. Surveys of ornamental nurseries and greenhouses growing vegetables in the area indicate that, at present, P. madeirensis seems to be restricted to ornamental plants. More surveys over larger areas are needed to determine its distribution and the likely origin of its introduction to Algeria.     

Tetranychus evansi (Baker & Pritchard) (Acari:Tetranychidae) acarien invasif signalé sur culture de tomate à Mostaganem dans le nord‐ouest de l’Algérie

Une population établie de Tetranychus evansi a été signalée pour la première fois sur cultures de tomate dans le nord‐ouest de l’Algérie. Des données sur l’origine, la répartition géographique actuelle, l’identification et les plantes‐hôtes sont également présentées.