First records of the invasive aphid species, Aphis spiraecola, in Kosovo, Slovakia, the Czech Republic, the United Kingdom and Denmark

In the last few decades, the spiraea aphid (Aphis spiraecola Patch) has become a widely distributed pest of apple and citrus orchards across Europe. In our study, A. spiraecola was observed for the first time in Kosovo, Slovakia, the Czech Republic, the United Kingdom and Denmark, in apple orchards in the growing seasons of 2016, 2018 and 2019. The presence of A. spiraecola was also recorded on other host plants such as the quince (Cydonia oblonga Miller) and Vanhoutte spiraea (Spiraea × vanhouttei) in Slovakia, and the quince, common pear (Pyrus communis Linnaeus) and firethorn (Pyracantha coccinea M.J. Roemer) in the United Kingdom. Based on the morphological characteristics and the sequencing of the DNA mitochondrial cytochrome c oxidase subunit 1 gene (COI fragment) barcode, our study confirms the presence of this pest in five additional regions in Europe.

Asymmetric Interaction between Aphis spiraecola and Toxoptera citricida on Sweet Orange Induced by Pre-Infestation

Indirect interactions between herbivorous insects that share the same host have been focused on insects feeding on herbaceous plants, while few studies investigate similar interactions on woody plants. We investigated performance and feeding behavior of two citrus aphids, Aphis spiraecola Patch and Toxoptera citricida Kirkaldy, on sweet orange as affected by prior infestation of conspecifics and heterospecifics. Results showed that pre-infestation-induced interactions between A. spiraecola and T. citricida were asymmetric, with A. spiraecola gaining more fitness. In detail, pre-infestation by A. spiraecola decreased adult weight, enhanced survival rate and accelerated phloem sap acceptance of conspecifics. However, A. spiraecola pre-infestation did not affect performance or feeding behavior of T. citricida. In another infestation sequence, the pre-infestation of T. citricida did not affect conspecifics, but positively affected heterospecifics, indicated as a decreased pre-reproductive period, enhanced survival rate, adult weight, fecundity, and feeding efficiency, i.e., faster access and acceptance of phloem sap, and longer phloem sap ingestion duration. Furthermore, we found A. spiraecola pre-infestation enhanced amino acid concentration, amino acid to sugar ratio, activated salicylic acid and jasmonic acid marker gene expression, while T. citricida pre-infestation only depressed jasmonic acid marker gene expression. Changes in nutrient and phytohormone-dependent defense probably underlie the asymmetric effect.

Relationship between Aphis spiraecola Patch, 1914 (Hemiptera: Aphididae) and citrus foliar minerals

<p>Spring and autumn flushes are generally the most infested periods by citrus aphids. Nevertheless, the role of citrus foliar minerals on aphids is not clear. Thus, this paper aims to study the correlation between certain minerals and the infestation degree of citrus varieties by <em>Aphis spiraecola</em>. Aphid counting was carried out on 12 leaves for each of the six species retained (clementine, lemon, grapefruit and three varieties of mandarin), during autumn (October 2014) and spring (April 2015) flushes. In addition, mineral contents of the leaves in P, K, Na, Ca and Li were measured for the same periods. The results showed that the infestation levels of the studied varieties were higher in the spring flush than in the autumn one. Moreover, analyzes of young leaves showed an important intraspecific (mandarin varieties) and interspecific differences in the mineral composition between the examined citrus trees. The study of the relationship between infestation levels by <em>A. spiraecola</em> and mineral content of the six examined species showed no significant correlation, suggesting a marginal role of the five analyzed minerals in the relation citrus – <em>A. spiraecola</em>.</p><div class="gdict-dialog" style="display: none;"> </div>

Aphids (Hemiptera: Aphididae) on Plum and Cherry Plum in Bulgaria

The species complex and infestations of aphids on plum (Prunus persica) and cherry plum (Prunus cerasifera) in Bulgaria were investigated during the period 2013–2018. Nine species from the family Aphididae were found: Brachycaudus helichrysi Kaltenbach (leaf-curling plum aphid), Hyalopterus pruni Geoffroy (mealy plum aphid), Phorodon humuli Schrank (hop aphid), Brachycaudus prunicola Kaltenbach (brown plum aphid), Brachycaudus cardui Linnaeus (thistle aphid), Brachycaudus persicae Passerini (black peach aphid), Rhopalosiphum nymphaeae Linnaeus (waterlily aphid), Aphis spiraecola Patch (spiraea aphid) and Pterochloroides persicae Cholodkovsky (peach trunk aphid). The dominant species on plum are Hyalopterus pruni and Brachycaudus helichrysi. The first species is more widespread and of significantly higher density. The dominant species on cherry plum are Phorodon humuli and B. helichrysi. The species Brachycaudus prunicola is widespread both on plum and cherry plum in Bulgaria. It was found only on twigs, and therefore cannot be considered as a dangerous pest on fruit-bearing plum trees. The other species, some of them described as dangerous pests on plum, are today fairly rare and occur in low density, thus posing no danger to orchards.

DNA Barcoding Subtropical Aphids and Implications for Population Differentiation

DNA barcoding has proven its worth in species identification, discovering cryptic diversity, and inferring genetic divergence. However, reliable DNA barcode reference libraries that these applications depend on are not available for many taxonomic groups and geographical regions. Aphids are a group of plant sap sucking insects, including many notorious pests in agriculture and forestry. The aphid fauna of the subtropical region has been understudied. In this study, based on extensive sampling effort across main subtropical areas, we sequenced 1581 aphid specimens of 143 morphospecies, representing 75 genera, and 13 subfamilies, to build the first comprehensive DNA barcode library for subtropical aphids. We examined the utility of DNA barcodes in identifying aphid species and population differentiation and evaluated the ability of different species delimitation methods (automatic barcode gap discovery (ABGD), generalized mixed Yule-coalescent (GMYC), and Bayesian Poisson tree processes (bPTP)). We found that most aphid species demonstrated barcode gaps and that a threshold value of 2% genetic distance is suitable for distinguishing most species. Our results indicated that ten morphospecies may have species divergence related to factors such as host plant or geography. By using two pest species Aphis spiraecola and A. gossypii as examples, we also discussed the effect of the sampling scale of host plants on the results and reliability of DNA barcoding of phytophagous insects. This DNA barcode library will be valuable for future studies and applications.

The effect of biorational insecticides on the citrus aphids and their predator, Coccinella septempunctata L.

<p>To determine selective effectiveness for specific pesticides on biological control species, we evaluated the contact toxicity of different treatments including 10 ml l^-1 dishwashing liquid, Dayabon 5, 6, 7, 8, 9 and 10 ml l^-1, Palizin 1.5, 2.5 and 2.5 ml l^-1, Palizin 1.5, 2 and 2.5­+­Citrol oil 5 ml l-1, Tondoxir 2 and 3­+­Bartar soap 1 ml l^-1, Malathion 2 ml l^-1 and control (water) on the adult aphids of the most important citrus gardens and their predator, <em>Coccinella septempunctata </em>L. in the laboratory conditions. The results revealed that the Palizin treatment 2.5­+­Citrol oil 5 ml l^-1, caused the highest rate of the mortality of the citrus green aphid, <em>Aphis spiraecola </em><a title="Edith Marion Patch" href="https://en.wikipedia.org/wiki/Edith_Marion_Patch">Patch</a>, 1914 in 36 hours. Concentrations of 7 to 10 ml l^-1, Dayabon and Palizin 2.5­+­Citrol oil 5 ml l^-1, as well as 3 ml^-1 Tondexir + Bartar soap 1 ml^-1 had the highest mortality of the citrus brown aphid, <em>Aphis citricidus </em>(Kirkaldy, 1907), 36 hours after treatment (100 %). In addition, the treatments of Palizin 2 ml^-1­+ Citrol oil of 5 ml^-1, as well as 2 ml l^-1 Tondexir­+­Bartar soap 1 ml l^-1 and concentrations of 5 ml l^-1 and 6 ml^-1 of Dayabon produced the same amount of the mortality of the citrus black aphid, <em>Toxoptera aurantii </em>(Boyer de Fonscolombe, 1841). Tondexir 3 ml l^-1­+­Bartar soap 1 ml l^-1 in 24 hours after treatment caused the highest rate of the mortality of the cotton aphids, <em>Aphis gossypii </em>Glover, 1877 (83.88 %). Malathion treatment caused a 100 % mortality of the predator ladybird 36 hours after treatment, while the lowest amount was observed in the Dayabon at 10 ml l^-1 with 33.34 % mortality.</p>