Ethyl Formate Fumigation for Controlling Two Major Aphid Pests, Aphis spiraecola and Aphis gossypii, on Passion Fruit, from Cultivation to Post-Harvest Storage.

Tropical and subtropical crops are being increasingly cultivated in South Korea, leading to an increase in damage by exotic insect pests. Consequently, ethyl formate (EF) is currently being considered for quarantine and pre-shipment fumigation. In this study, we evaluated the effectiveness of EF fumigation for controlling Aphis spiraecola Patch and Aphis gossypii Glover, two representative quarantine pests on passion fruit ("Pink Bourbon") during greenhouse cultivation and post-harvest storage. The efficacy of EF against both aphids in terms of the lethal concentration causing 50% mortality (LCt50%) and LCt99% was 1.36-2.61 g h/m3 and 3.73-7.55 g h/m3 under greenhouse conditions (23 °C), and 1.37-2.02 g h/m3 and 3.80-14.59 g h/m3 post-harvest (5 °C), respectively. EF at 4 g/m3 for 4 h resulted in 100% mortality of A. spiraecola, which was more resistant to EF, without causing phytotoxic damage to the trees in a 340 m3 greenhouse. Post-harvest fruit fumigation at 10 g/m3 for 4 h in a mid-size (0.8 m3) fumigation chamber resulted in complete disinfection. Moreover, the EF level decreased below the EF threshold within 10 min after natural ventilation in the greenhouse. Therefore, our results suggest EF fumigation as an effective method for controlling A. spiraecola and A. gossypii.

Chemical composition, Insecticidal and antifungal activities of Pinus halepensis mill. and Acacia cyanophylla sp. wood tars.

Pyrolysis of plant through the rotative oven is a promising and more eco-friendly way to produce charcoal, tar and pyroligneous acid, and other gaseous products with useful purposes. In this research using the Tar of 2 of the most common species in Tunisia Pinus halepensis and Acacia cyanophylla we tried to prove their Insecticidal and fungal activities. For that we started by assessing the Tars' secondary metabolites. Both tars presented important rates but P. halepensis tar presented higher levels of secondary metabolites especially flavonoids with 1.92 mg/ml QE comparing to 1.47 mg/ml QE for A. cyanophylla tar. The antioxidant activity and antioxidant capacity of the 2 tars revealed more pronounced antioxidant activity of P. halepensis tar with 89.5% (%DPPH) and 2.91 mg/ml AAE compared to 75.70% (%DPPH) and 2.72 mg/ml AAE for A. cyanophylla tar. The insecticidal activity against Aphis spiraecola showed faster and stronger efficiency of A. cyanophylla tar extract 25% inducing 73.3% mortality within 2 Hours of exposure and reached 100% mortality after 10H. P. halepensis tar extract 75% showed slower response with 73.3% mortality after 6H of exposure. The results of the antifungal activity of P. halepensis tar extract 10% and A. cyanophylla tar extract 0.75% revealed that P. halepensis tar was more inhibiting of the mycelium growth of many fungi including F.solani, F.nyagami and M.nivale with an inhibition rate of 77% but less effective on other like F.rodelens that reached 77% mycelium growth. On the other hand, cyanophylla tar extract 0.75% was less effective with only 30% inhibition rate of Phoma sp. the other fungi had more than 79% mycelium growth.

Voltage-gated sodium channel gene mutation and P450 gene expression are associated with the resistance of Aphis spiraecola Patch (Hemiptera: Aphididae) to lambda-cyhalothrin.

Aphis spiraecola Patch is one of the most economically important tree fruit pests worldwide. The pyrethroid insecticide lambda-cyhalothrin is commonly used to control A. spiraecola. In this 2-year study, we quantified the resistance level of A. spiraecola to lambda-cyhalothrin in different regions of the Shaanxi province, China. The results showed that A. spiraecola had reached extremely high resistance levels with a 174-fold resistance ratio (RR) found in the Xunyi region. In addition, we compared the enzymatic activity and expression level of P450 genes among eight A. spiraecola populations. The P450 activity of A. spiraecola was significantly increased in five regions (Xunyi, Liquan, Fengxiang, Luochuan, and Xinping) compared to susceptible strain (SS). The expression levels of CYP6CY7, CYP6CY14, CYP6CY22, P4504C1-like, P4506a13, CYP4CZ1, CYP380C47, and CYP4CJ2 genes were significantly increased under lambda-cyhalothrin treatment and in the resistant field populations. A L1014F mutation in the sodium channel gene was found and the mutation rate was positively correlated with the LC50 of lambda-cyhalothrin. In conclusion, the levels of lambda-cyhalothrin resistance of A. spiraecola field populations were associated with P450s and L1014F mutations. Our combined findings provide evidence on the resistance mechanism of A. spiraecola to lambda-cyhalothrin and give a theoretical basis for rational and effective control of this pest species.

Characterization and phylogenetic analysis of the complete mitochondrial genome of Aphis spiraecola (Hemiptera: Aphididae).

Aphis spiraecola is an important pest of citrus and transmits a number of plant viruses. Here, we sequenced and annotated the complete mitochondrial genome (mitogenome) of A. spiraecola. This mitogenome was 15,465 bp long and encoded 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), and 2 ribosomal RNA unit genes (rRNAs). Gene order was conserved and identical to that of Drosophila yakuba and to most other previously sequenced Aphididae. The whole mitogenome exhibited heavy AT nucleotide bias (81.8%). All 13 PCGs were initiated by the ATN (ATG, ATT and ATA) codon. Except for cox1 and nad4 which end with the incomplete codon T-, all PCGs terminated with the stop codon TAA. Phylogenetic analysis showed that A. spiraecola got together with the same genus species Aphis gossypii and Aphis craccivora with high support value, and Aphis had a close relationship with Schizaphis and Rhopalosiphum.

Spatial and temporal spread of Citrus tristeza virus and its aphid vectors in the North western area of Morocco.

First report of Citrus tristeza virus (CTV,Closterovirus) in Morocco datesback to 1961 in collections of citrus varieties. An exhaustive survey of citrus in the north of the country in 2009 revealed that CTV was spread all over the citrus production area. We attempted to evaluate the relative contribution of different aphid species in the spread of CTV disease in a Citrus reticulata orchard at the Loukkous region during 2 years (2012 and 2013). The overall CTV incidence estimated in the experimental site increased from 17.8% in 2012 to 31.15% in 2013. The most abundant aphid species colonising clementine trees was Aphis spiraecola and A. gossypii. Both aphid species reached their maximum peaks during the spring season. The rate of viruliferous aphids, estimated by real-time RT-PCR of single aphid, revealed that 35.4% of winged A. gossypii and 28.8% of winged A. spiraecola were viruliferous, confirming a high inoculum pressure in the area surrounding the experimental site. The aphid species Toxoptera citricida, which is able to transmit the aggressive isolates of CTV, was not found in the Loukkous region. The study of the spatial distribution of the CTV showed that in general, the disease was randomly distributed in the field. Overall, the results seem to indicate that A. spiraecola may be considered as the major aphid species contributing to CTV spread in our experimental conditions. The prevalence of mild strains in the region and the high level of aphid flight activity could explain the rapid evolution of CTV incidence in the experimental area.

Why the aphid Aphis spiraecola is more abundant on clementine tree than Aphis gossypii?

Aphis spiraecola and Aphis gossypii cause harmful damages on clementine tree orchards. Weekly surveys measured the abundance of aphids (larvae, winged and wingless adults) as well as of auxiliary insects and parameters of energy metabolism. Correlatively, soluble carbohydrates, total free amino acids, free proline and condensed tannins were quantified in control and infested leaves. Both aphid species showed parallel temporal variations, but A. spiraecola was consistently more abundant regardless of the stage. Amino acids had a positive effect on both aphid species abundance, but neither condensed tannins nor auxiliary insects seemed to modulate aphid populations. Interestingly, the leaf carbohydrate content was positively correlated with the abundance of A. spiraecola, but not with that of A. gossypii. Moreover, A. gossypii's abundance was significantly down-regulated by high proline concentrations. Thus, the higher abundance of A. spiraecola could be explained by a better tolerance to high proline contents and a better conversion of foliar energy metabolites.