Macropsis mendax as a vector of elm yellows phytoplasma of Ulmus species

A 3-year study was carried out in north-east Italy, the site of recent elm yellows epidemics, to identify vectors for the elm yellows phytoplasma. Using PCR analysis, Ulmus minor and Ulmus pumila , each with and without symptoms, were positive for the elm yellows phytoplasma. Macropsis mendax , a univoltine and monophagous leafhopper, was shown to be the vector of the elm yellows-associated disease agent. PCR analyses demonstrated that the insect was infected both in natural conditions and in the screenhouse after acquisition-feeding on infected elm plants. Groups of M. mendax , collected from naturally infected elm trees, transmitted elm yellows phytoplasma to elm test plants. In nature, Alnus glutinosa trees affected by alder yellows were found in the surroundings of yellows-affected elm trees; the associated disease agent of alder yellows was transmitted under controlled conditions from alder to elm test plants by grafting.     

Transmission of Rhus (Rhus javanica L.) Yellows by Hishimonus sellatus and Host Range of the Causal Phytoplasma

In 1998, rhus (Rhus javanica L.) yellows (RhY), caused by phytoplasma, was found in Miyagi Prefecture, Japan. In vector transmission tests, Hishimonus sellatus acquired RhY phytoplasma from diseased R. javanica and transmitted it to healthy R. javanica. Twenty-two species of herbaceous plants in 10 families were infected with RhY phytoplasma by H. sellatus. The host range and main symptoms on test plants of RhY phytoplasma differed from those of Macrosteles striifrons-transmitted phytoplasmas, which belong to the same 16Sr I group phytoplasma. Received 6 December 1999/ Accepted in revised form 14 May 2000     

A Leafhopper (Hishimonus sellatus) Transmits Phylogenetically Distant Phytoplasmas: Rhus Yellows and Hovenia Witches' Broom Phytoplasma

Phytoplasmas causing a severe decline of three tree species, i.e., Rhus javanica, Hovenia tomentella and Zizyphus jujuba, in Japan were examined for their transmissibility by a leafhopper species Hishimonus sellatus, and for their phylogenetic relatedness. By H. sellatus, Rhus yellows (RhY) phytoplasma was transmissible to white clover and periwinkle seedlings, causing typical symptoms in these plants. Jujube witches' broom (JWB) phytoplasma was also transferred to the host plant, Z. jujuba, by the leafhopper. Because JWB phytoplasma was transmitted to Hovenia tomentella and caused the same symptoms as Hovenia witches' broom (HWB), JWB phytoplasma may be very closely related to HWB phytoplasma. RFLP analysis of the PCR products of 16S rDNA revealed that RhY phytoplasma belongs to the Aster yellows (AY) group, and JWB and HWB phytoplasmas belong to a different group (possibly Elm yellows group). Thus, we found that one species of leafhopper can carry phylogenetically distant phytoplasmas. Received 23 April 2001/ Accepted in revised form 29 October 2001     

A New Natural Planthopper Vector of Stolbur Phytoplasma in the Genus Pentastiridius (Hemiptera: Cixiidae)

A new disease of sugar beet called Syndrome des Basses Richesses, which appeared in Burgundy and Franche-Comté, France, in 1991, is of uncertain aetiology. However, evidence for aerial transmission of the disease, symptom similarity with yellow wilt and preliminary results of phytoplasma detection, support the hypothesis of a phytoplasma being associated to the disease. A search for a natural phytoplasma vector, was conducted in Franche-Comté in 1997 and 1998, in an area where sugar beet crops had been affected since 1996. A cixiid, tentatively identified as Pentastiridius beieri, not described in the preceding years and not formerly reported as a phytoplasma vector, was present in sugar beet plots in high populations from June to August in 1997 and 1998. Individuals were captured and used for transmission experiments to periwinkle and sugar beet seedlings. They were further tested for the presence of a phytoplasma in their body, using PCR amplification of 16S rDNA of phytoplasmas. In 1997 and 1998, from 2% to 13.3% of the individuals carried a stolbur phytoplasma and insects which tested positive, appeared to have transmitted, through feeding, a stolbur phytoplasma to periwinkles and to sugar beets. This cixiid, whose vectoring capacity of stolbur phytoplasma to plants, is now clearly demonstrated, is available for experimental inoculations, in order to examine the role of phytoplasmas in the Syndrome des Basses Richesses, through the observation of symptom expression in phytoplasma-inoculated plants.     

Development of a specific assay using RISA for detection of the bacterial agent of 'basses richesses' syndrome of sugar beet and confirmation of a Pentastiridius sp. (Fulgoromopha, Cixiidae) as the economic vector

A technique for the specific diagnosis in insects of SBRp (the γ-3 proteobacterium associated with the syndrome 'basses richesses' (SBR) of sugar beet crops in eastern France), using the RISA (rDNA intergenic spacer analysis) technique, was developed. PCR using the Alb1/Oliv1 primer pair specifically amplified a 16S-ITS region of SBRp and produced a characteristic DNA fingerprint. This PCR assay did not detect other closely related organisms, including the Arsenophonus endosymbiont of Diaphorina citri , the secondary endosymbiont of Glycaspis brimblecombei , or ' Candidatus Phlomobacter fragariae', a related phytopathogenic γ-3 proteobacterium. Six different ribosomal operons, differing in their ITS region or partial 16S sequence, were identified in SBRp. PCR amplification with Alb1/Oliv1 of DNA samples from Hemiptera species (suborders Fulgoromorpha and Cicadomorpha) collected in sugar beet fields confirmed Pentastiridius sp. as the economic vector of SBR disease. The high percentage of field- Pentastiridius sp. specimens which tested positive for SBRp reflected the importance of SBR disease in sugar beet crops. This is the first time that the RISA technique has been used as a diagnostic test for a plant pathogenic bacterium in insects.     

Insecticide resistance management of permethrin and acephate against the cowpea curculio,Chalcodermus aeneus Boheman (Coleoptera: Curculionidae), a pest of the southern pea,Vigna unguiculata (L.) Walp.

To evaluate strategies for management of potential resistance of the cowpea curculio, Chalcodermus aeneus Boheman, to sprayer‐applied permethrin and acephate, five management regimes were evaluated on early, midseason and late sequential plantings of southern peas, Vigna unguiculata (L.) Walp. during 1991–1993. Management regimes were: (1) consecutive permethrin (0.11 kg a.i./ha early‐midseason‐late); (2) consecutive acephate (1.1 kg a.i.ha early‐midseason‐late); (3) consecutive mixture (0.055kg a.i./ha permethrin and 0.55kg a.i./ha acephate early‐midseason‐late); (4) alternation (0.11 kg a.i./ha permethrin early and 1.1 kg a.i./ha acephate midseason and late plantings); and (5) an untreated check early, midseason and late. The effect of management regime on the toxicities (LC₅₀) of permethrin and acephate was determined by topical application to next generation adult cowpea curculios reared from infested southern pea pods harvested from untreated plants in the management fields. In the field, infestation varied more by planting date than by management regime. Toxicity of permethrin to adults selected in the consecutive mixture regime was significantly lower in 1991 and 1992 late season and in 1993 midseason than in early season for the respective years. There was a seasonal decrease in the laboratory toxicity of acephate to adults with all management regimes.     

Synthesis of allylic trifluoromethyl ketones and their activity as inhibitors of the sex pheromone of the leopard moth, Zeuzera pyrina L. (Lepidoptera: Cossidae)

BACKGROUND: Trifluoromethyl ketones (TFMKs), structurally related to the pheromones, are good inhibitors of pheromone communication in insects. To determine their activity on Zeuzera pyrina L. (Lepidoptera: Cossidae), a polyphagous pest, the authors have prepared two diunsaturated TFMK analogues of the major (3) and the minor (4) pheromone components, and two monounsaturated ones (5, 6). Their biological activity in electroantennogram (EAG), wind tunnel and field tests is presented. RESULTS: The synthetic strategy to obtain the allylic TFMKs 3 and 5 is based on the reactions of diene 10 and 1‐octadecene with trifluoroacetaldehyde ethyl hemiacetal, followed by Dess–Martin oxidation of the resulting homoallylic trifluoromethyl alcohols. In EAG, topical application of analogues 3 and 4 on male antennae significantly reduced the pheromone response. In the wind tunnel, compound 4 reduced the number of contacts with the pheromone source. In the field, traps baited with mixtures of pheromone and inhibitors captured significantly fewer males than the pheromone alone. CONCLUSION: An efficient synthesis of allylic TFMKs is reported, with good overall yield, regiospecificity and diastereoselectivity. These compounds are good inhibitors of the pheromone in electrophysiology, wind tunnel and field tests. The results show the importance of two unsaturations at positions 2 and 13 of the trifluoroacyl group in the structure of the analogues, the latter being critical for inhibitory activity. Copyright © 2011 Society of Chemical Industry     

Bacterial leaf blight of strawberry (Fragaria (x) ananassa) caused by a pathovar of Xanthomonas arboricola, not similar to Xanthomonas fragariae Kennedy & King. Description of the causal organism as Xanthomonas arboricola pv. fragariae (pv. nov., comb. nov.)

A new bacterial disease of strawberry is described. This disease, called bacterial leaf blight of strawberry, is characterized by dry, brown necrotic leaf spots and large brown V-shaped lesions along the leaf margin, midrib and major veins. Symptoms are different from angular leaf spot of strawberry caused by the bacterium Xanthomonas fragariae . Strains of the bacterial leaf blight pathogen were characterized in a polyphasic approach by biochemical tests, fatty acid analysis, protein electrophoresis, serology, PCR, pigment analysis, ice-nucleation activity, AFLP analysis, DNA:DNA hybridization, pathogenicity and host range tests, and compared with a number of reference strains of X. fragariae and other Xanthomonas species. Bacterial leaf blight strains formed a homogeneous group in all tests, completely different from X. fragariae . They were the only strains causing leaf blight of strawberry upon artificial inoculation into strawberry. Fatty acid and protein electrophoretic analysis showed that the strains belong to the phenon X. campestris ( sensu latu , including pathovars now classified as belonging to X. arboricola ). AFLP analysis and DNA:DNA hybridization further clarified their taxonomic position as belonging to X. arboricola. The name X. arboricola pv. fragariae is proposed for the bacterium causing leaf blight of strawberry with strain PD2780 (LMG 19145) as pathovar type strain. Criteria for routine identification are given and the taxonomic status is discussed.     

Subacute and delayed toxicity of iminoctadine liquid formulation,which contains iminoctadine triacetate as an antifungal component on a nontarget domesticated insect,the silkworm,Bombyx mori L. (Lepidoptera: Bombycidae)

We investigated insecticidal effects of iminoctadine liquid formulation, a fungicide containing iminoctadine triacetate, on the silkworm Bombyx mori that is an important domesticated insect. Iminoctadine liquid formulation was incorporated in an artificial diet and fed to silkworms for 24 h on the first day of either the third or fourth instar, thereafter reared without the fungicide. Third instar larvae that ingested the diet containing 1% (wt/wt) iminoctadine liquid formulation died within 24 h (subacute toxicity), and those that ingested either 0.1% or 0.3% iminoctadine liquid formulation developed to the pharate fourth stage and then became deficient in molting (delayed toxicity). In fourth instar larvae, iminoctadine liquid formulation exhibited subacute toxicity and delayed toxicity at 0.3% and >1%, respectively. Furthermore, we fed the larvae a diet with iminoctadine liquid formulation for 24 h at different intervals in the inter-molting period of the third and fourth instar. Iminoctadine liquid formulation administered at an earlier stage in the inter-molting period exerted a more severe effect than a later administration. Iminoctadine triacetate, an anti-fungal ingredient in the iminoctadine liquid formulation, exhibited toxicity similar to that of the liquid formulation.