Is attract‐and‐kill technology potent against insecticide‐resistant Lepidoptera?

Attract-and-kill techniques, associating an attractant and a contact insecticide in a sticky formulation, are a new way of controlling Lepidopteran pests. Insecticide resistance may, however, limit the effectiveness and even the attractiveness of such formulations where resistance pleiotropic effects influence pheromone perception. We have tested this hypothesis on resistant codling moths Cydia pomonella (L) using a commercial formulation containing (E,E)-8,10-dodecadien-1-ol (codlemone), the major component of the sex pheromone, as an attractant and permethrin as toxicant. We first compared the attractiveness of codlemone in a wind tunnel and the contact toxicity of pyrethroids on males of one susceptible and of three strains selected for resistance to diflubenzuron, deltamethrin and azinphos-methyl. The dose-response relationships of males of susceptible and resistant strains to codlemone did not differ significantly. The deltamethrin-selected strain was the most resistant to pyrethroids, exhibiting 138-, 25- and 18-fold resistance ratios to deltamethrin, cypermethrin and permethrin, respectively. The efficiency of the attracticide formulation, applied successively on filter paper support, glass support and wood support, was estimated by recording the mortality delay of males after natural contact with the formulation in the wind tunnel. The deltamethrin- and diflubenzuron-resistant strains were significantly less affected than the susceptible strain by contact with the attracticide on the wooden support, exhibiting 58- and 2.3-fold greater LT50 ratios, respectively. Mortality of deltamethrin-resistant moths did not exceed 40% after 48 h. The LT50 value was significantly greater on filter paper support than on the two other supports. Surprisingly, the LT50 ratio of the deltamethrin-resistant strain was markedly higher on filter paper support (1021-fold), which was more absorbent, than on the glass support (31-fold). No sublethal effects in terms of pheromone response, mating or fecundity occurred in moths surviving contact with the attracticide. Choice of insecticides in attracticide formulations will be influenced by the resistance background of the target pests. Principles of insecticide resistance management may also be applied to attract-and-kill technology by alternating with other insecticides or control methods.     

How can natural hybridisation between self‐compatible and self‐incompatible species be bidirectional?

Self‐compatible (SC) plants often deposit pollen on their own stigmas before flowers open. Thus, if we find natural hybrids between a SC species and a closely related self‐incompatible (SI) species, the pollen donor is usually expected to be the SC species. However, in previous studies of naturally occurring mixed populations of invasive Cakile maritima (SI) and Cakile edentula (SC) in Australia, hybridisation was found to have been bidirectional. Here, we explored the floral development of these species in order to test the hypothesis that there might be a short opportunity for pollinators to visit open SC flowers before the self‐pollen is released. Results indicated that both species showed reverse herkogamy during early development, though by the time pollen was ripe the four long anthers always overtopped the stigma; in C. maritima, most of the short anthers remained below the stigma. In both species, ripe, compatible pollen was able to germinate on the stigmatic surface at all stages of floral development. Anther dehiscence commenced earlier in C. edentula and well before flowers opened, in contrast to C. maritima, but the timing of pollen release varied between individual flowers, with a small proportion of uncontaminated stigmas after flowering; therefore, C. edentula can be either pollen recipient or pollen donor when interspecific outcrossing occurs. In summary, our results suggest that the variation between individual flowers of C. edentula contributed to the bidirectional hybridisation despite being a predominant selfer, providing new insights into plant colonisation.     

Is acetyl/butyrylcholine specificity a marker for insecticide‐resistance mutations in insect acetylcholinesterase?

Substrate specificity has been widely studied in vertebrate cholinesterases and it has been shown that two phenylalanines in the acyl pocket of acetylcholinesterase govern the acceptance of the acetyl/butyryl moiety of the choline esters. As an insecticide‐resistance mutation has been evidenced in the acyl pocket of Drosophila melanogaster and Musca domestica acetylcholinesterase we investigated the possibility of linking changes in acetyl/butyrylthiocholine specificity with mutations in insect acetylcholinesterase. We thus analyzed the effect of 28 mutations in Drosophila enzyme on acetyl/butyrylthiocholine, N‐methyl/N‐propyl‐carbamates and ethyl/methyl‐paraoxon preference. It appeared that the highest changes on acetyl/butyrylthiocholine and N‐propyl/N‐methyl‐carbamates preference were due to mutations in the acyl pocket. Nevertheless, other insecticide‐resistance mutations, not located in the acyl pocket, also modified these substrate preferences. Moreover, the effect of mutations in the acyl pocket was hidden when some other insecticide‐resistance mutations were combined in the enzyme. Consequently, acetyl/butyrylthiocholine preference alteration cannot be used as a marker to localize a mutation in the insect AChE. © 2000 Society of Chemical Industry     

Can the parasitic weeds Striga asiatica and Rhamphicarpa fistulosa co‐occur in rain‐fed rice?

Striga asiatica and Rhamphicarpa fistulosa are important parasitic weeds of rain‐fed rice, partly distributed in similar regions in sub‐Saharan Africa (SSA). It is not evident whether their ecologies are mutually exclusive or partially overlapping. In Kyela, a rice‐growing area in south Tanzania where both parasites are present, three transects of about 3 km each across the upland–lowland continuum were surveyed in June 2012 and 2013. A total of 36 fields were categorised according to their position on the upland–lowland continuum as High, Middle or Low and soil samples were taken. In each field, parasitic and non‐parasitic weed species were identified in three quadrats. Additionally, in two pot experiments with four different moisture levels ranging from wilting point to saturation, influence of soil moisture on emergence and growth of parasites was investigated. Striga asiatica was observed in higher lying drier fields, while R. fistulosa was observed in the lower lying wetter fields. Furthermore, non‐parasitic weed species that were exclusive to S. asiatica‐infested fields are adapted to open well‐drained soils, while species that were exclusive to R. fistulosa fields are typical for wet soils. The experiments confirmed that S. asiatica is favoured by free‐draining soils and R. fistulosa by waterlogged soils. These results imply that changes in climate, specifically moisture regimes, will be crucial for future prevalence of these parasitic weeds. The non‐overlapping ecological range between their habitats suggests that their distribution and associated problems might remain separate. Thus, management strategies can be focused independently on either species.     

Can the storage effect hypothesis explain weed co‐existence on the Broadbalk long‐term fertiliser experiment?

Understanding how plant species with similar resource requirements co‐exist has been a long‐standing ecological question with several theoretical explanations. One potential mechanism is the storage effect hypothesis. According to this hypothesis, species co‐exist because they differ in when they are most actively using resource and, therefore, respond differently to environmental perturbation. The hypothesis is based on two main assumptions: (i) two competitors have different responses to climate and (ii) the responses to climate are mediated by changes in the relative importance of intra‐ and interspecific competition. The hypothesis could provide useful insights into the role of climate in maintaining weed species diversity and potential shifts in dominant species under climate change. This study tested the basic principles of the storage effect hypothesis on weed communities using data from the Broadbalk long‐term fertiliser experiment. Relative abundance of weeds in 10 plots with contrasting fertility but no herbicides was assessed for 21 years. Multivariate analyses and generalised additive mixed models were used to analyse the data. The following pairs of species were found to be adapted to similar fertiliser levels, but diverged in their response to climate: (i) Papaver rhoeas–Tripleurospermum inodorum, (ii) Medicago lupulina–Vicia sativa and (iii) Scandix pecten‐veneris–Ranunculus arvensis. Contrasting responses to spring temperature within these species pairs modified the competition balance providing evidence for the storage effect hypothesis and helping to explain weed co‐existence in the Broadbalk experiment.     

Is <Emphasis Type="Italic">Roesleria subterranea</Emphasis> a primary pathogen or a minor parasite of grapevines? Risk assessment and a diagnostic decision scheme

In the past the root rot pathogen Roesleria subterranea (Ascomycota) was generally considered as a minor parasite, a view with which we were often confronted during field work in German wine-growing regions where this ascomycete recently caused serious problems in established vineyards and at replant sites. To irrevocably demonstrate that R. subterranea is not a minor, but a primary pathogen of grapevines (and fruit trees) a pest risk analysis was carried out according to the guidelines defined by EPPO standard series PM 5, which defines the information needed, and contains standardised, detailed key questions and a decision support scheme for risk analysis. Following the provided decision scheme, it becomes apparent that R. subterranea must be considered as a serious, primary pathogen for grapevines and fruit trees that can cause massive economic losses. Based on the literature, the pathogen seems to be ubiquitous in wine growing regions in cool climates of the northern hemisphere. It is likely that because of its growth below ground, the small fruiting bodies, and ambiguous symptoms above ground, R. subterranea has been overlooked in the past and therefore, has not been considered as primary pathogen for grapevine. Available published information together with experience from field trials was implemented into a diagnostic decision scheme which will, together with the comprehensive literature provided, be the basis (a) to implement quick and efficient diagnosis of this pathogen in the field and (b) to conduct risk analysis and management in areas where R. subterranea has not established yet.     

Regulated non‐quarantine pests: fact or fiction?

A new category of officially regulated pests has been introduced during the past decade. The aim of this new categorization is to protect plant health and, in particular, farmers’ and growers’ crops against the introduction of pests via propagation material. The phytosanitary term ‘regulated non‐quarantine pests’ (RNQPs) is relatively new. It was introduced in 1997 as part of the new revised text of the International Plant Protection Convention. These RNQPs differ from the common category of quarantine pests in that they can be widespread within the territory of concern. Unlike quarantine pests, a level of tolerance could be applied for RNQPs infesting certain plants for planting. Some certification systems for the production of propagation material may specify certain tolerance levels, however, these systems are usually not regulated by national plant protection organizations and the tolerance levels are usually not based on scientific evidence. To date, only a few countries have applied the concept of RNQPs: notably Uruguay and Brazil. To apply the concept and, in particular, to determine specific tolerance levels presents many challenges. The concept may be embraced in the coming years by the European Community as part of the revision of the EU Council Directive 2000/29/EC.     

Are herbicide‐resistant crops the answer to controlling Cuscuta?

BACKGROUND: Herbicide‐resistant crop technology could provide new management strategies for the control of parasitic plants. Three herbicide‐resistant oilseed rape (Brassica napus L.) genotypes were used to examine the response of attached Cuscuta campestris Yuncker to glyphosate, imazamox and glufosinate. Cuscata campestris was allowed to establish on all oilseed rape genotypes before herbicides were applied. RESULTS: Unattached seedlings of C. campestris, C. subinclusa Durand & Hilg. and C. gronovii Willd. were resistant to imazamox and glyphosate and sensitive to glufosinate, indicating that resistance initially discovered in C. campestris is universal to all Cuscuta species. Glufosinate applied to C. campestris attached to glufosinate‐resistant oilseed rape had little impact on the parasite, while imazamox completely inhibited C. campestris growth on the imidazolinone‐resistant host. The growth of C. campestris on glyphosate‐resistant host was initially inhibited by glyphosate, but the parasite recovered and resumed growth within 3–4 weeks. CONCLUSION: The ability of C. campestris to recover was related to the quality of interaction between the host and parasite and to the resistance mechanism of the host. The parasite was less likely to recover when it had low compatibility with the host, indicating that parasite‐resistant crops coupled with herbicide resistance could be highly effective in controlling Cuscuta. Published 2009 by John Wiley & Sons, Ltd.     

Can rice genetic diversity reduce Echinochloa crus‐galli infestation?

Pot and field experiments were conducted to test whether rice genetic diversity can reduce Echinochloa crus-galli infestation through rice variety mixed-plantings. Two weed-suppressive rice ( Oryza sativa ) varieties, Guodao No. 1 (GD) and PI312777 (PI), and three non-suppressive varieties, Xiushui No. 63 (XS), Zhongjian No. 2 (ZJ) and Chunjiang No. 016 (CJ) were used. Monocultures (GD, PI, XS, ZJ and CJ), two-variety mixtures (GD + XS, GD + ZJ, GD + CJ, PI + XS, PI + ZJ, PI + CJ) and three-variety mixtures (GD + PI + XS, GD + PI + ZJ and GD + PI + CJ) were tested. Effects of herbicide on rice grain yield of non-suppressive varieties were compared between monocultures and mixtures. Pot experiment showed that E. crus-galli germination rate in all mixed-planting except CJ + PI, and E. crus-galli biomass in mixed-planting with GD decreased compared with monocultures. In a field experiment, E. crus-galli density decreased in all mixed-planting models of XS and CJ and ZJ + GD. Echinochloa crus-galli biomass reduction was found in XS + GD, XS + GD + PI, ZJ + GD and CJ + GD. Rice grain yield increased in XS + GD, ZJ + GD, CJ + GD, CJ + PI and CJ + GD + PI. Rice grain yields of non-suppressive varieties under mixtures without herbicides were lower than that in monoculture with full herbicide, but were not significantly different from monocultures with half rate herbicide. Moreover, rice yields of ZJ and CJ under mixtures with half rate herbicides did not decrease compared with monocultures with full rates. The results suggested that rice genetic diversity could reduce E. crus-galli infestation and herbicide utilisation through rice variety mixed-planting.     

近50 a中国≥10 ℃有效积温时空演变

根据全国583个气象站点近50 a（1961-2010年）日均气温资料,以ArcGIS为技术平台,采用反距离插值和Mann Kendall趋势性检验等方法,研究了我国≥10 ℃有效积温等值线中心和典型有效积温带面积的变化规律,以及≥10 ℃有效积温、起始时间和持续时间的时空分布特征。结果表明：我国≥10 ℃有效积温的时空分布在1985年前后差异性显著。≥10 ℃有效积温整体上呈上升趋势,其变化率在0~10 ℃•d•a^-1,≥10 ℃典型有效积温带整体北移显著。≥10 ℃有效积温为0~3 400 ℃•d的区域面积显著减小,而 ≥10 ℃有效积温为3 400~8 000 ℃•d的区域面积明显增加,增速达2.0×10⁴ km²•a^-1。1985年后我国≥10 ℃有效积温起始时间提前和持续时间增加的区域面积显著增加;有效积温的起始时间整体有所提前,提前幅度集中在0~4 d•(10a)^-1;有效积温持续时间均有所增加,增加梯度集中在0~6 d•(10a)^-1。     

Identification of a novel point mutation in the <Emphasis Type="Italic">β</Emphasis>-tubulin gene of <Emphasis Type="Italic">Botrytis cinerea</Emphasis> and detection of benzimidazole resistance by a diagnostic PCR-RFLP assay

The molecular basis of resistance to benzimidazole fungicides with laboratory and field mutant isolates of Botrytis cinerea was investigated. After chemical mutagenesis with N-methyl-N-nitrosogouanidine (NMNG) two different benzimidazole-resistant phenotypes were isolated on media containing carbendazim or a mixture of carbendazim and diethofencarb. The mutant isolates from the fungicide-mixture-containing medium were moderately resistant to carbendazim with wild-type tolerance to diethofencarb while mutant isolates from carbendazim-containing medium were highly resistant to carbendazim but sensitive to diethofencarb. The studied field isolates were highly resistant to benzimidazoles and sensitive to diethofencarb. Study of fitness characteristics of benzimidazole highly-resistant isolates showed that the resistance mutation(s) had no apparent effect on fitness-determining parameters. Contrary to this, the moderately benzimidazole-resistant strains, with no increased diethofencarb sensitivity, had a significant reduction in certain ecological fitness-determining characteristics. Analysis of the sequence of the β-tubulin gene revealed two amino acid replacements in the highly benzimidazole-resistant mutants compared to that of the wild-type parent strain. One was the glutamic acid (GAG) to alanine (GCG) change at position 198 (E198A), identified in both laboratory and field highly benzimidazole-resistant isolates, a mutation previously implicated in benzimidazole resistance. The second was a novel benzimidazole resistance mutation of glutamic acid (GAG) to glycine (GGG) substitution at the same position 198 (E198G), identified in a highly benzimidazole-resistant laboratory mutant strain. Molecular analysis of the moderately benzimidazole-resistant strains revealed no mutations at the β-tubulin gene. A novel diagnostic PCR-RFLP assay utilising a BsaI restriction site present in the benzimidazole-sensitive (E198) but absent in both resistant genotypes (E198G and E198A) was developed for the detection of both amino acid replacements at the β-tubulin gene.     

<Emphasis Type="Italic">Amaranthus</Emphasis> spp.: a new host of “<Emphasis Type="Italic">Candidatus</Emphasis> Phytoplasma aurantifolia”

Mexico is considered to be one of the centers of origin of grain amaranth species. Recently, plants with abnormal anatomical features were observed in experimental fields established in Central Mexico. The most noticeable symptoms, which consisted of excessive stem and bud proliferation, mosaics and unusual coloration, suggested that they might be phytoplasma-induced disorders. Thus, different accessions of grain amaranth (Amaranthus hypochondriacus and A. cruentus) plants were subjected to polymerase chain reaction (PCR) analysis specifically designed to detect these pathogens. Two universal phytoplasma-specific primer pairs were tested in a nested PCR assay, with primer pair P1/tint (followed by primer pair R16F2/R16R2). Further DNA sequencing analysis of the resulting amplicons indicated that these phytoplasmas may be related to others already affecting important agricultural crops in Mexico, such as soybean. Data are presented that disclose the etiology of these syndromes by the use of molecular techniques. To the best of our knowledge, this finding constitutes the first report of a phytoplasma-related disease in grain amaranth.     

East Adriatic—a reservoir region of severe <Emphasis Type="Italic">Citrus tristeza virus</Emphasis> strains

Citrus tristeza virus (CTV) represents one of the major threats to citrus production worldwide. In the East Adriatic region, CTV symptoms are mostly absent due to traditional citrus grafting on trifoliate orange (Poncirus trifoliata), a CTV-tolerant rootstock. Therefore, the virus has been continuously spreading by the propagation of infected material. The genetic variability of CTV was studied on nineteen citrus samples, collected from orchards in the coastal region of Croatia, Montenegro and Albania, that previously tested positive by ELISA and immunocapture RT-PCR. Single-strand conformation polymorphism of the amplified coat protein gene demonstrated the presence of different CTV variants in each amplicon, while sequence analysis of cloned CP gene variants confirmed their clustering into six out of the seven phylogenetic groups so far delineated. Four of these groups include sequences of severe quick decline, seedling yellows and stem-pitting (SP) isolates, thought to be found only rarely in the Mediterranean region. Regardless of the lack of symptoms in the field, CTV isolates from the East Adriatic displayed high genetic variability and pathogenic potential, additionally confirmed by biological characterisation. The high percentage of mixed infections suggest the potential for further diversification and a greater risk of severe variants spreading into new areas.