Responses of Rhynchophorus ferrugineus adults to selected synthetic palm esters: electroantennographic studies and trap catches in an urban environment

BACKGROUND: The red palm weevil (RPW), Rhynchophorus ferrugineus Olivier, accidentally introduced into the European countries facing the Mediterranean basin, is becoming the most serious pest for ornamental palms in the urban environment. In the present work, tests were conducted on the electroantennogram (EAG) and behavioural responses of RPW adults to five selected synthetic palm esters, ethyl propionate, ethyl butyrate, ethyl isobutyrate, ethyl lactate and ethyl acetate, to assess the application of a mass trapping technique in an urban environment. RESULTS: In the laboratory, EAG bioassays on RPW adults with the synthetic palm esters showed: (1) positive dose‐dependent responses; (2) differences among the treatments; (3) a greater response to ethyl propionate; (4) a higher sensitivity of female antennae compared with male antennae. In the urban environment, RPW behavioural responses, evaluated over six biweekly observations on pheromone‐ and molasses‐ baited traps, showed that more adults were caught by traps supplemented with ethyl propionate and ethyl acetate than by traps supplemented with only ethyl propionate. Similar catches were recorded in the traps supplemented with ethyl propionate or ethyl acetate. CONCLUSION: This study supports the application of the mass trapping implemented with synthetic palm esters as a potential tool for the management of RPW populations to protect ornamental palms in urban environments. Copyright © 2010 Society of Chemical Industry     

Host plant stimulation of detoxifying enzymes in a phytophagous insect

The midgut microsomal aldrin epoxidase of variegated cutworm larvae (Peridroma saucia, Hübner) fed bean or peppermint leaves was up to 10 and 45 times more active, respectively, than that of larvae fed a basic control diet. Large increases in oxidase activity and cytochrome P-450 levels also occurred in larvae fed mint plant constituents such as menthol menthone, α-pinene, and β-pinene. Mint-fed larvae were more tolerant of the insecticide, carbaryl, than bean-fed larvae.     

Host plant recognition by two odorant-binding proteins in Rhynchophorus ferrugineus (Coleoptera: Curculionidae)

BACKGROUND

Rhynchophorus ferrugineus, the red palm weevil (RPW), is a key pest that attacks many economically important palm species and that has evolved a sensitive and specific olfactory system to seek palm hosts. Odorant-binding proteins (OBPs) not only play crucial roles in its olfactory perception process but are also important molecular targets for the development of new approaches for pest management.

RESULTS

Analysis of the tissue expression profiles of RferOBP8 and RferOBP11 revealed that these two Rhynchophorus ferrugineus odorant binding proteins (RferOBPs) exhibited high expression in the antennae and showed sexual dimorphism. We analyzed the volatiles of seven host plants by gas chromatography–mass spectrometry and screened 13 potential ligands by molecular docking. The binding affinity of two recombinant OBPs to aggregation pheromones and 13 palm odorants was tested by fluorescence competitive binding assays. The results revealed that eight tested palm volatiles and ferrugineol have high binding affinities with RferOBP8 or RferOBP11. Behavioral trials showed that these eight odor compounds could elicit an attraction response in adult RPW. RNA interference analysis indicated that the reduction in the expression levels of the two RferOBPs led to a decrease in behavioral responses to these volatiles.

CONCLUSION

These results suggest that RferOBP8 and RferOBP11 are involved in mediating the responses of RPW to palm volatiles and to aggregation pheromones and may play important roles in RPW host-seeking. This study also provides a theoretical foundation for the promising application of novel molecular targets in the development of new behavioral interference strategies for RPW management in the future. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

The use of sniffing dogs for the detection of Rhynchophorus ferrugineus

The red palm weevil (RPW) Rhynchophorus ferrugineus (Olivier) (Coleoptera: Dryophthoridae) is the most serious pest of Canary Island date palms (Phoenix canariensis Hort. ex Chabaud) and date palms (Phoenix dactylifera L.). Early infestations of this invasive weevil are difficult to detect under field conditions. The adults are very elusive and not visible inside the dense frond of the palms. Efficient methods for detecting this pest are needed for its successful management under field conditions and in particular at ports of entry to avoid its' spreading via infested imported palms. The present study evaluated the ability of Rottweiler and Golden Retriever dogs (Canis familiaris L.) to detect Canary Island palms that were baited with RPW adults or larvae under field conditions. During these experiments, the dogs successfully detected 78% of the baits hidden in the crown of the palms. These encouraging results need to be confirmed by evaluation of the performance of sniffing dogs in detection of naturally infested palms of different species.     

Attraction and antennal response of the common wasp,Vespula vulgaris (L.), to selected synthetic chemicals in New Zealand beech forests

BACKGROUND: The common wasp, Vespula vulgaris (L.), and the German wasp, Vespula germanica (F.), are significant problems in New Zealand beech forests (Nothofagus spp.), adversely affecting native birds and invertebrate biodiversity. This work was undertaken to develop synthetic attractants for these species to enable more efficient monitoring and management. RESULTS: Seven known wasp attractants (acetic acid, butyl butyrate, isobutanol, heptyl butyrate, octyl butyrate and 2,4‐hexadienyl butyrate) were field tested, and only heptyl butyrate and octyl butyrate attracted significantly higher numbers of wasps than a non‐baited trap. Accordingly, a series of straight‐chain esters from methyl to decyl butyrate were prepared and field tested for attraction of social wasps. Peak biological activity occurred with hexyl butyrate, heptyl butyrate, octyl butyrate and nonyl butyrate. Polyethylene bags emitting approximately 18.4–22.6 mg day^?1 of heptyl butyrate were more attractive than polyethylene bags emitting approximately 14.7–16.8 mg day^?1 of heptyl butyrate in the field. Electroantennogram (EAG) studies indicated that queens and workers of V. vulgaris had olfactory receptor neurons responding to various aliphatic butyrates. CONCLUSION: These results are the first to be reported on the EAG response and the attraction of social wasps to synthetic chemicals in New Zealand beech forests and will enable monitoring of social wasp activity in beech forests. Copyright © 2009 Society of Chemical Industry     

Evaluation of the entomopathogenic fungiMetarhizium anisopliae andBeauveria bassiana against the red palm weevilRhynchophorus ferrugineus

The red palm weevil (RPW,Rhynchophorus ferrugineus (Olivier) (Coleoptera: Curculionidae) is one of the most severe pests of various palm species, including date palms. While examining the susceptibility of RPW to two entomopathogenic fungi,Metarhizium anisopliae andBeauveria bassiana, strains of the former were found to be more virulent than those of the latter, achieving 100% larval mortality within 6–7 days. The most virulent strains ofM. anisopliae were then tested on RPW eggs and adults. Incubation in a substrate treated withM. anisopliae spores increased egg mortality and reduced their hatchability. The total percentage mortality of eggs and hatched larvae was 80–82%, compared with 34% in the controls. RPW adults were challenged with two types of fungal formulation: dry powder and aqueous suspension. Cumulative adult mortality of 100% was achieved in 2–3 weeks for the dry rice-based formulation and in 4–5 weeks for the spore suspension. As a result of decreased longevity, treated females had a shorter oviposition period and three times lower fertility than the controls. Possible strategies for fungus application are discussed in the light of the high susceptibility of eggs and larvae to fungal infection. http://www.phytoparasitica.org posting July 19, 2006.     

斑鞘豆叶甲成虫对非寄主植物挥发物的触角电位和行为反应

为筛选对斑鞘豆叶甲Colposcelis signata（Motschulsky）成虫有生物活性的行为调控剂,选取非寄主植物16种挥发物,采用触角电位技术（Electroantennogram,EAG）和Y型嗅觉仪测定了斑鞘豆叶甲成虫对挥发物的触角电位及行为反应。结果表明：10^-1mol/L浓度下斑鞘豆叶甲成虫对6种萜烯类挥发物EAG反应较强,驱避反应显著,雄虫反应强于雌虫。成虫对（1R）-（+）-α-蒎烯和（-）-β-蒎烯的EAG反应显著强于其他4种萜烯类挥发物,对雄虫的驱避率分别为86.7%和81.3%。斑鞘豆叶甲对5种醇、醛类挥发物EAG反应差异显著,除芳樟醇外均表现引诱反应。雌虫对反-2-己烯-1-醇、2-乙基-1-己醇和反-2-己烯醛3种绿叶气味挥发物的引诱反应强于雄虫,其中反-2-己烯-1-醇的引诱作用最强,引诱率达68.9%,推测雌虫产卵定位与绿叶气味挥发物有关。斑鞘豆叶甲对5种其他挥发物的EAG反应相对值较低,具有引诱作用,雄虫反应均强于雌虫,雌、雄虫对水杨酸甲酯的反应强于其他4种挥发物。浓度反应结果发现当浓度从10^-2 mol/L增加到10^-1mol/L时,成虫对（1R）-（+）-α-蒎烯和（-）-β-蒎烯的EAG反应相对值稍降低,对（-）-β-蒎烯和β-月桂烯的驱避反应降低,表现出浓度阈值。但在10^-5 mol/L浓度下（1R）-（+）-α-蒎烯、（-）-β-蒎烯、（R）-（+）-柠檬烯和β-月桂烯仍然表现为明显的驱避作用,这些挥发物可作为驱避剂组分加以开发利用。     

Metabolism of a phosphoramidate by Pyricularia oryzae in relation to tolerance and synergism by a phosphorothiolate and isoprothiolane

Metabolism of dibutyl N-methyl-N-phenylphosphoramidate (BPA) by mycelial cells of Pyricularia oryzae was studied to elucidate the mechanism of synergism and negatively correlated cross-resistance in fungicidal action between phosphoramidates and phosphorothiolate derivatives. Rapid metabolism of BPA by a wild-type strain through hydroxylation and N-demethylation was observed. The metabolism was inhibited by diisopropyl S-benzyl phosphorothiolate (IBP; Kitazin P) and by isoprothiolane (diisopropyl 1,3-dithiolan-2-ylidenemalonate; Fuji-One). This inhibition of BPA metabolism is probably the mechanism of synergistic fungicidal action between the phosphoramidate and the thiol derivatives. The metabolism was, however, not inhibited by S-1358 (S-butyl S′-p-tert-butylbenzyl N-3-pyridyldithiocarbonimidate; Denmert) or triarimol [α-(2,4-dichlorophenyl)-α-phenyl-5-pyrimidinemethanol; EL-273], both of which are considered to be inhibitors of hydroxylation of a methyl radical in ergosterol biosynthesis. The metabolism of BPA by P. oryzae was much slower when mutants selected for IBP resistance and for isoprothiolane resistance were used. This phenomenon probably explains the differential sensitivity to phosphoramidate of wild-type strains and mutants resistant to the thiol derivatives.     

Current status of red palm weevil infestation in date palm plantations in Israel

The red palm weevilRhynchophorus ferrugineus (Olivier) (RPW) is the most serious pest of date palms in the Middle East. Weevil infestation was first detected in Israel in the summer of 1999 in date plantations in the Jordan Valley, on the west bank of the Jordan River and in the northern area of the Dead Sea. For 2 years following the discovery of the pest, prophylactic insecticide chemical treatments as well as adult weevil trapping were carried out over 450 ha of date palm plantations. Traps loaded with a commercial aggregation pheromone, ferrugineol, supplemented with ethyl acetate and a fermenting mixture of dates and sugarcane molasses, were posted in high trap density (approx. ten traps per ha) in order to monitor weevil infestation and reduce the RPW population by mass trapping. A significant decrease in number of trapped beetles and infested trees was observed in 2001 and continued in the following years. No infested trees have been found since 2002, indicating a decrease in RPW population. The sex ratio of trapped adults during 3 years of study was significantly female-biased (∼2.5:1). Therefore, mass trapping might have played a significant role in the suppression of RPW populations in date plantations. http://www.phytoparasitica.org posting Dec. 19, 2004.     

Optimizing components of pheromone-baited trap for the management of red palm weevil,Rhynchophorus ferrugineus (Coleoptera: Curculionidae) in date palm agro-ecosystem

Journal of Plant Diseases and Protection - The red palm weevil (RPW), Rhynchophorus ferrugineus (Olivier), is managed in date palm groves, inter alia, with food-baited pheromone traps. Laboratory...     

Ilyonectria palmarum sp. nov. causing dry basal stem rot of Arecaceae

During surveys conducted in 2010–2013, a complete breakage or bending of the trunk and a dry basal stem rot were observed on containerised Brahea armata, B. edulis, Howea forsteriana and Trachycarpus princeps plants in different nurseries located in eastern Sicily (southern Italy). A cylindrocarpon-like species was consistently obtained from diseased palm tissues, while known pathogens of these hosts such as Ganoderma, Phytophthora and Thielaviopsis were not found associated with symptomatic tissues or isolated on standard or selective media. A total of 40 cylindrocarpon-like isolates were collected and characterised based on morphology and DNA phylogeny. Multigene analyses based on the β-tubulin, histone H3, translation elongation factor 1-α, and the internal transcribed spacers (ITS1, 5.8S, ITS2) genes facilitated the identification of a new species, described here as Ilyonectria palmarum. The pathogenicity of one representative isolate collected from each palm species was tested on plants cultivated under nursery conditions and in a growth chamber. All isolates were pathogenic to B. armata, B. edulis, H. forsteriana, and T. princeps and symptoms identical to that observed in nurseries were reproduced. Dry basal stem rot and stem bending caused by Ilyonectria palmarum represents a potentially serious problem for nurseries cultivating containerised palms.     

The Potential of Semiochemicals for Control of Phorodon humuli (Homoptera: Aphididae)

Field experiments employing yellow water-traps with vials releasing methyl salicylate, butyl isothiocyanate, 4-pentenyl isothiocyanate and diethyltoluamide were conducted during the spring migration of Phorodon humuli (Schrank), with the aim of identifying substances which might be used in the field to deter landing on hop plants. Methyl salicylate and the two isothiocyanates reduced trap catches of P. humuli. During the spring of 1994 a slow-release formulation of methyl salicylate and a β-acid-rich hop resin sprayed on to hop plants did not reduce aphid infestations significantly. In autumn cis,cis-nepetalactol, the main component of P. ‘humuli’s sex pheromone, prepared by various synthetic routes, increased trap catches of males and gynoparae equally. Catches of males in pheromone traps situated in a hop garden decreased with increasing trap height. Catches of males in traps charged with increasing doses of the cis,cis-nepetalactol peaked at 1 mg and then plateaued, whereas catches of gynoparae peaked similarly at 1 mg and then decreased. The effects of kairomones from an extract of the primary host, sex pheromone and a visual cue from yellow compared with clear water-traps were additive. The prospects for developing a semiochemicals-based control strategy against P. humuli, using some or all of the above elements, are discussed.     

Management of wheat blast with synthetic fungicides,partial resistance and silicate and phosphite minerals

Field trials conducted on a yellow-red latossol (pH 6.0), replicated in 2010 and 2011, sought to examine the effect of silicon, phosphite minerals, synthetic fungicides and genetic resistance for wheat blast management (Magnaporthe grisea) in Central Brazil. Disease intensity was measured on cvs. BRS 264 and BR18 subjected to the following Si treatments: pre-plant furrow application of Ca & Mg silicate (300 kg ha^-1); post-plant scattered application of Ca & Mg silicate on top of the soil (1 ton ha^-1); multiple foliar SiO₂ applications (30 g l ^-1); and non-treated control. Blast incidence and severity were scored. Further experiments were conducted on cv. BR-264, for examination of the effect of potassium phosphite and synthetic fungicides on wheat blast intensity, with the following treatments: K₂HPO₃ (1ml l ^-1); epoxinazole + pyraclostrobin (700 ml ha^-1); tebuconazole (600 ml ha^-1); tebuconazole + trifloxystrobin (750 ml ha^-1); and non-treated control. In 2010, disease intensity was lower than in 2011. In the silicate experiments, disease was significantly lower when plants were treated with foliar or furrow silicate. Si applications significantly reduced disease in BRS-264. While BR-18 consistently demonstrated lower disease levels, cv. BRS-264 generally responded more markedly to silicon applications. In the phosphite/fungicide experiment of 2010, all treatments reduced disease when compared with the control, and in 2011 phosphite efficiency was not significantly different from some fungicide treatments. Synthetic fungicides demonstrated an average blast control of 55% by severity values. Yields were increased in the phosphite-treated plots (by 9–80%), in the Si treatments (by 26–92%), and more so, and more consistently, with synthetic fungicides (by 90–121%). Combined results of all field studies, carried out under environmental conditions highly conducive to disease, indicated that control of wheat blast necessitates the joint integration of several alternatives for efficient disease management.     

Antifungal activity of the essential oil of Zanthoxylum bungeanum and its major constituent on Fusarium sulphureum and dry rot of potato tubers

The composition of the essential oil of Zanthoxylum bungeanum was analyzed by gas chromatography-mass spectrometry (GC-MS). A total of 35 components, which constitute 99.10% of the oil, were identified. The major constituent was α-pinene (19.59%). Minimum inhibitory concentrations (MICs) of the essential oil and α-pinene against Fusarium sulphureum were determined to be 6.25% and 12.50%, respectively. A determination of the antifungal activity and inhibitory effect of the essential oil and α-pinene showed that the essential oil more significantly decreased cell membrane integrity and inhibited spore germination than α-pinene. Observations using scaning electron microscope revealed morphological modification including mycelium asymmetry, hyphal swelling, curling, and a secretory appearance. Ultrastructural alterations were also observed including cell empty cavity and osmiophilic granule generation. In vivo testing showed that the oil and α-pinene effectively controlled dry rot of potato inoculated with F. sulphureum. These findings indicated that the oil and α-pinene directly inhibit fungal growth, and the essential oil showed pronounced potential than α-pinene.     

Spread of local electroantennogram response of the European corn borer, Ostrinia nubilalis

The electroantennogram (EAG) responses of male moths of the European corn borer (Ostrinia nubilalis) to locally applied pheromone, (Z)-11-tetradecenyl acetate, were studied with multiple electrodes. The amplitude of the locally elicited EAG was different depending on the stimulated point and also on the recorded locus, and a gradient in the amplitude was observed along the antennal axis. The locally stimulated region responded as a local negative deflection relative to the resting region, and the response spread from the stimulated point in an asymmetric way, more effectively in the proximal direction than in the distal direction. A possible mechanism of the local EAG spread is discussed.     

Summation and gradient characteristics of local electroantennogram response of the European corn borer, Ostrinia nubilalis

Summation and gradient characteristics of the electroantennogram (EAG) responses of male moths of the European corn borer (Ostrinia nubilatis) to their pheromone, (Z)-11-tetradecenyl acetate, were studied. Direct evidence that the summation of the locally elicited EAGs contribute to the overall response amplitude is presented; if two simultaneously stimulated loci were separated by more than 1 mm, the observed response was the summation of the two independent local EAGs. Configuration of the local EAG response was obtained at various loci of the antenna. It was demonstrated that a gradient in the amplitude of the local EAG exists along the antennal axis and that this gradient has its origin in the epithelial layer of the antenna. Several possible morphological and physiological factors affecting the response characteristics were considered.     

不同水稻挥发物对稻虱红螯蜂雌蜂的引诱作用

为了解水稻挥发物在稻虱红螯蜂雌蜂寻找寄主过程中的作用,采用触角电位仪和Y-型嗅觉仪测定了稻虱红螯蜂雌蜂对不同水稻挥发物的触角电位（electroantennogram,EAG）反应和行为反应。不同生育期水稻挥发物中,稻虱红螯蜂雌蜂对幼苗期挥发物的EAG反应最强烈,显著高于分蘖期及抽穗期。行为测定显示中优5617和湘优109幼苗期稻株挥发物对稻虱红螯蜂雌蜂具有显著引诱作用。稻虱红螯蜂雌蜂对虫害植株挥发物的EAG反应最强烈,与健康植株和机械损伤植株之间均存在显著差异。稻虱红螯蜂雌蜂明显趋向于湘优109、黔香优302和宜香481三个品种的虫害处理植株。结果表明,幼苗和虫害稻株挥发物在稻虱红螯蜂雌蜂寻找寄主过程中起到了重要作用。     

Host plant induction of glutathione S-transferase in the fall armyworm

The influence of various host plants on glutathione S-transferase activity was studied in the fall armyworm, Spodoptera frugiperda (J. E. Smith). Fall armyworm larvae were maintained on a semidefined artificial diet until the end of the fifth instar. The newly molted sixth instar larvae were then fed fresh leaves of various host plants for 2 days prior to glutathione S-transferase assays using 3,4-dichloronitrobenzene as substrate. The order of the midgut glutathione S-transferase activity of larvae after the worms fed on these plants was: mustard > turnip > cowpeas > peanuts > cotton > corn > cucumber > potato > Bermudagrass > millet > sorghum > soybeans. The difference in the transferase activity between soybean- and mustard-fed larvae was 10-fold. Kinetic study revealed a quantitative, but no qualitative difference in the glutathione S-transferase between soybean- and cowpea-fed larvae. Monoterpenes, such as α-pinene, β-pinene, menthol, and peppermint oil, had no effect on the enzyme. Cowpea-fed larvae were more tolerant of the insecticides diazinon, methamidophos, and methyl parathion than soybean-fed larvae were. These new observations help explain what has been happening in the field and might be of use in the development of pest management programs.     

Effects of β-pinene,a nonsubstituted monoterpene,on rat liver mitochondria

β-Pinene uncouples oxidative phosphorylation and inhibits respiration in isolated rat liver mitochondria. The uncoupling effects are observed at lower concentrations (100 to 200 μM) than the inhibition of respiration (400 μM). At low concentrations, the effects observed could be explained by an increase of the passive permeability of the mitochondrial membrane produced by the terpene. Higher concentrations seemed to inhibit respiration through an effect on the electron transport chain. At the highest concentrations tested (600 to 1200 μM), β-pinene seemed to produce a partial resealing of the mitochondrial membrane. All effects can be explained by the interaction of β-pinene with the mitochondrial membrane. Other hydrophobic molecules tested do not show the effects of β-pinene or limonene on mitochondria.