Androconial hairbrushes of the Syntomis (Amata) phegea (L.) group (Lepidoptera, Ctenuchinae): a synapomorphic character supported by sequence data of the mitochondrial 16S rRNA gene

Males of several palaearctic Syntomis/Amata species (Lepidoptera: Arctiidae) possess androconial hairbrushes in connection with the foreleg coxa. The cuticular structure of these potentially behaviour-related and pheromone dissipating brushes is described. Such male-specific organs and signals play a crucial role in the female choice procedure. The presence of hairbrushes was found in 17 out of 28 inspected species of the tribe Syntomini. All members of the Syntomis phegea group (Europe to Central Asia, as well as Caspian, Caucasian and near-middle East species) have these structures, and only three oriental and south Asian, but none of three African species, carry this trait. The common genetic base of this morphological character is supported by an analysis of mitochondrial 16S rRNA from 19 representative taxa; species with hairbrushes form a monophyletic clade and the brushes are a synapomorphic character. This genetic finding corroborates the ethological significance of these organs. Phylogenetic data show a substantial genetic divergence between the tribe Ctenuchini (New World species) and the Old World Syntomini. Furthermore, DNA sequence data suggest a split of the genus Amata (sensu Obraztsov, 1966) in two distinct genera, Amata (without hairbrushes) and Syntomis (with hairbrushes).     

Seasonal population fluctuations of the diamondback moth,Plutella xylostella (L.) (Lep.: Plutellidae) on different cauliflower cultivars

The diamondback moth, Plutella xylostella (L.) (Lep.: Plutellidae) is one of the most important pests of cruciferous plants throughout the world. In recent years, it has been identified as a serious pest of the cauliflower fields in Tehran province. Resistance of P. xylostella to all main groups of insecticides has been recorded and it is ranked in the 20 most resistant pest species reported until now. According to many researchers, to solve the problem of pest resistance to chemical pesticides, an integrated pest management programme should be used. Despite this condition, it seems that the use of resistant cauliflower cultivars is an appropriate policy for integrated control of the pest in the field. In order to identify the most resistant cultivar in the field, eight cauliflower cultivars in a completely randomised design with five replicates were planted at the Shahed University research field (south of Tehran). Density of eggs, larvae and pupae of P. xylostella were measured every 10 days in these cultivars. The results showed that there is no significant difference between numbers of eggs per plant on different cultivars. But number of larvae and pupae per plant were significantly different among different cultivars. Smilla and Snow mystique cultivars had the highest number of larvae and pupae. On the other hand, Buris and Snow crown cultivars had the lowest number of pupae and Snow crown and SG cultivars had the lowest number of larvae per plant. According to the results, the Buris and Snow crown cultivars had the lowest infestation and had a kind of resistance to pest.     

Resistance of the codling moth Cydia pomonella (L.) (Lep., Tortricidae) to pesticides in Israel

Abstract:  Resistance of the codling moth Cydia pomonella (L.) (Lep., Tortricidae) to the organophosphorus compound (OP) azinphosmethyl was observed in apple orchards in Israel. The level of resistance varied with the pest control strategy. Compared with a sensitive laboratory population, the resistance level was highest in insects from the preventative pest control strategy, intermediate in integrated pest management (IPM) orchards, and relatively low in the organic orchards. The level of azinphosmethyl resistance in larvae (but not in adults) exposed for 17 generations in the laboratory to a pesticide-free diet was reduced by 50%. Codling moth larvae resistant to azinphosmethyl were also resistant to various insect growth regulators (IGRs). The IGRs include three chitin synthesis inhibitors (diflubenzuron, novaluron and teflubenzuron), two juvenile hormone mimics (pyriproxyfen and fenoxycarb) and one ecdysone agonist (methoxyfenozide). Codling moth resistant to azinphosmethyl was tolerant to methoxyfenozide and novaluron without previous history of application in apple orchards, indicating the possibility of cross-resistance. According to this study, managing resistance programs in apple orchards should be based on IPM principles with minimum use of conventional neuroactive pesticides.     

Selection for resistance to acetamiprid and various other insecticides in the diamondback moth, Plutella xylostella (L.) (Lep., Plutellidae)

Abstract:  A diamondback moth (DBM) colony (KOBII) originally collected from cabbage fields of Iwaoka-cho in Kobe City, Japan, where acetamiprid is the primary insecticide for DBM control was selected for studies on resistance to acetamiprid, phenthoate, esfenvalerate and cartap, using the leaf-dipping method. Resistance to acetamiprid was slow to develop in KOBII compared with the other insecticides. Three selection experiments each with phenthoate and esfenvalerate yielded a resistance ratio (RR) of 140 and 222, respectively, in the selected strains compared with a part of KOBII that was not exposed to any insecticide (KOBII-NS). Three selection experiments with cartap also gave an RR of 15. However, six selection experiments with acetamiprid yielded an RR of just 9.5 in the selected strain. When cross-resistance to acetamiprid was evaluated, the cartap-resistant strain showed a moderate level of cross-resistance to acetamiprid. In the case of the phenthoate-resistant strain, a very low cross-resistance to acetamiprid was observed. There was however no discernible cross-resistance to acetamiprid in the esfenvalerate-resistant strain.     

Effect of the entomopathogenic fungus Metarhizium anisopliae (Metsch.) Sorokin on cellular defence response and oxygen uptake of the wax moth Galleria mellonella L. (Lep., Pyralidae)

Remarkable changes in the cellular response and oxygen uptake in the wax moth Galleria mellonella were observed when larvae were infected with the entomopathogenic fungus Metarhizium anisopliae . The number of haemocytes increased 48, 72 and 96 h after infection with fungal conidiospores. Extensive blebbing of the cell membrane in the haemocytes and large numbers of vacuoles were noticed as a result of fungal infection. The study showed a significant difference in oxygen uptake between healthy and infected larvae and the greatest uptake was recorded 72 h after fungal infection. The results suggested that the rate of cellular reaction and oxygen uptake were associated with the development of fungal infection.     

A contribution to the embryology of Desmodium motorium (Houtt.) Merr. (= D. gyrans (L.f.) DC.) (Fabaceae)

Abstract

The anthers are tetrasporangiate. The anther wall comprises epidermis, fibrous endothecium, middle layer and tapetal layer. The tapetum is of the Glandular type and its cells remain uninucleate. Meiosis in pollen mother cells is normal and simultaneous cytokinesis leads to the formation of tetrahedral and decussate microspore tetrads. The pollen grains are shed at 2-celled stage. The ovule is campylotropous, bitegmic and crassinucellate. Meiosis in megaspore mother cell results in the formation of linear or occasionally T-shaped megaspore tetrad. The chalazal megaspore develops into Monosporic Polygonum type of embryo sac. Endosperm development is of the Nuclear type.     

Dual pheromone dispenser for combined control of codling moth Cydia pomonella L. and oriental fruit moth Grapholita molesta (Busck) (Lep., Tortricidae) in pears

Codling moth (CM) and oriental fruit moth (OFM) are very important orchard pests worldwide, and particularly in Victoria, Australia, where both species damage pome fruit. Individually CM and OFM have been controlled successfully by pheromone‐mediated mating disruption, but treatment of pome fruit with full registered rates of two individual hand‐applied dispensers for CM and OFM could be uneconomical for growers. Field trials conducted over three seasons in plots sprayed with insecticides consistently demonstrated that dual Isomate C/OFM TT dispensers, designed to disrupt both CM and OFM, were as effective as Isomate CTT and Isomate OFM Rosso dispensers applied individually in pears for control of CM and OFM respectively. The dual‐ and individual‐species dispensers reduced moth catches and fruit damage to a similar degree. The results suggest that combined control of CM and OFM in pears by applying dual Isomate C/OFM TT dispensers at the full‐recommended rate of 500 dispensers per hectare will be more economical than use of individual species dispensers, because the price and application cost of dual dispenser is about half that for individual dispensers.     

Conserving the efficacy of insecticides against Plutella xylostella (L.) (Lep., Plutellidae)

Abstract:  The diamondback moth (DBM), Plutella xylostella (L.) (Lep., Plutellidae), is one of the most destructive insect pests of crucifers worldwide. It was the first crop insect reported to be resistant to DDT and now in many crucifer-producing regions it has shown significant resistance to almost every insecticide applied in field including biopesticides such as crystal toxins from Bacillus thuringiensis and spinosyns from Saccharopolyspora spinosa . In certain parts of the world, economical production of crucifers has become almost impossible because of its resistance to insecticides and resulting control failure. A coordinated resistance management program needs to be implemented with the involvement of pesticide industry, local pesticide regulatory authorities, scientists and farmers. The judicious use of chemicals in conjunction with other control measures (e.g. biological control agents, resistant varieties, proper fertilization rates) is the best way to manage DBM and other pests of cruciferous crops. Introduction of glucosinolate-sulphatase inhibitors as plant-incorporated-products or sprayable material may also lead to a novel pest management strategy.     

Pheromones and body coloration affect mate recognition in the Japanese nine-spotted moth Amata fortunei (Lepidoptera: Arctiidae)

Adults of the Japanese nine-spotted moth, Amata fortunei, are diurnal and have white-spotted black wings and a black-and-yellow striped body pattern. We evaluated whether this species uses sex pheromones and whether visual cues from the female body are used in mate recognition. We introduced extracts of potentially scent-bearing abdominal tips of females to males. Males responded more to the extracts than to dried female specimens, suggesting the presence of sex pheromones in the extracts. Indeed, no males responded to the dried female specimens. To evaluate the importance of visual cues, we conducted the experiments with crude extract and an additional model stimulant. Males responded more to model females with the same number and similar area of yellow bands to the original conspecific females than to those with more bands and greater total band area, suggesting that dissimilarity in band number and area to conspecific females could interrupt male mating behavior. Males of A. fortunei likely find mating partners using olfactory cues over relatively long distances, while using both olfactory and visual cues over short distances. These results suggest that olfactory cues play a major role in mate recognition, whereas visual cues play a supplementary role.     

Comparative bioassay of different isolates of Bacillus thuringiensis subsp. kurstaki on the third larval instars of diamondback moth,Plutella xylostella (L.) (Lep.: Plutellidae)

The diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae) is one of the most important pests of cruciferous plants throughout the world. In recent years, this insect has been a serious pest for cabbage fields in Tehran province. Resistance of P. xylostella to all main groups of insecticides has been recorded and it is ranked in the 20 most resistant pest species reported up to now. According to many researchers, to eliminate the problem of pest resistance to chemical pesticides, an integrated pest management programme should be used. In line with this, the uses of microbial control agents (MCAs) are discussed. The bacterium, Bacillus thuringiensis (Bt) is one of microbial control agents of pests. It is characterised by its ability to produce proteic crystalline inclusions during sporulation. Cry1 protein has insecticidal activity and is highly specific to certain insects and not toxic to unrelated insects, plants or vertebrates. In this work, the pathogenicity of some Bt isolates, including Dipel, 20, 29, 79 and 87, was tested against P. xylostella and the lethal concentrations (LC₅₀) of their crystal proteins to P. xylostella third larval instar was determined. The experiment was designed in factorial in randomised complete design with 5 treatments (different concentrations including 10⁴, 10⁵, 10⁶, 10⁷, 10⁸ CFU/ml and 5 replications and with 10 third larval instars. Spore–crystal complex was applied to the surface of natural diets (cabbage leaves) and the mortality of P. xylostella larvae was assessed 120?h after exposure of Bt toxin in each treatment. Results showed that percentage of survival was significantly higher for control treatment. Results also showed that after 5?days, LC₅₀ for isolates of Dipel, 20, 29, 79 and 87 were equal to 1?×?10⁶, 1?×?10⁵, 5?×?10⁵, 4?×?10⁵ and 1?×?10⁴ CFU/ml, respectively. LT₅₀ were equal to 93.71, 48.04, 71, 40.49 and 75.28?h. Of and most the percentage larval mortality relate to attendance 87 and also at least percentage mortality is related to the groom Dipel.     

Population structure and movement patterns within an isolated and endangered population of the moth Dysauxes ancilla L. (Lepidoptera, Ctenuchidae): implications for conservation

Population structure and movement patterns were studied in a geographically isolated and endangered Swedish population of the moth Dysauxes ancilla. Mark-recapture experiments were conducted between 1993–97 and observations made of adult behaviour between 1993–99. The population size was estimated to be 2356 individuals and the average male residence time 2.6 days. Adults of D. ancilla were sedentary and all movements occurred within the breeding area, despite searches up to 0.5 km away. Mean (± S.D.) distance between two successive captures in males was 43 ± 36 m and the longest single move was 144 m. The moths showed a behavioural reluctance to enter heavily grazed meadows or dense vegetation at the edges of the breeding habitat. Since there are no suitable habitats in the surroundings, conservation efforts should focus on managing the continuity of the current breeding area. Further, the restoration of a former breeding habitat situated 1 km to the north should be considered as well as establishing connections with the extant population.     

Oviposition site selection by the diamondback moth,Plutella xylostella (L.) (Lepidoptera: Plutellidae)

AlthoughPlutella xylostella (L.) is a worldwide pest of cruciferous crops, relatively little is known about its oviposition behaviour. This study was undertaken to provide necessary information about mechanisms involved inP. xylostella host selection. Four oviposition behaviours were described. Moths were given artificial substrates treated with water, sinigrin, orBrassica napus (cv. Westar) squashes, combined withB. napus volatiles and/or grooves in the substrate. No eggs were deposited in the absence of olfactory and gustatory stimuli. Moths given gustatory but not olfactory stimuli deposited similar numbers of eggs but spent significantly more time performing olfactory-related behaviours. Conversely, moths given olfactory but not gustatory stimuli did not oviposit.SSubstrate grooves did not influence egg numbers but appeared to influence egg location. The order in which oviposition behaviours occurs and the relative importance of stimuli type are discussed.     

Ovicidal and larvicidal effectiveness of several insect growth inhibitors and regulators on the codling moth Cydia pomonella L. (Lep., Tortricidae)

Several insect growth inhibitors (IGIs) and regulators (IGRs) were tested in the laboratory for their ovicidal and larvicidal properties on the codling moth C. pomonella , by dipping apples in solutions of them. The IGIs which block chitin synthesis – diflubenzuron, hexaflumuron and teflubenzuron – were noticeably more effective against eggs than on newborn larvae with preventive ovicidal 50% lethality concentrations (LC₅₀) values of approximately 0.6, 1.3 and 15 p.p.m., respectively, and larvicidal LC₅₀ values of 104, 1208 and 204 p.p.m. Flufenoxuron, on the other hand, is almost as effective on larvae (LC₅₀ : 9.9 p.p.m.) as on eggs (LC₅₀ : 5.4 p.p.m.). Fenoxycarb, an IGR juvenile hormone analogue, acts as an excellent ovicidal product with an LC₅₀ value of 0.05 p.p.m. Tebufenozide, an IGR ecdyson (moulting hormone) agonist, is exclusively larvicidal with an LC₅₀ at 0.4 p.p.m. Methoxyfenozide, an IGR of the same family and currently being developed, acts as effectively on eggs as on larvae with ovicidal and larvicidal LC₅₀ values of about 0.6 and 0.8 p.p.m., respectively. When ovicidal products are applied as a curative treatment on eggs less than 24 h old, their effectiveness is much lower than that obtained from preventive application.     

Malting and brewing qualities of some Nigerian rice (Oryza sativa L.) varieties and some thoughts on the assessment of malts from tropical cereals

The maiting qualities of six varieties of Nigerian rice were studied and compared with malts from sorghum and barley. A minimum of seven days was necessary for maximum yield of extract from malted rice. The beer brewed from the six rice malts were similar to each other and to those from sorghum and barley in analytical properties. The appropriateness of using methods designed for assessing barley malt should be re-examined for studying malts from tropical cereals. Meanwhile, it should be sufficient to determine the extract and the nitrogen content of the wort using the European Brewing methods to assess a tropical cereal for mall.

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Résumé Les qualités de maltage de six variétés de riz nigérians ont été étudiées et comparées avec des malts de sorghum et d'orge. Un minimum de 7 jours de maltage est necessaire pour le rendement maximum de l'extrait de riz malté. Les bières brassées à partir de ces six malts de riz étalent samblables entre elles et à celles du sorghum et de l'orge quant à leurs propriétés analytiques. Le caractère approprié de l'emploi de méthodes concues pour évaluer le malt d'orge devrait être réexaminé quand il s'agit d'étudler des malts de ceréales tropicales. Entretemps, pour évaluer le potentiel en malt d'une céréale tropicale, ll devrait être suffisant de déterminer l'extrait EBC et le contenu en azote du moüt, tous deux par la méthode de la Convention Européenne Brassicole.

     

Effects of injecting cadherin gene dsRNA on growth and development in diamondback moth Plutella xylostella (Lep.: Plutellidae)

Two laboratory diamondback moth (DBM) strains were used to study the effects of injecting cadherin gene double‐stranded RNA (dsRNA) on the growth and development of Plutella xylostella (L.). Specifically, the susceptible strain named DBM.1Ac‐S and the low resistant strain DBM.1Ac‐R selected with Cry1Ac toxin were studied. The third larvae of the two strains were injected dsRNA of cadherin gene and their corresponding controls, DBM.1Ac‐RH and DBM.1Ac‐SH, were both injected diethypyrocarbonate (DEPC)‐treated water respectively. The basic biological properties such as death rate, hatching ratio, fecundity, weight of pupa and eclosion rate of the strains mentioned above were likewise studied. Meanwhile, the length and width of the egg and pupa were also measured. The results showed that the cadherin gene dsRNA injection resulted in a significant increase of the death rate and sex ratio. On the other hand, hatching ratio, fecundity, weight of pupa, eclosion rate and adult longevity for male and female of treatments decreased compared to their corresponding controls. As such, there was no significant difference on the length of egg and pupa in between treatments and the corresponding controls. However, their width increased inversely with their corresponding controls. Hence, the results suggest that cadherin gene dsRNA injection retarded the larval growth and development of P. xylostella. Also, these results can help reveal the function of cadherin gene through the RNA interference technique.     

Aestival dormancy in the cabbage moth Mamestra brassicae L. (Lepidoptera: Noctuidae)

Summary In a geographically wide distribution the life cycles of different populations of the cabbage moth Mamestra brossicae are adapted to a remarkable diversity of climatic conditions. This is undoubtedly a proof of its success in adaptation. Some populations living in regions characterized by a drought period interrupting the growth season are capable of distinguishing between one critical day length signalling the onset of the drought period and another signalling the end of the growth season. This study, therefore, is primarily concerned with the geographical patterns in the variability of the adaptional responses of populations exposed to environmental conditions requiring different strategies and tactics in, synchronizing individual, life cycles. It is also a contribution to our understanding of evolutionary mechanisms maintaining median responses to photoperiodically inductive day lengths in geographically different populations. The populations investigated originated from regions differing in predictability of the incidence, onset and duration of a drought period: Freiburg (48.0°N, Southern Germany), Avignon (44.0°N, Southern France), and Argelès (42.5°N, Southern France). Geographical variation with respect to both onset and duration of a drought period consequently results in clinal variation of the variability of innate day length thresholds triggering aestival dormancy and of innate duration of aestivation. In this paper we considered the influence of geographically changing temperatures on aestival dormancy induction. Even in southern populations of M. brassicae a temperature dependent switch off-mechanism exists which prevents aestival dormancy under certain environmental conditions. The effective temperatures vary geographically, too. What the geographical patterns in adaptive responses really are, is discussed.This research was supported by the Deutsche Forschungsgemeinschaft (Sa 259/3-1)     

Queen succession in the primitively eusocial tropical waspRopalidia marginata (Lep.) (Hymenoptera: Vespidae)

Females of the primitively eusocial wasp Ropalidia marginata can be classified into three behavioral groups: Sitters, Fighters, and Foragers. It has been speculated that both Sitters and Fighters may be hopeful queens and that the Foragers may have little or no opportunities for direct reproduction. Here we show that in 9 of 12 queen-removal experiments where such a behavioral differentiation could be discerned, the individual that became a queen (the potential queen) was a Sitter in 6 cases, a Fighter in 2 cases, and a Forager in only 1 case. Although potential queens spent significantly more time absent from the nest and showed significantly higher rates of dominance behavior compared to the mean values for nonqueens in their colonies, they were intermediate with respect to all behaviors and age when compared to the range of values for nonqueens in their colonies. Potential queens were not necessarily the highest-ranking individuals among the nonqueens. The pattern of queen succession in this species appears to be quite different from the temperate pattern, where an old and active forager of high dominance rank is the potential queen. Although somewhat similar to the tropical pattern of a relatively younger female that has performed relatively little foraging being the potential queen, it is perhaps more accurate to describe the potential queens of R. marginata as unspecialized intermediates.     

Effects of a kaolin-based particle film on oviposition and feeding of gypsy moth (Lep., Lymantriidae) and forest tent caterpillar (Lep., Lasiocampidae) in the laboratory

Abstract:  In the laboratory we investigated a kaolin-based crop protectant, Surround^® WP, that was mixed in a spray carrier (94% water, 2% methanol, 4% Triton X100) and applied as particle film against gypsy moth Lymantria dispar (L.) and forest tent caterpillar Malacosoma disstria Hubner. Paired-choice feeding tests showed that gypsy moth larvae were significantly (P < 0.05) less disposed to feed on red oak Quercus rubrus L. treated with high concentrations (60 and 120 g/l carrier) of kaolin than on untreated foliage. There was no significant difference (P > 0.05) between gypsy moth's consumption of kaolin-treated and untreated red oak when given a single food choice, but the adults were less inclined to oviposit on the kaolin-treated surfaces than on controls. However, no kaolin treatment completely deterred gypsy moth feeding or oviposition. Kaolin particle film did not influence forest tent caterpillar feeding and there were insufficient data to evaluate the effect of kaolin on the species' oviposition. The spray carrier did not increase the efficacy of the kaolin, but as an independent, albeit impractical treatment it constrained feeding by both insect species but did not affect gypsy moth oviposition. These initial laboratory findings suggest that applying kaolin-based particle film to forests would present significant challenges; but if these could be surmounted, the technique might assist in the management of gypsy moth but not likely in that of forest tent caterpillar.