Bruchidius Atrolineatus Research Articles

Analysis of multiparasitism by Eupelmus vuilleti (Craw) (Eupelmidae) and Dinarmus basalis (Rond) (Pteromalidae) in the presence of one of their common hosts, Bruchidius atrolineatus (Pic) (Coleoptera Bruchidae).

Bruchidius atrolineatus (Pic) is a tropical beetle (Coleoptera Bruchidae) that develops during the larval and pupal stages in the seeds of a legume Vigna unguiculata (Walp). Two species of Hymenoptera, Dinarmus basalis (Rond) and Eupelmus vuilleti (Craw), solitary ectoparasitoids of the larvae and pupae of B. atrolineatus, were introduced successively in the presence of their hosts, varying the interval between the two introductions. When D. basalis females were introduced 24 h, 3 days or 7 days after E. vuilleti, multiparasitism was low. The females had low fecundity, and their eggs were not distributed randomly over the different available hosts. When E. vuilleti females were introduced second, they oviposited on the different hosts availabe and did not avoid multiparasitism. The presence of hosts already parasitised by D. basalis increased the reproduction of E. vuilleti, and the fecundity of the females was higher than in control batches with E. vuilleti alone. E. vuilleti seems capable of detecting the ovipositor shafts drilled by the D. basalis females, and by introducing its own ovipositors killing the D. basalis eggs or larvae. When interspecific competition was occurring the number of E. vuilleti adults emerging from the seeds was no different from that observed in control batches with E. vuilleti alone, and there were always fewer D. basalis adults than in control batches (D. basalis alone). This interspecific competition reduces the influence of the two parasitoids in the biological control of bruchid populations.

Effect of changes in the thermoperiod on reproductive diapause in Bruchidius atrolineatus Pic (Coleoptera: Bruchidae)

Abstract. Bruchidius atrolineatus (Pic) is a tropical bruchid developing in Vigna unguiculata (Walp) pods. Adults are in reproductive diapause during the dry season. In conditions of 40:25d̀C or 35:25d̀C, diapause is induced when larvae develop in thermophases longer than 14 h, in thermophases shorter than 10 h and in continuous darkness. Thermophases of 12 h cause a reduction of the proportion of diapausing beetles. This proportion also depends on the thermoperiod temperatures. Development at low temperatures (23: 16d̀C, 12: 12 h) induces a high percentage of diapausing beetles. However, at low temperatures, the developmental times of the beetles are long and show important interindividual variability. When larvae develop in decreasing temperatures, small changes in thermoperiod temperatures (35:25d̀C to 3O:2Od̀C) have a strong effect on diapause induction. When larvae develop at low temperatures (25:15d̀C) and then at high temperatures (40:25d̀C), the proportion of diapausing beetles depends on the duration of development at low temperatures. Whatever the developmental conditions, both sexually active and diapausing beetles always emerge from the seeds. This interindividual variability is important in this species which has a wide geographical distribution in Africa.

Localization and fine structure of the female sex pheromone-producing glands in Bruchidius atrolineatus (PIC) (Coleoptera : Bruchidae)

The sex pheromone glands of female Bruchidius atrolineatus (Coleoptera: Bruchidae) have been localized by recording the electric response of the antenna of males subjected to a stream of air, containing the volatile sex pheromone (electroanntennography-EAG). Some 50 unicellular glands are distributed irregularly in the ventral and dorsal intersegmental membranes situated at the extremity of the pygidium, each gland containing a short ductule with an evacuation pore, 0.5–1 μm in diameter. The receiving canal is composed of a network of fine epicuticular filaments. The glands are type 3. The ultrastructure of these sex pheromone-producing glands is described in females whose production-emission activity had been previously verified with EAG. Deep basal invaginations and inflated intercellular spaces indicate the transport of substances from the hemolymph to the gland cells. The presence of numerous elongated mitochondria, diverse inclusions, vesicles containing crystalline bodies, and abundant apical microvilli, all reveal elevated cellular activity, which is never observed in young or diapausing females that do not produce sex pheromone. The ultrastructural differences in different types of females (sexually active or diapausing), combined with comparative EAG recordings obtained with intact females or those in which the suspected glandular zone was masked, made it possible to localize the glands.

Effect of larval density on development and induction of reproductive diapause in Bruchidius atrolineatus

AbstractIn Bruchidius atrolineatus (Pic), an increase in larval density inside the seed led to a reduction in the survival rate during post‐embryonic development, with only a limited decrease in the weight of adults. A high larval density increased the proportion of adults in reproductive diapause under certain thermoperiodic conditions. Under other conditions that already promote the emergence of a high proportion of diapausing beetles, an increase in larval density had no effect on diapause.There was no correlation between the larval developmental time and the weights of adults in a strain with a very low incidence of diapause. However, such a correlation was observed when both sexually‐active and diapausing beetles emerged. This correlation was explained by the longer developmental times and lower weights of diapausing beetles.RésuméInfluence de la densité larvaire sur le développement et l'induction de la diapause reproductrice chez Bruchidius atrolineatus Pic(Coléoptère, Bruchidae)Chez Bruchidius atrolineatus, l'accroissement de la densité larvaire à l'intérieur de la graine entraîne une augmentation de la mortalité alors que la réduction de poids des individus à l'émergence est relativement limitée. L'accroissement de la densité larvaire provoque une augmentation du taux d'adultes en diapause reproductrice, dans certaines conditions thermopériodiques. Dans d'autres conditions, permettant l'émergence d'un fort taux d'adultes diapausants, l'effet de la densité larvaire est nul. Lorsque l'on analyse l'effet de la densité chez les individus d'une souche ne présentant pas de phénomène de diapause, il n'y a pas de corrélation entre la durée de développement et le poids des adultes. Par contre, lorsqu'il y a émergence d'adultes sexuellement actifs et diapausants, il existe une corrélation entre la durée de développement et le poids des adultes émergeants. Cette corrélation est due au fait que les adultes diapausants, qui présentent les durées de développement les plus longues, sont ceux qui ont les poids les plus faibles.

Influence of thermoperiod and photoperiod on reproductive diapause in Bruchidius atrolineatus (Pic) (Coleoptera, Bruchidae)

Abstract Bruchidius atrolineatus (Pic) is a common pest infesting cowpea seeds (Vigna unguiculata Walp) in Africa. In the Sahelian zone, the adults are in reproductive diapause during the dry season. Diapause induction depends on the climatic conditions during embryonic and post‐embryonic development. A strain of B. atrolineatus originating from the Niamey (13oN) was reared in different thermoperiodic and photoperiodic conditions. In the thermoperiodic regime 40:25oC, in continuous darkness, induction of diapause was dependent on the duration of the thermophase. Photoperiod could also influence diapause induction but the response depended on the temperature. When the beetles were reared in conditions of LD 12:12 h, 40:25oC, for seven generations, the proportion of diapausing adults decreased and their sensitivity to photoperiod increased. In LD 14:10 h, 40:25CC, the proportion of diapausing adults remained high regardless of the photoperiod. In these conditions, the first emerging adults were sexually active and were used for selection of a strain with a low incidence of diapause. After twelve generations, the proportion of diapausing beetles was lower than 5%. The responses of this selected strain to photo‐ and thermoperiods were reduced. The sensitivity of B. atrolineatus to photoperiod and thermoperiod could be controlled by genetic systems as observed in other insect species.

Uscana lariophaga (Hymenoptera: Trichogrammatidae), an egg parasitoid of bruchid beetle (Coleoptera: Bruchidae) storage pests in West Africa: host-age and host-species selection

AbstractUscana lariophaga Steffan is an egg parasitoid of bruchid species in West Africa. The hosts are Callosobrucbus maculatus (Fabricius) and Bruchidius atrolineatus Pic, insect pests of stored cowpea. Experiments were carried out to study the selection between hosts of different ages and of different species in choice and no-choice situations. Results were obtained through parasitization studies and by direct behavioural observations. A description of the parasitization behaviour of Uscana lariophaga is given. At 30°C, C. maculatus eggs of 0–2 day old are readily accepted for parasitization, but in a choice situation the 0 day old eggs are preferred. Of the older eggs only those of 3 days old are parasitized but significantly less than those of 0–2 days. At 30°C, B. atrolineatus eggs older than 24 hours are significantly less parasitized than younger eggs also in the no-choice situation. When eggs are older than one day, the time needed for penetrating the egg increases with host age. Both bruchid species are suitable hosts for U. lariophaga. In a choice situation B. atrolineatus is the preferred host and especially so when U. lariophaga has been reared on this species. However, in a no-choice situation the highest rate of successful parasitization is obtained on hosts of the species from which they have been reared. The higher parasitization rate of C. maculatus in the field in Niger can be explained by the difference in the susceptible period between the two host species.

A histological and ultrastructural comparison of the male accessory reproductive glands of diapausing and non-diapausing adults in Bruchidius atrolineatus (Pic) (Coleoptera : Bruchidae)

Cytological variations of the median and the 2 lateral accessory glands of Bruchidius atrolineatus Pic (Coleoptera : Bruchidae) were examined as a function of age and the reproduction of the male. In sexually active virgin males, the secretory epithelium is columnar at emergence, but progressively flattens, and the secretions formed and stored by its cells are expelled by exocytosis into the glandular lumen. After 10 days, the male accessory glands exhibit a stage of repletion, characteristic of glands temporarily storing their secretions in their lumen. In diapausing males, the genital tract is relatively undeveloped and the accessory glands are reduced to tubules, whose lumen, surrounded by an epithelium composed of narrow cells, contains little secreted material. The presence of secretion aggregates in the secretory epithelial cells, the abundance of rough endoplasmic reticulum in them, and the release of a part of their secretions into the glandular lumen, indicate that reproductive diapause in B. atrolineatus is characterized by a decrease in the reproductive function. and not its total arrest.

The influence of intercropping millet ( Pennisetum typhoides Burm) with cowpea ( Vigna unguiculata Walp) on the egg-laying and development of Bruchidius atrolineatus (pic) (coleoptera: Bruchidae)

Infestation of cowpea ( Vigna unguiculata Walp) by Bruchidius atrolineatus (Pic) (Coleoptera: Bruchidae) is similar in monoculture or when intercropped with millet. The percentage of egg-infested pods and the average number of eggs per pod are similar in both types of crop. In mixed crops, the influence of the leaf cover decreases during the egg-laying period as the leaves dry up. When the leaf cover is very dense, there is no difference in the number of eggs laid on the pods in the two cropping systems. However, mortality is reduced under the dense millet leaf cover, through more favourable temperature and humidity conditions. Present evidence suggests that a millet-cowpea intercropping system enhances the likelihood of seed losses from Bruchidae.

Induction of reproductive diapause in Bruchidius atrolineatus during the dry season in a Sahelian zone

AbstractBruchidius atrolineatus (Pic) (Bruchidae: Coleoptera) is a bruchid beetle infesting Vigna unguiculata (Walp). During the dry season, adults are in reproductive diapause. Studies of adult populations in a traditional store containing contaminated pods of V. unguiculata show that the reproductive diapause is induced during the first larval instars. The temperature decrease from November to January probably is the main climatic factor inducing this diapause. The percentage of diapausing adults depends on the duration of the larval development at low temperatures. Experiments in climatic boxes confirm these results. At 12 h 25 °T–12 h 20° C 11–13 LD, a high proportion of the adults emerging from the V. unguiculata seeds are in reproductive diapause and the duration of their growth is variable. L1 L2 L3 larvae probably are sensitive stages to the thermal variations and the processes allowing emergence of diapausing adults probably are induced during these larval instars.RésuméInduction de la diapause reproductrice chez Bruchidius atrolineatus coléoptère bruchidae durant la saison sèche en zone SahélienneBruchidius atrolineatus (Pic) est un Coléoptère Bruchidae se développant en zone sahélienne aux dépens d'une légumineuse Vigna unguiculata. Pendant la saison sèche, les adultes sont en diapause reproductrice. Un suivi des populations d'adultes a été réalisé dans un grenier traditionnel en ‘terre séchée’ contenant des gousses récoltées dans la nature et portant des œufs de B. atrolineatus. Il a permis de constater que la diapause reproductrice était induite durant les premières phases du développement larvaire. La décroissance des températures de Novembre à Janvier avec des minima de 15 °C et des maxima de 25 °C est probablement le principal facteur permettant l'induction de cette diapause. L'introduction dans le grenier de gousses portant des œufs venant d'être émis à différentes périodes de la saison sèche montre que le pourcentage d'adultes diapausants dépend de la durée du développement larvaire aux températures ‘basses’. Des expériences réalisées dans des étuves programmées confirment ces résultats. A 12 h 25 °T/12 h 20 °C 11–13 LD, un taux élevé d'adultes émergeant des graines est en diapause reproductrice et la durée de leur développement post‐embryonnaire est très variable. En conditions plus chaudes 12 h 40 °C/12 h 25 °C 11–13 LD, le taux d'adultes diapausants est plus réduit et la durée du développement plus courte. L'analyse de la croissance larvaire montre que les premiers stades larvaires sont probablement des stades sensibles aux variations thermiques. Les modifications physiologiques permettant l'émergence d'adultes diapausants ou sexuellement actifs seraient induites durant ces stades.

Electrophysiological investigations of sex pheromone reception and release in Bruchidius atrolineatus

ABSTRACT. Male antennal sensitivity to female sex pheromone in Bruchidius atrolineatus was investigated electrophysiologically (EAG). The existence of receptors for this pheromone was shown in the antennae of males. (No such receptors exist in the antennae of females.) Young (age < 24h) males gave an EAG of amplitude 25–30% of the response of older males. Diapausing males several days old gave a much smaller response than active males of the same age.EAGs were used to test the production/release of pheromone by groups of twenty females. Before they are 24 h old, active females do not produce/release the pheromone; older females release it at an almost constant rate. Sexually diapausing females do not produce and/or release the sex pheromone.In sexually active females, mating inhibits pheromone release almost immediately. There is a correlation between reproductive status of the females (development of ovaries, oogenesis) and the production or release of the pheromone. A corresponding correlation also exists in the males whose antennae show a very low sensitivity when they are young or when they are in reproductive diapause.

Mise en evidence de l'effet insecticide de composes Soufres (disulfures et trisulfures) sur Bruchidius atrolineatus (Pic) (Coleoptere, Bruchidae)

Bruchidius atrolineatus Pic is a Coleopteran Bruchid developing in cowpea ( Vigna unguiculata Leguminosae) seeds. This insect causes important damage in tropical countries during storage of cowpea seeds. The influence of some volatile sulfur compounds is studied on adults and larvae of B. atrolineatus . Dimethyl trisulfide and diethyl trisulfide produce the highest mortality to adults, eggs and larvae. The toxicity of the sulfur compounds is higher than that of carbon tetrachloride but is less than that of Dichlorvos at a dosage of 500 g/l. It is suggested that the sulfur compounds produced by the leaves of some tropical plants (Alliaceae, Bignonlaceae, Mimosaceae) could be used for control of Bruchid populations in the stored products.

A female sex pheromone in Bruchidius atrolineatus (Pic) (Coleoptera, Bruchidae): analysis of the factors affecting production or emission of this pheromone

ABSTRACT. . The females of the tropical Bruchid Bruchidius atrolineatus (Pic) (Coleoptera) produce a sex pheromone that influences male behaviour. This pheromone, tested on males in an olfactometer, triggers characteristic antennal movements followed by a distinct chemo‐anemotaxis. Sex pheromone production depends on the age of the females and is partly correlated with their ovarian activity. Females 0–24 h old are not attractive, but they begin to attract males on the second day of adult life. Vitellogenesis seems to correlate with the emission or the production of the pheromone but there is no precise synchrony between the two phenomena which are probably induced by the same endocrine factors. Within 1 h after mating there is a decrease in the females' attractiveness, which lasts at least 48 h. Under our experimental conditions no particular rhythm of production or emission of the sex pheromone in B. atrolineatus could be observed.

Oviposition and development of Bruchidius atrolineatus (Pic) and Callosobrochus maculatus (F.) (Coleopterae: Bruchidae) in Vigna unguiculata (Walp) cultures in Niger

Bruchidius atrolineatus (Pic) is present in crops of Vigna unguiculata towards the end of the dry season at the beginning of September when pods start to form. Females lay many eggs on most available green pods. However, this oviposition behaviour results in an important egg mortality. During September, pods gradually reach maturity whilst new pods are formed. Females therefore have at their disposal a growing number of differently mature pods. Confronted with such a situation, B. atrolineatus females show an opportunist behaviour and lay most of their eggs on the most abundant stage, i.e. the most easily discovered stage (ripening green pods in mid-September or dry pods towards the end of September). However, they also lay eggs on other phenological stages no matter how abundant they are. B. atrolineatus females therefore show a certain behavioural plasticity enabling them to reproduce on all stages of pods whose maturity, chemistry and texture may differ. Larvae can develop either in maturing or dry seeds. The number of eggs laid from mid September is lower and lower whatever the phenological stage attacked. This decrease would be due to a reduction of the first generation adult bruchids and of the reproductive potential of females. Callosobruchus maculatus appears in crops at the same time as B. atrolineatus, but oviposits preferentially on dry pods. Eggs are observed during the whole period of study, but the numbers laid are always low. With the increase in pod number, eggs are dispersed among the different substrates available. However, the average number of eggs laid on the pods remains constant. Despite the high mortality due to the oviposition behaviour of B. atrolineatus and to other factors (impact of hymenopterous parasitoids), these two bruchids cause important losses to seeds of V. unguiculata. Control methods against these pests should be envisaged.in the field before harvesting.

Bruchid infestation of cowpea varieties in the field

Cowpea is one of the most widely grown leguminous crops in Africa: in Kenya it occupies over 66,000 ha and Coast Province ranks second to Eastern Province with about 5200 ha. It is an important food item consumed both as a vegetable and as a grain. Unfortunately, it suffers from both preharvest and postharvest infestations which accounts for serious losses of the crop. With the introduction to Kenya of improved varieties from IITA, Nigeria, such losses would be increased due to varying susceptibility in different pest ecosystems. The objective of this study therefore was to observe the infestation of the IITA varieties and compare them with local cowpea varieties collected from different parts of Kenya. The work was conducted at C.A.R.S., Mtwapa from 1979 to 1981 inclusive. From the study, five different bruchid species were identified as infesting cowpea varieties in the field. These were Collosobruchus rhodensienus; C. phaseoli; C. chinensis; Bruchidius atrolineatus; and C. analis; in order of decreasing abundance. Over 50% of the bruchids found in the field were C. rhodensienus while Zabrotes spp. and C. maculatus (F) were never encountered in the field. Although the IITA materials were introduced because of their yield potential, it was found that some of them were as susceptible to preharvest bruchid attack as the locally available materials. The short rains season had more bruchid infestations than the long rain season. There were also fewer eggs on pods of local varieties and fewer bruchids emerging from seeds of local as compared to IITA varieties. The results however were not significantly different. Further work should be done to establish the complex of bruchids found in stored cowpea varieties, the losses caused and control measures applicable to reduce damage.

L'activité reproductrice et le développement de Bruchidius atrolineatus (Pic) sur les gousses sèches de Vigna unguiculata (Walp) en zone sahélienne, mise en évidence d'une diapause imaginale

Bruchidius atrolineatus appears at the end of the rainy season when pods of its host plant Vigna unguiculata begin to mature. The eggs are deposited along the ventral suture of pods in the vicinity of the seeds. When the eggs are not attacked by Trichogrammatidae their larvae penetrate the seeds and mortality is low during the post-embryonic development. Most of the adults emerging at pod maturity have functional reproductive organs. In that case the females laid on the same mature pods and larvae develop inside the seeds during the first part of the drying season characterised by high diurnal temperature and low relative humity. If the first emerged adults have functional reproductive organs, the following (60% of the population) are in reproductive diapause. Such diapausing insects have been found during the dry season in shelters near the cultivated fields of Vigna unguiculata . Induction or termination of this reproductive diapause are not yet studied. This diapause probably allows the maintenance of populations during the dry season in absence of host plant.

L'oeuf de Bruchidius atrolineatus (Pic) et son système de fixation

Scanning electron microscope studies of eggs of Bruchidius atrolineatus were made and the system of egg fixation on cowpea pods (Vigna unguiculata Walp) was described. The egg is fusiform and asymmetrical. Its upper part is convex and polygonal structures are present. Its lower surface is flat and exhibits small protuberances. The convex side is 8 μm thick whilst the flat side is only 1 μm thick. A strengthened band-like zone separates the convex side from the lower part of the egg. When laid, the egg is coated with a sticky mucus-like substance. This substance hardens when entering stomata of the pods. An efficient egg-fixation system thus covers the stomata.

Observations on three Bruchids associated with cowpea in Northern Nigeria

Three species of Bruchidae, Callosobruchus maculatus (F.), C. rhodesianus (Pic) and Bruchidius atrolineatus (Pic) were found associated with cowpea ( Vigna unguiculata) in Northern Nigeria. The infestation in the field was at a low level with an average of 2 per cent of the seeds being affected. B. atrolineatus was the most common of the three species and C. rhodesianus was comparatively scarce. Only C. maculatus continued infestation in store for any length of time. It is concluded that this was because B. atrolineatus and C. rhodesianus have a mean developmental period and a period of emergence which are longer than those for C. maculatus. In addition B. atrolineatus and C. rhodesianus have a much reduced level of egg production soon after the storage period begins. An account is given of the wild hosts of B. atrolineatus and it is concluded that Vigna triloba and possibly other legumes are primary hosts of this species whereas cowpea is not. Nearly ten per cent of the seeds of V. triloba were attacked in the field. Observations on the biology of C. maculatus in the laboratory showed that the period of pre-adult development is negatively correlated with temperature and is also affected to a lesser degree by humidity, low humidity lengthening the pre-adult developmental period. The majority of eggs were laid during the early part of the female's life and there was a decrease in the viability of eggs laid later. C. maculatus has been bred on several hosts, but the only host comparable to cowpea is Phaseolus aureus, other hosts lead to heavy mortality and extension of developmental period. There are differences in the susceptibility to attack of different cowpea varieties, the larger seeded varieties of those tested being, in general, better as hosts. This was shown not to be due to larval competition within the seeds. There was a definite preference for oviposition on seeds with a smooth testa when there is a choice of smooth and rough, but there seemed to be no colour preference. One insect can cause a 3–5 per cent weight loss in a cowpea seed. The decrease in weight loss per individual insect is lower when there are several larvae per seed. Germination is adversely affected when there are three or more insects per seed.

Field infestation of cowpea (Vigna unguiculata) pods by beetles of the families Bruchidae and Curculionidae in Northern Nigeria

SummaryAn account is given of a study of infestation of cowpea pods in the field in Northern Nigeria by the weevil, Piezotrachelus varius (Wagn.), and the Bruchids, Bruchidius atrolineatus (Pic) and Callosobruchus maculatus (F.). Oviposition by Bruchids did not commence until the pods were fully formed and light green in colour, whilst infestation by P. varius originated in the young pods. Observations indicated that a high level of parasitism of Bruchid eggs occurred, but that the majority of Hymenopterous parasites emerging from within the pods were related to P. varius.When pods were harvested at regular intervals, large numbers of P. varius emerged from the early harvests only. B. atrolineatus was the predominant Bruchid species emerging, particularly from early harvests. In the case of a single final harvest of pods, large numbers of P. varius, and a higher level of infestation by B. atrolineatus than in pods collected at regular intervals, were recorded.Shelling of four batches of pods indicated a mean of 11 per cent, of seeds attacked by Bruchids in the case of single final harvests, and a mean of only 3·5 per cent, in the case of regular harvests as pods became dry. It is concluded that a considerable improvement in quality would result from an adoption of the latter method by farmers, provided that some method of control in respect of the harvested pods were introduced.From the observations made it is concluded that P. varius is a true field pest, B. atrolineatus primarily a field pest able to continue infestation in store to a very limited extent, and C. maculatus primarily a store pest able to commence its infestation in pods in the field and to build up in numbers rapidly during the immediate post-harvest storage period.The normal manner of cultivation precludes the use of field methods of control at oviposition peaks but observations suggest that elimination of secondary hosts of P. varius and B. atrolineatus might be worthwhile. A reduction in oviposition by C. maculatus by treatment of stored cowpeas in growing areas, and treatment of pods during the immediate post-harvest storage period, should considerably reduce the level of infestation by this species.