Biological activity of Cassia occidentalis L. against Callosobruchus maculatus (F.) (Coleoptera: Bruchidae)

In developing countries, traditional control methods are commonly used against stored-product insects and mites. In Senegal, the leaves of Cassia occidentalis L. (Caesalpiniaceae) are used to protect cowpea seeds (Vigna unguiculata L. (Walpers)) against Callosobruchus maculatus (Coleoptera: Bruchidae). The biological activity of the leaves, the seeds and oil of C. occidentalis was evaluated in controlled conditions (28 ± 2°C, 45 ± 5% r.h.) against C. maculatus. At the rate of 10% (w/w), both fresh and dry leaves as well as whole and ground seeds had no contact toxicity on the cowpea beetle. In contrast, seed oil induced an increase in mortality of C. maculatus eggs and first larval instar at the concentration of 10 ml/kg cowpea. The basis of the ovicidal and larvicidal activities are discussed in this paper. Several trials using pure compounds have highlighted that several fatty acids (linoleic, oleic and stearic) are responsible for C. occidentalis toxicity. C. occidentalis seed oil did not reduce the oviposition of C. maculatus at 10 ml/kg seed.     

Nutritional behaviour of Trogoderma granarium Everts (Coleoptera: Dermestidae) on leguminous seeds

To make out the nature of dietary deficiencies of pulses for Trogoderma granarium, brewer's yeast was added in different proportions. Additions resulted in no improvement of the dietary values of green gram (Phaseolus aureus Roxb.), black gram (P. mungo L.), Bengal gram (Cicer arietinum L.), kabuli gram (C. arietinum L.) and cowpea (Vigna sinensis Savi.). But in soybean (Glycine max Merr.) or lentil (Lens esculenta Moench.) addition of yeast gave higher adult populations. In French bean (P. vulgaris L.) with or without yeast no adults were formed. Yeast alone proved to be a poor food, but with glucose the growth of insects improved significantly. The addition of cholesterol to lentil, or glucose to French bean greatly increased their food value. This indicated that lentil was qualitatively and/or quantitatively deficient in sterol, but the poor food value of French bean was due to the presence of non-utilizable carbohydrates in the seeds.     

Efficacy of ash for controlling infestations of Callosobruchus maculatus (F.) (Coleoptera: Bruchidae) in stored cowpeas

Storing cowpeas, Vigna unguiculata (L.) Walpers, with ash to protect them against Callosobruchus maculatus (F.) is a traditional storage method in northern Cameroon. The amount of ash used and the details of the methodology (i.e. mixing vs layering, the source of ash used) varies among farmers. In experiments designed to simulate traditional ash-storage procedures, it was found that a minimum ratio of 3 parts of ash to 4 parts of cowpeas prevented population growth of C. maculatus and that a 3 cm layer of ash on top of stored seeds prevented infestation by adults.     

Characterization and insecticidal properties of globulins and albumins from Luetzelburgia auriculata (Allemao) Ducke seeds towards Callosobruchus maculatus (F.) (Coleoptera: Bruchidae)

We evaluated the development of Callosobruchus maculatus growing in artificial seeds composed of Vigna unguiculata (cowpea) seed flour mixed with exogenous proteins from Luetzelburgia auriculata. Albumin and globulin fractions from Luetzelburgia auriculata were characterized in terms of protein content, amino acid composition and antimetabolic proteins (trypsin/chymotrypsin inhibitory, porcine pancreatic alpha-amylase inhibitory, lectin activity and presence of chitin-binding proteins). Both fractions were distinct in terms of protein content and diversity as determined by electrophoresis. Lectin activity was present only in the globulins. Neither fraction exhibited inhibitory activity towards porcine pancreatic alpha-amylase but trypsin inhibition was observed. Interestingly, chitin-binding proteins were detected in both protein classes. Albumins had a severe effect upon larval development and were detrimental to insect emergence (LD₅₀=0.4%) while globulins displayed slight toxicity upon larval development and no effect towards insect emergence. The presence of serine proteinase inhibitory activity and chitin binding proteins could explain, at least in part, the harmful effects on C. maculatus development while lectin activity and amino acid availability seem not to correlate with any deleterious effects. Luetzelburgia auriculata would be an interesting source of seed proteins to study behavior of C. maculatus upon infestation and genes coding for insecticidal proteins could become candidates for molecular biology programs devoted to producing transgenic seeds expressing resistance towards the beetle.     

Efficacy of protectants against Callosobruchus phaseoli (Gyll.) and C. maculatus (F.) (Coleoptera: Bruchidae) in mungbeans

The organophosphorus (OP) compounds chlorpyrifos-methyl, fenitrothion, methacrifos and pirimiphos-methyl, synthetic pyrethroids (SP) deltamethrin and permethrin, and the insect growth regulator (IGR) fenoxycarb were evaluated as protectants against Callosobruchus phaseoli (Gyll.) and C. maculatus (F.) in mungbeans (Vigna radiata (L.) Wilczek). Treated mungbeans were sampled for efficacy testing using C. phaseoli after various periods of storage in hot and humid conditions (30°C, 70% r.h.). Minimum effective application rates were determined for different periods of protection. During storage the OP compounds (chlorpyrifos-methyl, fenitrothion, methacrifos and pirimiphos-methyl) lost activity against C. phaseoli much faster than the SPs (deltamethrin and permethrin) and the IGR (fenoxycarb). Tests were carried out on mungbeans which were infested with C. phaseoli before treatment with pirimiphos-methyl, fenoxycarb or deltamethrin. These tests showed that immature insects in the treated beans were protected from insecticides. Finally, freshly-treated mungbeans were exposed to C. maculatus for comparison with the results for C. phaseoli. The four OP compounds, two SPs and the IGR tended to have similar potency against C. maculatus and C. phaseoli.     

Technique to isolate Callosobruchus chinensis (L.) (Coleoptera: Bruchidae) eggs

A simple technique to isolate the eggs of Callosobruchus chinensis from the surface on which they are laid is described. An aqueous extract of their natural food, green gram, Vigna radiata, is used to coat glass beads that attract adult females for oviposition. The thin layer of extract on the glass beads allows separation of the eggs from the bead surface after a 15–20 s immersion in water. When transplanted onto fresh grain treated with glue, the separated eggs exhibit normal development and up to 97% hatching.     

Intraspecific and interspecific competition in Callosobruchus maculatus (F.) and Callosobruchus subinnotatus (Pic) on stored bambara groundnut, Vigna subterranea (L.) Verdcourt

Intraspecific competition was studied in Callosobruchus maculatus and Callosobruchus subinnotatus. Interspecific competition between the two bruchids was also studied to determine which of these species is likely to cause more damage to stored bambara groundnuts, Vigna subterranea in cases of joint infestation. Results showed that increasing the adult density up to 8 females per 10 g of bambara groundnut seeds did not significantly reduce the mean number of eggs laid per female, the number of eggs developing to the adult stage, or the weight of emerged adults of either species. The developmental period of the two species was also not significantly affected. The adult emergence curve of C. maculatus was similar to that of C. subinnotatus and was of the scramble type. C. maculatus performed better than C. subinnotatus in interspecific competition and it achieved this through a higher egg-laying ability and a higher rate of progeny production coupled with a shorter life-cycle. The implications of these findings with respect to damage and possible loss of stored bambara groundnut are discussed.     

Simulation studies on the effects of solar heat on egg-laying, development and survival of Callosobruchus maculatus (F.) and Callosobruchus subinnotatus (Pic) in stored bambara groundnut Vigna subterranea (L.) Verdcourt

The effects of simulated solar heat on oviposition, development and survival of Callosobruchus maculatus (F.) and Callosobruchus subinnotatus (Pic) in stored bambara groundnut, Vigna subterranea (L.) Verdcourt, were evaluated at three high temperatures (40°C, 45°C and 50°C) at a constant, low humidity (30% relative humidity). Exposure to these temperatures for 6 h significantly reduced oviposition in C. maculatus and C. subinnotatus females. Females of both species that were exposed to 50°C laid significantly fewer eggs than those exposed to 40°C; and in the case of C. maculatus, females exposed to 45°C also laid significantly fewer eggs than those exposed to 40°C. The percentage of eggs laid by females of both species that reached adulthood after exposure to 50°C for 2–6 h was significantly lower than the percentage that developed from eggs laid by females that were exposed to 40°C. No adult developed from eggs of C. maculatus exposed for 6 h at 50°C or from eggs of C. subinnotatus exposed for 2 h at this temperature. For both species, no adult progeny subsequently emerged from seeds harbouring first instar larvae when exposed at 50°C for 2, 4 or 6 h. Older larvae of C. maculatus were more tolerant of exposure at 50°C: 26.8, 10.2 and 0.9% of late instar larvae exposed for 2, 4 and 6 h, respectively, developed to the adult stage. In contrast, no adults of C. subinnotatus emerged from seeds harbouring late instar larvae when exposed at 45°C for 6 h nor in seeds exposed to the temperature of 50°C for 4 or 6 h. On average, immature stages of C. subinnotatus were more susceptible to heat treatment than those of C. maculatus.     

Egg distribution on seeds by Callosobruchus subinnotatus (Pic.) (Coleoptera: Bruchidae)

This study investigated the ability of the females of Callosobruchus subinnotatus (Pic.) to discriminate between seeds with differing egg loads. It established the presence of an oviposition marker in C. subinnotatus which enabled the female bruchids not only to distinguish between egg-laden and pristine control seeds, but also to assess egg loads quantitatively. Observations after the second and third days of setting up the experiments showed that the females tended to distribute eggs uniformly on the control and the treated seeds once the number of eggs on the control seeds equals that on the treated seeds. The oviposition marker was soluble in ether as egg-laden seeds could not deter oviposition after washing them twice with ether. Washing once with ether was not effective and this suggested that traces of the marker were effective in deterring oviposition. Males did not produce oviposition deterrents that could be recognised by the females. There was cross-effectiveness of the C. subinnotatus marker for the females of Callosobruchus maculatus (F.) and vice versa.     

Hardness of some fabaceous seed coats in relation to larval penetration by Acanthoscelides obtectus (Say) (Coleoptera: Bruchidae)

A simple device is described for the measurement of seed coat hardness of Phaseolus vulgaris L., Phaseolus lunatus L., Phaseolus coccineus L., and Lablab purpureus L. The ability of Acanthoscelides obtectus (Say) larvae to penetrate P. vulgaris seeds is strongly affected by seed coat hardness. Comparisons between the four species suggest differences in the chemical properties of the seed coat of P. lunatus seeds. Some hypotheses are suggested for the relationship between A. obtectus larvae and their host plant.     

Resistance to Callosobruchus maculatus (F.) (Coleoptera: Bruchidae) in pigeonpea (Cajanus cajan (L.) Millsp.) and other Cajanus species

Seeds of 24 accessions of pigeonpea (Cajanus cajan (L.) Millsp.) and four other species of Cajanus (formerly Atylosia) were evaluated for their resistance to infestation by Callosobruchus maculatus (F.). None of the pigeonpea accessions was resistant but resistance was evident in three species of Cajanus. In C. platycarpus most of the larvae failed to enter the hard seed coats but the few which did enter the seeds, developed normally. Adults did not emerge from the seeds of C. scarabaeoides, even though most of the larvae entered the seeds. In A. sericeus, the number of larvae entering the seeds as well as adult emergence was significantly reduced.     

Egg production and development of three strains of Callosobruchus maculatus (F.) (Coleoptera: Bruchidae)

The numbers of eggs laid by individual females of three geographically isolated strains of C. maculatus (F.) on different numbers of cowpeas were counted. Females of strains originating in the Yemen and Brazil laid about 40 eggs when provided with a single cowpea, whilst females of a Nigerian strain laid 75. Given 40 cowpeas, females of all three strains laid between 80 and 90 eggs. Only one or two adults of the Yemen strain emerged from cowpeas irrespective of the initial number of eggs present, compared with the ten or more adults of the other two strains which emerged when the cowpea bore numerous eggs. The daily levels of oviposition did not differ among the strains when females had access to cowpeas changed daily for others bearing no eggs. The periods of development differed among the three strains, the greatest median value being 33 days in the Yemen strain where the greatest individual variation in development times was also noted. The significance of the results to the development of possible control measures for this pest is discussed.     

Effect of monoterpenoids on oviposition and mortality of Callosobruchus maculatus (F.) (Coleoptera: Bruchidae) under hermetic conditions

Monoterpeniods have been shown to cause mortality in certain stored-product insect pests. The current report investigated the prospects of using monoterpenoids as oviposition deterrents of the cowpea beetle, Callosobruchus maculatus (Fabricius), as well as in the management of populations of the beetle. The monoterpenoids investigated include E-anethole, estragole, S-carvone, linalool, L-fenchone, geraniol, γ-terpinene and DL-camphor, and at the concentrations of 66.7, 33.3, 16.7, 8.33 and 0 μL/L. Exposure of the life stages of the beetle, which included eggs, young larvae (first instar), 4th instar, pupae and adults to different concentrations of the monoterpenoids over 24 h period caused varying levels of mortality. The stages of the beetle that were the least susceptible to the monoterpenoids were the 4th instar, and the pupae, which required high concentrations of the monoterpenoids to achieve 99% mortality. The adults and the eggs exhibited the highest susceptibility to the monoterpenoids. Mated C. maculatus females that were offered cowpea seeds upon treatment with low doses (8.33 μL/L) of the monoterpenoids did not lay eggs, while control female beetles offered untreated seeds laid several eggs. However, mated C. maculatus females laid eggs on cowpea seeds treated with monoterpenoids 3 weeks before to the day of experimentation. The monoterpenoids did not exhibit residual toxicity to the cowpea beetles. These monoterpenoids could be further investigated for the postharvest management of seed beetles of grain legumes.     

Effect of constant temperature and humidity on oviposition and development of Callosobruchus maculatus (F.) and Callosobruchus subinnotatus (Pic) on bambara groundnut, Vigna subterranea (L.) Verdcourt

The effect of different conditions of temperature and humidity on oviposition and development of Callosobruchus maculatus and Callosobruchus subinnotatus was investigated in the present study. Four temperatures (25°C, 30°C, 35°C and 40°C) and three humidities (30%, 60% and 90% r.h.) were evaluated on both species in pure and mixed populations on bambara groundnut (Vigna subterranea) seeds. In both pure and mixed populations, temperature influenced oviposition and progeny development of both species significantly more than humidity. Egg-laying and progeny development in C. maculatus were optimal at 35°C. In contrast, oviposition and progeny development in C. subinnotatus were optimal at 30°C. In mixed populations, where eggs were laid by females of C. maculatus and C. subinnotatus held together, more C. maculatus adults than C. subinnotatus adults were produced at the various temperatures and humidities. No adult progeny of either species developed in pure or mixed populations at 40°C. C. maculatus was more fecund than C. subinnotatus and development from egg to adult took much longer in C. subinnotatus than in C. maculatus in both pure and mixed populations. The implications of these findings for the development and survival of both species in the different agroecologies and seasons in Nigeria are discussed.     

Biology of an egg parasite of Callosobruchus maculatus (Fab.) (Coleoptera: Bruchidae)

Uscana mukerjii (Mani) (Chalcidoidea, Trichogrammatidae) parasitizes eggs of Callosobruchus maculatus. Mated adult U. mukerjii lived for 5.0 ± 0.8 and 4.7 ± 0.9 days (males and females, respectively) at 27 °C. The female copulated only once, whereas males did so up to 4 times. The maximum parasitization of host eggs took place within the first 24 hours of egg laying and declined thereafter. The parasite completed its development inside the host egg in 7.2 days at 27 °C and 60–63% r.h. and emerged after cutting a circular hole in the chorion of the host egg. Mated and unmated females laid 35.4 ± 1.4 and 36.0 ± 2.2 eggs in their life time of which 27.3 ± 1.8 and 23.2 ± 2.8, hatched respectively. Parasitized host eggs did not hatch and were ultimately destroyed. The degree of parasitization varied with the pulses on which the host eggs were laid. This egg parasite may be useful in controlling the populations of C. maculatus and thus help in reducing the damage caused.     

Fumigant toxic activity and reproductive inhibition induced by monoterpenes on Acanthoscelides obtectus (Say) (coleoptera), a bruchid of kidney bean (Phaseolus vulgaris L.)

The toxic activity of some characteristic monoterpenoids: p-cymene, -pinene, camphor, linalool, terpineol, cuminaldehyde, cinnamaldehyde, anethole, carvacrol, thymol, estragole and eugenol, was tested against Acanthoscelides obtectus (Say), a bruchid pest of kidney bean (Phaseolus vulgaris L.). A fumigant toxic effect was observed and LC₅₀ concentrations for 24h and 48h were calculated for adults.

Besides this effect, a reproductive inhibition was observed. This inhibition involved female fecundity, oviposition, and the development of neonate and intracotyledonal larvae. The effects of monoterpenes on oviposition, larval penetration inside the seeds and emergence were determined. All monoterpenes revealed a more or less pronounced vapour toxicity and significantly inhibited beetle reproduction. Oxygenated monoterpenoids: carvacrol, thymol, eugenol, linalool and terpineol were identified as the most efficient compounds in both respects and the structure-activity relationship is discussed.     

Factor inhibiting growth of Trogoderma granarium Everts (Coleoptera: Dermestidae) in lentil and French bean: Suppression by addition of natural diets

It is demonstrated that wheat flour suppresses the activity of inhibitors and increases the dietary efficiency of lentil (Lens esculenta Moench.) and French bean (Phaseolus vulgaris L.) for Trogoderma granarium Everts. This antagonism of the inhibitory activity is less marked in green gram (P. aureus Roxb.) and least in semisynthetic glucose-brewer's yeast mixture. Such inhibition of the antagonistic property of natural foods has not been demonstrated before in insects.     

Field infestation of pigeonpea (Cajanus cajan (L.) Millsp.) by Callosobruchus chinensis (L.) in Uganda

Studies were conducted in Uganda to determine the importance of field infestation of pigeonpea by bruchids, and whether or not the susceptibility of the pigeonpea pod to infestation changes during pod and seed development. A survey of farmers’ fields in the major pigeonpea growing areas in northern Uganda showed that bruchids did infest pigeonpea in the field. In all three districts surveyed (Apac, Gulu and Lira), infestation levels were similar and by one species only, Callosobruchus chinensis. Once harvested, infestation of stored seeds was four times greater than stored pods. In a separate study, caged pigeonpea pods were infested at seven different developmental stages by C. chinensis. The number of eggs laid increased with development, from pod formation to the mature yellow stage, but declined thereafter. When pods were incubated, there was no adult emergence from pods infested after they had matured and started to dry. The frequency of C. chinensis adult emergence varied significantly over time; a bimodal frequency pattern of emergence was observed from pods infested at mature green stage and, to a lesser extent at the preceding late pod filling state, suggesting the occurrence of polymorphism.     

黔江烟田病毒与周边作物及杂草携毒关系分析

为明确烟田烟叶携带病毒与周边作物和杂草携带病毒的亲缘关系,利用RT-PCR克隆烟田烟叶与周边杂草和作物携带病毒外壳蛋白（CP）,通过MEGA序列比对分析黔江烟田烟叶和周边杂草与作物所带病毒种类及其亲缘关系。结果显示,黔江地区烟草感染病毒有烟草普通花叶病毒（TMV）、黄瓜花叶病毒（CMV）和马铃薯Y病毒（PVY）;在烟田周边杂草和作物番薯、四季豆、糯米团、三悬叶钩草、杂草中检测到了TMV;自番薯、四季豆、蓬蘽、千里光、糯米团、三悬叶钩草中扩增出CMV;自番薯、四季豆、假酸浆、杂草中扩增出了PVY。进化关系分析显示,三悬叶钩草、四季豆、糯米团以及番薯为黔江烟田烟叶TMV的主要来源,蓬蘽为烟叶病毒病CMV的侵染源,假酸浆为烟田PVY的主要来源。     

Comparative life history studies of four Callosobruchus species infesting cowpeas with special reference to Callosobruchus rhodesianus (Pic) (Coleoptera: Bruchidae)

A comparative study of the ecology of Callosobruchus analis (F.), C. chinensis (L.), C. rhodesianus (Pic) and two strains of C. maculatus (F.) was made at three temperatures (25, 30 and 35°C) and three relative humidities (60, 70 and 80% r.h.). The performances of C. rhodesianus and the strain of C. maculatus from Brazil were also compared at 20°C. The intrinsic rates of increase of each species at each temperature were estimated. The optimum temperature for multiplication of all species was around 30°C. Total oviposition was highest at 30°C for all species, but survival from egg to adult was highest at 25°C for C. rhodesianus and the Malawi strain of C. maculatus compared with 30°C for the others. Development of both strains of C. maculatus was fastest at 35°C, but all other species developed most rapidly at 30°C. Relative humidity in the range 60–80% had no appreciable effect on any of the biological characteristics studied. The performance of C. rhodesianus was better at 20°C than that of the Brazilian strain of C. maculatus, and the results are discussed in relation to the distribution of the two species in Africa.