Effects of chemical- and bio-fertilizers on cowpea resistance to cowpea weevil,Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae)

The cowpea weevil, Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae) is a destructive pest of cowpea grains in the field and storage. Effects of two chemical fertilizers (triple superphosphate (TSP) and urea) and three bio-fertilizers (Bradyrhizobium japonicum, Pseudomonas putida and mycorrhizal fungi) compared to control were studied on resistance of cowpea pod and grain to C. maculatus. Pod resistance was evaluated as oviposition preference, egg-to-adult survival and developmental time, and grain resistance was measured as life history and life table parameters of the pest. Cowpea plants treated with tested fertilizers were grown under field condition. Then, the full-size green pods and their immature grains were harvested and used in the experiments. The highest oviposition preference and percentage of adults emergence were on control (untreated) pods as compared to treated ones. The longest developmental times were recorded on the pods obtained from TSP and B. japonicum treatments. In most cases, significant differences were observed for the life history and life table parameters of C. maculatus on the grains treated with examined fertilizers. Delayed developmental time was recorded when C. maculatus was fed with P. putida- and B. japonicum-treated grains. The highest and lowest number of eggs laid by each female (fecundity) was on the grains obtained from TSP and control treatments, respectively. The net reproductive rate (R₀), intrinsic rate of increase (r_m) and finite rate of increase (λ) were the lowest on cowpea grains fertilized with B. japonicum and highest on the grains treated with urea. Our results showed that B. japonicum can be suggested to utilize, as an alternative for chemical fertilizers, to minimize cowpea infestation by C. maculatus. These findings could be helpful in developing integrated management of the pest on cowpea.     

Allyl isothiocyanate actions on populations of Sitophilus zeamais resistant to phosphine: Toxicity,emergence inhibition and repellency

The risks associated with the use of synthetic insecticides have caused increased interest in the research of essential oils and their main constituents for use in the pest management of stored products. Allyl isothiocyanate (AITC) is the main component of mustard essential oil and has been reported as a potential replacement pesticide for conventional insecticides that control stored product insect pests. Here, we assessed the toxicity (including emergence inhibition) and repellent actions of AITC on Brazilian populations of the maize weevil Sitophilus zeamais (Coleoptera: Curculionidae) resistant to conventional insecticides (e.g., phosphine). We also evaluated physiological (e.g., respiration) and behavioral (e.g., walking and flight) traits of AITC-exposed insects. The AITC showed consistent insecticidal activity against the populations resistant to phosphine and other synthetic insecticides, with LC₅₀ values ranging from 1.5 to 2.9 μL L⁻¹. Significant inhibition of the offspring emergence was achieved after the exposure of parental adults to sublethal levels (i.e., LC₁ and LC₅) of AITC. Reductions in respiration rates were also registered in all the populations sublethally exposed to AITC. In all five populations, a high number of insects avoided AITC-treated (1.5 μL L⁻¹) grain masses, and although individuals of a phosphine-susceptible (i.e., Abre Campo) population increased walking and reduced flight activities, individuals of another phosphine-susceptible (i.e., Tunápolis) population exhibited higher flight activity under AITC exposure. Thus, our findings suggest that AITC is a potential tool that may be integrated into the control strategies of maize weevils where resistance to phosphine and other conventional insecticides is a problem.     

Efficacy of ozone for Callosobruchus maculatus and Callosobruchus chinensis control in cowpea seeds and its impact on seed quality

The insecticidal efficacy of ozone was evaluated against the adults of Callosobruchus maculatus (F.) and C. chinensis L. on stored cowpea seeds under laboratory conditions. Ozone was assessed at concentrations of 0.25, 0.5, 1.0, 1.5, and 2.0 g/m³. The effect of ozone treatments on the adult mortality after 1, 3, 5 and 7 days of treatment, progeny production after 45 days, cowpea seed weight loss, seed germination and chemical constituents of cowpea seeds were determined. Adult mortality of C. maculatus and C. chinensis was improved with the increase in ozone concentration. Thus, all tested concentrations caused complete adult mortality of C. chinensis after 7 days of treatment, while the concentrations of 1.0, 1.5, and 2.0 g/m³ caused complete adult mortality of C. maculatus after the same periods. Progeny of both species was significantly decreased in all ozone concentrations after 45 days of treatment. Nevertheless, strong suppression in progeny production was achieved at the highest concentration of ozone (2.0 g/m³). Also, the ozone treatment at the highest concentration protected the cowpea seeds from damage caused by C. maculatus and C. chinensis for 45 days. In addition, there was no significant effect of ozone treatments on the cowpea seed germination compared with untreated seeds. Moreover, the chemical analysis of treated cowpea seeds showed a slight decrease in protein, fat, carbohydrate, moisture, total phenolics, total flavonoids and tannins contents, and a slight increase in fiber and ash contents compared with untreated cowpea seeds. Our findings suggest the ozone can be effectively used for the control C. maculatus and C. chinensis and can provide sufficient protection of stored cowpea seeds.     

Control of Callosobruchus maculatus (FABR.) (Coleoptera: Chrysomelidae: Bruchinae) in Vigna unguiculata (L.) WALP. with essential oils from four Citrus spp. plants

The cowpea weevil, Callosobruchus maculatus (F.), is a major pest of cowpea Vigna unguiculata (L.) Walp. in storage units, making the grains unsuitable for consumption. The adverse effects of chemical control methods have been motivating the demand for alternatives in pest control, such as the use of natural products like essential oils. The aim of this study was to obtain and chemically identify the components of essential oils extracted from fruit peels of Citrus latifolia Tanaka, Citrus reticulata Blanco, Citrus sinensis L. Osbeck and Citrus paradisi Macf., as well as to determine the contact and fumigant toxicity of these oils and their repellent effect on C. maculatus adults. The GC-MS analysis identified 45 compounds in the essential oils; the major components were described as follows: C. latifolia (limonene 57.7%, γ-terpinene 17.2%, β-pinene 12.3%, α-pinene 2.0%), and C. sinensis (limonene 93.8%, myrcene 2.1%), C. reticulata (limonene 94.2%, myrcene 1.6%) and C. paradisi (limonene 94.2%, myrcene 1.8%). In the contact toxicity tests using treated cowpeas the LC₅₀ values ranged from 943.9 to 1037.7 ppm, with the lowest value for C. latifolia and the highest for C. sinensis. The number of eggs and newly emerged adults was inversely proportional to essential oil concentration increase. In the fumigant toxicity test, LC₅₀ values ranged from 10.2 to 12.98 μL/L air, with C. latifolia showing the best results. In the repellency test, the essential oils were classified as neutral at all concentrations. The percentages of oviposition reduction ranged from 29.74 to 71.66%, while reduction in emergence varied from 15.43 to 85.31%. Essential oils of citrus peels (industrial waste) could be widely used for C. maculatus control. Moreover, they could gain economic value if used on a large scale to produce essential oils.     

Semiochemical modulation of host preference of Callosobruchus maculatus on legume seeds

Host preference of Callosobruchus maculatus (F.) on seeds of three legume cultivars, Ife-brown and black-eyed cowpeas [Vigna unguiculata L. (Walp)], and soybean (Glycine max L.), was investigated. Mated female C. maculatus showed high (90–95%) attraction to the three legume cultivars in Y-tube bioassays. However, the weevils discriminated among the cultivars in four-choice tests and showed greater attraction to Ife-brown cowpea (50%) than to soybean (30%) and black-eyed cowpea (15%). Coupled gas chromatography-electroantennography (GC-EAD) and GC–MS analyses of the headspace volatile organic compounds (VOCs) emitted by the legume seeds identified 2-ethyl hexanol as the principal EAD active component. Emission of 2-ethyl hexanol was two-fold greater in Ife-brown cowpea (∼0.54 μg g⁻¹ seeds) compared with black-eyed cowpea (∼0.23 μg g⁻¹ seeds) and soybean (∼0.21 μg g⁻¹ seeds). Synthetic 2-ethyl hexanol attracted 68% of female C. maculatus at 0.01 μg dose in Y-tube bioassays. These results demonstrated that host preference in C. maculatus is odor-mediated, and identified 2-ethyl hexanol as a potential attractant for C. maculatus.     

Contact and fumigant toxicity and repellency of Eucalyptus citriodora Hook., Eucalyptus staigeriana F., Cymbopogon winterianus Jowitt and Foeniculum vulgare Mill. essential oils in the management of Callosobruchus maculatus (FABR.) (Coleoptera: Chrysomelidae,Bruchinae)

The weevil Callosobruchus maculatus (Fabr.) is considered the most important pest of cowpea, Vigna unguiculata (L.) Walp., stored in tropical and subtropical countries. Secondary compounds extracted from plants can be used in its control, as a potential alternative to synthetic insecticides. Therefore, the present study aimed to: (a) make the chromatographic and mass spectrometry analyses of the essential oils of Eucalyptus citriodora Hook, Eucalyptus staigeriana F., Cymbopogon winterianus Jowitt and Foeniculum vulgare Mill; (b) to evaluate the contact and fumigant toxicity; (c) test the repellent effect. The oils' main compounds were: E. citriodora (citronellal 89.59%; citronellyl acetate 3.34%; 1,8-cineole 2.87%), E. staigeriana (limonene 28.75%; geranial 15.20%; neral 12.16%), C. winterianus (geranial 21.83%; citronellal 10.94%) and F. vulgare (limonene 41.82%; (E)-anethole 17.91%; α-pinene 11.13%). The LC_50s of F. vulgare, E. citriodora, C. winterianus and E. staigeriana in contact tests were estimated at 178.13, 298.17, 328.42 and 345.57 ppm cowpea grains, respectively. According to regression analyses, the higher the oil concentration, the lower the number of laid eggs and emerged insects. In fumigation tests with adults, LC_50s ranged from 2.58 to 7.85 μL/L of air, while the toxicity ratios ranged from 1.25 to 3.04. In all concentrations tested, the E. citriodora and C. winterianus oils were repellent to adult C. maculatus; F. vulgare was classified as neutral, while E. staigeriana was neutral at lower than 558 ppm concentrations and repellent at higher concentrations. Regarding the essential oils tested, the percentage of oviposition reduction varied from 6.3 to 100%, while emergence percentages varied from 0.9 to 100%.     

A laboratory assessment of the potential of different strains of the entomopathogenic fungi Beauveria bassiana (Balsamo) Vuillemin and Metarhizium anisopliae (Metschnikoff) to control Callosobruchus maculatus (F.) (Coleoptera: Bruchidae) in stored cowpea

Twelve indigenous and exotic isolates of Beauveria bassiana and Metarhizium anisopliae were evaluated for their virulence and their ability to suppress populations of Callosobruchus maculatus in stored cowpea. LT₅₀ values ranged from 3.11 to 6.12 days following immersion in aqueous suspensions containing 1×10⁸ conidia ml⁻¹. Indigenous isolates that had been recovered from C. maculatus were more virulent in laboratory bioassays than exotic isolates from other insects. The two isolates with the shortest LT₅₀ values were compared in dose-response assays by immersion and by exposure to cowpea grains treated with dry conidia. In both assays B. bassiana 0362 was consistently more virulent than M. anisopliae 0351. By immersion, LC₅₀ values on day 6 post-treatment were 9.10×10⁴ and 7.10×10⁵ conidia ml⁻¹ for B. bassiana 0362 and M. anisopliae 0351, respectively. Exposure to treated grains gave LC₅₀ values of 1.15×10⁷ and 4.44×10⁷ conidia g⁻¹ grain for B. bassiana 0362 and M. anisopliae 0351, respectively. In 1 kg batches of cowpea stocked with 50 adult C. maculatus, B. bassiana 0362 at both 1×10⁷ and 1×10⁸ conidia g⁻¹ grain led to significant adult mortality and reduced F₁ emergence relative to untreated populations. At 1×10⁸ conidia g⁻¹ the effect of the fungus persisted into the F₁ generation. The net reproductive rates, R₀, measured 26 days after insects were released were 5.16 and 7.32 for the high and low doses compared to 9.52 for the untreated control.     

Insecticidal potential of a synthetic zeolite against the cowpea weevil,Callosobruchus maculatus (Fabricius) (Coleoptera: Bruchidae)

The insecticidal potential of a synthetic zeolite was evaluated against the cowpea weevil, Callosobruchus maculatus (Fabricius). The synthetic zeolite was applied to concrete surfaces at 0, 2.5, 5, 10 and 20 g/m², and the mortality of adults was assessed after 1, 3, 6, 9, 12, 24, 36, 48, and 72 h at 28 °C and 65% r.h. The residual efficacy of zeolite applied at 5 g/m² was evaluated on concrete surfaces at 0, 1, 2, 3, and 4 months post-treatment. Adults of C. maculatus were exposed to cowpeas treated with zeolite at 0, 0.1, 0.5, 1, 2, 3, 4, and 5 g/kg. The number of eggs deposited on cowpea kernels and their hatchability were determined after 7 and 14 d, respectively. The cumulative adult mortality was recorded after 1, 2, 3, and 4 d, and adult progeny production after 42 d. The residual efficacy of zeolite on cowpeas was tested at 0, 1, 2 and 3 months after treatment. On concrete, zeolite applied at ≥ 5 g/m² resulted in 100% mortality of C. maculatus adults after 24–72 h of exposure. Zeolite at 5 g/m² exhibited high residual efficacy with 100% mortality of C. maculatus adults after 36 h exposure on treated surfaces for up to 4 months. The mortality of C. maculatus adults exposed to zeolite-treated cowpeas increased with increasing concentration and exposure time. The number of eggs laid by C. maculatus, number of kernels with eggs, and adult progeny production decreased with increasing zeolite concentration. Zeolite applied to cowpeas at 1 g/kg produced 100, 99 and 77% adult mortality at 1, 2, and 3 months post-treatment. Progeny production on zeolite-treated cowpeas was significantly lower than that on untreated cowpeas. These results show that the synthetic zeolite is effective on concrete surfaces and on cowpeas in controlling C. maculatus.     

Genetics of bruchid (Callosobruchus maculatus Fab.) resistance in cowpea (Vigna unguiculata (L.) Walp.)

Bruchid resistance has been measured using a variety of techniques. Mean development period (MDP) and percentage adult emergence (PAE) are two of the more important traits measuring bruchid (Callosobruchus maculatus Fab.) resistance in cowpea. The objective of the study was to evaluate the genetic relationship between MDP and PAE in C. maculatus resistant cowpea. Seventy-two F₂ population plants were developed from the cross between C. maculatus resistant TVu-11953 (with delayed MDP and low PAE) and C. maculatus susceptible Ife Brown (with early MDP and high PAE) which were evaluated for resistance to cowpea C. maculatus. MDP at 45 days after infestation (DAI) and PAE at 60 DAI were taken as analysed measures for resistance to C. maculatus infestation. Data generated were subjected to chi-square analysis. Varied resistant response to C. maculatus infestation was observed among the F₂ generation plants but their responses showed inclination to the susceptible parent. A 15:1 ratio for susceptible to resistant genotypes was observed with MDP among the F₂ genotypes evaluated which is an indication of the presence of two recessive genes that control of MDP. The segregation of PAE also showed a 15:1 ratio goodness of fit (P > 0.05) for susceptible to resistant genotypes. Test of independence between MDP and PAE was not significant (χ² = 2.19, P = 0.19). This study revealed that the recessive genes controlling these two traits (MDP and PAE) were independently assorted and showed no linkage. This was also evident in the observed F₂ genotypes with C. maculatus resistance expressing either delayed MDP or low PAE and not both in the study.     

Resistance screening of 14 Cajanus cajan (L.) Millsp. cultivars to Callosobruchus maculatus (F.) (Coleoptera:Bruchidae)

Pigeonpea, Cajanus cajan, is a rich source of human dietary protein and carbohydrate as well as an income generator for farmers especially in developing countries. However, a major limiting factor to the viable production and post-harvest preservation of pigeonpea is infestation by the cowpea weevil, Callosobruchus maculatus. An experiment to screen for resistance in 14 newly developed C. cajan cultivars from The University of the West Indies (UWI) was conducted. The experiment compared oviposition preference based on eight parameters, namely, testa thickness, testa hardness, seed sphericity, surface area, total adult emergence, larval + pupal mortality, seed hardness and surface roughness. Four of the pigeon pea cultivars screened were resistant and could be ranked in the order of decreasing resistance as: A16 = A66PL1> A112 > A196PL2. Seed surface roughness, seed testa hardness and seed grain hardness were all found to play a major role in oviposition deterrence with seed roughness being the most effective deterrent. The results suggest that breeding for pigeonpea cultivars with rougher seed coats, harder seed testa and harder grains could enhance pigeonpea seed resistance to C. maculatus by reducing infestation and damage while in storage.     

Individual and combined effects of insecticides,inert dusts and high temperatures on Callosobruchus maculatus (coleoptera: Chrysomelidae)

In this study individual and combined effects of some chemical and physical factors including cypermethrin, dichlorvos, ash, kaolin and high temperatures were assessed on adults of cowpea seed beetle Callosobruchus maculatus (F.) at laboratory conditions. The adults were exposed to the studied factors on concrete arenas prepared in plastic Petri dishes. Twenty up to 24 h old adults were released in each Petri dish, and their mortality was recorded 72 h after treatment. The LC₂₅ values of the insecticides, LD₂₅ values of the inert dusts and LTi₂₅ values of high temperatures were estimated and used for determining combination effects of the two factors. To determine combination effects of three factors, LC₁₅ values of insecticides, LD₁₅ values of inert dusts and LTi₁₅ values of high temperatures were estimated and used in the bioassays. The LC₅₀ and LD₅₀ values for cypermethrin, dichlorvos, ash and kaolin were 1286.96 mg a. i./L, 1350.55 mg a. i./L, 36.64 g/m² and 45.18 g/m², respectively. The LTi₅₀ values at 45, 48, 50, 52 and 55 °C were 34, 29, 18, 11 and 8 min, respectively. The results indicated that the effect of simultaneous exposure to cypermethrin, high temperatures and ash or kaolin was significantly more than sum of individual effects of these factors. It means the effects of cypermethrin, high temperatures and inert dusts were synergized by each other. If similar treatments performed at larger scales give comparable results, it may be concluded that reduced dosage of cypermethrin, high temperatures and ash or kaolin combinations would be effective alternative control methods and can be used in cowpea seed beetle management programs.     

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.     

Base-line susceptibility of field populations of Rhyzopertha dominica (F.) to spinosad in Australia

Spinosad has recently been registered in several countries for long-term protection against a range of stored grain insects including the lesser grain borer, Rhyzopertha dominica (F.). The potential for development of resistance to spinosad is demonstrated by the existence of resistance in many insect pests of agriculture. The aim of this study was to determine the base-line susceptibility of R. dominica to spinosad, to provide a basis for future resistance monitoring. Eighteen insect populations of R. dominica were collected from field storage sites across four States within Australia, and exposed to a range of spinosad rates, including its current registered rate of 1 mg kg⁻¹ (1 ppm). Base-line susceptibility was assessed based on adult mortality and production of F₁ adults. Comparison of LC₅₀ and LC_99.9 indicated the existence of low level of variation among the tested R. dominica populations, in their susceptibility to spinosad. For adults, there was a narrow range of LC₅₀ values with the highest (0.027 ppm) being 2.5 × the lowest (0.011 mg kg⁻¹). Similarly, LC_99.9 values showed a narrow range with the highest (0.36 mg kg⁻¹) being 3.6 × the lowest (0.10 mg kg⁻¹). For adult progeny produced in spinosad treated grain, there was a narrow range of LC₅₀ values with the highest (0.025 mg kg⁻¹) being 5 × the lowest (0.004 mg kg⁻¹) and the highest LC_99.9 values (0.67 mg kg⁻¹) being 5 × the lowest LC_99.9 (0.13 mg kg⁻¹). Based on the data generated from this study, we recommend a dose of 1 mg kg⁻¹(1 ppm) to be used to discriminate between susceptible and resistant populations for future resistance monitoring programs.     

Effects of cowpea varietal susceptibility and low pressure on the mortality of life stages of Callosobruchus maculatus (Coleoptera: Bruchidae)

Low pressure creates a low-oxygen controlled atmosphere that can kill all developmental stages of Callosobruchus maculatus (F.) (Coleoptera: Bruchidae). This study investigated the interaction of low pressure with seed variety to determine the susceptibility of different cowpea varieties to developmental stages of C. maculatus. Laboratory studies were performed to determine exposure periods to low pressure (32.5 ± 1.0 mm Hg) necessary to kill all life stages of C. maculatus on different cowpea varieties. The results indicated that with the exception of eggs, differences in exposure periods required to achieve 100% mortality varied with life stage and variety. The larval stages were the most susceptible, and larvae required shorter exposure periods to low pressure when reared on C. maculatus resistant varieties (24-125B-3 and IT89KD-288) than on susceptible varieties (CB-3, CB-5, CB-46 and UC-27). Analysis of variance (ANOVA) showed a significant interaction between the life stages of C. maculatus, exposure time and cowpea varieties on mortality. Integration of low pressure applications with storage of cowpea varieties resistant to C. maculatus has the potential of providing an alternative pest management tool to fumigants, which are sometimes used in protecting cowpea in storage from infestation by C. maculatus.     

Genetic analysis of seed resistance to Callosobruchus chinensis and Callosobruchus maculatus in cowpea

Callosobruchus chinensis (azuki bean weevil) and Callosobruchus maculatus (cowpea weevil) are the most destructive pests that cause significant losses to cowpea (Vigna unguiculata) seeds during storage. Development of cultivar(s) resistance to bruchids is a major goal in cowpea breeding program. Cowpea accession “TVu 2027” has been identified as moderately resistant to C. maculatus. Genetic studies of the seed resistance in this accession using strains of C. maculatus from Africa and America have demonstrated that the resistance is controlled by one or two recessive genes. However, there is no reports on genetics of the resistance to C. chinensis and to strain(s) of C. maculatus from Asia. Therefore, the objective of this study was to investigate genetics of the resistance to C. chinensis and C. maculatus in TVu 2027. TVu 2027 (P₂) and PK2015VTN001 (P₁; susceptible cowpea) were used to develop six basic generations (populations), viz. P₁, P₂, F₁ (P₁ × P₂), F₂ (P₁ × P₂), BC₁P₁ (P₁ × F₁) and BC₁P₂ (P₂ × F₁). The population were evaluated for percentage of damaged seeds (PDS) and area under the disease progress stairs (AUDPS; indicating infestation severity) by C. chinensis and C. maculatus. The results showed that TVu 2027 was moderately resistant to both bruchid species. Broad-sense heritability for PDS and AUDPS was moderate, being 70% and 73% for C. chinensis, respectively, and 64% and 61% for C. maculatus, respectively. Number of genes controlling C. chinensis resistance and C. maculatus resistance was two genes and one gene, respectively. Generation mean analysis revealed that genes with additive effect and additive × dominance gene interaction are involved in the resistance to both bruchid species. Correlation analysis suggested that the genes controlling resistance to C. chinensis and those conferring resistance to C. maculatus are unlinked.     

Toxicity of some citrus peels to Dermestes maculatus Deg. and Callosobruchus maculatus (F)

The toxicity of powdered sun-dried orange and grapefruit peels to Callosobruchus maculatus and Dermestes maculatus was evaluated in the laboratory. LD₅₀ values of orange and grapefruit peels admixed with cowpea grains on adult C. maculatus were 4.00 g (peel)/100 g (cowpea) and 5.62 g (peel/100 g (cowpea) respectively. LD₅₀ values of the ground peels on adult D. maculatus were much higher at 14.13 g (orange peel)/100 g (fish chips) and 14.29 g (grapefruit peel/100 g (fish chips). Orange and grapefruit peels deterred adult test insects from admixed cowpea and dried fish chips respectively. Orange peel at high dosages was also shown to depress progeny development of D. maculatus. The possible use of ground orange peel as a protectant for at least cowpea grains from C. maculatus infestation in small-scale storage in Nigeria is discussed.     

Contact toxicity of filter cake and Triplex powders from Ethiopia against Sitophilus oryzae

Contact toxicity of filter cake and Triplex powders from Ethiopia were evaluated against the rice weevil, Sitophilus oryzae (Linnaeus). The study was aimed at determining the lethal and effective concentrations and times for both powders against S. oryzae. The lethal concentrations for 50 and 99% mortality (LC₅₀ and LC₉₉) of filter cake and Triplex against S. oryzae were determined at 14 d after exposing 10 adults for 12 h to concrete arenas inside Petri dishes treated with filter cake concentrations of 0.5–8 g/m² and Triplex concentrations of 1–9 g/m². Lethal times for 50 and 99% mortality (LT₅₀ and LT₉₉) were determined at 14 d after exposing adults for 1–24 h to 3 g/m² of filter cake and 9 g/m² of Triplex. Effective concentrations (EC₅₀ and EC₉₉) and times (ET₅₀ and ET₉₉) for 50 and 99% reduction of adult progeny production were determined from reduction in adult progeny production relative to production in control treatments at 42 d after exposure to filter cake and Triplex. LC₅₀ and LC₉₉ values for S. oryzae adults were 0.70 and 8.49 g/m², respectively, when exposed to filter cake and 2.27 and 21.38 g/m², respectively, when exposed to Triplex. The corresponding LT₅₀ and LT₉₉ values were 3.13 and 27.21 h, respectively, for filter cake and 4.72 and 38.60 h, respectively, for Triplex. EC₅₀ and EC₉₉ values for progeny reduction were 0.57 and 7.95 g/m², respectively, for filter cake and 2.77 and 18.82 g/m², respectively, for Triplex. The corresponding ET₅₀ and ET₉₉ values were 2.57 and 17.73 h, respectively for filter cake and 3.39 and 24.74 h, respectively, for Triplex. S. oryzae exposed to filter cake produced significantly less number of insect damaged kernels and grain weight loss than those exposed to Triplex. Filter cake was more efficacious against S. oryzae than Triplex.     

Effect of different legume seeds on life table parameters of cowpea weevil,Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae)

The cowpea weevil, Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae) is one of the most important storage pests of legume seeds. The effect of various legume species including chickpea (Cicer arietinum L.) (cultivars Hashem and Mansour), cowpea (Vigna unguiculata L.) (cultivars Mashhad and 1057), green gram (Vigna radiata L.) (cultivar Parto), lentil (Lens culinaris Medikus) (cultivar Bilehsavar) was studied on the life history and life table parameters of C. maculatus at 30 ± 1 °C, relative humidity of 65 ± 5% and complete darkness. The developmental time was longest on lentil and shortest on cowpea 1057. The fecundity (number of eggs laid per reproductive period) of the pest was the lowest on lentil. The longest oviposition period was observed on chickpea Hashem. The gross and net reproductive rates were the highest on chickpea Mansour and lowest on lentil. The intrinsic rate of increase and finite rate of increase were the lowest when C. maculatus was reared on lentil and highest when it was reared on other hosts. The longest and shortest mean generation times were observed on lentil and cowpea 1057, respectively. According to the obtained results, lentil was relatively resistant and the other tested legumes were more susceptible hosts for feeding and population increase of C. maculatus. It is concluded that the resistant host cultivar can be proposed to be incorporated into breeding programs to minimize the economic losses incurred by C. maculatus.     

CFD simulation of ozone gas flow for controlling Sitophilus zeamais in rice grains

Ozone gas (O₃) is a prominent alternative for the integrated pest management of stored products. The present study fitted a computational fluid dynamics (CFD) model to elucidate the ozone gas flow dynamics in an aeration system, at a lethal concentration for Sitophilus zeamais Mots in rice grains. First, an experiment was carried out to understand the flow of ozone gas (2.2 mg L⁻¹; 2 L min⁻¹) in a cylindrical PVC column filled with 4 kg of rice grains. The ozone gas concentration was monitored every 12 h, at a point immediately above the grains. The gas flow was modeled using the CFD technique. The parameters used to feed the model and adjust it to the experimental data were the mass transfer coefficient and ozone-rice grain reaction constant. Then, a simulation of ozone gas injection in a silo with a static capacity of 69.6 tons of rice was performed. In the ozone gas injection experiment, 100% of insect mortality was observed on the sixth day, when the O₃ concentration reached 0.1 mg L⁻¹. In this case, the mass transfer coefficient was 0.55 m s⁻¹, and the reaction constant was 0.78 s⁻¹. At the concentration of 0.8 mg L⁻¹, it is possible to treat 69.6 tons of rice grains within 9 days.     

Influence of fermentation parameters on phytochemical profile and volatile properties of mulberry (Morus nigra) wine

In the present study Box–Behnken Design was employed to analyse the effects of fermentation parameters such as temperature (T _F), pH, inoculum size (I _S) and °Brix (B_X) on total phenolic concentration (TPC), total flavonoid concentration (TFC), total anthocyanin concentration (TAC), ethanol concentration (ETHC), total higher alcohol concentration (THAC) and total ester concentration (TESC) for the development of a phytochemical‐rich wine using mulberry as a substrate. The results demonstrated that fermentation parameters significantly alter the wine characteristics. Hence, a wine with excellent consumer preference (overall acceptability of 8.51) and high concentration of phytochemicals (TPC = 6014.03 ± 27.80 mg L⁻¹, TFC = 4791.35 ± 21.22 mg L⁻¹, TAC = 1480.72 ± 5.33 mg L⁻¹) as well as good aromatic properties (ETCH =82.85 ± 0.87 g L⁻¹, THAC =249.91 ± 0.31 mg L⁻¹ and TESC =52.55 ± 0.17 mg L⁻¹) with high antioxidant activity (DPPH =220.18 mmol·l⁻¹) was obtained at optimized fermentation conditions of T _F = 25°C, pH = 4.00, I _S = 10% (v /v) and B_X = 26. The results from the present study might contribute to strengthening the development of wine containing high concentrations of phytochemical compounds with attractive olfactory attributes. Copyright © 2017 The Institute of Brewing & Distilling