Phytochemical Constituents and Insecticidal Efficacy of the Root and Leaf Powders of Mimosa diplotricha and Aspilia africana against Callosobruchus maculates (Fab.) (Coleoptera: Chrysomelidae)

This study investigated the efficacy of the root and leaf powders of Aspilia africana and Mimosa diplotricha against the cowpea beetle, Callosobruchus maculatus. Newly emerged adults of C. maculatus were exposed to grains treated with one of four treatments (powders: 0.5, 1.0, 1.5 and 2.0 g) of the two plants at different exposure period of 24, 48, 72 and 96 hours. Both A. africana and M. diplotricha exhibited a high level of mortality which was a function of treatment concentration and of exposure time. At 96 hours of exposure, 2 g of the root and leaf powders of A. africana caused 70% and 54% mortality respectively, in C. maculatus. When C. maculatus was exposed to 2 g for a 96-hour exposure, the root and leaf powders of M. diplotricha, however, resulted in 52% and 50% mortality respectively. Although powders from all four treatment types exhibited insecticidal activities by causing varying levels of mortality in C. maculatus, the highest death rate was caused by the root powder of A. africana. Qualitative analysis of the plants revealed that alkaloids, flavonoids, saponins, steroids, tannins, terpenoids and glycosides were present in the leaf extracts of A. africana and M. diplotricha. The moderately high insecticidal activity demonstrated by the root powders suggest that they hold more potential in the control of C. maculatus compared to the leaf powders. Keywords: Mimosa diplotricha, Aspilia africana, phytochemical constituents, Callosobruchus maculatu

Phytochemical constituents and larvicidal efficacy of methanolic extracts of Cymbopogon citratus, Ocimum gratissimum and Vernonia amygdalina against Culex quinquefasciatus larvae

This study assessed the larvicidal efficacy of the methanolic extract of Cymbopogon citratus, Ocimum gratissimum and Vernonia amygdalina against the third instar larvae of Culex quinquefasciatus. Qualitative analysis of the plants revealed that alkaloids, flavonoids, saponins, steroids, tannins, terpenoids and glycosides were present in all three plant extracts. Phlobatannins was present in trace amounts in O. gratissimum and absent in C. citratus and V. amygdalina. Larvicidal activities of the leaf extracts were studied on laboratory reared larvae of Cx. quinquefasciatus at a concentration range of 250 ppm to 1000 ppm. The percentage mortality was calculated and LC50, LC90 values were obtained from probit analysis using SPSS version 16.0 at 95% confidence limit (CL). Result of this study indicated that the percentage mortality of O. gratissimum extract was dose dependent with 250 and 1000 ppm having the percentage mortality of 18.33 and 43.3% respectively after 72 hrs. The percentage mortality in C. citratus extract after 72 hrs was 66.67% at 1000ppm concentration whereas at 750 ppm mortality was 8.33%. The percentage mortality for V. amygdalina increased from 250 to 750 ppm but decreased at 1000ppm with 750 ppm having a mortality of 63.33% and 1000ppm having a percentage mortality of 56.6% after 72 hrs. The LC50 and LC90 values of the methanolic leaf extract obtained after 72 hrs was 1008.19 and 1930.992 ppm for C. citratus, 1148.47 and 2210.727 ppm for O. gratissimum and 754.712 and 1548.499 ppm for V. amygdalina respectively. The methanolic extract of V. amygdalina exhibited a higher degree of potency when compared with the methanolic extract of C. citratus and O. gratissimum with a low LC50 value of 758.403ppm, 758.03 ppm and 754. 712 ppm at 24, 48 and 72 hrs respectively. In summary, this study reports the larvicidal effects of C. citratus, O. gratissimum and V. amygdalina against Cx. quinquefasciatus larvae which can serve as an  lternative to synthetic pesticides in Nigeria.Keywords: Leaf extracts, Culex quinquefasciatus, larvae, toxicity, mortalit

Noxious to ecosystems, but relevant to pharmacology : four South African alien invasive plants with pharmacological potential

Alien invasive plants pose a huge threat to natural and semi-natural ecosystems in their introduced ranges thereby compromising ecosystem integrity. However, anecdotal and empirical evidence suggests that some invasive alien plants are used in traditional medicine due to their pharmacological activities. Here, we evaluated the antimicrobial activity of 70% ethanol, dichloromethane, acetone and hot water extracts of four invasive alien plants in South Africa viz. Dolichandra unguis-cati, Cardiospermum grandiflorum, Chromolaena odorata and Gomphrena celosioides against pathogenic and non-pathogenic microbes. The test organisms included Staphylococcus aureus, Salmonella enterica serovar Typhimurium (S. Typhimurium), Salmonella Dublin, Klebsiella pneumoniae, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, Mycobacterium aurum, M. fortuitum, M. smegmatis, Candida albicans, Aspergillus fumigatus and Cryptococcus neoformans. Phytochemicals that may be responsible for antimicrobial activity were determined using standard phytochemical methods. A further objective was to investigate the safety of these plants by conducting cytotoxicity and genotoxicity tests. All solvent extracts of plants investigated exhibited a broad spectrum of antibacterial activity with minimum inhibitory concentration (MIC) values ranging from 0.039 to 2.5 mg/ml, with the acetone and dichloromethane extracts showing better activity against E. coli, K. pneumoniae and E. faecalis (MIC between 0.039 and 0.078 mg/ml). Of all extracts tested, only the ethanol extracts of C. grandiflorum showed good antimycobacterial activity with MIC of 0.078 mg/ml against M. smegmatis. In contrast, C. grandiflorum only showed moderate antifungal activity, while dichloromethane and acetone extracts of the other three plants were very effective against C. neoformans and A. fumigatus with MIC values ranging from 0.019 to 0.078 mg/ml. All four plants moderately inhibited C. albicans at MIC of 0.156 mg/ml. The plant species were rich in phenolics, flavonoids and tannins in varying amounts and had relatively low levels of cytotoxicity and none was mutagenic. Promising selectivity index values (between 10 and 50) highlight the potential of these plant species as sources of antimicrobial remedies. Despite the ecological noxiousness of these alien invasive plants, our findings suggest that they possess some antimicrobial properties that are too pharmacologically relevant to ignore.AGO is grateful to the National Research Foundation-The World Academy of Science (NRF-TWAS) for the provision of a PhD grant. The NRF is also acknowledged for providing research funding to LJM (Grant No 105993).http://www.elsevier.com/locate/sajb2019-07-01hj2019Paraclinical Science

Reduced mobility but high survival: thermal tolerance and locomotor response of the specialist herbivore, Pareuchaetes insulate (Walker) (Lepidoptera: Erebidae), to low temperatures

Disentangling the responses of insects to variations in their thermal environment is central to our understanding of the evolution of temperature-dependent performance in these species.Here,we report results of experiments examining the effects of high(upper lethal temperature = ULT) and low (lower lethal temperature = LLT) temperature and exposure time on the survival of larvae and adults of a multivoltine, nocturnal moth species, Pareuchaetes insulata, a biological control agent whose impact on an invasive weed, Chromolaena odorata has been variable in South Africa. The influence of temperature and acclimation on locomotion performance of the moth was also investigated. Temperature and duration of exposure significantly affected survival of both adults and larvae of P. insulata with more extreme temperatures and/or longer durations proving to be more lethal. Third instar larvae and adults are both freeze intolerant and had LT50 of −5.9 and −4.7°C, respectively, after a 2 h exposure. Although cold acclimation was beneficial to the nocturnal larvae, temperatures below 10°C significantly reduce their locomotion activities. The average daily minimum temperatures in the coldest months at three locations in South Africa are over 5°C lower than those of Fort Lauderdale, Florida, USA, where P. insulate was originally collected. Our results suggest that lethal high or low temperatures at short timescales are trivial in explaining the variable performance of P. insulata, but reduced locomotion at sub-lethal temperatures may be and important driver of the population dynamics of the biocontrol agent (especially in winter months) and may consequently explain the low population levels of the moth because of possible reduced feeding by larvae during night-time low temperatures