Bioactivity of some natural products against the cowpea storage weevil Callosobruchus Maculatus L.

This work was carried out to evaluate the insecticidal activity of extracts from 14 plant species of Ghanaian origin against Callosobruchus maculatus adults under laboratory conditions. Phytochemical screenings of the 14 plant species were performed using standard laboratory methods to determine the types of secondary natural products present in the plant species. Aqueous, petroleum ether and ethanolic extracts of the 14 plant species were screened for their bioactivity against Artemia selina in a brine shrimp lethality test. The pesticidal activities of the plant products against Callosobruchus maculatus were investigated in laboratory experiments. Contact toxicity (filter paper impregnation method), grain treatment with plant products for insect population and mortality assays, and also effect of the plant products on grain damage were obtained and compared with Actellic Super EC (synthetic insecticide) during a three-month observation period. Cymbopogan winterianus oil caused the highest mortality, least damage to grains and the highest antireproductive effect. All grain-protective properties of the natural products were concentration and time dependent. Extracts of Cassia alata showed good potential in protecting cowpea and gave better protection than the powder, whilst Griffornia simplicifolia did not significantly protect the grains. Phytochemical investigations of the plants revealed the presence of terpenes, saponins, tannins, glycosides, alkaloids, anthraquinones and flavonoids. The presence of some of these compounds may be responsible for the pesticidal action of the plants.Keywords: Phytochemical screening, Extracts, Insecticidal, Brine shrimp lethality test, Cowpea

Executive cash compensation and tax aggressiveness of Chinese firms

We examine the influence of corporate compensation policies on firms’ tax aggressiveness in an emerging market where executive compensation is primarily in cash form. Based on a hand-collected dataset of 958 firm-year observations of Chinese listed firms for the 2006-2012 period, we find that firms paying higher executive cash compensation are associated with lower tax aggressiveness. This relationship also holds for the excess cash compensation measures which control for executive shareholding, firm profitability, size, growth opportunity, and board independence. We further document that mutual funds ownership pressure firms paying higher compensation to reduce their tax aggressiveness, suggesting adverse selection by mutual funds on firms exhibiting risky tax avoidance activities. High leverage offsets the negative link between cash compensation and tax aggressiveness, indicating a complementary effect between debt and tax avoidance, and, hence, suggesting that creditor monitoring is weak. These results are robust to the system-GMM estimation, which simultaneously account for the endogeneity of executive compensation, tax aggressiveness, ownership and control, leverage, and corporate governance. Our findings on Chinese firms have important policy implications for developing countries around the world with concentrated ownership structure, weak institutional environment, widespread corruption, ineffective rule of law, and ongoing significant social and political transformation

Agronomic performance of sweet potato with different potassium fertilization rates

ABSTRACT Sweet potato is a vegetable with great potential due to its versatility of use, which covers human food, animal feed and biofuels. However, it is still little studied, especially regarding mineral nutrition and potassium. Thus, a study was conducted to evaluate potassium fertilizer doses (0, 30, 60, 90, 120 and 150 kg/ha K2O) on mineral nutrition and yield of 'Beauregard' sweet potato in a typic Hapludult soil with low K level (0.3 mmolc/dm3). The experimental design was of randomized blocks with four repetitions. Harvest took place 123 days after seedling transplanting. Foliar K content, shoot, root and total dry matter, root total yield, root commercial yield, K accumulation, K content in the soil and K optimal economic dose were assessed. The highest foliar K content was observed at the dose of 100 kg/ha K2O, with K value of 44.6 g/kg on leaf dry matter. In soils with low K availability, the highest yield (38 t/ha) was observed at the dose of 87 kg/ha K2O. Maximum commercial yield (24.3 t/ha) was obtained at the dose of 85 kg/ha K2O, and K accumulation of 150 kg/ha in the shoot and 57 kg/ha in the root, respectively, were observed (72.5 and 27.5%). Optimal economic production was of 71 kg/ha K2O, which corresponds to 83% of the dose that maximized commercial production