No abstract

The tomato leaf miner (Tuta absoluta) destroyed tomato plants in seven of the Northern states in Nigeria, and has been found in two other states in the South in 2016. The study assessed the incident of the tomato leafminer attack using a questionnaire survey in one of the affected states, for a case study of the problem. A short literature review on bio-ecology of T. absoluta was also conducted, and responses to questionnaires were presented. It appeared that knowledge of farmers on pests and management procedures was poor. The results showed that farmers were not properly oriented on pest reporting, and many farmers were unaware of the existence of government pest support programs. Pest monitoring programs and post attack response systems were found inadequate. Many farmers perceived that the pest was new while some respondents reported that similar attacks occurred on their farms in the previous year. Most respondents declined to answer questions on the possibility of agrobioterrorism being the cause of the attack. We found a lacuna in the government policy which could be potentially exploited by agro-terrorists to inflict attack on crops in a new dimension, but there is no evidence of agro-terrorism in relation to attack on tomato by T. absoluta in Nigeria. The findings could be useful in the development of pest mitigating strategies in agro-dependent developing countries.

The objective of this study was to examine the effect of interacting conditions of water stress (0.995-0.96 water activity; a w ), elevated temperature (25-37°C) and CO 2 (350, 1000 ppm) on growth and sporulation of strains of three entomogenous fungi, Beauveria bassiana, Metarhizium anisopliae and Isaria farinosa. Subsequently, using bioassay systems with locust (Schistocerca gregaria), we examined the effect of elevated CO 2 (control, 350; 650; 1000 ppm CO 2 ) on efficacy of strains of all three species and used crickets (Acheta domesticus) to examine interacting conditions of elevated temperature and CO 2 at two relative humidities (25-35°C; 350, 1000 ppm CO 2 ; 96, 98 and >99% RH) on efficacy of a strain of B. bassiana for the first time. The 3-way interacting factors had a significant effect on growth of the strains of all three species, especially at 35-37°C and 0.96-0.98 a w and 1000 ppm CO 2 . Under these conditions, only one strain of B. bassiana and M. anisopliae was able to grow at a reduced rate as compared to the controls. No strain of I. farinosa was able to grow at 35-37°C either in normal air or in elevated CO 2 at 0.995-0.96 a w showing a high level of sensitivity to these interacting factors. Sporulation of the three strains of each species was also significantly affected by these three-way environmental interactions. There were some intra-strain differences and in most cases for the three species, water stress (0.98-0.96 a w ) at 35-37°C and 1000 ppm CO 2 resulting in either no sporulation or no growth. One strain of M. anisopliae (Ma 29) was particularly tolerant at 0.96 a w at 37°C and 1000 ppm CO 2 . Bioassays with the S. gregaria showed when CO 2 was elevated from 350 to 650 and to 1000 ppm, the relative virulence of two strains of each species was reduced over a 6-day temporal study. Further studies with B. bassiana in a detailed bioassay using crickets under three way abiotic interactions (25-35°C, 99-96% RH and 350 or 1000 ppm CO 2 ) showed that virulence was decreased with no efficacy occurring at 30-35°C and 1000 ppm CO 2 at 96% RH. This study suggests that climate change factors could have a profound impact on the efficacy of such biocontrol agents and thus have major implications for pest control using such approaches.

No abstract

Laboratory study was conducted to evaluate the effect of leaf extracts of five indigenous plant on conidia germination, growth and sporulation of Pseudoperenospora cubensis causing downy mildew disease of muskmelon. Extracts of five plant; mexican sunflower (Tithonia diversifolia), bush banana (Uvaria chamae), salt and oil tree (Cleistopholis patens), goat weed (Ageratum conyzoides) and African eggplant (Solanum macrocarpon) at Four concentrations (15, 30, 45 and 60%) were tested against the growth, conidial germination and sporulation of Pseudoperenospora cubensis in vitro. Results show that all the plant extracts significantly inhibited conidia germination and radial growth compared to the control. The extracts had no significant (p≤0.05) effect on sporulation. The rate of inhibition of growth and conidia germination was concentration dependent being highest at 60% for the extracts. The extracts of Solanum macrocarpon was the most effective followed by Ageratum conyzoides, Cleistopholis patens and Uvaria chamea whileTithonia diversifolia caused the least inhibition of growth and conidia germination. At 15, 30, 45 and 60% concentrations growth of Pseudoperenospora cubensis on PDA modified with Solanum macrocqrponwere 3.79, 3.65, 3.33 and 2.87; and 4.25, 4.12, 3.92 and 3.89 for PDA modified with Tithonia diversifolia. Similarly, conidia germination percentages recorded at same concentration of extracts S. macrocarpon were 87, 85, 70 and 62% while that of T. diversifolia were 91, 87, 84 and 72%. The study shows that the plant extracts has the potential for inhibition of the pathogen.