Reducing pesticide risks to farming communities: cotton farmer field schools in Mali.

We provide results from a study of two separate sectors within the cotton-growing region of southern Mali. In one sector, farmers have engaged in a farmer field school (FFS) training programme since 2003--the other not. One goal of the training was the adoption of alternatives to the use of hazardous insecticides, through integrated pest management (IPM) methods. Over an 8-year period, analysis showed that with roughly 20% of the 4324 cotton-growing farm households having undergone training, hazardous insecticide use for the entire sector fell by 92.5% compared with earlier figures and with the second (control) sector. Yields for cotton in both sectors were highly variable over time, but no evidence was found for changes in yield owing to shifts in pest management practices. Evidence is presented for a likely diffusion of new practices having taken place, from FFS participants to non-participants. We discuss strengths and weaknesses of the FFS approach, in general, and highlight the need for improved baseline survey and impact analyses to be integrated into FFS projects.

Plant parasite control and soil fauna diversity.

The use of pesticides to control plant parasites and diseases has generated serious problems of public health and environmental quality, leading to the promotion of alternative Integrated Pest Management strategies that tend to rely more on natural processes and the active participation of farmers as observers and experimenters in their own fields. We present three case studies that point at different options provided by locally available populations of soil organisms, the maintenance of diverse populations of pests or increased resistance of plants to pest attacks by their interactions with earthworms and other useful soil organisms. These examples demonstrate the diversity of options offered by the non-planned agro-ecosystem diversity in pest control and the need to identify management options that maintain this biodiversity.

Variability and Parasitoid Foraging Efficiency: A Case Study of Pea Aphids and Aphidius ervi.

When a parasitoid is searching for hosts, not all hosts are equally likely to be attacked. This variability in attack probability may affect the parasitoid functional response. Using a collection of experiments, we quantified the functional response of Aphidius ervi (Hymenoptera: Braconidae), an insect parasitoid of the pea aphid Acyrthosiphon pisum (Homoptera: Aphididae). We measured variability in the number of hosts attacked by a foraging parasitoid both among plants and within plants. At the first scale, A. ervi, searching among plants containing different numbers of aphids, showed both aphid-density-dependent and aphid-density-independent variability in the number of aphids attacked per plant. Within plants, A. ervi selectively attacked second and third instar aphids relative to other instars. Furthermore, there was variability in the susceptibility of attack among aphids independent of instar. Variability in attack rates among aphids both among and within plants decreased parasitoid foraging efficiency, with the greatest decrease caused by among-plant variability. Furthermore, the decrease in foraging efficiency was greatest when the average number of aphids per plant was low, thereby transforming a strong Type II functional response into one approaching Type I.