Annual Report: CIRAD 2007

Malian cotton growers have been using fewer pesticides since 2001. They only conduct pest control treatments if infestation levels exceed certain preset thresholds, thus enabling them to save over 60% on pesticides in one or two sprays instead of four to six as recommended in conventional farming conditions. The aim is to decrease production costs while also lowering the impact of treatments on human health and the environment. Drawing up guidelines to help farmers decide when to treat their fields was, however, a complicated joint task for CIRAD and IER. This collaboration is ongoing to refine the treatment conditions and promote clean practices for reducing pests and diseases in cotton crop fields.

Defining treatment thresholds

Crop fields should be regularly monitored to count numbers of different types of pest using a special procedure. The results of these counts are compared to preset thresholds beyond which pesticide treatments should be conducted. These vary for different cropping conditions, eg the treatment threshold will be lower for fields with a low planting density (common in Mali) than for dense crop stands. The crop yield potential in the field should also be considered when determining the treatment threshold.

The treatment thresholds can also be adjusted according to the development stage of the crops, ie pests have a greater impact on the early plant growth and fruiting stages. The threshold will be low at the beginning of the cropping period (only minor infestations are tolerated) whereas it can be higher near the end. This will save the first fruiting organs, which are essential for production.

Simple guidelines investigated

The treatment threshold is still a relatively complicated concept to put into practice—farmers often just focus on whether or not pests are present in their fields rather than on their density. Simple guidelines to facilitate decisionmaking are thus currently being tested, eg the presence of just one pest is enough to decide on whether or not to conduct a pesticide spray. These new guidelines could lead to an increase in pesticide use when infestation peaks occur at the end of the cropping period, but they simplify field monitoring and could address the concerns of some farmers who do not want to take any crop pest and disease risks. Tests are also under way on another possible simplification, ie the presence of just one type of pest (bollworms) would seem to be enough to decide on whether or not to conduct a pesticide spray.

A set of practices to reduce infestations

Other practices could reduce insect pest populations. Some hairy-leaved cotton varieties could be planted to reduce infestations of jassids, which are serious pests in Mali, by hampering their egg laying. Cotton plants can also be topped at the peak of the flowering period to reduce infestations of bollworms, which are the main cotton pests in Mali. Moreover, planting at high densities will promote earlier and faster fruiting, thus sidestepping potential attacks of bollworms, which are generally more numerous at the end of the cropping cycle.

These results will be validated on a larger scale in participatory research to be carried out in 2008 within the framework of the PASE* II project, funded by the Agence française pour le développement. In addition to investigating issues concerning agricultural techniques, this project will focus on determining the best decision-making scale (plot, set of plots, cropping area) and on preventive measures to avoid the development of pest resistance to the pesticides used.

* Pase: Programme d’appui aux systèmes d’exploitation

Contact

Alain Renou, e-mail , Annual Cropping Systems (UPR)

Partners

• Agence française de développement (AFD, France)
• Compagnie malienne pour le développement des textiles (CMDT, Mali)
• Institut d’économie rurale (IER, Mali)

For further information

• Fok M., Renou A., Vaissayre M., 2007. Challenge of improving cotton competitiveness in a distorted market: analysing the role of crop protection in Francophone Africa. In : BCPC conference, 16-18 octobre 2007, Glasgow, Royaume-Uni.
• Renou A., Bagayoko B., Téréta I., Togola M., 2007. Topping cotton plants: a promising alternative to late insecticide spraying in Mali. In : Beltwide cotton conferences, 9-12 janvier 2007, Nouvelle-Orléans, Etats-Unis.