Assessment of insects, diseases and weeds occurrence in rice farming systems in Cambodia: opportunities for agroecological management and reduction of pesticides

Auteur de la fiche (Prénom, NOM, structure, email) : Mathilde, SESTER, CIRAD,
CoAuteur(s) de la fiche (Prénom, NOM, structure, email) : Florent TIVET, CIRAD,; Régis GOEBEL, CIRAD,
Défis du cadre stratégique : Renforcer la durabilité environnementale des agricultures irriguées , Réduire les risques et augmenter la résilience de l’agriculture irriguée
Aires géographiques concernées : Asie du Sud Est
Terrains concernés : Cambodia? Rice fields around the Tonle Sap
Types de systèmes irrigués : A large diversity of rice farming systems will be studied, from upper sandy terraces to flood plains, rainfed management to irrigated schemes.
The diversity of rice farming will be crossed by a range of intensification strategies, from one rice crop a year to two rice crops a year, from monocrop to the use of legume as relay crop, from intensive use of chemicals to organic crop management.
Contexte et problématique : Rice production in Cambodia has increased during the last decades and the country has been exporting rice since 1996 and more significantly since 2010 ( Cambodia?s rice yield was estimated at 3.3 t/ha in average (FAOSTAT, 2014). The increase in rice production was mainly due to a better water management but also to an increase in crop intensification with a high level of input and pesticide use in certain regions. The vast hydromophic fields around the Tonle Sap, represent 700,000 ha of rice crops in Cambodia, on a total of 2.5 million ha. One part of the rice fields benefit from water management systems. These fields, in general, can produce two rice seasons. An efficient water management system should limit rice susceptibility to biotic constraints; however irrigated areas exhibited in many situations the highest level of intensification in term of fertilizer and pesticide use. Even under lower efficiency of water management, pesticides are also used as soon as the first symptoms appear. Farmers are mainly advised by pesticide salesmen and chemicals spraying look sometimes inappropriate to the constraint. Intensive pesticide use, according to application rate, chemical formulation and way of spraying, can be detrimental for human, animal health but also raise concerns on food safety (national and international markets). To improve the sustainability of rice farming and to benefit from appropriate water management systems, it is crucial to strengthen famer?s knowledge on biotic constraints, their impacts on yield losses and the accurate methods to control them.
Implication des acteurs de l'irrigation : The General Directorate of Agriculture (GDA) through his own departments and partnership with IRRI will be the main stakeholders involved in this study.
Objectifs de l'action (cibles, intérêts opérationnels, etc) : Our aim in this project is to better know, through field surveys/interviews the importance and impact of biotic constraints in rice crops in different irrigation and cropping systems, and to link them to farmers practices in term of pesticides use. The final objective of the project is to propose innovative solutions for insects, disease and weeds management to farmers, based on agroecological crop management and reduction of pesticide use.
This action will be developed in three related work Packages:
1. Assessment of insects, diseases and weeds prevalence and occurrence in rice crops: An inventory of the pests, diseases and weeds will be conducted in fields all along transects of contrasted water management (from rain-fed, irrigation scheme to flood plains); their evolution during the crop development will be monitored. Simple identification procedure will be used to confirm the presence of diverse biotic constraints, and the potential impact of the most important ones will be assessed in each cropping system. Models have been developed in Asian countries to assess the impact of several constraints on yield, including diseases, insects and weeds (Willocquet et al., 2002). The damage mechanisms corresponding to 8 types of injuries were described and used to estimate their impact on yield losses. This model will be used or adapted to major constraints identified in Cambodia?s rice crops, if different of those studied by Willocquet.

2. Built a participatory platform for a better characterization of farmer management strategy:
? Characterize farmers? knowledge regarding biotic constraints (insects pests, diseases and weeds): field survey frequency, estimation of incidence and impact on yield,
? Build a knowledge database on pesticides, application rates and method of spraying, as well as all agronomic practices currently in use and their impact on insects, diseases and weeds, with the objective of establishing a decisional framework of farmer practices.

3. Measure the impact of agroecological crop management strategies on rice biotic constraints: Monitoring will be completed by surveys in and around experimental fields that have been set up to optimize agroecological irrigated rice cropping systems. Complementary experimentations
Contenus, moyens et calendrier à mettre en place : WP1: Field surveys monitoring diseases, insects and weeds prevalence
- Constitution of a team of local experts to identify the targeted areas and conduct an inventory of major constraints
- Field surveys, monitoring and methods to check and confirm the identifications (insects, diseases and weeds)
- Implementing local recruitment to conduct field surveys during the different cropping seasons
- Estimation of constraints potential impact on yields according to a literature review

WP2: Participatory platform
Setting up participatory platforms with farmers and development operators (GDA, NGO, Provincial department of agriculture) and conduct individual interviews to characterize the agricultural practices in terms of pesticide use (treatments, application rates, spraying methods, farmer?s protection): 2 Master students will be involved.

WP3: Field surveys in agroecological crop management experiments
Setting up of field experiments to evaluate the impact of agroecological practices on pests/diseases/weeds occurrence and of crop susceptibility.
Livrables : WP1: Database for biotic constraints occurrence, assessment of their potential impact on yield losses
WP2: 2 master thesis, farmer?s platform constituted, decisional framework on farmer practices in different context of water management established.
WP3: identification of agroecological practices impacting biotic constraints and their impact on rice development and yield establishment
Budget détaillé : (total : US$ 52,000 on 3 years)

WP1: US$ 28,500
Field mission (CIRAD staff): US$ 3,500
Local recruitement (2 years): US$ 20,000
Local experts meetings (3): US$ 3,000
Monitoring and small equipment for constraints analysis: US$ 2,000

WP2: US$ 18,500
Field mission (CIRAD staff): US$ 3,500
Master Thesis: 2 x US$ 5,000
Organization of farmers? platforms: US$ 5,000

WP3: US$ 5,000
Field experiments (2 years): US$ 5,000
Autres éléments nécessaires à la compréhension de ce chantier :
  • Activities are implemented by GDA and CIRAD in the irrigation scheme of Stung Chinit (Santuk district, Kampong Thom) since 2011 under different sources of funding (AFD, CIRAD and USAID) and in the flood plains of the Tonle Sap lake in Battambang province (Banan district). Main objectives are (i) to improve crop diversification after wet season rice and (ii) enhance soil ecosystem services through the use of a large diversity of cover/relay crops.