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In the late 1980s, after a long period during which insecticides were sprayed at preset dates to control cotton pests and their damage, some French-speaking countries in sub-Saharan areas decided to disseminate a more sustainable crop protection approach among smallholders: targeted staggered control (LEC, for Lutte étagée ciblée). According to this approach, decisions on some insecticide sprays were made on the basis of infestation levels or the extent of crop damage induced by major pests: Aphis gossypii aphids, Haritalodes (= Syllepte) derogata leaf-eating caterpillars, and more generally Helicoverpa armigera, Diparopsis watersi, Earias insulana and E. biplaga bollworms. Polyphagotarsonemus latus mites were sometimes included on this list. Due to changes in cotton production conditions over the past 10 years, especially the development of pyrethroid resistance in H. armigera, and depending on the country, this programme has been abandoned, preserved or replaced by other programmes. The strict use of thresholds in Mali was thus taken to be a logical follow-up to LEC, which is still widely implemented. A targeted 'threshold-based' programme was developed in Togo. Cameroon abandoned LEC and opted for a 'sequential plan for individual decision' (SPID) programme (LOIC, for Lutte après observation individuelle des chenilles), based on control after sequential sampling of bollworms. In Benin, LEC has been presented in two forms, i.e. 'complete' and 'partial', tailored to two regions delineated according to the extent of damage of some bollworms that live inside cotton bolls, i.e. Pectinophora gossypiella, Thaumatotibia (= Cryptophlebia) leucotreta. In Ivory Coast, where these Lepidopteran pests are also present, the use of treatment thresholds is limited to the beginning of the cotton crop cycle. On the contrary, in Burkina Faso, thresholds are used after the first two calendar sprayings. The present article fully describes these new crop protection programmes, sampling methods and associated intervention thresholds, in addition to the advantages and constraints associated with their adoption. |
