In general, from the human point of view, any insect that is not at the right place is a pest (Williams, cited by ). Pests are also harmful or awkward species, which need to be controlled for economic or social reasons (Clark, cited by ). Zonocerus variegatus is reported in the literature as a pest of many crops in West and Central Africa. The first reports on damages of this grasshopper on crops were in 1910 by Peacock and Lamborns in Southern Nigeria, Schoutedem and Mayne in Zaire and Small in Uganda (In ). Its geographical range and impact on the crops increase with time. In 1948, Z. variegatus accounted for 10% yield loss in the banana harvest in Guinea . On garden eggs, it can cause 25 – 80% yield loss . In Nigeria, it causes 50% loss in annual cassava yield . Z. variegatus has been implicated in the transmission of okra mosaics viruses in Ivory Coast and cowpea mosaics viruses in Nigeria [3,5]. It is thought to be responsible for the transmission of the bacterial burn of cassava in Nigeria [2,3]. Due to the high damages it inflicts on crops, it is considered as an important agricultural pest in Nigeria [4,6-8], Ivory Coast , Ghana , Congo Brazzaville , Southern Benin (Coffi, cited by ) and in the Sahel . Z. variegatus is currently the most important of grasshopper pests for crops in the humid forests of low altitude and savannas of West and Central Africa [2,4,11,12]. However, no scientific literature exists on the pest status of Z. variegatus in Cameroon. Apart from two works [13,14] and one report , most other literature on the problems caused by Z. variegatus in Central and West Africa only have generalities on Cameroon [4-6,9,15,16]. Determining the importance of an insect in any agro-ecosystems, contributes to the description of its status . Such information is necessary for the formulation of a good pest management strategy.
This paper present the results of a group survey, administratered to the farmers of the humid forest zone of Southern Cameroon, to assess the importance of variegated grasshoppers Zonocerus variegatus in the agricultural production systems. The survey approach was justified by the concern of having a fast idea on the Z. variegatus status in the production systems in the southern Cameroon and the need of collaboration between farmers, scientists, and extension services in term of priorities definition about the crop protection strategies. Recent trends in agricultural research and development emphasize the need for farmer participation . There has been increasing interest in the incorporation of farmer's knowledge into agricultural research and development programs . The Participatory Action Research framework provides one useful approach towards achieving farmers' capacity building . Farmers in general are good decision-markers (Goldman, cited by ) and their views have contributed to the understanding of various aspects of the bio-ecology of insects and the real situation of other pests. Taking their knowledge base and combining them with scientists'/extentionists' expertise can contribute to the improvement of local practices in pest management . An ethnoentomological study, conducted in Tharu, a village in Nepal, offered a basis to improve pest management programs in terms of efficacy and acceptance . In African farmer communities, insects are much more known as pest though others such as Apis mellifera (Hymenoptera: Apidae), Gryllotalpa africana (Orthoptera: Gryllotalpidae), Gryllus bimaculatus (Orthoptera: Gryllidae) have a great importance in the communities. In general, A. mellifera (bees) produce honey. In West Cameroon G. africana are heralding misfortune whereas the cries of G. bimaculatus at certain periods of the year, announce good news (Kwecheu Marie, Personal Communication). Farmers' knowledge of insects varies in quality and quantity depending on their interest in the subject, their environment, and the relevance of insects to their lives .
The objective of the present study was to determine farmers' perception on: (1) the incidence of Zonocerus variegatus in the humid forest zone of Southern Cameroon; (2) the factors responsible for variations of Z. variegatus incidence in the humid forest zone of Southern Cameroon; and (3) to assess how the farmers manage this grasshopper in their agro-ecosystems.