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Zonocerus variegatus (Linnaeus, 1758) (Orthoptera: Pyrgomorphidae) is known as an agricultural pest in …

Biology Articles » Agriculture » Farmers' perception on the importance of variegated grasshopper (Zonocerus variegatus (L.)) in the agricultural production systems of the humid forest zone of Southern Cameroon » Discussion

- Farmers' perception on the importance of variegated grasshopper (Zonocerus variegatus (L.)) in the agricultural production systems of the humid forest zone of Southern Cameroon

The study shows that farmers regard Zonocerus variegatus as an important annual crop pest in the humid forest zone of Southern Cameroon. It is a minor pest of young perennial crops. Similar results have also been reported in many countries in Africa, notably Nigeria [4,6-8], Ivory Coast [6], Ghana [4], Congo Brazzaville [9], Southern Benin (Coffi, cited by [4]) and the Sahel [10]. In most of these countries, Z. variegatus is known mainly as a food crop pest.

From the farmers' point of view, the definition of an insect pest has primarily economic implications, given that the insect causes significant damage to warrant the implementation of a control measure. This implies that having reliable information on crop damage at different pest densities is vital in understanding the interaction between pest and host plants. However, crop damage by Zonocerus variegatus is very difficult to evaluate, especially on food crops [2]. This underscores the importance of farmers' perceptions in understanding the pest status of a given insect [17]. Farmers' perceptions have contributed to the understanding of various aspects of the bio-ecology of insects [18]. These perceptions can be significantly different from scientific knowledge but have major implications for development [27,5,31,18].

The crops mentioned by the farmers in this study as food sources for Zonocerus variegatus have also been reported in previous studies [2,38]. For the farmers of southern Cameroon, groundnut, cassava and vegetables are the most susceptible crops to Z. variegatus. The majority of the authors are unanimous on the high vulnerability of cassava [4,6,7] while the susceptibility level of vegetables and groundnut varies from one country to another. Cassava, groundnut and vegetables are the principal food crops of the humid forest zone of Southern Cameroon [22]. It thus gets clear a need for developing strategies of protection of these crops against Z. variegatus.

Many reports have also mentioned the growing importance of Zonocerus variegatus as a pest elsewhere as in the humid forest zone of Southern Cameroon. For example, before 1950, Z. variegatus was already known as a pest of primary or secondary importance in most countries of intertropical Africa [2,5]. However, it was later reported as an important pest in the 1970s in Nigeria [6,7,12].

The farmers in this study recognize as Kumar [1] that several factors affect the pest behavior of Zonocerus variegatus. For example Z. variegatus avoids pure forest compared to deforested areas [6,3,32,2,4]. This preference of deforested areas had also been reported in earlier studies [6,7,2,37]. Deforestation induces biotopes and conditions favorable for Z. variegatus such as increase in surfaces of herbaceous fallow. In addition, after deforestation, empty spaces are occupied by C. odorata, the main host plant of Z. variegatus. These may partly explain the high pressure of Z. variegatus observed by the farmers in the fields adjacent to C. odorata fallow [8] and herbaceous fallow compared to fields adjacent to forests. The increased damage observed in the dry season suggests that it is a seasonal pest as reported in other studies [3]. Probably, rains (natural mortality factor) induce morbid fungical infections in the natural populations of Z. variegatus among other mortality factors that would reduce the pest population.

The study showed that, Zonocerus variegatus is an item of diet. This agrees with the findings of Iduwu & Modder [8] and Page & Richards [38] in Nigeria. In Nigeria as in Cameroon, the insect is eaten after being fried [8,38]. In fact, Z. variegatus is an important source of proteins [39].

In the present study, the main control method of Zonocerus variegatus in the humid forest of Southern Cameroon was through the physical removal of insects feeding on crops for human consumption. The consumption of Z. variegatus as control method has also been reported by Nigerian farmers [8]. However, physical control of Z. variegatus is generally difficult and not very effective. The high population of Z. variegatus in the humid forests of Southern Cameroon [33] indicates the lack of an adequate crop protection measure against the pest. Egg-pod exposure used by few Nigerian subsistence farmers is not known in southern Cameroon [4]. Southern Cameroon farmers seldom use chemical control, certainly because of the fall of the state aid, related to the economic crisis. This method, very much used by the farmers in Nigeria [8], was the main crop protection strategy in the tropical forest zones. Their utilization, in large areas has been one of the first important factors of reduction in crop loss due to pests [9]. However, because of their harmful effect on the environment, their utilization became weakly recommended [34,10,1,36]. The fact that biological control methods are not used here show that the 'green muscle' (biological acridicid) used successfully in the savannah zones may not have been introduced to farmers of Southern Cameroon. These farmers' perceptions showed a need to carry out an urgent control strategy in the agricultural production system against Zonocerus variegatus. However, the strategy needs to be directed a little more towards the integrated pest management as described by Modder [7]. An integration of the farmers is necessary [38].

This study also showed some perceptional gender differences in the humid forest zone of southern Cameroon. In Yaoundé (for the annual and perennial crops) and Mbalmayo (for the perennial crops only), females perceived the pest's incidence with an equal importance while males recognized Z. variegatus as one of the major and minor pests in the annual and perennial crops respectively. On young perennial crops, only the females rated Z. variegatus as monophagous. In these perennial crops, more female groups perceived Z. variegatus as non-harmful insect than male groups. The increase of Z. variegatus incidence in the fields has been more reported by men than women groups. For the female groups, block effect appeared significant only in the garden crops while in the male groups they also appeared in groundnut fields ('affub owondo') and Assan (Marsh field). More male groups observed that, the magnitude of Zonocerus variegatus pressure varied with the type of adjacent fallows in field crops. These perceptional gender differences have also been observed in Nepal [18]. In Nepal, with regard to the depredatory insects, men generally used more vague attributes like harmful or harmless, while women were more specific, often referring to the host plant [18]. The rate for instance, was referred to by women as a hole-making storage pest, while men did not refer to burrows at all [18]. This clearly reflected that in Nepal, women normally repair and clean the damage [18]. In fact, the perceptional gender differences have their origin in the division of labor [18]. In the humid forest zone of southern Cameroon, men and women spend most of their time in the field (agriculturals activities) but, women are also involved in tasks at household while other male tasks are community oriented.

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