433
(Crozier et al. 2009). O. smaragdina and O. longinoda can control more than 50
different pests in multiple crops and forest trees (Way and Khoo 1992). Their ability
to control pests can be similar or more than chemical pesticides (Peng and Christian
2005; Dwomoh et al. 2009; Offenberg et al. 2013).
The first report on O. longinoda in East Africa was made in the early 1950s
(Way 1954) when the predator was found colonizing plants in natural forests, particularly along the coasts of Kenya and Tanganyika and islands of Pemba, Unguja
and Mafia. In West Africa, the use of O. longinoda was first reported in Benin in the
1980s by Majer (1986) and thereafter Way and Khoo (1992). In different African
countries, O. longinoda has been reported as an effective biocontrol agent against
citrus (Ativor et al. 2012) and cashew pests (Dwomoh et al. 2009) in Ghana; coconut (Way 1953; Varela et al. 2012; Seguni et al. 2011) and cashew pests in Tanzania
(Olotu et al. 2013) and Mozambique (Peng et al. 2010) and cashew and mango
pests in Benin (Adandonon et al. 2009; Anato et al. 2015; Sinzogan et al. 2008; Van
Mele et al. 2007). The missing link in all the reports was how to make use of the
predator and critical analyses of its comparative efficacy and economic advantages,
over the commonly used cashew pest control methods which are mainly
pesticide-based.
The knowledge gaps that would otherwise hinder the effective exploitation of
this predator as an alternative means in controlling pests of diverse crops was
recently addressed through collective undertaking by researchers at Sokoine
University of Agriculture in Tanzania and University of Abomey-Calavi (Université
d’Abomey-Calavi) in Benin, in collaboration with scientists at Aarhus University of
Denmark, who undertook detailed studies on how to effectively exploit O. longinoda in managing cashew pests as detailed in the sections that follow. It is imperative to realize that O. longinoda is a generalized predator for many insect pests, and
once introduced into the crop, it takes care of almost all kind of insect pests, regardless of the species, except for a few with which they survive symbiotically such
as aphids.
5 Methodology
5.1 Oecophylla longinoda Colony Identification and Mapping
Weaver ants survive in natural forest and other bushes whose plant leaves are suitable for their nest construction. During a four-year experimentation with O. longinoda in Benin and Tanzania, the initial colonies of weaver ants used in cashew were
either obtained from bushes around the target experimental plants or collected elsewhere at a distance and transported to the experimental units (Abdulla 2016).
Identification of the existence of weaver ants were by spotting of nests on trees,
followed by tracking of the adult weaver ant trails as they moved for foraging. Each
weaver ant colony was mapped by testing for enmity among insects of the
neighbouring trees, since weaver ants of different colonies tend to fight and kill each
Economic Rationale of Using African Weaver Ants, Oecophylla longinoda…
(Crozier et al. 2009). O. smaragdina and O. longinoda can control more than 50
different pests in multiple crops and forest trees (Way and Khoo 1992). Their ability
to control pests can be similar or more than chemical pesticides (Peng and Christian
2005; Dwomoh et al. 2009; Offenberg et al. 2013).
The first report on O. longinoda in East Africa was made in the early 1950s
(Way 1954) when the predator was found colonizing plants in natural forests, particularly along the coasts of Kenya and Tanganyika and islands of Pemba, Unguja
and Mafia. In West Africa, the use of O. longinoda was first reported in Benin in the
1980s by Majer (1986) and thereafter Way and Khoo (1992). In different African
countries, O. longinoda has been reported as an effective biocontrol agent against
citrus (Ativor et al. 2012) and cashew pests (Dwomoh et al. 2009) in Ghana; coconut (Way 1953; Varela et al. 2012; Seguni et al. 2011) and cashew pests in Tanzania
(Olotu et al. 2013) and Mozambique (Peng et al. 2010) and cashew and mango
pests in Benin (Adandonon et al. 2009; Anato et al. 2015; Sinzogan et al. 2008; Van
Mele et al. 2007). The missing link in all the reports was how to make use of the
predator and critical analyses of its comparative efficacy and economic advantages,
over the commonly used cashew pest control methods which are mainly
pesticide-based.
The knowledge gaps that would otherwise hinder the effective exploitation of
this predator as an alternative means in controlling pests of diverse crops was
recently addressed through collective undertaking by researchers at Sokoine
University of Agriculture in Tanzania and University of Abomey-Calavi (Université
d’Abomey-Calavi) in Benin, in collaboration with scientists at Aarhus University of
Denmark, who undertook detailed studies on how to effectively exploit O. longinoda in managing cashew pests as detailed in the sections that follow. It is imperative to realize that O. longinoda is a generalized predator for many insect pests, and
once introduced into the crop, it takes care of almost all kind of insect pests, regardless of the species, except for a few with which they survive symbiotically such
as aphids.
5 Methodology
5.1 Oecophylla longinoda Colony Identification and Mapping
Weaver ants survive in natural forest and other bushes whose plant leaves are suitable for their nest construction. During a four-year experimentation with O. longinoda in Benin and Tanzania, the initial colonies of weaver ants used in cashew were
either obtained from bushes around the target experimental plants or collected elsewhere at a distance and transported to the experimental units (Abdulla 2016).
Identification of the existence of weaver ants were by spotting of nests on trees,
followed by tracking of the adult weaver ant trails as they moved for foraging. Each
weaver ant colony was mapped by testing for enmity among insects of the
neighbouring trees, since weaver ants of different colonies tend to fight and kill each
Economic Rationale of Using African Weaver Ants, Oecophylla longinoda…