In mortality and consequently reducing their capacity of providing

In tropical region, forest ecosystems are well known for being
the most important in terms of abundance and diversity of natural resources. In
general, forests in Africa contain several tree species, which without being
useful only for timber production play key socio economical roles. In this
regards, they are not only source of foods but also used as tradition medicine,
fuel and agroforestry (Agbahoungba, 2001). They have always attracted the world’s attention
because of their magnificence and potential for economic exploitation.

Well
managed forests are essential for sustainable natural resource management.
However, like any other ecosystems, they are subject to many threats leading to
tree mortality and consequently reducing their capacity of providing many goods
and services (FRA, 2005).  These tree
mortalities can be natural, caused by human activities or both. For instance,
fungal and insectivorous attack can cause direct or indirect economical and
environmental losses. While insects are an integral part of forest ecosystem
and play important ecological roles such as pollination and nutrient recycling,
some categories can have detrimental effects on the growth and survival of
trees.

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Besides
risks induced naturally by pests in forest ecosystems, with demographic growth
some anthropogenic activities also increase the risk of tree infestation. These
activities consist mainly of non-sustainable exploitation of resources in
forests managed by communities, where most of the populations used plants as
medicinal goods. All
cultures have used medicinal plants from time immemorial (Oryema, 2010).  Even at present when many people are treated
by modern drugs, many still use herbal medicine (Kokwaro, 1993, FAO, 2005). In
recent decades, many ethnobotanical and ethnopharmaceutical studies have been
undertaken to document and describe traditional herbal products and to validate
their use (Light et al. 2005). During that period, however, many plants
have become threatened due to a lack of local control on harvesting levels. Global
demand for herbal medicine is not only large, but also steadily growing (Srivastava
2000, Nalawade, et al. 2003; Light et al., 2005; Cole et al. 2007 ). However,
about 15,000 species are threatened with extinction from overharvesting and
habitat destruction (Williams et al. 2000; Shingu 2005, Bentley, 2010)
and 20 % of their wild resources have already been nearly exhausted with the
increasing human population and plant consumption (Ross, 2005). Nowadays, the
use of medicinal plant barks is becoming increasingly important, especially for
species with high economic value. High levels of unemployment, rapid
urbanization, and low levels of formal education among rural-to-urban migrants
are some of the reasons behind the increasing trade in herbal medicine, especially
in West Africa (van Andel et al., 2014). This results in over-harvesting of
target species from both protected and unprotected areas, posing a major
challenge to resource managers and this situation is worsened by missing of
basic data on resource exploitation. In fact, it is difficult to develop
mechanisms/recommendations for sustainable use of those resources and for
forest protection.

Ring
barking, by completely removing a strip of bark around a tree’s outer circumference may lead to more or less
immediate tree death (Delvaux, 2009). According to Cunningham and Mbenkum (1993), 35,000 trees of Prunus
africana are barked annually
therefore, threatening the survival of forest resource (WWF, 1994). In
South-Western Cameroon, there has been a decline in Gnetum plants due to commercial exploitation. From 1986 to 1991, bark commercial value of Prunus
africana has been estimated at 150.000.000
US$ per year, and represented 1923 barking-tonne (Cunningham et Mbenkum, 1993).

In Benin, because of plants therapeutic used and the
lower live level of the population, 80 % of them depend on medicinal plants,
and the most of them are debarked (Adjadohoun, 1998). Furthermore, these
anthropogenic pressures on these plants may have negative consequences on their
survival because cuttings done while barking consist a source of entry for
xylophagous infection that leads to death (Williams et al., 2000 ; Shingu, 2005). Previous studies on bark
regeneration have revealed that medicinal plants are more vulnerable to
insects’ infection (Delvaux, 2009). Bark removal results in a disturbance of the internal system of the
tree, on the one hand by interrupting phloem sap circulation, and on the other
hand by modifying the anatomy of the wood produced after the wound. Medicinal
plants face extinction or severe genetic loss being threatened by over harvest.
They have been given less attention in many areas. Most often, the Non Timbers
Forest Products NTFPs are collected in the natural environment without specific
guidelines, with the well known consequences: disturbance of population
structure, of population density, of their reproductive capacity, and of the
ecosystem (Cunningham et Mbenkum 1993; Cunningham et al. 2002; Ticktin
2004; Gaoue & Ticktin 2008).

Despite the
diversity and impact of xylophagous insects on forestry species, few studies
have been conducted on this group of insects particularly in developing
countries (FAO, 2009). Past studies on pests of wild species are often ignored
during planning of forest conservation programmes. Tchibozo (2004) mentioned
that there have been few studies on insects in natural reserves of Benin.
Although, a lot of studies have been done on pests of cultivated crops in
Africa (FAO, 2009, Mwatawal, 2006 ; Siskos, 2007 ; Ekesi, 2007,
Ndanza et al., 2008) and particularly
in Benin (Vayssières, 1995 ; Vayssières & Kalabane, 2000 ; Vayssières et al., 2004). However some research
have been carried out in Benin, such as Ahononga (2002), Cakpo (2003) ;
Attingnon (2005) ; Lachat (2006) ; Tchibozo (2004, 2008), Agboton
(2009). According to Robiche et al, (2002), Benin, is not well
documented when it comes to its entomological fauna. In 2002, Ahononga had
inventoried teak pest but his result cannot related pest damage on the specific
insect which have caused the damage. Through this research, it’s stipulated
that, about 15 % of teak plantation are infested by the xylophagous in which
coleopteran have the most important diversity. 
In 2004, Tchibozo has taken out the prelimary note on forest pest in Lama
Forest and noted that, Analeptes
trifasciata is the most damage pest in the forest. This borer pest has also
collected in Nigeria, Ivory Coast (Brunk, 1976); in Ghana (Wagner, 2006) etc…
Arthropod diversity related on the vegetation type was studied by Lachat et al in 2006 targeted on saproxylic
beetle. In Lokoli swampy
forest, few researches have been carried out about entomology diversity. The
only study is about Lepidopteran and odonateran diversity (Tchibozo, 2008). None
research on the xylophagous pest did not undertake in this forest yet. However,
some damage such as bark-harvesting is making by the population in Lokoli
swampy Forest. Researches
on insect pests of medicinal plants are extremely important as they will
provide information on the diversity of these xylophagous insects. Furthermore, it will provide information, which can be used in long term
to maintain pharmacopy production by identifying vulnerable plants for the
purpose of their sustainable use.

All the above justifies the choice of this study on xylophagous
which can help to build up database for the long-term monitoring of entomological
fauna. In view of the comparative study on the impact of bark-havesting on
medicinal plants, this research was carried out in Lokoli Swampy Forest a free
access forest managed by community and in Lama Protected Forest which is
managed by Forestry administration.