Boffa Prefecture is an administrative subdivision of the Republic of Guinea. Located in the west of the country on the Atlantic coast, in the natural region of Maritime Guinea, this prefecture is part of the administrative region of Boké with an area of 910,000 ha = 9100 km² (10˚11'03" north, 14˚02'38" west). Distant 150 kilometers from the Guinean capital, Conakry, Boffa has nearly 227,217 inhabitants and a density of 25 inhab./km² in 2016. Its capital is the city of Boffa. The prefecture is divided into eight sub-prefectures: Boffa-Centre; Kolia; Douprou; Koba; Lisso; Mankountan; Tamita; Tugnifili.

The Laboratory of Organic Chemistry of the Gamal Abdel Nasser University of Conakry, the laboratory of the National Office of Quality Control of Matoto Conakry, served as a framework for studies.

Ethnobotanical surveys were carried out using a series of questionnaires pre-developed on a survey sheet designed for this purpose. This investigation was conducted in some localities of the prefecture of Boffa for 4 months. The collection of information covered respondents, pests and insecticidal and medicinal plants in selected Districts of Kolia and Tugnifili (Table 1). On the survey sheet used was distributed farmers, herbalists, breeders, option leaders according to Districts, method of acquisition, age group, by socio-professional category, modes of use of the parts used, citation frequencies, scientific and vernacular names, the list of plants (Tables 1-5). Among the most cited plants, Capsicum chinense was the most cited; it is for this reason that we have specifically chosen this plant in this study.

The fruits of Capsicum chinense have been the cause of its frequency of citations. The fruits of Capsicum chinense were collected in Boffa and surrounding areas in January 2019. They were subjected to drying in the shade and in the open air for 30 days. Then they were pounded and sieved. The powders thus obtained were used as raw materials for the evaluation of their insecticidal activity.

The corn and groundnut kernels) that were used for this test were purchased at the yenguema market in (Boffa) prefecture. These purchased grains were sorted to remove bad grains, foreign matter, and then washed and dried at room temperature in the laboratory for 72 hours. Then, a second drying at 40˚C in the oven for 15 minutes removed residual contaminants.

The maize and groundnut kernels infected with Sitophilus zeamaïs and Aphis craccivora were purchased at the yenguema market (Boffa), and their farms continued under the ambient conditions of the Matoto natural and industrial products quality control laboratory (temperature 20˚C ± 40˚C) and humidity in the vicinity (81% ± 5%).

Procedure: Weigh 6 kg of corn kernels (or peanuts) already infested with Sitophilus zeamaïs or Aphis craccivora of peanuts and placed in glass jars then cover with a porous fabric for better aeration and prevent insects from escaping. Keep these jars at room temperature in the laboratory for 30 days away from foreign infestations. Then, sift to eliminate the adult Sitophilus zeamaïs and Aphis craccivora and continue rearing with the grains infested by the eggs for 29 days to obtain new insects.

A total of 42 jars were used for this experiment; they were arranged in 02 batches of 21 and each bio-insecticide was repeated three times. Of these 02 lots, 01 was intended to study the insecticidal effect of Capsicum chinense powders, 01 others to assess the damage caused by Sitophilus zeamaïs (or Aphis craccivora) for 120 hours. The jars were kept in a well-ventilated room under laboratory conditions.

Procedure: According to the Food Africa Programme-African Research on agriculture, food, and nutrition method [11], 100 g of non-infested maize (or peanut) grains were weighed and then introduced into the jars previously marked as: T0 (control), Fch1, Fch2, Fch3 (the powder of the fruits of Capsicum chinense). Then weigh 2 g, 4 g, 8 g of powder, add to 100 g of homogenized corn or peanut in the jars. Control jars (T0) did not receive treatment [5]. Then introduce into each jar 20 adult insects and cover with a porous cloth for better aeration; sealed with elastic fronds to prevent external contamination.

Procedure: The moisture levels of the corn and groundnut kernels were determined by the method of complete desiccation in the oven between 100˚C - 105˚C for 3 hours according to the (formula) [12] [13].

H % = P 2 − P 1 P e × 100 (1)

wherein “H%” represents Percentage of humidity; P₁; P₂ = Weight of capsule and sample before and after drying; Pe = Weight of the test portion.

The percentage of mortality was determined using W.S. Abbott’s formula [13] after 5 days of observation of the contents of the jars taking into account the natural mortalities observed in the control jars according to (the formula):

M c = M o − M t 100 − M t × 100 (2)

Mc = Adjusted mortality; Mo = Mortality in treated boxes and Mt = Mortality in control boxes.

The germination test was performed at the beginning of the experiment on infested grains that were in constant contact with capsicum chinense fruit powders for 6 days [14] [15] [16]. The grains were spread in jars containing soil moistened with water at 26˚C and sealed at laboratory temperature. The germination rate was evaluated by counting sprouted grains versus seeded grains according to (the formula).

G % = N G G N G E × 100 (3)

G% = Percentage of germination; NGG = Number of sprouted grains; NGE = Number of seeded grains.

Our ethnobotanical surveys in the (02) sub-prefectures allowed us to identify 71 people, including 20 women and 51 men (or 71.83%) (Table 1). Indeed, of the 71 respondents who use insecticides of plant origin and their methods of acquisition, 39 (54.93%) acquired on the basis of parental transmission (Table 2). It is also noted that the age of respondents varies from 30 to 70 years (Table 3). The age groups that practice effectively are around 41 - 50 years (39.44%) and 51 - 60 years (29.58%). On the other hand, the other age groups are less represented: 30 - 41 (18.31%) and 61 - 70 (12.67%). The results also show that only 18.31% of respondents were in school compared to 35.25% of farmers; 19.72% marabouts and sage; 15.49% merchants and 8% of traditional hunters (Table 4).

In this ethnobotanical survey, eight (8) native plants with insecticidal effects were identified and grouped into eight families which are: Solanacea (98%), Liliacea (10%), Zingiberaceae (10%), Combretaceae (15%), Labiae (15%), Myrtaceae (16%), Chrysobalanaceae (20%), Lamiaceae (20%) (Table 5). The results of the ethnobotanical survey showed that the plant species most used as an insecticide

during the conservation of corn and groundnut grains is: Solanacea (98%), it is followed by the other species. The parts of the plants regularly used are: fruits, bulb, leaves and bark. Table 6 shows the average values of the moisture content of maize and groundnut grains which are respectively: 14.51% and 12.25%. These values are at the limit of appreciation of the moisture content of drugs, which is 14% [12] [13].

Table 7 shows the different doses used of Capsicum chinense powders on Sitophilus zeamaïs and Aphis craccivora as well as the standard deviations for assessing their insecticidal effects, and the photo of the experimental device of jars containing maize and groundnut grains. (Figure 1)

Table 8 shows the different doses of Capsicum chinense powder used in the treatment of corn and peanut kernels infected with Aphis Craccivora and Sitophilus zeamaïs and the different germination rates, followed by the Figure 2 showing the stage of three (3) leaves after germination of corn and peanut grains treated with Capsicum chinense powder in the laboratory.