Boris Fouelifack-Nintidem

Synthetic pesticides present risks of pollution of the environment, humans and livestock and the alternative proposed today is to use botanical extracts in the fields against crop pests. But in North Cameroon, little information exists concerning the effect of these extracts on useful pollinating insects in general and no information exists in particular on foragers of the genus Amegilla Friese, 1897 (Apidae: Apinae: Anthophorini). The frequency and foraging activities of Amegilla , on newly blooming flowers of Vigna unguiculata (L.) Walp., 1843 (Fabales: Fabaceae) were recorded during five consecutive days in 2021 and 2022 planting campaigns. Plants were divided into untreated plots and plots treated using the synthetic insecticide Parastar (l p.c..ha ^-1 ) or 10%, 20% and 30% aqueous leaf extracts of Calotropis procera (Aiton) Aiton, 1811 (Gentianales: Apocynaceae), Eucalyptus camaldulensis Dehnh., 1832 (Myrtales: Myrtaceae) and Tithonia diversifolia (Hemsley) Gray, 1883 (Asterales: Asteraceae) respectively. Among 8,987 insects collected (48.9% in 2021), Amegila calens Le Peletier. 1841 with stockier foragers (2021 campaign: 2.2% of the total collection, entomophily F _{A. calens} =4.5%; 2022 campaign: 0.7%, F _{A. calens} =1.3%; pooled campaigns: 2.9%, F _{A. calens} =2.9%) and Amegilla sp. with slender foragers (2021: 3.8%, F _{Amegilla sp.} =7.7%; 2022: no data) were recorded. Foragers started activity from 6 a.m. and stopped foraging before noon, with a peak of activity in 8 to 9 a.m. time slot for A. calens and 10 to 11 a.m. time slot for Amegilla sp.. During the five consecutive days from the first blooming day of the flowers, 598 visits (89.8% in 2021 and 10.2% in 2022) were recorded with a peak of visits during the 3 ^rd day and then declined until it stopped during the 5 ^th day. Treatments including the synthetic insecticide (which was the most repellent to the wild bees), did not significantly reduce the frequency of visits. But 20% aqueous extract of Ca. procera showed a significant increased of the mean duration of visits of the bees, compare to the results recorded in Parastar-treated plots. Therefore, the tested extracts, especially 20% aqueous leaves extract of Ca. procera may be recommended to control field insect pests and for preservation of foraging activities of Amegilla genus.

Synthetic pesticides present worldwide risks of contamination of humans, livestock and the environment due to the strong persistence and the toxic residues in fruits and vegetables. Natural biopesticides of local plant origin present low persistence and are the best alternative for the control of crop pests. In the Adamaoua region (Northern Cameroon), few studies exist concerning effects of botanical pesticides on the behavior of beneficial insects. Studies aimed to draw up a list of pollinating insects on flowers of Vigna unguiculata (L.) Walp., 1843 (Fabales: Fabaceae), in situations of treatment with botanical pesticides compared to the situation of the use of synthetic insecticide and to determine the effect of the biopesticides on the behavior of the main floricultural insects. Field investigations were carried out during two cowpea cultivation campaigns (June to September 2021 and June to October 2022) in Dang (suburb of Ngaoundere) on the effect of leaves extracts of local plant origin on the foraging behavior of Apis mellifera Linnaeus, 1758 (Hymenoptera: Apidae) and the main sap-sucking insect Aphis craccivora Koch, 1854 (Hemiptera: Aphididae). Forty-four cowpea plots of 4x3.5 m each distributed according to the randomized complete block model (four untreated plots as negative control, four plots treated with the synthetic insecticide Parastar (40EC 535/ 10/IN, 20 g/l of imidacloprid and 20 g/l of lamda-cyhalothrin) as positive control, and 36 experimental plots treated with three concentrations (10%, 20% and 30%) of aqueous leaves extract of Calotropis procera (Gentianales: Apocynaceae), Eucalyptus camaldulensis (Myrtales: Myrtaceae), and Tithonia diversifolia (Asterales: Asteraceae) respectively, made it possible to conduct four treatments: (1) flowers left to freely pollination, (2) flowers protected against pollinators, (3) flowers visited exclusively by Ap. mellifera and (4) flowers protected against insects. Among eight species (four orders, four families and seven genera) recorded on the flowers of V. unguiculata, the domestic bee Ap. mellifera was the most common and collected nectar and pollen. The control plots and those treated with 10% or 20% aqueous leaves extracts allowed the bee to carry out its activity. Plots treated with 30% extract of each plant and those treated with the synthetic insecticide Parastar, drastically altered the rhythm and speed of activity in Ap. mellifera foragers. This behavior became less coordinated and slow on treated plants. It would be wise to use 10% or 20% aqueous extracts as botanical insecticides and an alternative to the synthetic insecticide Parastar.

Aims: Mealybugs are protected on plants by ants for honeydew. They were identified and assemblages were characterized in Douala suburbs (Littoral-Cameroon). Study Design: Basic information is needed on pest’s occurrence for the pest control strategies. We determined host plants and characterized the community structure of mealybugs and foraging ants. Place and Duration of Study: Field investigations were conducted from March to August 2020 in Douala suburbs in 16 transects (10x1,260 m each) and 126 quadrats (10x10m each). Methodology: Stems, the underside of leaves, flower buds and fruits were inspected on weeds, plant bases and canopy of trees. Mealybugs and ants were captured. When the plant was highly infested, the average number of insects was determined on 10 randomly chosen plant organs. Abundances were noted and captured specimens were stored in vials containing 70° alcohol, identified to the species level and the community structure was characterized. Results: A total of 24,640 specimens belonged to 23 families, 54 genera and 85 species were collected in this research. A low species richness, low diversity and low dominance were detected. Assemblage of foraging ants in Yassa functioned according to the brokend-stick model. Scale insects in Ngoma functioned according to Motomura’s model. Assemblages of host plants in Lendi, Yassa, global host plants, global scale insects, foraging ants in Lendi and the global settlement, functioned according to the lognormal model. Host plants in Ngoma, scale insects in Yassa, and foraging ants in Ngoma functioned according to Zipf’s model while Zipf-Mandelbrot was adapted to scale insects in Lendi suggesting that these communities had sufficient time to develop a complex network of information close to natural environments and presented a fairly regeneration force. Conclusion: Due to the abundance pest insects, resources are available and once they will be well developed; they will cause plant pathologies and yield loss.

The Douala harbour represents the main gateway through which human activities introduce invasive ants, so that Solenopsis geminata (Fabricius, 1804) originating from Neotropics has been reported in several areas of the Littoral region of Cameroon. But nothing is known about the ant community structure and composition of the coastal zone. We hypothesized that environmental perturbations around Douala have repercussions on the native litter-dwelling ants. Collections conducted in 33 houses, six gardens of 225 m² each, 41 plantations of one hectare each and 34 two-year old fallows of one hectare each suggested lowly even communities, low species richness, low diversity and low dominance by a few species. Among 28 species recorded four species were mostly represented: two foreign origin species [S. geminata (Fabricius, 1804) and Trichomyrmex destructor (Jerdon, 1851), from tropical America and India respectively], one native species [Pheidole megacephala (Fabricius, 1793)] and two ambiguous native range species [Paratrechina longicornis (Latreille, 1802) and Tapinoma melanocephalum (Fabricius, 1793)] since they have long been recorded as having a widespread distribution. Alien species were highly represented than native ones (52.9% and 47.1% respectively, p<0.001). Inside houses, gardens and plantations the ant species were distributed according to the geometrical progression (Motomura’s model) while in the old fallows abundance distribution suggested an evolved ecosystem (Mandelbrot’s model). Between the three dominant species [Pa. longicornis (Latreille, 1802), Ph. megacephala (Fabricius) and S. geminata (Fabricius)], the first species was positively correlated with the third one while other associations were not significant. These dominant species appeared influencing the abundance of the rare species. Dominance and high abundance of a few species indicated that areas were influenced mostly by interspecies competition and/or disturbance by human activities.