Insect pollinators and productivity of soybean [Glycine max (L.) Merr. 1917] at Maroua, Far North, Cameroon

To determine the insect species richness, relative frequency, food products, potential pollinators and their impact on the yields, the flowers of Glycine max (Fabaceae) were observed from September 3rd to 27th in 2015 (Mayel–Ibbé) and from September 6th to October 10th in 2018 (Wourndé). Two hundred plant flower clusters in 2015 and in 2018 they are divided in two treatments, differentiated according to the presence or absence of protection against insect’s activities. The diversity of the flowering insects of soybean was 19 and 12 species respectively in Mayel–Ibbé and Wourndé. These insects visited the flowers of the soybean from 6 am to 5 pm with the activity peak situated between 10 am and 11am. These insects developed and elaborated behaviour when they collected the nectar and/or pollen. Thus, they can be grouped into major pollinators, minor pollinators and occasional pollinators. By comparing yield of unprotected plants to yield of protected plants from insect visits, it is appeared that insects have a positive impact on this yield. The influence of the insects on the increasing of soybean yield is estimated at 39.29%, 11.70%, 22.88% and 03.76% for the pod/plant, the number of seeds/pod, the percentage of the mass of seeds and the percentage of normal seeds respectively. In order to improve the yield of G. max, it is advisable to preserve the flower-dwelling insects in the farm by avoiding pesticide treatments during the period of flowering when they are not justified.