Among the four orders of insects involved in plant pollination, insects belonging to the order Hymenoptera, especially bees, play a very essential role because of their morphology, diet, asphalting behaviour and mode of action with flowers [
14,
15]. Compared to honeybees, bumblebees have the great advantage of ensuring both the pollination of several flowers in a few minutes and the biological control of insect pests and diseases through the principle of entomovectorization [
16]. This study explored the potential for biological control of B. bassiana (strain GHA) against the mite P. pallidus by conventional spraying and bumblebee vectoring. Our results show that, regardless of the mode of application of B. bassiana on strawberries, it had a significant effect on the cyclamen mite as well as on the damage caused by this pest compared to the control treatments (T1 and T2). These results corroborate the study of [
17] He noted that entomopathogenic fungi have a good capacity to manage insects and crop pests, such as mites. Because of their specificity, these fungi can induce epizootics in pests and thus regulate their population. [
18] had demonstrated the efficacy of two strains of B. bassiana on the mortality of two-spotted spider mite (TSM) populations up to 70%. The B. bassiana strain GHA used in this work is a fungal strain registered in Proposed Registration Decision 1925-0908PRD2009-03 [
19]. This is a strain that, once in contact with the insect, germinates and enters the body of the latter. It produces a filament called a hyphae that induces white muscardine disease to its host and eventually kills it. It is indeed this mode of action that was identified in the dead mites at the end of the collection of samples whose spore concentration was noted at 3.4 x
CFU. As for the spraying of
B. bassiana, it induced a high mortality of P. pallidus compared to entomovectorization by bumblebees (T7, 5.833 ± 0.226ab; T3, 2,389 ± 0,229ab; T4, 0.611 ± 0.118b; and T5, 1.667 ± 0.114b). These results are in line with those of Macharia Kanyi et al. (2020) who have shown that spraying
T. harzianum had a significant effect on the control of grey mould in strawberries than treatment with the use of entomovecteurs. Since mites hide in the hollows of young leaves, spraying has promoted contact between spores and pests; and thus created the conditions favourable to their development to the detriment of these pests. In addition, through the process of entomovectorization, bees need to carry a sufficient amount of colony-forming units on their bodies in order to ensure effective mite control, which would require bees to pass in several turns over the different plant parts to ensure a good deposition of inoculum capable of controlling this population. Macharia Kanyi et al. (2020) have demonstrated the effectiveness of bees in transmitting
T. harzianum on the parts of the plant, which corroborates our results on the mortality of mites in the face of the use of bumblebees and the fungus
B. bassiana. It should be noted that few studies have been conducted on the pathogenicity of GHA
B. bassiana on pathogenic insects. [
12] have shown that the use of
B. bassiana of the active strain Balsamo was able to suppress 49% of T. vaporariorum on tomatoes, on flowers and leaves, respectively. As for the INRS IP and INRS-CFL isolates from
B. bassiana Used as an insecticide, they have been shown to be 80% effective in the laboratory against tarnished plant bug adults and adults of strawberry flower anthonoma and strawberry root weevil at day seven after inoculation [
21]. These results are in line with our results in the sense that either the damage caused by the
P. pallidus are reduced from the seventh day after spraying. In terms of beneficial organisms, the case of the ladybird considered useful for the biological control of aphids and certain mites, no significant effect was noted with regard to the use of
B. bassiana on the latter. These results are in line with those of [
22] who have shown that the use of
B. bassiana vectored by bees had no impact on certain beneficial insects such as the parasitoid species and
A. swirskii. In addition [
23] also demonstrated that
B. bassiana has no effect on predators
Coccinella undecimpunctataand
Hippodamia variegata survival, duration, longevity of adults and fertility.