Vectoring of fungal agents by bumble bees for pest control and disease suppression in greenhouse tomato and sweet pepper

The ability of the bumble bee, Bombus impatiens, to vector Beauveria bassiana and Clonostachys rosea for control of Trialeurodes vaporariorum, Lygus lineolaris, Myzus persicae, and Botrytis cinerea in greenhouse tomato (Lycopersicon esculentum) and sweet pepper ( Capsicum annuum) was investigated. Trials were conducted in cages to evaluate the effects of these two fungal agents on insect pests and a major greenhouse plant disease, and under commercial greenhouse tomato production conditions to assess the impact of Beauveria on bee activity and its pollination efficiency. Three concentrations: low, 9x109; middle, 6.24x1010 and high, 2x1011 conidia of Beauveria/g of inoculum were tested for controlling pest insects, and a mixture of 6.24x1010 Beauveria + 1.38x10 7 conidia of Clonostachys/g of inoculum was evaluated for simultaneous control of insect pests and grey mould. A randomized complete block design was applied to all treatments for all experiments. Results showed that the middle concentration killed similar numbers of insect pests as did the high concentration (70% Lygus and 54% whiteflies) but more than the low concentration (33% Lygus and 18% whiteflies). The mixture of Beauveria and Clonostachys killed the same percentage of pests as did the middle concentration of Beauveria when used alone, and suppressed 58 and 45% of the grey mould in the flowers and leaves of both crops respectively. More bees were killed in the high than the middle concentration (44% vs 13%), but no significant difference was found between the latter and the low concentration or controls. Thus, the middle concentration is considered the optimal treatment, because it killed the similar proportion of pest insects as did the high concentration, but with less negative impact on bees. In the commercial trials, bee activity (trips to and from the hive) was the lowest when the bumble bees were exposed to the highest concentration of Beauveria. The dispenser also appears to have a negative impact on bee activity and needs to be further investigated. However, pollination level was satisfactory at all commercial greenhouses and harvested tomato fruit quality met commercially recommended standards even though bees were vectoring the Beauveria. Further trials need to evaluate the effect of the dispenser with and without inoculum to determine more precisely the effect, if any, of the inoculum on bee activity. This study has demonstrated that the bee vector technology could be a new integrated pest management tool that can be used to deliver microbial fungal control agents, singly or in combination, for insect pest control and plant disease suppression for greenhouse tomato and sweet pepper.