Using bees to vector fungal control agents and plant health inoculums for arthropod and plant pathogen control
Project Code : MUR06-300
Les Shipp - Agriculture and Agri-Food Canada
To optimize the delivery of the biofungicide Clonostachys rosea in combination with insect fungal biocontrol agent Beauveria bassiana by bee pollinators for effective, simultaneous control of grey mould and Lygus in greenhouse vegetables
Summary of Results
Using bumble bees (Bombus impatiens) to vector microbial control agents for insect pest control has been demonstrated to be an effective new application technology for fungal control of greenhouse pests. Greenhouse cage trials have shown that bee-vectored Beauveria bassiana can cause substantial mortality of Lygus, whiteflies, thrips and aphids (up to 80% mortality) when tested on greenhouse tomato and sweet pepper.
The bees deliver the fungal spores directly to the flowers and leaves where the pests are found. This approach reduces the amount microbial agent applied, minimizes human handling of the fungal control agents, eliminates the use of pesticides for insect control and is more environmentally-friendly and cost effective than the application of chemical pesticides.
Since bumble bees are the standard pollination method in greenhouse vegetables, pollination and pest control activities can be combined together. In addition, preliminary greenhouse cage trials have found that bumble bees can simultaneously deliver both a bio-insecticide (Beauveria bassiana) and a plant inoculum (Clonostachys rosea) to sweet pepper for Lygus (ca. 80% infection) and grey mould (45-55% suppression) control. The impact of these fungal agents on bumble bees appears to be minimal.
The bumble bee was used to vector a combined inoculum consisting of Beauveria bassiana (BotaniGard 22 WP) and Clonostachys rosea (ADJ 710 OMRI) in greenhouse tomato and sweet pepper to determine the optimal concentration of both microorganisms for simultaneous control of insect pests (Lygus lineolaris and Trialeurodes vaporariorum) and plant disease (grey mould).
Four different concentrations of the combined inoculum (B. bassiana and C. rosea) were assessed. Ninety-six, 47 and 88% of the bee, pest insect and plant samples respectively contained detectable amounts of Beauveria and Clonostachys. Infection levels for both pest species as well as disease suppression were greatest at the highest concentrations of both agents. However, bee mortality was also significantly greater at the highest concentration of Beauveria. Therefore, the optimal combined concentration ratio of Beauveria and Clonostachys was 6.24 x 1010 B. bassiana + 1.38 x 107 C. rosea.
Preliminary greenhouse cage trials were undertaken to determine the impact of bee-vectored Beauveria / Clonostachys on non-target parasitoids and predators. The results indicated that bee vectored B. bassiana was not harmful to the whitefly parasitoid, E. eremicus, and also that it didn't affect its rate of parasitism. Replicated greenhouse cage trials will have to be done to determine the impact of bee-vectored Beauveria / Clonostachys on other parasotids, predatory bugs and predatory mites used in greenhouse biological control.
This study has shown that two fungal agents can be combined into a single inoculum for delivery by bumble bees to plants for effective pest and disease control. Furthermore, this technology could be easily adapted for other cropping systems that use bees as pollinators.
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