Design of a commercial dispenser for delivery of biocontrol agents in greenhouse by bee pollinators

Project Code BPI10-010

Project Lead

Les Shipp - Greenhouse and Processing Crops Research Centre, Agriculture and Agri-Food Canada

Objective 

To determine the optimal dispenser design for pollinator delivery of biopesticides and to demonstrate use of selected dispenser with commercial products suitable for bee vectoring

Summary of Results

Background

Pollinator biocontrol vector technology is a new approach that uses bees to disseminate microbial biocontrol agents to pest-infested crops. As bees exit their hive, they pass through a microbial inoculum dispenser and accumulate the biocontrol product on their legs and body hairs. The bees then transport the product and deposit it on plant foliage and fruit during foraging and grooming. Compared to spray technology, there are several advantages of this unique application method. Among other advantages, the pollinator vector technology (i) provides continuous, targeted application of the pest control product; (ii) reduces loss to ground deposition; (iii) limits aerosol concentration; (iv) minimizes labour costs for application; (v) minimizes impact on non-target insects; and (vi) integrates pollination with pest control.

The Pest Management Centre's Pesticide Risk Reduction Program has funded two previous studies that have helped develop this technology using BotaniGard 22 WP (active ingredient: Beauveria bassiana strain GHA) as a ‘model product’, and has facilitated the first time registration of this delivery method in Canada. To make this technology suitable for implementation by growers, the dispenser designs used in these research trials needed to be adapted for commercial use. The objectives of this project were: (i) to improve dispenser design; (ii) to quantify the amount of inoculum that the bees deliver, the viability of the inoculum in the dispenser over time, and impact of the inoculum on hive colony growth, and; (iii) to demonstrate the bee delivery technology to growers.

Approaches

The greenhouse trials were conducted in three greenhouse compartments in Harrow, Ontario. Dispensers of different lengths, widths and configurations for exit and entry of the bees from the hive were evaluated to determine the optimal dispenser design using Beauveria bassiana as the test biocontrol agent. In addition, new microbial control agents being considered for bumble bee vectoring, Bacillus thuringiensis subspecies Kurstaki, the baculovirus, AcMNPV FV#11, and Metarhizium anisopliae F52 were evaluated for insect pest control on greenhouse tomato.

Laboratory trials were conducted to determine if dispenser length using the Sutton design (which has a dispenser length x (times) width x height of 20 xx 1.5 centimeters) as the standard had an impact on fungal biocontrol agent acquisition by the bumble bee. To detect the quantity of Beauveria spores picked up by bees in different dispensers, the dispenser trays were filled with Beauveria bassiana at the label rate of 1.32 x 1010 viable spores per gram of inoculum. Twenty individual bees were allowed to pass through each dispenser design, and were collected and processed to determine the number of spores on the bees’ bodies.

In greenhouse experiments, five dispensers using different materials and designs were compared to determine their effect on delivery of the pest control agent to the crop, and on bee hive health. Hives, with the different dispensers filled with Beauveria bassiana spores according to label directions, were placed in fine meshed screen cages along with 24 tomato plants. Leaf, flower and bee samples were collected weekly and the inoculum was quantified by colony forming unit counts. Hive health was determined by counting the number of bees and brood cells before the trial, at the end of the greenhouse trial, and three weeks after removal from the greenhouse. All treatments were replicated twice, and the trial was repeated two times.

Further greenhouse cage trials were conducted to evaluate three commercial products: Baculovirus (AcMNPV FV#11), Bacillus thuringiensis subspecies kurstaki, and Metarhizium anisopliae F52 to determine feasibility of pursuing the expansion of these product labels to include the pollinator vectoring uses.

Results

Trials to determine optimum dispenser design proved inconclusive, and impacts on bee hive health were similarly unsuccessful due to unexpected problems with initial bee hive condition.

Results indicated that four days after inoculum filling, bees from all dispensers acquired similar amounts of Beauveria spores. Bees collected 7 days post inoculum filling exhibited a reduction in the bee “loads”. Beauveria viability in the inoculum after 7 days was the same as at the beginning of the trial (greater than 95% viability). It may be helpful to conduct additional studies to determine the impact of continuous exposure of bee-vectored Beauveria to commercial hive population dynamics using the Sutton dispenser, as results were somewhat inconclusive on this point in this study.

The evaluation of three commercial products (baculovirus (AcMNPV FV#11), Bacillus thuringiensis (Bt) subspecies kurstaki, and Metarhizium anisopliae F52) suitable for bee vectoring for label expansion packages of these products indicated that bumble bees are excellent vectors for the delivery of Bt and the baculovirus AcMNPV FV#11 to greenhouse tomatoes for control of cabbage looper larvae.

Data also showed that the infection levels of cabbage looper larvae exposed to Bt via bee vectoring and spray application were not significantly different.

Conclusions

Although results of the different dispenser designs were inconclusive, the data generated within this project did indicate bee vectoring has potential as an efficacious and cost effective approach to integrating production practices with pest management measures in greenhouse production.

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