Application and Management of Biopesticides for Efficacy and Reliability (AMBER) 

AMBER is a 5-year project with the aim of identifying management practices to improve the performance of biopesticide products within an IPM programme.

IPM is now required under the EU Sustainable Use Directive on pesticides.  In order to make IPM successful, it is vital that growers have access to a full range of control agents that can be used as part of an integrated approach, and not just rely on traditional pesticides. One group of alternatives are ‘biopesticides’ these are pest control products based on natural agents, and there are three types; living microbes, insect semiochemicals and botanical biopesticides. These types of pest control agent are based on living organisms and so it takes more knowledge and understanding to use them successfully compared to traditional pesticides.

AMBER aims to identify practices to optimize biopesticide use and understand the reasons why some biopesticides are giving sub-optimal results in current commercial practice. Using this information can help develop and demonstrate new IPM compatible strategies for pest control.

Making biopesticide spray application more efficient. 

To determine the lowest volume of water required to provide biopesticide efficacy the effect of spraying different water volumes mixed with tracer dye (used as a proxy for a biopesticide) that’s retained on chrysanthemum plants was investigated. It was found that the most efficient way to deliver an active substance to this kind of plant is with as low volume and as high concentration as possible (within legal requirements) Water volumes currently recommended for most biopesticides (1000 L / ha or higher) are unlikely to be helpful in terms of optimising the quantity and distribution of biopesticide active substance on the plant.

Understanding the persistence of biofungicides on crop foliage.

There is currently a lack of information on how long microbial biofungicides survive for after they have been sprayed onto crops. Experiments have investigated the survival of Ampelomyces quisqualis (agent of biofungicide AQ10, used against powdery mildew), Gliocladium catenulatum (agent of Prestop for management of botrytis) and Bacillus subtilis (agent of Serenade for botrytis management) Biofungicides are recommended for application before, or at the first signs of, disease symptoms. If they do not survive for long, then they will have to be reapplied frequently.

The survival experiments found that there was a steep drop in the number of viable propagules of A. quisqualis recovered from leaves sprayed with AQ10 after four days. This biofungicide is parasitic on powdery mildew and because it does not survive on the plant for long in the absence of its host, then the correct timing and frequency of application is going to be very important for its efficacy. In contrast, Gliocladium catenulatum reproduced on the plant and about twice as many propagules were retrieved 7, 10 and 14 days after Prestop application than present on initial application. This biofungicide works as an antagonist and competitor so is applied preventatively. After seven days from Serenade ASO application, Bacillus subtilis bacteria were recovered in similar numbers to within hours of application, again showing good persistence.

Optimal biopesticide control strategies

Microbial biopesticides are usually slower acting than conventional pesticides as the speed of pest kill is affected by a wide range of variables such as the pest’s biology and the environmental conditions. This complexity means that fungal biopesticides can give variable results depending on the situation in which they are used.

Taking this complexity into account a computer model has been developed to simulate the impact biopesticide has upon pest population dynamics and growth over time. The pest glasshouse whitefly and entomopathogenic fungi biopesticide were used as the initial model pest and biopesticide. The model includes the main factors that influence the growth of the pest population as well as factors relating to the ability of the biopesticide to limit pest growth. The model can make predictions on the development of the pest population and by using the prediction, the model can be used to make practical recommendations about the best ways for growers to use biopesticides.  For example, how frequently (and at what time in the crop growing season) the biopesticide should be used.