Time for a biopesticide revolution?

In order to keep pace with the move to more sustainable integrated pest management (IPM), the horticultural industry needs to rapidly increase its knowledge of biopesticides.

With the continued withdrawals of conventional actives, as seen recently with the non-renewal of thiram, diquat, metam 510 and fenamidone, biopesticides are becoming more vital in the management of pest, weeds and diseases.

However for biopesticides to be effective, a better general understanding of this new crop protection technology is needed in the industry, in order to change some current practices of application, storage and handling.

Gill Prince, University of Warwick, researcher for AMBER, stresses: “It is important to remember that many biopesticides are living organisms, so they need to be treated differently from conventional chemistry.”

AHDB is currently funding AMBER, a five year project to help UK growers improve the performance of biopesticides by sharing knowledge about the factors which impact their efficacy.

Water Volumes

Horticulture has different practices compared to wider arable practices, as water volumes are often being applied at around 2000 litres / hectare, whereas arable farmers rarely exceed rates of 200 l/ha.

There are several reasons behind the differences, but Andrew Lane, Silsoe Spray Applications and a researcher for AMBER, argues growers could benefit from reducing volumes, and for low crops the optimum is likely to be no more than 600 litres/ha.  

Clare Butler Ellis, Silsoe Spray Applications, researcher for AMBER, said: “Biopesticides may require more water than conventional pesticides because of their very different mode of action, but there isn’t enough data available to know what the optimum is yet.  Where the label gives a range of volumes and/or concentrations, aim for the lowest volume and highest concentration to maximise the quantity of biopesticide on the plant.

Andrew says: “People seem to believe that simply by throwing more water at the crop you will get better coverage, but that isn’t the case and will lead to greater run-off.

There are simple steps growers can make that could help to reduce their water volumes. Andrew recommends that basic housekeeping, from regular calibration of equipment, thorough cleaning, including nozzles and tanks, and checking for damage could make a big difference.

Andrew also urges growers to consider the different types of sprayers and nozzles available on the market that will work with the structure of the crop canopy and the type of biopesticide you are applying.

Significant reductions in the use of water volumes used in biopesticide application could not only put more biopesticide on the plant, but could also help save costs due to reduced product use and labour inputs if tanks are being refilled less often.

Gary Woodruffe, Bordon Hill Nurseries, says: “We have recently made an investment in a boom sprayer to help with our application. This has helped to reduce our pesticide use by around 30 per cent and significantly reduced the labour hours involved in applying the spray.”

Storage

Growers need to consider shelf-life, which for some products is often quite short, or can reduce once the product has been opened. Certain products will need to be stored in refrigerators, as heat or even short exposure to direct sunlight, can kill the natural organisms in the product. Gill recommends that growers speak to their distributors to ensure their product is being kept in the optimal condition throughout the delivery.

Christine O’Sullivan, Silsoe Spray Applications, researcher for AMBER, is encouraging growers to consider just how clean their spray tanks are. She explains: “Even with a thorough three-tank clean, you can see a lot of residue from conventional chemicals in standard dye tests.

“If the previous chemical used has been a fungicide, and you follow with a fungal biopesticide, the beneficial spores in your product can be killed before you apply it.”

Ideally, Christine recommends growers should consider investing in a separate tank for biopesticide use to avoid contamination issues.

For the same reason, Gill argues that the timing of spray applications also need to be considered when biopesticides are used within IPM, as some biopesticides can be slow acting.

Agitation

Many biopesticides can quickly separate, therefore sustained rigorous agitation, even during the spray process, will ensure you get a good crop coverage. It will also avoid any leaf scorch from high patches of concentration and ensure the product doesn’t get caught in nozzles.

Dr David Chandler, University of Warwick and research lead for AMBER, argues: “If growers aren’t putting thought in to the application of their biopesticides, they might as well be pouring them down the drain.”

To find out more about the AMBER project, visit bit.ly/AMBERproject.

A workshop was held on 23 October 2018 at Bordon Hill Nurseries, Stratford-upon-Avon, for horticultural growers to find out more about how different factors effect biopesticide performance.