Walking down the row of cabbages the air is full of movement and quiet buzzing.
The abundance of beneficial insects moving between the plants is making the grower whose farm we are visiting very happy.
His farm is part of a research trial testing the impact of flowering plants grown amongst vegetable crops on populations of beneficial insects and the pest species they attack.
Post-doctoral researcher Dr Syed Rizvi has set up flowering trial plots on vegetable farms across New South Wales, Victoria, South Australia and Queensland as part of a Hort Innovation funded project led by Charles Sturt University.
Results from the trials have indicated a positive correlation between the presence of flowering plants grown within brassica crops and increased beneficial insect populations. Importantly, the work has also shown reduced numbers of pests in vegetables grown alongside these flowering strips.
Flowering plants are known to attract beneficial insects by providing shelter, nectar, pollen, honeydew and alternative prey. For the trials, Dr Rizvi planted select flowering species such as sweet alyssum, buckwheat and cornflower that offer attractive resources for a variety of beneficial species.
Biological pest control
Dr Olivia Reynolds, Research Lead at cesar and Graham Centre for Agricultural Innovation Adjunct Associate Professor – as well as one of Dr Rizvi’s supervisors for the project, explains to me how beneficial insects play a crucial role in keeping pest numbers in check in natural environments.
According to Dr Reynolds, the field trials look to replicate part of these natural systems and promote beneficial populations that can support growers’ integrated pest management strategies.
Walking along Dr Reynolds was able to point out a range of beneficial species moving between flowering plants and the cabbage crop including ladybeetles, brown lacewings and parasitoid wasps.
The importance of beneficial species for pest control in agroecosystems is increasingly being recognised by the industry, with effective techniques to promote these beneficial communities important for farmers looking to move towards integrated pest management.
This project builds on recent studies undertaken both in Australia and overseas investigating the role of beneficial insects in agroecosystems. A growing body of research is demonstrating that more complex farm landscapes support greater diversity of beneficial populations with a number of overseas trials showing strong correlations between inclusion of suitable floral vegetation in crops and improved pest population suppression outcomes.
A recent survey of conventional and biological-based vegetable farming systems around Australia compared insect levels in vegetable fields. The study found no observable difference in pest numbers between the different farm types, but substantially higher levels of beneficial insects in the biological-based fields.
Providing suitable habitat for these beneficial invertebrate communities is crucial to protecting this natural pest control resource and ensuring growers have a variety of tools available for managing pests sustainably. These flower trials offer the possibility of an additional biological control tool in the growers’ pest management toolbox.
The findings from this research will be developed into information packages for growers looking to improve their biological pest management options, including a website currently under development that will aid vegetable growers identify suitable habitat manipulation strategies and flowering plant species to increase beneficial populations, and suppress pests.
This article provides information on research activities undertaken as part of the Hort Innovation investment ‘Field and landscape management to support beneficial arthropods for IPM on vegetable farms (VG16062)’. Project partners include Charles Sturt University, cesar, NSW Department of Primary Industries, University of Queensland, and IPM Technologies. The project has been funded by Hort Innovation, using the vegetable research and development levy and contributions from the Australian Government. Hort Innovation is the grower-owned, not-for-profit research and development corporation for Australian horticulture.
The article draws on findings from:
Balzan et al. 2016. Landscape complexity and field margin vegetation diversity enhance natural enemies and reduce herbivory by Lepidoptera pests on tomato crop. BioControl 61:141–154.
Gagic et al. 2018. Ecosystem service of biological pest control in Australia: the role of non‐crop habitats within landscapes. Austral Entomology. 57:194– 206.
Kopta et al. 2012. Attractiveness of flowering plants for natural enemies. Horticultural Science. 2:89–96.
Tschumi et al. 2016. Tailored flower strips promote natural enemy biodiversity and pest control in potato crops. Journal of Applied Ecology. 53:1169-1176.
Thanks to Dr Olivia Reynolds, Julia Severi, Ashley Zamek, Emily Malone and Professor Geoff Gurr for their input in developing this article.