Can we use less water while still staying on top of scab in potatoes? How can we control cabbage stem flea beetle safely and effectively without neonicotinoids? And how can we help plants to strengthen their own defences against aphids? These are just some of the key questions facing farmers that are being tackled by scientists at the Norwich Research Park. Non-chemical pest control was the subject of a Agri-Tech Week 2020 webinar, hosted by the Norwich Research Park.
As both climate and legislation continue to change, harnessing beneficial insects and understanding relationships between microbes becomes increasingly important in the search for non-chemical pest control.
Tackling water use for scab control in potatoes
“Costing growers £3m annually, and requiring huge quantities of irrigation water to control, scab in potatoes is a real problem for the potato industry in the UK,” explained Dr Jake Malone, a research scientist at the John Innes Centre (JIC). “But a better understanding of how microbiological activity could help us to tackle it would allow growers to use considerably less water in its control.”
The bacterium causing scab, Streptomyces scabies, is just one of the millions of species found in soils.
Could advances in non-chemical pest control making growing oilseed rape viable without neonicotinoids?
“A 35% drop in oilseed rape (OSR) production in the UK since neonicotinoids were withdrawn, and a jump in pyrethoid resistance in cabbage stem flea beetle (CSFB) from less than 2% to 22% over the last three years.”
These figures, from Dr Rachel Wells, JIC researcher in molecular genetics and plant breeding, underpin her drive to discover how growers can tackle CSFB as the current chemical armoury becomes ever more depleted. “Key to this is to develop a greater understanding of crop pests, and their interactions with plants” she explains.
One of the first challenges to better understanding the cabbage stem flea beetle, was studying them in laboratory conditions. “Looking at insect resistance in crop variety trials is challenging for a range of reasons, so we had to develop a means of rearing them in the lab, which is now how we do much of our research into them.”
Breakthough shows tiny wasp can control cabbage stem flea beetle
But an incident which compromised a particular batch of lab-reared CSFB led to a valuable breakthrough. In 2017 rapid deaths in several CSFB colonies was seen following the introduction of some new colonies to the laboratory. These newly-introduced insects brought with them tiny wasps which parasitise the flea beetle. Further lab research showed that control of up to 53% could be achieved using this species of wasp, Microtonus brassicae.
Unpalatable varieties of OSR reduce loss
“Adjusting management regimes, such as reducing soil disturbance, improved habitat in field margins and providing nectar sources for adult wasps can all make a difference to how well they control CSFB in the field, especially as we’re seeing pyrethoid resistance in flea beetle increasing,” said Dr Wells.
Further research shows that by selecting different traits relating to plant palatability could allow breeders to create new varieties which were less appealing to flea beetle.” Usually the pathway from lab to commercial crop production can take around fifteen years, by using ‘speed-breeding’ and working closely with plant breeders we hope to have viable new varieties of OSR on the market within the next five years.”
Understanding plant response to aphids
As our warming climate increases the damage caused to crops by aphids, JIC postgraduate researcher James Canham explained the importance of tackling these problems at the molecular level. “Sap-feeding insects, such as the green peach aphid, transmit more than 50% of plant viruses in the UK. As successive insecticides are withdrawn alternative approaches to their control are required.”
Recent advancements have revealed previously hidden plant responses to attack by aphids. Calcium has been found to play a key role here, and localised changes in calcium levels indicate that the plant is being attacked and is showing a strong immune response.
But James’ research has shown that ‘effectors’, introduced to the plant in the saliva of aphids, interfere with and suppress this immune response, increasing the aphids’ ability to colonise the host plant. By better understanding and manipulating these effectors he sees potential in developing mechanisms to confer resistance to aphid attack.
Plant’s immune response could provide protection
“However, an effector-mediated defence may not confer resistance to the disease carried by the aphids, as it might occur too late, after the virus has already passed into the plant. A very early host plant immune response (i.e. one which occurs before the virus can pass from the aphid’s saliva into the host plant) holds considerably more potential and is an area where we’re researching further.”
Delegates at the webinar also heard about a number of other exciting research areas:
- Nasmille Larke-Mejia described her work studying soil microbiological diversity and the impacts that changes in agricultural practice can have have on this microbiome.
- Dr Victor Soria-Carraso explained the role that the JIC Entomology & Insectary facility plays in supporting research involving insects, and their potential role in providing solutions to some of today’s problems.
- And finally, Dr Lewis Spurgin talked about how ‘citizen science’, where sugar beet growers and the British Beet Growers Organisation have sent in samples of sugar beet leaf miner insects, has helped to improve understanding of this little-known species.