Nectria Canker is a significant issue for the top fruit sector in the UK, which can be attributed to a combination of our maritime climate, and a limited range of control options available.
We investigate how a novel approach to achieving Emergency Authorisations has provided access to vital chemistry, and could bring major benefits to the apple industry.
In recent years Nectria canker has become a greater issue in the apple sector due to the rise in popularity of new varieties such as Jazz, Kanzi and Envy, which are highly susceptible to the pathogen.
In established orchards, the disease can cause a loss of productivity due to the need to prune out affected branches, and associated Nectria eye rot leading to downgrading of fruit. Whereas in young orchards, Nectria canker infections often result in the loss of the entire tree, explains Rob Saunders, Chairman of the AHDB Tree Panel board.
“Disease pressure is severe when wet weather occurs during the bud burst and leaf fall stage, as the trees are more susceptible to infection at this time.
“New EAMUs for tebuconazole products, which protect against Nectria canker, are limited to a reduced rate of use, and stipulate just one application per year. Therefore, to provide protection throughout the periods of highest risk, the role of copper based treatments is more important than ever,” he says.
He adds that although cultural controls should not be neglected, crop protection chemistry also has a role to play. “With such a limited armoury we’ve had to think about novel approaches to help support the future of the industry.”
It was with this in mind that an Emergency Authorisation application was submitted by the AHDB. Following lobbying from concerned growers including The Organic Growers Association, the Soil Association, and Certis, among others, a derogation was recently granted to allow access to the copper based product, Cuprokylt, for use on apple and pear trees, he explains.
“The new approach taken for this 120-day Emergency Authorisation means it’s split between the two highest risk periods for the disease, at leaf fall in autumn and after bud burst in spring.
“The fact that the Chemicals Regulation Division (CRD) have agreed to split this Emergency Authorisation across the two usage periods is a significant breakthrough,” says Rob.
“It shows that they recognise the importance of the product to the industry and clearly demonstrates that they are listening and responding to grower’s needs.”
There is a vast amount of work that goes on behind the scenes to attain Emergency Authorisations, explains Certis’ Regulatory Affairs Officer Maria McKelvie.
“The entire process can be extensive and takes up to six months to complete. The representatives involved submit the application documents and support the application through to completion, but a large amount of preparation and research takes place before the process even starts,” says Maria.
She adds that to gain a derogation, firstly the group making the application must satisfy the CRD and the Expert Committee for Pesticides (ECP) that unless an approval is granted there will be significant consequences to crops and growers.
“Where the issues are complex, the group must then present their argument to the ECP, explaining why the derogation is required, and take questions from the panel.
“Emergency Authorisations are the last resort, and therefore there is a rigorous decision-making process in place before a decision is made and a derogation granted.”
When applying for any derogation there must be reassurance that a long-term plan for tackling the disease or pest has been developed, to ensure that protection of the crop is sustainable and supported over a period of time.
“Finding alternative approaches to tackling diseases such as Nectria canker is vital,” Maria explains.
“Certis are committed to a long-term plan that offers support to growers for the future. Therefore, we’re currently looking at alternative copper-based fungicides, and have some promising candidates in the pipeline.”
Rob adds that AHDB Horticulture is also focusing on a long-term control strategy for Nectria canker.
“AHDB Horticulture has commissioned NIAB EMR to undertake work to advance the understanding of disease expression, how the disease interacts with resident endophytes and to investigate novel approaches to control.
“The project is already providing useful insights, which will help to maintain tree health in the face of the diminishing range of products available.
“Ultimately these derogations mean that top fruit crops will be secured, but also demonstrates that the industry is working together with governing bodies to support the industry for the future,” he says.