IPM focus to target PCN populations
Early intervention with an Integrated Pest Management programme is now recognised as crucial for long-term sustainable control of Potato Cyst Nematode (PCN).
Every cyst left in the soil at the end of the nematodes’ life cycle typically contains 400 to 600 eggs, each with a viable juvenile.
Research reported by the AHDB identified populations of G. pallida multiplied 46 to 100-fold from an initial population of fewer than 10 eggs per gram of soil. Multiplication of PCN is greater when the initial infestation is low, it warned.
“Given the evidence that PCN can multiply from population levels that are not detected to highly damaging levels in one susceptible crop, even the slightest infestation should be taken seriously.”
AHDB PCN Grower Guide, 2018
Issues have been amplified in recent seasons with the more difficult to control G. pallida becoming by far the dominant PCN species, compared to G. rostochiensis, highlighted Syngenta Technical Manager, Michael Tait.
“The viability of G. pallida cysts is 30% slower to naturally decline, creating greater concerns through the rotation,” he pointed out.
“It has also been shown the hatching period of G. pallida can last 50% longer - potentially for about 18 weeks after planting.”
That emphasises the importance of accurate Nemathorin application and incorporation, to ensure an effective concentration of nematicide remains evenly distributed throughout the target soil profile for as long as possible.
Nemathorin best practice advice for PCN
- Follow advice from the Nematicide Stewardship Programme
- Calibrate application equipment before use
- Apply at 30 kg/ha broadcast overall
- Fully Incorporate immediately with a single pass, to an even depth of 15 cm
- Do not desiccate or harvest crops for at least 17 weeks after application
“Using the full rate of the most effective nematicide, Nemathorin, is crucial to protect crop yield and minimise the risk of populations multiplying through the season, even from very low levels of PCN infestation.”
Independent trials in the UK, by VCS, showed a 7.5 t/ha yield uplift from full rate Nemathorin, with a 9% increase over fluopyram alone. Where fluopyram was used in conjunction with half rate Nemathorin, yield was 1.8 t/ha lower than full-rate Nemathorin alone.
“Research has shown reducing the application rate of Nemathorin, even in combination with other products, could seriously compromise results and PCN multiplication levels,” Michael warned.
He advocated growers should still utilise intensive soil sampling to detect early-stage infestations. However, even sampling 49 cores per hectare and submitting 2.6 kg of soil to be analysed, there was still only a 67% probability of detecting a population of five million cysts - potentially two billion eggs - per hectare; if the same sample was reduced to 400 g for analysis the probability of detection would fall to just 31%.
“Soil sampling is the best tool we have available to track changes in PCN populations over the course of successive crop rotations,” advocated Michael.
“That is essential to implement appropriate IPM tools to manage populations at sustainable levels.”
IPM tools for PCN control
- Soil sampling for PCN counts
- Extended rotations
- Control of volunteers
- Growing biofumigants
- Understanding variety PCN resistance and tolerance
- Soil and machinery sanitisation to avoid spread
- Nematicide treatment
Renewal actively sought for Nemathorin 10G
The existing approval for the active substance fosthiazate (as contained in Nemathorin 10G) remains valid until the end of October 2024. The government’s Chemicals Regulation Division (CRD) has already acknowledged that a renewal is being actively sought for this key granular nematicide for the potato industry.
As the approval holder for fosthiazate, ISK Biosciences, along with Syngenta, are fully committed to supporting the renewal of this active substance, both in GB and the EU.
Significant investment in extensive field studies and laboratory research has already been completed to demonstrate compliance with new regulatory demands, along with an ongoing evaluation of all R&D data to answer potential questions and issues. A supplementary dossier of information to support the renewal of fosthiazate will be submitted to CRD by the end of April 2022.