Improvements will make PCN model site-specific

Improvements are being planned to the Potato Council-funded SCRI potato cyst nematode control model, the council’s Mike Storey has confirmed.

The model allows growers to test various different control strategies to see the effect on yields and PCN populations over several potato rotations and is being promoted by the Potato Council as a way of testing and demonstrating long-term strategies to reduce PCN levels in response to the forthcoming EU PCN Directive.

Responding to a presentation by Harper Adams University College‘s Pat Haydock pointing out where improvements could be made to the model at the Cambridge University Potato Growers Research Association annual conference, Dr Storey said more work was being undertaken to add to varietal tolerance and resistance data. Other trials would investigate nematode decline rates and nematicide efficacy to make the model more user-friendly.

Both improvements were suggested by Dr Haydock to further improve an already useful model. “For relatively little effort it could be updated substantially.”

He also wanted the model to include the economic implications of different nematode management decisions. By allowing growers to input key cost data from the council’s benchmarking model about the cost of nematicides and potato crop values, he said growers would be able to calculate gross margins.

“They would be useful when looking at the difference between using a nematicide and fumigant, which can cost £1000/ha, and just a nematicide at £300/t, for example.”

Other factors that influenced severity, such as rhizoctonia, which Harper Adams research had suggested had a synergistic effect, also needed to be incorporated, he said.

Growers could also manipulate the current model to make its predictions more accurate, he said. For example, it used a 20% annual decline rate in PCN infestation, which could be altered within the programme. Research had suggested that decline rates of the Globodera pallida strain of PCN tended to be lower than G rostochiensis, but had more variability, he said.

“Growers can get their own information about decline rates by marking out areas and monitoring over a number of years,” he suggested.

Repeated nematicide use

Repeated use could cause some nematicides to become less effective, new research from Harper Adams University College suggests.

In the trials soils were exposed to repeated nematicide applications at 35-day intervals, Dr Haydock explained. “We found that repeat applications reduced the persistence of some nematicides.”

In particular, oxamyl and aldicarb were affected, but fosthiazate didn’t appear to be, he said.

Increased selection of soil bacteria able to degrade the nematicide was thought to be the cause, he added.

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