Potato Review

www.potatoreview.com POTATO REVIEW MARCH/APRIL 2021 17 NEMATODE CONTROL E FFORTS to manage populations of potato cyst nematodes have led to calls on growers and their advisers to develop integrated programmes that combine all the available control measures. The intention of such programmes is often two-fold. First, to achieve a reduction in the population of infested land to promote profitability while reducing reliance on nematicides, and secondly to protect the PCN- free status of uninfested land through good machinery hygiene and the use of clean seed. Delivering this objective in practice, however, is often far from easy. External factors such as the limited choice of resistant varieties or a reliance on rented land over which the grower can exert little influence, can make protecting land for the long-term difficult. For Spunhill agronomist and group potato specialist Paul Cawood, such considerations are just part of life. Confronting such issues, he says, involves a considered approach and occasionally, the need to deliver advice that is not always what the customer wants to hear. “We have accepted for a long time that granular nematicides are under threat, but the loss of Vydate has increased the pressure on all of us involved in potatoes, be they growers, agronomists or processors, to develop new programmes that manage both free-living nematodes (FLN) as well as PCN,” he said. In a bid to reduce the nematode pressure of crops under his guidance, his first consideration is suitability of the ground to be planted. “Where the PCN population is such that it necessitates the sequenced application of two nematicides, the first response would be to avoid planting potatoes,” Paul said. “High pressure is a matter of interpretation, but where egg counts are routinely 20 or more per gram of soil, this land should be avoided. Egg counts should be regarded as an indicator of risk,. As the number rises there comes a point where the risk outweighs the return. “In higher pressure situations, the most suitable course of action is to give the land a rest for a few years to allow populations to decline naturally. Unfortunately, it is rarely the advice the grower wants to hear, but in many cases, it is the right course of action and the right advice to give,” Paul added. Where land is to be cropped however, factors such as PCN species present, soil type, cropping history, variety choice and the performance of other interventions, such as catch crops and nematicides, have a bearing on the management decisions that follow. Appreciating how the trade-offs involved influence populations will be central to improving long-term control, Paul told Potato Review . To support efforts to keep PCN populations in check, Paul has developed a management protocol to aid decision-making: 1. Don’t be sentimental about potatoes. Be prepared to take rational decisions based on the situation before you. 2. Wherever possible, employ a rotation of not less than six years between potato crops. 3. Soil sample soils and make decision based on the assessed risk. ➜ PCN control is a hot topic at the moment, with the withdrawal of vydate, debates over granular and liquid control methods and integrated programmes. Stephanie Cornwall reports on how the Nematicide Stewardship Programme, manufacturers, growers and agronomists are responding. Changing control strategies