Nematode species mix up costs grower £3500
Nematode species mix up costs grower £3500
POTATO growers need to check that the nematode testing labs they use know the difference between potato cyst nematodes and other nematode species.
The inability of two commercial labs to do so cost one Lincs grower £3500 in wasted nematicide.
Survey work by Harper Adams University College shows 20% of PCN samples sent to commercial labs contain some non-potato nematodes and 9% contain non-potato nematodes only.
Misidentification can lead to wasted nematicide use, warned HAUC nematologist Pat Haydock. "It is imperative that labs know the difference between potato cyst nematodes and others, such as cereal and sugar beet nematodes."
One Lincs grower was told by two labs that he had PCN, but subsequently discovered he had spent £3500 on nematicide application needlessly, the nematodes detected being cereal not potato cyst nematodes. The grower subsequently recouped costs through an out-of-court settlement.
But such errors should not be made, Dr Haydock insisted.
A new test on offer from SAC, NIAB, CSL and HAUC offers sensitive identification of nematode species, even at low populations, he continued. "Knowing which species is present and whether you have Globodera pallida or rostochiensis is important for management strategies, yet it is something growers do not get done often enough."
Evidence is now emerging that population decline could be up to four times faster in G rostochiensis than G pallida, for example. That could have a big impact on rotation planning, G pallidas 10% annual decline requiring over 10 years to drop from a 100-egg/g population to something more acceptable for commercial production, compared with five years for a similar population of G rostochiensis declining at 40% a year. *
Protect land
PCN-free potato land is at a premium, so work hard to keep it that way by cleaning machines before entering fields and soil sampling to check there has been no pest movement, advised Dr Haydock. "Even grassland should be tested. Machines can put the pest into gateways and if you are not testing you will not know the pest is there, so will be unable to catch it at a low level, which is the best time for control."
Rocket science aids PCN control
Novel work at Harper Adams University College could help growers combat PCN more successfully, by harnessing satellite images of crop development. Work over recent years has already shown the type of light reflected from a potato crop can indicate nematode attack. Now studies using aerial imaging from aircraft are being evaluated. "We are finding there is a link between the reflectance signature and nematode attack, although it is still quite a way from becoming practical," explained Dr Haydock. If successful such techniques could be used to interpret data collected by imaging satellites to help growers pinpoint hotspots for trap cropping and for targeting soil sampling to aid patch treatment with nematicides.
Sacrificial crop
Setting a sacrificial potato crop to stimulate PCN egg hatch, then removing it and the nematodes with it before egg laying, could help combat PCN. Debated since 1962 the technique now looks more promising using partially resistant varieties such as Karaka from New Zealand. Those stimulate egg hatch but do not succumb to pest attack thanks to their PCN tolerance. They also help suppress egg laying if the timing is wrong, thanks to their partial resistance, said Dr Haydock. If crop removal is well timed, so egg laying does not worsen the problem, populations can be cut by 50%. Trials suggest lifting after 400-500 day degrees is the optimum, which is about six weeks after spring planting. Planting a late second crop could be an attractive alternative, allowing the crop to be sold as a late new potato, he added.