New spraing label approval for Nemathorin

A new approval for Nemathorin now gives potato growers the chance to reduce the costly tuber damaging effects of spraing caused by TRV. The welcome new label recommendation for the reduction of spraing enables growers to opt for an overall incorporation, or a new in-furrow application - which is also now approved for wireworm.

Characteristic brown necrotic spraing rings within the tuber flesh are caused by Tobacco Rattle Virus (TRV) infection, which is spread by the free living Trichodorid nematodes. Spraing damage will seriously reduce the value of potato crops, with very low tolerances for many fresh and processed markets. Yields, tuber shape and quality of crops grown from spraing infected seed can also be severely affected.

Nemathorin has been shown to effectively reduce the incidence of spraing - by killing or paralysing the virus transmitting nematodes and consequently preventing infection by preventing them from feeding on tubers. It will also limit the effects of nematode feeding damage, which will reduce yields.

Syngenta Potato Technical Manager, Jon Ogborn, highlights the persistent activity of Nemathorin gives good protection through the crucial tuber formation phase, when crops are most vulnerable to TRV transmission by infected nematodes.

Mr Ogborn adds the relatively low water solubility of Nemathorin further increases its effectiveness, particularly in a wet spring and irrigated crops. "Dry soils reduce the risk of spraing, since the nematodes need soil moisture to move and attack newly forming tubers. However growers on light loam and sandy soils, where the incidence of spraing is highest, will almost certainly be irrigating at this stage to encourage tuber numbers."


Results of trials in high risk situations - with large numbers of nematodes infected with TRV - show Nemathorin reduced the number of tubers affected by spraing by an average of 60%. "Higher levels of reduction should be seen where risk levels are lower, helping growers achieve a market specification," reports Mr Ogborn. "Spraing can cause the complete rejection of pre-pack and processing crops, with losses running to thousands of pounds per hectare."

The trials show similar results from either overall incorporation at 30kg/ha, or the new in-furrow application at 150 g/100m per row.

Increasing nematode numbers

The numbers of Trichodorid free living nematodes in the soil are on the resurgence, warns Dr Andy Evans of SAC. Soil testing by SAC has revealed an average 300% increase in nematode numbers in recent years, with 30% of samples submitted by growers testing positive for TRV.

"Even without the virus, the high levels of nematodes present could be sufficient to cause physical feeding damage to potato crops and result in problems at emergence," he reports. And the problem is not isolated to potatoes, with feeding damage witnessed in other crops, including cereals.

"Free living nematodes feed on many other crops and weeds in the rotation, and a large number of weeds can also act as host for the TRV virus. The reservoir of infection and increasing nematode numbers will perpetuate the problem through the rotation," he advises. "Once growers have encountered spraing in a particular field, it will prove difficult to eradicate."

Dr Evans also highlights the fact that the virus can spread between fields in weed seeds, and through infected potato seed planted in hitherto clean soils. The problem is made more difficult to manage since some varieties could be carrying TRV, without exhibiting any visible signs of spraing in the seed. If nematodes feed on infected plants, they will pick up the virus and subsequently pass it on to weeds which can act as a reservoir for the virus.

"The only real option is to keep the nematodes at bay and protect the crop as it grows, to maintain yield and keep the virus out. Dr Evans reports that SAC trials encouragingly show Nemathorin can provide the necessary persistence to protect the crop from spraing symptoms.


The in-furrow Nemathorin application rate for spraing is the same as that approved for wireworm, whilst the 30 kg/ha overall application will also control PCN populations.