Biofumigant crops could play an important role in controlling free-living nematodes (FLN), results from trials carried out by RAGT and Agrovista suggest.
The findings are potentially good news for organic potato growers as well as conventional growers who currently rely on nematicides, as this chemistry is under considerable scrutiny from EU legislators.
The 1ha trial site at Elgin on the Moray Firth is under organic production on a farm that has suffered high FLN counts, says Agrovista agronomist Andy Steven.
The farm operates a fairly intensive cropping regime cereals,potatoes, the occasional carrots crop and grass, but spraing, the disease caused by the tobacco rattle virus transmitted by FLN, is a fairly common problem here and on other lighter soils in Morayshire. Around half the samples show high FLN counts.
The site was split into five sections one untreated and four area seach planted with a different biofumigant crop oilseed radish, white mustard,Hardy Mix (a blend of oilseed radish, Ethiopian mustard and rocket) andJapanese oats. These were drilled in late July to ensure there was plenty of biomass to be chopped and incorporated in mid-November.
Nematode numbers on the untreated area went up pretty significantly between June and November, Mr Steven says. This would be normally expected as soils become wetter in the autumn, encouraging nematodes to move upwards through the soil profile.
All four biofumigants reduced numbers across all three FLN species(pratylenchus, trichodorus and longidorous), apart from the Japanese oats which struggled to contain longidorous.
We cant say statistically that everything worked better the HardyMix and the Japanese oats worked reasonably well. But in this trial at least,the oilseed radish did the best job and white mustard came a good second, hesays.
If these results were repeated in the field, Mr Steven predicts significantly less feeding damage as well as potential disease reduction.
Growers in this area have achieved 4t/acre yield increase where feeding damage has been reduced. Potatoes will be planted across the trial site so wewill be able to measure this effect.
The trials also show it is possible to establish biofumigant crops in the far north of the UK, albeit in a relatively mild climate, says Mr Steven.
A big challenge in this area is getting a cover crop established on time to provide enough green material for it to work.
In practice it might be best to plant biofumigant crops after winter barley or EFA fallow, he adds.
RAGT Seeds head of forage, Helen Wilson says the results look promising and give every confidence to push ahead with further work.
Although we cant assess these un-replicated strip trials statistically,we can say we’ve seen a decrease in population size with all four treatments,giving a definite indication of a trend that warrants further investigation,she adds.
FLN is becoming a more important pest in the UK. Crop damage thought to be caused by poor fertility, compaction and/or poor drainage can often be anFLN problem.
Growers are becoming more aware of it and it appears to be more widely spread than many people think.
While biofumigants may not replace nematicides as long as they are available, the results show they could keep potato growers in business if such chemistry does disappear, she adds.