The declining
options for seed treatments on potatoes increases the risk
of rhizoctonia - and reinforces the importance of in-furrow fungicides. Geoff Hailstone outlines the key issues and how in-furrow fungicides can mitigate these.
The declining options for seed treatments on potatoes increases the risk of rhizoctonia - and reinforces the importance of in-furrow fungicides.
Geoff Hailstone, Potato Crop Specialist at UPL UK & IE
“Rhizoctonia solani is a fungus that causes stem and stolon canker, black scurf, damping off, skin netting, tuber growth distortions and has been associated with higher levels of internal rust spot. It can be soil or seed borne, with potential to survive in soil, on volunteers, weeds such as nightshade and crop debris. It can also infect many other crops in the rotation
Mitigating the risk of this disease is important for protecting potato crop establishment, skin quality and yield. Seed treatments have historically played a key role in controlling this disease, however with the loss of both pencycuron and penflufen last summer, the industry is left with flutolanil as the only planter seed treatment option. This means the value of in-furrow fungicides is greater than ever as planting commences for the 2021 crop.
Applied in the furrow at 3l/ha at planting, ZOXIS and AFFIX from UPL provide 750g of azoxystrobin per hectare to help reduce the impact of rhizoctonia, and the products are effective against all anastomosis groups (AGs) and consistently reduce levels of black dot and silver scurf.
Clean, certified seed should be the first line of defence. The risk of Rhizoctonia can also be reduced by managing PCN. Root leachates associated with the nematodes will attract the fungal hyphae and increase infection.
IPM (Integrated Pest Management) strategies should also be used, including cultural practices such as extended rotations and taking measures which promote early emergence e.g., planting in warm, well drained seed beds and avoiding deep planting.
At the end of the season, not leaving the crop in the ground longer than necessary at harvest will help.
The loss of key actives used to tackle economically important diseases in potatoes is a continuous threat, and the potential loss of mancozeb in Great Britain is another example of how the toolbox is depleting.
With Rhizoctonia solani, the ability to reduce stem and stolon canker and black scurf is more challenging, but still possible, and in-furrow actives will have an important part to play in 2021.”
