We must take IPM on board across all cropping where we can – Arable Farming – Darryl Shailes
The weather has been very variable in the Waveney Valley over the last few weeks. One minute everything's freezing cold, then it is 14degC ...
The crocuses look great one minute, the next they have dropped their heads as it is -5degC.
What’s not changed is that it is still pretty dry despite the recent rains. In the winter of 2020, we had seven fairly big floods in the garden with the highest levels recorded in the valley for over 50 years on Christmas Day.
The valley generally floods when heavy rain coincides with a spring tide, and despite the spring tides that have caused the issues at Hemsby on the Norfolk coast, the River Waveney is still only just full. We had a pond cleared in October and the level in that is only just a bit higher now than back then.
The first full moon that occurs on or after the spring equinox determines Easter Sunday, and will also mark the next potential for a flood but if we don’t get heavy rain, it won’t happen.
When we consider that potatoes and sugar beet need to process a large volume of water through the growing season, not having good groundwater reserves or river flows to fill reservoirs mean we will be relying on spring and summer rains. Winter groundwater fill has been limited so abstraction licenses may come under pressure – we must make sure we use water wisely.
We can mitigate water availability a little by ensuring there is no compromise on root growth in either potatoes or sugar beet. Ensuring there is no compaction at planting and drilling can have a huge effect, especially if water is limiting.
Even though we have had quite a lot of frost over the winter the emergency EAMU for Cruiser SB (thiamethoxam) fell within the Rothamsted model and we have got the seed treatment for the coming season.
The model utilises the temperature in January and February so the frosts that came in December are not included as they don’t affect aphid migration very much, as was explained at the recent BBRO updates.
The first migration of myzus persicae (peach potato aphid), the aphid vector of virus yellows, is predicted for April 20. The more recent frosts in March may delay migration but we should be vigilant from mid-April onwards and read the updates from BBRO, especially where Cruiser SB is not used.
Aphid migration will also have an effect on virus transmission in potatoes, especially seed crops.
The viruses spread by aphids in beet are of a persistent type and even though the time for infection to take place is different between the three different viruses that make up virus yellows, the spread can be controlled by aphicides either as a seed dressing or foliar sprays. However, the virus with the major economic impact on potatoes, virus Y, is non-persistent.
A non-persistent virus is carried in the mouth parts of the aphid vector, mainly myzus persicae and cavariella aegopodii (carrot willow aphid) and is transmitted as aphids probe the potato leaves to feed.
This makes controlling virus Y transmission with aphicides very challenging, as the aphicide needs to be ingested by the aphids before it takes effect, by which time the aphids have already transmitted the virus.
The consequence is that although myzus persicae is the main vector in both sugar beet and potatoes and we can control the aphid, there will be very little effect on PVY transmission.
Recent work has shown that mineral oils and barrier crops to clean the aphids’ mouthparts before they can infect the crop have shown good effect on control of PVY.
This integrated pest management (IPM) approach in virus transmission has had to be adopted due to the method of transmission of PVY, and shows how we can adopt control strategies without over-reliance on pesticides.
IPM is definitely the way forward in crop protection and with the Government now recognising this in the new Environmental Land Management Scheme and Sustainable Farming Incentive strategies, we must take it on board across all cropping areas where we can.
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