Pushing the boundaries is critical to success, according to McCain Foods regional CEO Nick Vermont.

Speaking at the East Midlands Potato Day held at QV Foods, Holbeach Hurn, Lincolnshire, (July 5) he spoke of McCain Foods’ objective of innovation to make it easy for everyone to enjoy good food.

Foods need to give consumers the ‘feel-good’ factor and be quick and easy to prepare, he said, using as an example McCain Foods’ new ready-baked jacket potatoes.

“Prepared foods are the way forward,” he affirmed.

Asda produce category director Rick Bourne looked at the changing consumer habits, noting the move to smaller shops that appear to put less financial pressure on spending. He emphasised the need to deliver what the customer wants at the same time as inspiring them to eat more potatoes.

Dr Reuben Morris, technical support manager for high value crops at Frontier Agriculture, advised growers to take into account varietal susceptibility to Alternaria in his workshop on prevention strategies for this type of blight.

“The disease is widespread in the USA and on the continent, and we seem to be catching up,” said Dr Morris. “Markies, a widely grown variety that is still increasing in popularity, seems particularly susceptible to Alternaria, so effective control is important. Other popular varieties like Saturna, Maris Piper, Hermes and Estima are also susceptible and need managing carefully.”

Hot weather encourages the disease, initiating spore release and predisposing plants to infection during the next humid period, such as after irrigation. Left unchecked, dark brown or black target spots that appear on leaves can coalesce into lesions and spread, defoliating the canopy. Yield loss can rise to 30 per cent in severe cases.

Fungicides have to be applied before the disease takes hold, as they are all protectant only, he warned. “You see the effects after a long, hot spell, but the disease takes hold a long time before that. The aim is to ensure the disease is controlled along with the normal Phytophthora blight protection programme during canopy development.”

Dr Morris also advised growers to examine activity of the fungicide they are using, so they can prepare a balanced programme, particularly where susceptible varieties are grown.

“There is an added cost as you have to use additional or different fungicides from those that protect against Phytophthora blight only,” he explained. “Some growers prefer to rely on the relatively cheap mancozeb containing fungicides rather than including the more expensive strobilurin products. This is OK when Phytophthora and Alternaria blight pressures are low, but if blight pressures increase the strategy needs to be changed.”

He warned growers that with susceptible varieties such as Markies, this mancozeb based strategy could be a false economy.

Three plots of Markies at the East Midlands Potato Day illustrated different control programmes for potato blights, stimulating discussion about how growers might best control Alternaria on their own farms.
 

One block had been treated with a Ranman (cyazofamid) / Revus (mandipropamid) Phytophthora blight protection programme only, while the other two received the same programme plus strobilurin (QoI) fungicide pyraclostrobin, or mancozeb for added Alternaria control.

“QoI fungicides are limited to a total of six applications per crop, so these have to be spaced out to ensure control starts in time without leaving the crop exposed later in the season, especially with indeterminate varieties like Markies,” he noted. Trials so far indicate the aim is to start the QoI programme during the rapid canopy growth phase.

The mancozeb-based programme received Ranman initially followed by Revus, both having mancozeb added to the mix. “We saw initial infection at the bottom of the crop, which is likely to have been established before we started the fungicide programmes. We are now examining the cost of each programme and discuss suitable levels of control to help growers devise the most cost-effective programmes for crops on their own farms.”

Dr Morris also warned growers that despite Alternaria often being denominated ‘early blight’ it can also occur at the end of the season as was seen in trials in 2010. “So control needs to be maintained until late in the season.” In his workshop, Eric Anderson from Scottish Agronomy called for growers to undertake a farm-fuel audit to understand where spending is highest and could be cut without sacrificing saleable yield.

“It’s about increasing operational efficiency,” he told growers. “There are areas where you could easily save over ten per cent of annual fuel costs.”

However, he advised growers to avoid false economies, such as planting when the ground is too wet, a practice often followed to decrease employee downtime.

“This strategy can compromise yield as ploughing in these conditions can cause compaction. This impacts on the root structure so that nutrient and water uptake is not as efficient as it could be, which may result in irrigation and extra applications of fertiliser. These extra costs are not only the actual costs of water and fertiliser, but also fuel and labour costs to apply them.

Recent studies undertaken by Scottish Agronomy monitoring diesel usage have shown that it takes 80 litres of diesel to pump 250 m3 of water (25mm/ha). Furthermore, bed tilling typically costs £80 to £140/ha, of which 35 per cent comprises diesel.

Other topics covered at the event included defoliation with Stuart Maltby, also from Frontier Agriculture, the latest updates on herbicides with John Keer from Richard Austin Agriculture and biofumigation with Andy Barker from Barworth Agriculture.