Late season potato management in a wet year

What a contrast in seasons -last year it was a struggle to keep crops alive, this year it’s raining every other day and in the main crops are still growing, says Hutchinsons root crop technical manager, Darryl Shailes.

“Last season dry matter was very high, in excess of 24%, and prone to bruising.  This year low dry matter and size is stopping chipping potatoes from being lifted for processing. However with prices very strong, above £500/tonne, crops will need to be cleared quickly when they get going, “ he says.

With regards to irrigation, Mr Shailes recommends holding off and not giving crops too much water in changeable weather as burst and swollen lenticels can get infected with late powdery scab affecting the skin finish on some packing varieties especially Marfona.

He suggests taking a chance on them getting a little dry as opposed to too wet as the cooler weather has meant that the daily ET figures will be relatively low, and crops are not using a huge amount of water in comparison with a more normal season .

“With blight being reported in some crops it very important to ensure that strong tuber blight products are used in the latter half of the season.

“Shirlan is still not recommended by Certis Belchim in the last 3 sprays where the crop is to be stored as there may be opportunity where the crop is to be lifted green top or marketed as soon as skins are set, and the zero-harvest interval is required.

“Where Shirlan is being used it should be supported by another active, not just cymoxanil.

Ranman Top and Infinito both have good tuber blight activity and should be used on stored crops.”

“In manufacturer trials both Ranman Top and Infinito have demonstrated similar activity to Fluazinam on zoospore motility and are supported for tuber blight activity in the last 3 sprays.”

“Blight control should be continued until all the haulm is dead.”

Haulm Desiccation:

Where flailing, Mr Shailes recommends the haulm should be directed into the furrow and stems should be 15-20 cm tall after flailing.

“Larger haulmed crops may benefit from an opener of Gozai/Albis/Spotlight Plus to aid speed of skin set and flailing.”

Gozai/Albis and Spotlight Plus should all be applied in a minimum of 200 L/ha.

Gozai and Albis will require the addition of Phase 2 @1.5 L/ha in 200 L water.

He points out in larger haulmed crops work from manufacturers has shown that higher water volumes i.e., 300 L/ ha gives better activity.

“Where water volumes are higher, the rate of Phase 2 should be increased accordingly.”

Speed of forward travel can also make a difference so not above 10 kph for better coverage.

“Bright sunshine and high temperatures will benefit the PPO’s so best applied when warm and sunny and not on a dull overcast day if possible.”

“Trials have shown that in non-flailed crops the available actives are best applied in sequence with a minimum 7 day interval and not applied together as the benefit of the tank mix is small if any at all.”

Skin set

In this season with late plantings and wet soils  don’t rush to get crops into store before the skins are well set, advises Mr Shailes.

“Think about planning ahead with crop desiccation for skin set which may take 4-5 weeks to ensure the crops aren’t too late. A reduced yield and slightly undersized crop will be a better prospect than a big bold crop going into store with the skin not set and sliding out the door.”