Spud Special: Aphids and alternaria

If ever there was any doubt that the east/west divide still existed, then I am sure regarding climatic conditions, it does. In early June I emptied over two inches of rainfall from my rain gauge, with less than half an inch falling in parts of the Vale of York and further west into Cheshire and Lancashire.

Overnight, temperatures have also been hugely variable with parts of the Yorkshire Wolds down to 3C about ten days ago. This is obviously having an effect on canopy development and a number of crops that I look at will not have reached full canopy cover by the longest day. This year, more than any other, yield and quality really will be influenced by the weather we get between now and harvest.

I am continuing to monitor seed crops closely for aphids. As yet the PCL-funded water trap, for which I am responsible, has produced very little, although I am aware that Peach Potato aphids have been found in other traps. I still recommend a seven day spray programme based around Lambda-cyhalothrin products, however I am fully prepared to add something more robust once colonisers are found.

I have yet to find significant aphid numbers in ware crops and as a rule of thumb I would only aim to treat once there was a rapid increase in their numbers.

I believe that it is generally accepted throughout the industry that Pirimicarb alone is no longer effective and therefore I suggest using any of the following; Thiamethoxam (Actara), Thiacloprid (Biscaya), Acetamiprid (Insyst), Pymetrozine (Plenum) or Flonicamid (Teppeki).

It goes without saying that all products should be applied according to label instructions and in accordance with specific crop protocols.

My other concern at present is Alternaria (early blight) which is just starting to show in one or two crops of Markies, other susceptible varieties include Saturna, Hermes, Maris Piper and Estima.

Based on my experience over the last couple of years, prevention is far better than cure, so I am proactive in my approach to controlling it by using products that offer protection. Late blight products containing Mancozeb seem to be reasonably effective although it is generally recognized that 1500g of active is required to keep control.

Consento (Fenamidone + Propamocarb hydrochloride) is another product that seems to give good results. The SOLA for Olympus (Amistar + Chlorothalonil) is very useful and mixed with Revus (Mandipropamid) during the rapid growth stage offers good all round protection of both early and late blight.

At the North of England Potato Event on 20th July 2010 there will be an opportunity for growers to discuss Alternaria in greater depth as there is a replicated trial, in a crop of Markies, looking at its control. 

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