Spud Special: Pests and disease appearing

Much need rainfall has fallen over many parts of the areas that I cover across the north of England, however amounts have varied considerably. Canopy development has been good, although I am now coming across damage caused by rhizoctonia, free living nematodes and PCN in patches within fields.

I firmly believe that if crops can achieve complete ground cover by mid-June they are in a good place to make the use of the radiation produced during the long daylight hours of midsummer and convert it to yield.

Having said that there are a number of crops, particularly seed crops which have yet to reach 50% ground cover, however they seem to be producing good tuber numbers.

A number of my clients this year have started using azoxystrobin. Applied in furrow it seems to be having an effect on soil-borne rhizoctonia, producing a much healthier root system. A healthier root system leads to increased nutrient and moisture uptake and as a consequence less stress.

In Australia last year I saw a crop treated with azoxystrobin with 6 rows left untreated, all other applications where the same. The six untreated rows were defoliated with alternaria, the rest of the field still had over 60% ground cover.

There is a lot of research work going on with regard to free living nematodes, treatments and potential varietal resistance, however the results are likely to be a year or two away. In the meantime, if you grow on light land it is always worth testing soils for free livers. Different species can cause different problems, some feed on the roots and some can transmit TRV spraing.

PCN is also a big issue and with a lot of the populations I am coming across now mainly Pallida. So with the lack of truly resistant varieties, the later egg hatch and the variability of nematicide application it is becoming increasingly difficult to maintain control.

Aphid numbers so far have been low, although predictions suggest that potato colonisers will start to fly early to mid July.

I know that a number of clients have said that they are starting to see aphids in cereal crops now, so seed growers be vigilant. At least with the addition of Esfenvalerate to the pyrethroid army there are more options for control available.

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