Growers finding wireworm in the run up to potato planting will get the best protection from overall granule treatment – that's the advice from Scottish Agronomy's Eric Anderson.
With wireworm damage to potato crops in all arable rotations becoming just as serious as in grassland rotations, risk assessment prior to planting is now an important precaution for all growers.
Wireworm get active above 5oC so with soils warming up now they should be found by bait trapping or digging. Seedbed cultivations can also reveal them on the soil surface immediately prior to planting. Finding just one indicates presence of a population likely to cause economic damage.
Treatment options are Nemathorin applied in-furrow at 150g per 100m row or Mocap incorporated overall at 60kg/ha. Last year Scottish Agronomy compared these two approaches by monitoring the build up of damage during August and September – the critical period when damage to daughter tubers escalates.
When wireworm impact was assessed in late August, based on the proportion of tubers affected by severe wireworm feeding holes (making them unacceptable to packers), the damage scores were; untreated 52%, Nemathorin treated 13% and Mocap treated 2%.
Mr Anderson says the results demonstrate the superior control growers can get from Mocap. "When you start to find wireworm damage in a crop it needs to be burnt off and lifted as soon as possible, particularly with severe infestations. Nematicides reduce pressure but cannot be expected to completely eliminate a serious infestation.
"Mocap is much more effective at restricting the onset and escalation of damage whilst skins are setting, so the chance of keeping the crop within market tolerance is increased. Wireworm move up and down the soil profile during the crop's growth so they are more likely to encounter granules applied overall. Granules applied in-furrow potentially leave daughter tubers exposed."
The recommended method for incorporating Mocap overall is by application immediately in front of a bed tiller he adds. Application via a separator with a star mechanism cannot be relied on for consistent incorporation of granules throughout the soil profile.
