Teagasc has confirmed that min-till crop establishment systems will reduce the impact of Barley Yellow Dwarf Virus (BYDV)-causing aphids, relative to the results achieved from ploughing and a conventional cultivation approach.
Published in 2020, a Teagasc review of the threat posed by BYDV in Irish cereal crops centred on a detailed analysis of trials carried out almost two decades earlier.
Oak Park-based entomologist Dr. Louise McNamara discussed the implications of the review on the most recent edition of the Teagsc ‘Tillage Edge’ podcast.
She explained: “There was not a consistent trend identified within the review carried out.
“However, the results do confirm that there were less aphid-related BYDV and subsequent grain yield reductions in certain years, when a min-till approach to cultivation was taken rather relative to ploughing.
“It is thought that the greater debris that exists courtesy of min-till cultivation, provides aphids with less of an opportunity to land on growing cereal plants,” she added.
“E.g., it has been noted that BYDV infection levels are always higher on those regions of crops directly adjacent to tram lines.
“This is, possibly, because the aphids have more of a contrast between soil and crop to target in these instances, making it that much easier for them to land.”
Insecticide resistant aphids
According to McNamara, insecticide resistance remains an issue within certain aphid populations.
She commented: “Some grain aphids found in Ireland have been found to have partial resistance to pyrethroids. This was confirmed courtesy of trials carried out on aphids collected from two suction towers last year – Oak Park and Ashtown.
“The results indicated that 22% of the aphids assessed at Oak Park had partial knockdown resistance. The equivalent figure for Ashtown was 18% .
“Partial resistance means that the aphids in question have one copy of the resistance gene only. There is no sign as yet of full resistance. But we are continuing to monitor for this,” she added.
Previous work had shown that partial aphid resistance to pyrethroids in Ireland had reached levels approaching 25%. However, McNamara confirmed that these figures were based on in-field testing.
“We have also tested grain aphids this year found in 50 fields around the country. The results of this work should be available for the tillage conference in January,” she continued.
She told the podcast that it always advisable for farmers to walk their crops at this time of the year in order to assess aphid pressure. This can vary with geographical location.
“The same principle holds after an insecticide has been applied. In this instance it is important to know has the treatment actually worked,” she concluded.