Grain and bird cherry oat aphids are major vectors of Barley Yellow Dwarf Virus (BYDV), a disease that can cause yield losses of up to 80% in cereal crops. That’s according to Louise McNamara and Stephen Byrne of Teagasc who have provided updates on the latest aphid monitoring work taking place in Ireland.
They gave a joint presentation to the recent virtual National Tillage Conference 2022, where they also said that they would be keen to work with farmers on more research.
McNamara said: “Disease control can be complicated due to levels of insecticide resistance. Where grain aphids are concerned, we now have partial resistance to pyrethroids.
“Our current research work is aimed at quantifying BYDV incidence and insecticide resistances, or kdr [knockdown resistance] mutations, in migrating aphids. And we want to know how this information helps farmers in terms of their decision making.”
Aphid monitoring
The current Teagasc aphid monitoring network comprises three suction towers, located in Carlow, Cork and Dublin.
Each is 12.2m in height. In essence, flying insects are caught at the top and then dragged down to collection units at the bottom.
The information gathered courtesy of each tower is representative of a zone that stretches out a distance of 80km in all directions from that point.
Insect samples are collected on a daily basis throughout the year. The trapped insects are then identified and counted. Aphids carrying kdr mutations are specifically identified, as are those carrying a virus.
“The suction tower data is confirming that aphid migrations commence around the middle of March and will continue through until November, McNamara continued.
“Where aphid flight is concerned, it kicks off when temperatures are in the range 11° to 15°C. But they can also fly at sub optimal temperatures.”
Teagasc is currently testing grain aphids for both BYDV and evidence of kdr.
According to McNamara, the vast majority of aphids tested at Oak Park, Co. Carlow have come up negative for both kdr and BYDV.
“But we don’t know yet how these numbers affect matters in the field. However, we have trials ongoing to determine these matters,” she explained.
Weather impact
Teagasc now knows that weather factors, in addition to temperature, impact on grain migrations.
“When rain levels are low and temperature is higher, we get the largest number of grain aphids,” McNamara confirmed.
“Conversely, where rain levels are high and temperatures are low, we do not catch significant numbers of aphids.”
McNamara went on to confirm a six-fold increase in aphids captured at Oak Park in 2021, relative the year previous. In addition there was a 50% reduction in the number of aphids carrying BYDV during the same period.
“The next step is to connect aphid monitoring results with in-field disease pressure,” she said.
Stephen Byrne confirmed the growth in the scope of Teagasc’s ability to monitor aphid numbers.
“This started off with a single suction tower to Oak Park in 2020. Both grain and bird cherry aphids were identified and the presence of kdr assessed using a PCR test.
“A second suction tower, located in Cork, was added to the system in 2021. Again, aphids were collected on a daily basis with PCR tests used to assess the presence of kdr and BYDV.
“As we enter 2022, another fixed suction tower plus six mobile units have been added to the system,” Byrne said.
Future research
According to Byrne, Teagasc is now well placed to assess the activity of aphids in a very accurate manner.
“We are now developing a high throughput and inexpensive diagnostics platform, which will be used to support routine monitoring,” he explained.
From a single aphid assay, Teagasc now has the ability to generate DNA profiles to monitor aphid diversity; identify if aphids are carrying kdr resistance; identify those aphids carrying BYDV; while also identifying the specific strain of the disease.
Louise McNamara confirmed the overall goal of this research as being that of introducing effective Integrated Pest Management (IPM) programmes for BYDV in Ireland.
“To do this we want to compare the local and long distance migration of aphids. We then want to pair the monitoring network with actual IPM trials in order to see how this data can inform farmers decisions,” she said,
“We want to validate the most important decision support systems for Ireland, in order to deliver the highest possible of BYDV control for growers, starting with spring barley.
“We also want to introduce tolerant varieties into our IPM programme.
“Delivering on both local and long distance aphid monitoring will require the in-field testing at crop height. And to this end, Teagasc would be very keen to work with farmers who would agree to host the yellow traps required for this work,” she said.