The threat of insecticide resistance is one that all tillage farmers should be taking very seriously, according to scientific experts in this field.
Rothamsted Research’s Dr. Steve Foster told Agriland: “The banning of neonicotinoid seed treatments some years ago meant that farmers were left with only one group of chemistries, the pyrethroids, to control aphids and other insects damaging their crops.
“And to use the tool box analogy, this is a very narrow base to be operating from.
“If resistance to pyrethroids was to become widespread, then farmers would be left with no insecticide options, from a crop management perspective.
“Insects will naturally evolve over time to develop a gene-based resistance to chemicals that they interact within the environment,” he added.
The scientists explained that this is why it is so important for farmers to use the pyrethroids that are available now properly.
Insecticide resistance in tillage
Most Irish grain farmers will be aware of the threat posed by aphids, where Barley Yellow Dwarf Virus (BYDV) is concerned.
But according to Foster, aphids and other insects act as vectors for a number of virus-related diseases that will impact on a range of crops. In all cases, the end result can be severe yield reductions.
“It is therefore important that farmers use the insecticides that are available now at the full and recommended spray rates,” Dr. Foster said.
“Going in with reduced rates simply gives the insects a greater chance to develop resistance.”
Research is currently ongoing in the UK and Ireland, centred on identifying insects with genes that are resistant to pyrethroid chemistries.
“Suction traps are useful in allowing the identification of specific aphid and other insect populations that are prevalent in a specific area at a particular time,” Foster continued.
“However, the collection containers within the traps contain alcohol and other organic solvents, which act to kill the samples taken, so screening bioassays that need live insects cannot be done.
“The identification of genomic resistance to an insecticide can only be achieved using live insects. This is why it is so important for farmers to play a role in collecting live aphids that are actually populating their crops.”
The Rothamsted scientist went on to point out that the threat of pyrethroid resistance is becoming a very significant issue to the arable farming sector is a very real one.
“Knock down resistance to these specific chemistries has already been identified in a wide range of insects,” he stated.
New chemistries
So is the development of new insecticide chemistries an option for the future?
“In theory, yes,” Foster confirmed.
“However, the cost of getting new insecticides over the line, purely in terms of the challenge posed by the current compliance measures, is prohibitive.
“In the meantime farmers can take fundamental management decisions, which will minimise the risk of losing pyrethroid chemistries.
“In the first instance, insecticides should only be applied to crops on a need-to-use basis.
“The inclusion of green bridges within fields at time of planting will act to prevent the migration of aphids on to growing crops and encourage beneficial insects into the crop,” he added.
Plant breeders will also play an important role in developing new crop varieties with in-built resistance to crop diseases, according to Rothamsted.
“However, if we were to lose the use of pyrethroid chemistries in the near future, either through greater resistance evolving or legislation, the consequences for the arable farming sector would be pretty devastating,” Foster concluded.
