The Dean of Science at NUI Maynooth leads an EU-funded research project into natural controls against a serious agricultural pest, writes Dick Ahlstrom.
You might not sit up nights worrying about the diamond backed moth but farmers around the world in tropical and sub-tropical regions certainly do. An international research team led by an Irish scientist hopes to help farmers rest easy by using natural predators to kill off the troublesome moth. The "Diabolo Project" got underway last September, headed by NUI Maynooth's dean of science, Dr Ann Burnell. It involves researchers in China, Indonesia, Ireland and Germany.
The moth mainly affects crucifers; members of the cabbage family including cabbage, Brussels sprouts and less obvious plants such as oil seed rape, Dr Burnell says. Ironically, the pest which now infests farms right around the world only rose to prominence since the 1940s, once insecticide usage became common.
"It only became a problem when pesticides started to be used against other insects," she explains. It was always there but wasn't a problem. "The diamond backed moth was being controlled naturally by existing predator-prey relationships." Pesticides broke this balance of nature, eliminating the predators and so allowing the moth to thrive.
"It is a voracious eater," she says, attacking the plants in all of the larval stages. The current practice is to dose it repeatedly with sprays. "If you didn't spray you would have nothing." Yet this also suppresses any natural fight-back by the parasitic worms and wasps that used to hold moth numbers in check. The moths are also developing resistance to many of the insecticides.
Dr Burnell's team plans to eliminate the sprays and get the natural defences working again. "Our proposal is to produce an integrated biological control strategy without using any insecticides," she explains.
It involves a range of weapons including a bacteria that produces a natural insecticide, Bacillus thuringiensis; soil nematodes, tiny millimetre-long worms that parasitise moth larvae; and a key enemy of the moth larvae, tiny parasitic wasps or parasitoids that lay their own eggs in the larvae and kill them off.
Field trials begin in Indonesia in May and a large farm in China will also be involved, she says. Initially, only the nematodes will be used so their contribution can be assessed and other weapons will be brought in as the trial progresses.
Maynooth has a world reputation in nematode research. Dr Burnell published some of her nematode work this month in the leading journal, Nature. A number of academics and labs joined forces to create a centre of excellence in nematode research at Maynooth that attracted funding from the Government's Programme for Research in Third Level Institutions, support which will be used to build a new biosciences centre. A member of this team, Prof Martin Downes, isolated and identified a new nematode that now carries his name, Heterohabditis Downesi.
A Heterohabditis species is one of two nematodes with Steiner nena now being put through their paces at Maynooth as a natural control against the diamond backed moth. Steiner is found around the world but was only discovered in 1976.
Dr Burnell is trying to overcome a particular problem with the use of live nematodes as a biological control: shelf-life. The worms do not live long and must find a host where they can lay their eggs quickly. This means they cannot be stored for very long before they die off.
DR BURNELL'S recent Nature report was about anhydrobiosis, the ability of some organisms such as yeast to survive for long periods in dry conditions before regenerating once moisture becomes available. "I was always interested in anhydrobiosis because of the shelf-life problem," she explains.
She identified an anhydrobiosis gene in a nematode, Aphelenchus avenae, and showed that the protein it produced was very similar to one seen in plants that can survive without water. She is studying the biochemistry behind this gene in the hope that it might be applied in other contexts. Lengthening the shelf-life of useful biological control nematodes such as Heterohabditis is an example.
Burnell is looking for any genes in Heterohabditis that increase their activity when the worm faces drought conditions. She then hopes to use the activity promoters for these genes coupled to the anhydrobiosis gene. This should cause the essential protein needed for drought survival to be produced at levels that could help other species of nematode to survive desiccation.