How to steal a march on an empire of biting red ants

ANOTHER LIFE:'IT'S LIKE the Borneo jungle in there!" A friend from Leinster, emerging from the polytunnel, could, at a pinch, have been admiring its luxuriant tangle of tomatoes, climbing beans, giant courgette plants and the rest. What had really startled her was to find an empire of the ants, roaming over the raised beds and teeming on the moist wood- chipping paths, writes MICHAEL VINEY

It's a few years since the red ant Myrmica ruginodis, delighting in the warmth of the tunnel, began to build nests in the rotting logs that edge the beds. They have stung me far too often, raising large, painful weals. I learned to move around them, avoiding piercing their nests with the hand fork or knocking into their logs, and going bare-armed, the swifter to spot them climbing to my jugular.

Respectful as I am of superorganisms with 100 million years of evolution, there are limits to my sacrificial role in Myrmican dramas. Now, as I write, a great stillness has descended on their domain – one tested with brave kicks where once I crept with care.

The solution has been the recruitment of some 50 million nematodes (or so the packet promised). Invisible within a creamy flour and watered into all the nests I could find, they have burrowed into the ants and killed them by releasing toxic bacteria. The ants’ innards become a food supply for the next generation of nematodes, which emerge from the empty carapaces to go hunting for more hosts to invade. They die away when they don’t find them, always leaving a percentage of their prey behind.

Nematodes are the planet’s great legion of parasitic roundworms, exploiting everything from plants to people. There are 10 million or more per square metre in the top few centimetres of soil and billions more in the bottom sediments of oceans, lakes and rivers.

Many of those in the soil, microscopic and transparent, are the “eelworms” that attack roots and stems, damaging farm crops such as potatoes and carrots. Others seek groups of insects as their hosts, helping incidentally to control their populations.

“Biocontrol”, or pest management with natural enemies rather than toxic chemicals, is the modern goal of plant husbandry. Control of the black vine weevil in Ireland’s strawberry crop, for example, was once achieved with persistent, highly toxic organochlorines, such as DDT, Aldrin and Dieldrin. Today, for more and more growers, “entomopathogenic” nematodes actively seek out the pests and kill them.

For commercial production two particularly effective ranks of nematodes have been isolated by crop scientists across the world: Steinernematids (which, marketed by Nemasys, have killed my ants) and Heterorhabditids.The second is worth trying to say, because Heterorhabditid downesiis now a native Irish species of international fame.

It was isolated in the 1990s by a scientific team from NUI Maynooth, led by Dr Christine Griffin, and named in honour of their professor, Dr Martin Downes, long an explorer of nematodes and their agricultural promise. Their work has put Maynooth’s Institute of Bioengineering and Agroecology at the forefront of world research, led by Dr Griffin. Dr Downes, now retired, is emeritus professor.

Until the 1990s, searches for the most useful nematodes found the Heteros (let’s call them) at only one site in Ireland and in Britain, and none in Scandinavia, suggesting the need for a warmer environment. But Dr Downes and his team found a native species, often in abundance, in the warmth of Ireland’s sand dunes and not least beneath the well-worn paths of North Bull island, in Dublin Bay.

With its long adaptation to Ireland's climate, H downesiis now the leading candidate for natural, self-limiting control of the destructive pine (not vine) weevil in Coillte's conifer forestry. The beetle breeds abundantly in the stumps of clear-felled spruce, and their young go forth to devour the tender saplings of newly replanted areas.

Current protection is by soaking the seedling in a chemical poisonous to fish, but in the trials of the Abate research programme, led by Dr Griffin, H downesi has proved tops in killing pine weevils, along with wider prey.

The limited target species of most nematodes has been a handicap of products trying to compete economically with wide-spectrum toxic chemicals. But one of Maynooth’s graduates, Dr Abdul Hamid Al-Amidi, has developed an application in which three species of nematode, recruited from the main predator groups, compete with each other to infect a wide range of pest insects. Some ambush their prey on top of the soil; others cruise deeply to seek them out.

To judge from Dr Al-Amidi’s patent application there is almost endless potential for tailoring combinations of nematodes to kill particular ranges of pests. Meanwhile, the many targets claimed for SuperNemos, his Ireland-based product, range from vine weevils and carrot fly to leatherjackets and cabbage caterpillars, while leaving beneficial insects alone. This seems plenty to be going on with.

Eye on Nature

I saw an almost-white swallow being mobbed by other swallows as it tried to feed on a hatch of black flies. The other swallows took it in turn to mob it until it moved off, followed by several escorts. Is this what that swallow can expect full time and, if so, will it survive?

Michael McCarthy, Fenagh, Co Carlow

Albino swallows rarely occur, and they are usually mobbed by the others. As their eyesight is weak and their wing and tail feathers brittle, they are unlikely to survive.

While walking on a beach in Co Donegal we came across a buoy with astonishing attachments. When we touched the shells, creatures emerged like worms with a mussel-like shell at the end.

Liz O’Donnell,

Blackrock, Co Dublin

They were goose-necked barnacles.

A sparrowhawk perched on top of our trampoline net for a few minutes last week.

Sadie (7) and Iris (5) Loughman,

Killester, Dublin

A hawk landed in our garden clutching a blackbird that it then plucked. Within minutes the carcass was feather free, and he flew to a wall to eat it. Then he flew away with the remains in his claws.

Alison Coffey, Drumcondra, Dublin

• Michael Viney welcomes observations at Thallabawn, Carrowniskey PO, Westport, Co Mayo. viney@anu.ie. Please include a postal address