Slicing slugs in half not a task for the lily-livered

The gruesomely repellent larvae of gooseberry sawfly can strip a fruit bush bare in a matter of days

The gruesomely repellent larvae of gooseberry sawfly can strip a fruit bush bare in a matter of days

SAWFLY on the currant bushes, aphids on the gooseberry bushes, fat slugs eying up the emerging dahlia shoots and mysteriously uprooted baby beetroot seedlings . . . Hmmm, it seems things are hotting up in the Office of Public Works (OPW) walled kitchen garden in the Phoenix Park.

All of which means that its hardworking gardeners, Meeda Downey and Brian Quinn, must now sally forth to defend the garden’s young crops from a host of hungry pests and predators.

And it’s not a job for the squeamish.


So if you are the lily-livered kind of gardener who involuntarily recoils from the idea of slicing a slug in half with a sharp secateurs (me too), then pray that you never encounter the gruesomely repellent larvae of gooseberry sawfly (a slight misnomer, by the way, as they like to eat the leaves of red and white currant bushes just as much as those of the gooseberry).

But if ever you do find yourself in such a horticultural dilemma, it might concentrate your mind – and perhaps gird your gardening loins – to know that these voracious larvae can strip a fruit bush bare in a matter of days.

Skeletally bare, that is, so that not even a single tattered leaf remain.

Superficially similar to a caterpillar, these pale green and black-spotted larvae can be up to 2-cm long. They are generally found in feeding clusters along the undersides of the bush’s leaves, especially low down and towards the centre of the plant where the adult female has laid her eggs.

The problem is that by the time you’ve noticed them, the damage to plants can be so severe that it can take affected fruit bushes a year or more to fully recover.

“We had a bad infestation of gooseberry sawfly in the garden a few years ago and they stripped some of the plants bare almost before our very eyes.

“We ended up handpicking the larvae off every bush, which took days,” explains Brian.

“We even tinkered with the idea of making our own pesticide using rhubarb leaves.

"But this time, we're using pyrethrum to control them [available as Herba Vetyl from]."

A natural, quickly biodegradable insecticide/pesticide which works by attacking the nervous system and causing paralysis of the targeted insect, pyrethrum is an extract of the daisy-like flowers of Chrysanthemum cinerariaefolium, a plant which first travelled into Europe from Persia via the silk route.

So effective is it as a pest controller that it's been called the organic bio-insecticide for the 21st century.

It has been used as a treatment for everything from head lice to stable flies (it's also a great mosquito repellent).

Even better from the OPW gardeners' point of view is the fact that pyrethrum breaks down naturally in sunlight within a few hours, leaving no worrying residues on harvested crops.

The only caveat is the slight risk it poses to bees if used at a stronger-than -recommended dilution rate, while the only downside to it being such a wonderfully biodegradable pesticide is the fact that once applied, its effectiveness is rather short-lived.

Aside from pyrethrum, parasitic nematodes (look out for Nemasys Grow Your Own, available from is another very effective method of control as regards this damaging pest, which can produce up to three generations in a year and is at its most active from late April until September. But not all garden pests are as ugly and unlovely as the sawfly larvae.

Elsewhere in the walled garden, the newly emerged beetroot seedlings have been performing a strange disappearing act over the past few weeks, to the point where the whole bed may have to be re-sown.

"They came up perfectly," explains Brian. "But then we noticed bare patches appearing." Presuming it was slug damage, the OPW gardeners sprayed the bed with Nemaslug, but the damage continued.

"I was baffled," admits Brian. But then one of the Phoenix Park's long-serving rangers, Jimmy Donoghue, who is also a keen and experienced GYOer in his own right, suggested a very different explanation for the damage.

Earlier that week, he had noticed blackbirds pulling up young beetroot seedlings in his own vegetable patch, as had a fellow gardener. Once Jimmy netted the seed beds in question, the damage stopped as suddenly as it had begun.

"I'm going to give it a go and see if it works for the beetroot seedlings," says Brian hopefully, although he worries that the damage is already so extensive that he may still have to re-sow.

"If that's the case, at least it was only beetroot, which germinates relatively quickly, rather than something like parsnips," he says sanguinely.

Meanwhile, despite the pests, the predators and the occasional nightly incursions of the hungry badger, the walled garden is looking lush and very, very beautiful.

Its vast, double herbaceous borders are already quickly filling up with the giant peach blooms of opium poppies, tender spikes of pink lupins and the delicate whorls of primulas whose flowers are dusted with the silvery "farina" that is so distinctive to the genus.

Even the delphiniums are beginning to flower. This both pleases and worries the OPW gardeners, who worry that it may all be past its peak by early June, and the arrival of the annual extravaganza that is Bloom (

Then again, if either Her Majesty or President Obama happened to pop in for a visit over the next few days, it wouldn't be such a bad thing to have the walled garden's herbaceous border looking so well.

Just as long as they don't stop to inspect the beetroot seedlings or the red currant bushes.

That really wouldn't do at all.


The West Cork College of Sustainable Food Production kicks off with a five-day summer school from Monday, June 13th.

While based at the renowned Glebe Gardens in Baltimore, the course will also include many sessions at the farms and gardens of west Cork growers who make a living from growing food.

Aimed at people who want to produce significant amounts of food either for themselves and their families or as a business, the course’s tutors includes Pete and Jean Perry of Glebe Gardens and cafe; Bantry House head gardener Lorna Finnegan; commercial growers Caroline and Eddie Robinson; organic growers Tim York and Anthony Boyle; Woodkerne Nursery owners Paul McCormick and Jacinta French; permaculturists Kai Schulz-Boeckenhoff and Geraldine Thomas; Madeline McKeever and Mike Sweeney of Brown Envelope Seeds; and smallholders Sandra Schmid and Tim Rowe who will give an introduction to working with horses.

The summer school runs from June 13th to June 17th, and costs €300 including lunch.

Tel 028-38184;; /187021504659366

** The Office of Public Work’s Victorian walled kitchen garden is in the grounds of the Phoenix Park Visitor Centre, beside the Phoenix Park Café and Ashtown Castle. The gardens are open daily from 10am to 4pm

** Fionnuala Fallon is a garden designer and writer

WHAT TO: sow, plant and do now

Sowin a heated propagator in pots or modules for tunnel cropping, or planting outside under cloches at the end of May: French beans, runner beans, sweet corn, courgettes, gherkins, pumpkins, summer squashes, marrows and melons. You can still sow cucumbers and tomatoes for late crops. Also herbs such as basil, coriander, dill, Greek oregano, parsley and fennel, Alpine strawberries (Rugen best), Florence fennel, and half-hardy single flowers such as tagetes, French marigolds for attracting beneficial insects to help with pest control and pollination both under cover and out in the garden. Shade propagators and young seedlings from strong sun at all times now.

Outdoors, sow in modules, in a seedbed for transplanting, or in situ where they are to crop: Asparagus, globe artichokes, beetroot, broad beans, carrots, all varieties of peas, savoy and other autumn/winter cabbages, all varieties of sprouting broccoli including calabrese and purple sprouting, cauliflowers, salad onions, Hamburg parsley, landcress, lettuces, perilla, orache, chicory, kohl rabi, kales (those for overwinter from the middle of May), radishes, rocket, salsify, swiss chards, spinach, white turnips and swedes, summer purslane, lamb’s lettuce, salad mixes and perennial hardy herbs including sorrel. Asparagus peas, cardoons, sweet corn, French and runner beans, and New Zealand spinach can be sown outside under cloches now. Also sow some single annual flowers such as limnanthes (poached egg flower), calendula, Californian poppies, convulvulus tricolour, nasturtiums, phacelia and sunflowers to attract beneficial insects like hoverflies to help with pest control, and bees to help with crop pollination. Sow fast-growing green manures like buckwheat, mustard (a brassica so watch rotations) and phacelia, to improve the soil, “lock-up” carbon and feed worms (after digging in), on any empty patches of ground that won’t be used for six weeks or more.

Plant out: Kale, cabbage, cauliflower, celery, celeriac, Brussels sprouts, celeriac, leeks.

Do: Earth-up potatoes, keep seedlings and young plants well watered, begin to harden off well-established, module-raised plants, keep glasshouse/polytunnel well-ventilated, put up protective netting (Bionet) against carrot fly, net brassicas, provide support for tall plants (beans, peas, tomatoes), hoe/handpick weeds.

All sowing details courtesy of

Fionnuala Fallon

Fionnuala Fallon

Fionnuala Fallon is an Irish Times contributor specialising in gardening