Armies of insects ravaged 19th century crops

Press, 1 April 1989, Page 22

Armies of insects ravaged 19th century crops

Country Diary

Derrick Rooney

An old friend took me mildly to task over a couple of jars the other day, about something I wrote in this column last week. “I see you’re going on about British birds again,” he said. “Moaning about them again. How about being positive for a change? “Have you considered,” he asked, “the real reason why these birds were brought in? It wasn’t for their beauty. It was because we needed them. Yes, they eat some fruit and seeds. But what would happen if these British birds weren’t here? We’d all be smothered by a plague of insect pests." Some fruit? More like the lot, in my garden. But he had a point.

There are now more than 2000 species of introduced plants growing wild in New Zealand, and along with them came a great variety of insect pests, which, in the absence of their natural predators and the presence of a gap left by the wholesale extermination of indigenous insects, multiplied at phenomenal speed. Captain James Cook himself is credited with being the first European to modify New Zealand’s insect flora — his men introduced the flea, a pest from V

which pre-European Maoris were free (they did, however, have lice). It’s impossible to say how many insect species were extinguished in the change of New Zealand from a thickly wooded country, with about 80 per cent of its area under forest, to open pasture, arable land and scrub, with only about 15 per cent now in natural forest. However, that renowned naturalist, G. M. Thomson, wrote in 1916: “The surface burning of $

open land which prevailed, especially in the South Island, and the wanton destruction and burning of forest which has marked so much of the North Island clearing, must have destroyed an astonishing amount of native insect life, and made room for introduced forms.

“The clearing of the surface for cultivation and grazing, the draining of swamps, and the sowing down of wide areas in European pasture plants, have all contributed to this wholesale destruction and displacement of indigenous species.”

The introduction of insectivorous birds must also have resulted in the. consumption of countless native insects.

So why, given the predictable consequences, were these birds brought in — and at great expense? An explanation often advanced is that nostalgia (for the birdsongs of “Home”) impelled the British colonists to import familiar European birds, just as it caused them to line out the countryside with hedges of gorse, briar, and thorn — also destined to become pests. As my friend noted, this explanation just doesn’t wash. The evidence suggests the contrary: that the colonists were hard-

headed people, not given much to romantic impulses. They had to be pragmatic to survive. A more tenable explanation is that the destruction of millions of indigenous insects and their habitat left a gap that was rapidly filled by foreign pests that came in with the new crops and plants. The wholesale conversion of huge areas of country from forest to grassland also opened a way for a population explosion of some indigenous pests, such as grass grubs and porina. In other words, New Zealand about 120 years ago suffered from a plague of insects. How bad was it? Bad enough, apparently, to stop trains. Consider this extract from a paper published in 1906 by James Drummond, a Govern-ment-employed biologist: “About 40 years ago this country was smitten with blasting plagues of insects which crawled over the land in vast hordes. The gathering of the caterpillars was a sight that caused consternation to agriculturists. They came not in regiments and battalions, but in mighty armies, devouring crops as they passed along and leaving fields as bare as if seed had not been sown. “In the Auckland district one

settler kept a paddock closed up for a short time in order to place some young stock in it, but when he completed his purchases he was astonished to find that the grass in the paddock had disappeared. In the same province a settler was driving his dray along the road through a colony of caterpillars which happened to be crossing the road at the time. They were present in such countless numbers that the wheels of his dray ran into a puddle, caused by the crushing of the insects.

“Telegrams published in the leading newspapers about that time stated that the morning and evening trains between Waverley and Nukumaru, on the way to Wanganui, were brought to a standstill owing to countless thousands of caterpillars being on the rails, which had to be swept and sanded before the trains could continue on their journeys.” According to Drummond, incidents such as these prompted the colonists to bring in the insecteating birds they had known in the “Old Country.” There were three main criteria: the birds must eat both insects and seeds, so that they could survive the winters; they must be non-migra-tory; and they must be prolific breeders.

“In weighing the evidence against the small birds it must never be forgotten that rapid increase was one of the principal qualifications set down by the early colonists as necessary to success,” he wrote. As for birdsong: this morning . there was a bellbird pealing in my garden, and in a week or two the grey warblers will be back for winter. Is there really an imported birdsong to compare with theirs?

Setting all this aside for the moment: our pears have now gone, and the starlings about which I wrote last week have departed, to seek food elsewhere.

Blackbirds have returned, to work on the quince tree outside the laundry window. We are working on the blackbirds. There’s an air rifle on top of the freezer, and the laundry window is left open all day, so that anyone who passes through can tgke pot-shots. The average score is three to five blackbirds a day, and still they come. A word of warning from a Sumner reader: steer clear of wild rowanberry jelly. The recipe for this product (March 18) prompted, she says, memories of jellymaking from wild rowans in her home county in England. “The rowans on Dartmoor,”

she writes, “are spectacular. The jelly was revolting.” Sympathy for the palate of anyone who tried the recipe led her to consult her “Oxford Encyclopedia of Trees of the World,” where she learned that the common rowan (Sorbus acucuparia) has a variety, “Edulis,” in which the berries are edible and were used to make jams and jellies. Is this variety naturalised in New Zealand, she asks. The short answer, according to the “Flora of New Zealand, Vol. 4,” is no. According to the flora, wild rowans in New Zealand belong to the common British variety. Variety “Edulis” is not mentioned. Since the rowan is of European origin, I pottered along to the public library to check it in the “Flora Europea.” Again, no mention of “van. Edulis.” My copy of the plantsman’s bible (W. J. Bean’s “Trees and Shrubs Hardy in the British Isles”) likewise fails to mention Sorbus aucuparia var. “Edulis.” But my copy is the seventh edition, in three volumes. Perhaps there is something in the eighth, revised, edition which runs to four volumes, and which I don’t have (the current price is about $600). But I found the name in Hilliers’ “Manual of Trees and

Shrubs.” “A strong-growing, extremely hardy tree,” says Hilliers, "differing in its larger leaves ... and its larger fruits which are sweet and edible and carried in heavier bunches. It originated about 1800.”

“Edulis” appears to be synonymous with the botanical variety listed in Bean and “Flora Europea” as S. aucuparia var moldavica, also sometimes known as “Dulcis.” Bean describes this as a native of northern Austria and adds that its large fruit is eaten in Germany and Austria. So there you have it. If you want to sample rowan jelly, make sure that the tree you pick the berries from is variety “Edulis,” or “Moravica,” or “Dulcis,” or whatever it’s called now.

While I was flitting from one reference book to another, a letter arrived from a Rangiora nurseryman, Mr A. B. Leech, who says that his nursery stocks Sorbus aucuparia var “Edulis.” “They are magnificent specimens already some three metres tall,” he writes. The original tree from which they were propagated was imported from Hilliers by an Amberley man. The nursery is located in Smarts Road, near Rangiora. Don’t get bowled over in the rush.