WAR ON PESTS

Greymouth Evening Star, 11 July 1931, Page 8

WAR ON PESTS

TINY STORM TROOPS. At Farnham House, Farnham Royal, in Buckinghamshire, I was shown round a garden full of weeds, and glasshouses in which the stems and twigs of plants were white with woolly aphis. And the men who* have carefully tended this garden for four years have reason to be highly satisfied with their work (says a writer in the “Evening News”). “Look,” said my guide, indicating some twigs of an apple plant in one of the glasshouses. The white wool that had covered the plant had turned black on these twigs. “That’s a result of our work,” he said.

For it is in this garden that the tiny armies are mobilised to go forth and fight our enemies of the 1 insect world in distant parts of the Empire. By June last year over 300,000 minute troops had gone to the perpetual war of pest and parasite. ' Farnham House Laboratory was founded in 1927, by the Imperial Bureau of Entomology, whose headquarters are the new wing of the Natural History Museum at South Kensington. I had come down to Farnham Royal from the museum, but before I left Major E. E. Austen, D. 5.0., whose, official title is “Keeper of Entomology,” explained something of the work of the bureau. One is apt to think of museums as venerable places living in the dust of the past, but that is not at all Major Austen’s view.

“I believe,” he told me, “that a museum should move with the times; and when ordinary Londoners write to us on some minor matter, asking, for instance, what steps they can take to rid their houses of earwigs or silver fish, I think it is our duty to advise them. The museum was not Yneant for a reference library in that way, however. Our work is chiefly concerned in the matter of biological control, with the identification and classification of pests and parasites.” Major Austen gave me an instance of a successful campaign against a destructive pest in Fiji. A pretty little purple moth, which he called Levuana Iridescens, was attacking the coconut palms there, and by 1925 it began to look as if in a few years there -would be no coconut crop at all. At last, in desperation, a prize of £5OOO -was offered to anybody who could find out how to get rid of this pest. When the bureau heard about the trouble, three entomologists went to Fiji, but for some time they could find no parasite to attack the coconut moth. At last, however, one of the scientists was sent to the Malay States to find out about the parasites ‘of a moth related to the Levuana —a very distant cousin. He found one, but it was being preyed upon by a hyper-parasite—a lesser flea, as it were —and it was necessary to rid the parasite of this. After three generations had been carefully bred the thing was done. And it had to be done, completely, for if even one hyper-parasite had bred later on, the parasites’ spread would have been much retarded. One female of a species with a threefold increase per generation, will have, in the; twentieth geheration, about eight million descendants.

Now a fresh problem had to be faced; how to ship the mobilised 'army of parasites 4000 miles from Malay to Fiji? An entire hold of a ship was chartered and filled with little coconut palms infested with Levuana, which in turn were infested with the parasites, which had been freed from their hyper-parasites. Only 315 insects survived the journey, but these were released over the islands. They were enough. Pretty little destructive Levuana perished, and the coconut palms throve. THE PINES. In Farnham House itself the rooms have been converted to laboratories and so forth. In one room my guide showed me a half-inch-long gelatine capsule with sawdust in it. “There is the larva of a parasite of the wood wasp in there ready for a journey half round the world,” he said. “The wood wasp is a very serious pest in New Zealand, where its larva bores not onb- into felled logs, but into the living pine trees. “The New Zealand Government asked us to investigate; and after a very long and difficult series of studies and a lot of manual labour sawing up dozens of logs and so on, two good parasites were discovered. This one’s name is Rhyssa persuasoria. Thousands of him have been shipped to New' Zealand.”

In one glass house, or insectary, as my guide called it, there were rosestocks that looked in very poor condii tion. “Here we are rearing insects which attack blackberry plants—they are a pest to agriculture in New Zealand,” he said, “and the ragwort and St. John’s wort we are cultivating in the garden are not meant to be ornamental; they are for breeding insects that attack them.” Some of the outhouses in this extraordinary garden contain, refrigerators for keeping insects in a larval condition until the scientists are ready for them. Others contain incubators, for hatching out parasites. And in one I saw not only an incubator and a refrigerator, but also a clever arrangement for keeping insects in a summer condition. A thermostat kept the temperature at summer heat by altering the current through electric bulbs,

and there was also a gadget which kept the air at the right humidity by heating a trough of water until vapour was given off. “One of our successes was the parasite of the leaf-cutting pear-midge” said my guide. ‘The little brute was accidentally introduced from Europe, where it has plenty of enemies to keep it down, to New Zealand, where it had

so few that it had a gay old time in all the pear-growing districts. “Modern rapid transport and coldstorage were probably responsible for them getting overseas; and after a time the pears suffered so terribly that no satisfactory crops were obtained for several years. “But the consignments of parasitised midge-infested material which we shipped out saved the situation, and now the crops are satisfactory once : again.” j: