Insect Dramas In the Making

Sun (Auckland), Volume IV, Issue 1064, 30 August 1930, Page 26

Insect Dramas In the Making

Parasites Bred For Export

WAR ON CROP PESTS The layman does not look for drama in entomology, which he is inclined to regard as a very matter-of-fact science; but if he cared to plumb some of the secrets of the Farnham Royal Parasite Laboratory, founded by the Imperial Bureau of Entomology three years ago in a charming country house in the heart, of “Beechy Bucks.’’ I fancy he would encounter another “insect play” quite as fascinating as Capek’s (says a writer in the “Observer”).

Here, for example, is one little drama disclosed by a visit there last week. Far away in Western Canada a pest known as the wheat stem sawfly has been inordinately busy, to the detriment of the crops. At present experts out there are “dosing” the wheat with a liberal supply of a certain parasite which destroys that particular pest. This parasite, by the thousand, has actually been bred for export in the charming country house at Farnham Royal.

Before this invaluable work could be inaugurated corn stubble containing the sawfly, together with its parasite, had to be brought over from Europe. Why Europe? Because there the two insects are found inhabiting the same plant. Not so iu Canada, curiously enough. When the sawfly attacks grass in Canada the parasite is there to attack it in turn; hut, for some unexplained reason, the parasite will not follow its hgst into the corn!

A pretty caprice of Nature calculated to elude the entomologist! But the entomologist.—that is, the Farnham Royal expert—merely says:

“Very well. Master Sawfly, since there are no parasites to spoil your little game in Canada, we’ll just have to get some from Europe, breed them up, and send them there.” And that is what Farnham Royal has done and is doing. Saving Apple Crops Dr. George Salt, in the absence of the superintendent, Dr. W. R. Thompson. indicated many such little dramas of the insect world in a tour of the laboratories, insectories, and garden. One room, for instance, was devoted almost entirely to the Ascogast.er and Ephialt.es. two-minute parasites which prey on the codling moth, the first upon its egg, the second upon its larva.

This codling moth does a lot of damage to apple crops, notably in Canada, Australia, and Cyprus. At Farnham Royal it is encouraged to do as much damage as it possibly can. It. lays its eggs on paper; each egg is “mounted” on a fragment smaller than a piece of confetti, and the fragment is carefully pinned to the apple so that there shall be no mistake about the larva emerging and doing its work. While it is doing its work the parasites get busy doing theirs, and are painstakingly “harvested” for export in the process.

“You see,” remarked Dr. Saut casually, “each parasite destroys between 100 and 200 moths; the moth multiplies 100 times each generation; with these 300 trays, each containing fifteen apples, we can turn out from about 10,000 parasities in each generation. We get two generations a year, and hope to get three. That will give us an output of 15,000 to 20,000 parasites.” And across the wide seas these parasites go to enlarge the bounty of dominion and colonial orchards —sometimes in cold storage, sometimes cosily packed in strips of corrugated cardboard, each corrugation forming a safe “cell.” In “constant temperature” chain-

bers, automaticlly controlled anc humid as the tropics, we found cul tures of the friendly parasite Micro bracon, which had come all the wa>

[from Egypt. together with its host. the pink hollwurm post. which battens 'on cotton. The parasite passes , through one generation here. and then ‘ its progcny is sent: out, to Barbados. . Parasites‘ Foster-Mother Remarkable indeed. seemed the case ‘of another t'ricntlly J'u'trasitc, 'l‘richo—,gramnia, which was being; reared to [combat tho sugar cane borer pr-st in the \Vcst Indies. Farnham Royal had in” natural host, the borer itself, to work upon. so it was rearing these parasites on an artificial host, a specks of dust, but. those in which the as a kind of foster-mother! The eggs of this moth looked little bigger than spects of dust. but thise in which the parasite was busy showed black in» stead of whith. "\\'G can produce .about 500 of those a. day. and there is a. six to twenty fold iucrcasc a getter» ation." was ltr. Salt‘a ronilnvnt. “One man in Barbados. Mr. It. \V. E. Tucker. liberated no fewer than 26,000.000 of these beneficial parasites last. year." An important part, of the Farilham Royal research is, of course. dmoted to finding parasites which. while be-t ing beneficial in one particular way, will not be harmful in others, in which case the cure might. be Worse than the. t ill. One insect was found. for ox-i ample, which attacked blackberry" right enough, but. went on to attack‘ apple and raspberry also. Naturally, he was relegated in favour of a certain beetle which bores into the stem at the blackberry and stops at that. Either in “lab“ or outdoor inscctorz'i which shields plants and pests from: all interference, the life history ofl every insect is patiently studied. aud‘ subsequently recorded, t The woolly aphis. which infests‘ apple trees, the scale of the hawthorn ‘ twig. the fluted scale of the citrusl fruits, a moth which attacks larchi trees—parasites or predators to fight! these and other pests-n'ere being: sedulously cultivated for export. i Pet Parasite : Perhaps the most remarkable i creature at .lt'arnham Royal is Rhyssa. an insect. with a thin. flexible oviposi-i tor which can actually penetrate the] hard wood of the silver fur tree, us-' ing its body as a. lever. in New Zea; land silver'firs are frequently spoilt, for use by the activities of a. pest: Sirex. the larva. of which bores intni the wood. But it. has to reckon with; the uncanny instinct and power of! Rhyssa. who divines the presence of! the larva beneath the surface, drive-5’ its ovtpositor deep into the wood,~ stings the larva. and lays its own eggi in the concealed tunnel. ' Rhyssa, ac~t cordingly, has become a special “pet"t at Farnham Royal, and is on view 111" a glass case. i

In addition to its director, Sir- Guy Marshall, and its superintendent. Farnham House is staffed by four entomologists, two botanists, a secretary, Mr. R. C. Jeffery, a few garden hands, and a carpenter, who is continually fabricating new devices for keeping the insect family safe and sound as it emerges into the light of research.

To date it has shipped some 363,000 beneficial insects of twenty-one different species to a dozen different countries. At present it has seventy-two separate projects in hand; it is always being approached to undertake new ones for some remote part of a dominion or colony.