ENTOMOLOGICAL ITEMS.

Otago Witness, Issue 1981, 11 February 1892, Page 5

ENTOMOLOGICAL ITEMS.

Injurious Insects (Wonderful Discoveries).

It is a but too common conviction with many people, and certainly not a very unnatural one with taxpayers, that every new Government official is one more friend of those in power, to be supported on one excuse or another at the public expense, and the idea of paying a scientific entomologist a handsome salary to deal with insect pests has not yet reached the gene, ral mind of our New Zealand taxpayers ; but the time is not far distant when all civilised countries will see (as most of them already have done) the enormous losses that afflict producers for want of scientific assistance, and the necessity of providing instruction. The noble example which the United States Government have set the world in providing assistance to its farmers in this respect has already been seen and felt in the having of millions cvory year, sums of money in comparison with which the expenses, even of a very extensive system of Agricultural department arrangements, i& but as a drop to a rivet. The gentlemen of the Division of Entomology nre' continually making discoveries and improvements in the mode of fighting insect pests, which bid fair to overwhelm the enemy, and are fahfc rendering our present methods of dealing with them, such ab poisoning with arsenical dressings, entrapping with bands round trees, &c, kc, clumsy and old-fashioned cures, more to be laughed at than used, and looked upon as unworthy of trial. One of the latest ideas is that of attacking insect pests by spreading contagious diseases amongst them, either of a bacterial or n fungoid nature. There is a vast number of these diseases, and certain varieties of them are found to attack certain varieties of insects The germs can now be produced by artificial means, and are becoming perfectly easy of control and application even by unscientific hands. In fact steps aye being taken to render them easy and safe in use, and "cultures" (as they are called) — that is, fluids or powders containing the germs, are becoming as much articles of commerce as our Paris green, London purple, or other such remedies, and will soon be sold and used as freely. There is of course as yet a feeling of considerable uneasiness at the bare idea of introducing frightful contagious diseases amongsb insects which prey upon products used as human food, but it is to be hoped that science and use will render all that easy and safe, and the time will certainly come when the fruit-grower or farmer, when he finds his crops suffering from any j'articular insect, will merely hav<2 to introduce a certain contagious disease iuto his orchard oi* fields to get rid of the enemy. As an example of whiit may be expected we have already what the Division of Entomology at Washington calls "a new branch of entomological commerce just instituted by a French fiim." There is a certaiu contagious disease known to destroy the beetle larvtu, usually known as "white grubs." This disease is very readily communicated by a Vegetable (fungoid) parasite, and is exceedingly deadly to the white grabs. The French scientists Prillioux, Delacroix, and C4i;>rd have established the fact, and a French firm have put in practice a method of producing large quantities of "culture" containing tha germs of the plant (known as Botrytis tenella). This culture is placed in small glass tubes and sold at so much per number, and when a fanner or other person is afflicted with the pest, which destroys the roots of the grapes, all that he has to do is to collect a number of these grubs, place them in a box with a little earth or sand at the bottom, spread out the grubs, and sprinkle them over with the deadly "culture." At the end of about six hours they will show unmistakeable signs of the disease, and they are then taken one by one and planted separately over the field at considerable distances a little below the surface, when the disease will spread rapidly over the whole field and kill every grub in an astonishingly short time. Some of the diseased grubs can be retained from which to infect others for jilanting purposes. The cost originally is not much, and from one tube several hundreds of these grubs can be infected to begin with, and .as many more as are desired by the introduction of healthy grubs into the box used. When the " culture " is sprinkled over the grubs in the box (say, about 100 in number) the disease lakes root upon them within six hours, and when dead they are .swollen and of a clear rose tint. As to the cost of the remedy, the .statement of the company is not very clear. " Trial tubes" are sent at "50 centimes," and the "commercial article costs 6fr." It is not stated how many tubes are .sold for "6fr,' ! but in another place it is assisted that each tube is warranted to infect "several hundred " grubs, from which others can be infected, so that in any case the article is not expensive. The while grub is a serious pest in many districts of New Zealand, and it is to be hoped that some enterprising Dunedin firm may see their way clear to take in band the importation of a stock of tubes to retail to their country customers.

Itiscasc.s of Insects.

In some of the States in America there has lately been observed a great mortality amongst several sprcies of flics. It comes in the form of a fungus, which attacks them in such numbers that there is in ninny places a very remarkable scarcity of these insects. In some of the grounds of the Agricultural department the numbers killed by this fungus may be imagined when it is btated that the underside of leaves

are often found thickly covered with the bodies of dead flies, "attached by the fungoid growth," and a small leaf will often contain six or eight dead specimens. This peculiar fungus is said not to be the same that sometimes kills the common house fly, but a newlydiscovered one, described by Mr R. Thaxter, and known to science as Empusa americana. Professor Riley in writing on this subject says: — "The discovery of this great mortality amongst flies is interesting, in view of the economic importance which the subject of the diseases of insects bids fair to assume in the near future, and would seem to indicate thab the season has been specially favourable for tho propagation of such diseases." The Cottony Cushion Scale (Icerya imrcliasi).

This insect, according to "Insect Life," ha* reappeared in considerable numbers in some districts of California, after having apparently been 'exterminated by Vedalia cardina i•, tho little oeetle procured from New Zealand. This is what waß expected by-the Division of Entomology, and by most other scientific men. Tho scale insect lives upon every kind of plant, and it breeds at an enormous rate ; whilst the beetle, although quite capable of overtaking it, lives on no other food, and if only a very few icery» eseapc the, voracity of their enemy they will soon begin to show an increase, whilst tho beetle seems extinguished in the meanwhile from want of food. A few of them, however, also contrive to exiat in some way, and where they come upon a number of icerya) they increase very rapidly and again rout their prey. In this way we may expect that Auckland and other once infected districts in New Zealand will again be attacked by the scale, and tho struggle renewed, but it ifl pretty certain that never again will that terrible pest be able to do the mischief of former days, as there will always be some vedalia to be had somewhere, and once introduced amongst the scales they tire a certain and speedy cure, if not a perfectly permanent one. Entomologist.