Another Garden Pest

Dominion, Volume 28, Issue 86, 5 January 1935, Page 16

Another Garden Pest

(By

J. Drummond,

, F.L.S., F.Z.S., for "The Dominion”.)

WITH about 1270 species of weevils of its own, among them the giraffe-weevil, which has a snout as long as its body and is one of the strangest weevils in the world, New Zealand is not in need of overseas weevils, but eight or nine species have come

here and have proved to be undesirables. In New Zealand, as elsewhere, weevils are attractive to the eye. Many New Zealand species deck themselves elegantly in pretty colours, choosing pinky-grey, pinky-white, bronzy-green, metallic-pink, metallic-green, chocolate-brown, greyish-green, coppery-red, shiny black, bright yellow, orange, fawn, cinnamon, crimson nnd, perhaps most beautiful of all, dark blue and metallic-blue. Beauty is only skin deep. Cleverness may intermingle with banefulness. This is so with weevils as a group. Beetles are the dominant insects, and weevils are the dominant beetles. There are good-fairy betties, like lady-

birds, destroyers of orchard pests. Weevils do nothing to mitigate thengreat destructiveness. They are vegetarians possessing insatiable appetites. There is no part of plants they do not destroy, from root and pith to flower and fruit. They have in their ranks the most destructive insects known, more to be dreaded than white butterflies and borers that crumble costly buildings.

The grain-weevil, the vine-weevil, the striped pea-weevil, the rice-weevil, the eucalyptus-weevil, and a few others, came years ago. The latest addition to the list is the vegetable-weevil, a little drab insect, active and tenacious of life. Mr. E. C. Wiltshire, when sending a consignment from Tauranga. wrote: “I find them at night chewing up my tomato plants. They are found on only one patch of ground, where I have a crop of lupins going to seed. They are the same colour as the earth, ravenous and hardy. They are strangers to me and to other old residents of Tauranga. This is our first

experience of the pest.” Dr. D. Miller, Chief of the Entomological Department of the Cawthron Institute, who kindly identified the weevils and supplied information about them, reports that the species, Listroderes obliquus is believed to be a native of Brazil, but has spread to the United States, South Africa, Australia and New Zealand. As to its habits, in autumn and

winter the grubs damage carrots, turnips and spinach. Adults do most of their mischief to tomato and potato plants in the late spring and the early summer. During summer, they aestivate, or pass the summer in inactivity. Methods of control are followed in the United States. A claim is made that one investigator proved that the weevil can be controlled economically and effectively by the use of sodium fluosilicate. To this Dr. Miller adds that repeated cultivations in the spring help to destroy the delicate grubs in the soil, and that a poison bait of dried apple-pulp coated with sodium fluosilicate may be broadcast in seed infested at the rate of 751 b. an acre.

‘ Before leaving the weevils, it may be stated that a small native New Zealand moth, destroyer of apples and peaches, a pest in orchard and garden, is a leaf-roller or leaf-twister. In this practice it is less skilful than the leaf-rolling weevil of the Old Country, which makes leafy funnels for its grubs to live in. No other weevil shows the same ingenuity. Incisions are cut in a leaf, and the leaf is rolled up to form a funnel. Using its legs, the weevil

rolls up one side of the leaf as a grocer rolls a paper funnel. It enters the part rolled up and brings it closer together. After attending to several details, it enters the funnel again, cuts three or four small cavities on the inside of the wall of the funnel, and places an egg in each. The opening to the funnel is closed in the same way as a grocer tucks in the opening to his paper funnel, but the weevil’s work is more complex and more precise. Incisions made in a funnel wall were examined by mathematicians, and were declared to have been made on satisfactory mathematical principles. .