BRONZE BEETLE

Nelson Evening Mail, Volume LXIII, 5 August 1929, Page 7

BRONZE BEETLE

In the course of a, short address on the Bronze Beetle. Miss Lysaght made- the following remarks: "In October the first beetles emerge' from the pupae, they are most abundant during November and December, though stray individuals may bo found as late as .March. They live, as long as eight weeks in captivity and most probably longer under natural conditions. They occur on many varieties of frail trees, apples, plums, peacheH, raspberries and blackberries to mention only a few of the introduced hosts, while on'manuka and other native plants they are also very numerous. The damage done lu apples constitutes the most serious, feature. The beetles cluster for shelter in bunches of short-stemmed fruit. One of the; most important varieties for export, namely. Coxs, are thus particularly liablo to attack. "If it were possible to cultivate, a long-stemmed Cox would probably be much more profitable. One grower is at present experimenting on these lines, but several seasons will have to elapse before stable results can bo obtained. The beetles are. most active) on sunny days, pairing takes place, and some time afterwards the females burrow underground to lay their eggs:, they prefer. dry soil that has not been recently disturbed. The eggs are laid from half to one inch below the surface, sometimes singly, but usually in batches of from three to fourteen in two or three adjoining earthen cells. They ale very small and can just be seen with the naked eye. In colour they are. creamy white, deepening to yellow as development proceeds. "Hatching takes place in from two to three weeks according to the temperature and moisture content of the soil, cold wet weather may prolong the incubation, to nearly four weeks-, while in hot dry spells it may occupy a period of only fifteen days. Some of the newlyhatched larvae remain quiescent in their cells for some' hours after hatching, most of them become, active immediately and begin wandering round searching for food. They probably live on the roots of many plants, but have been observed only on those of grasses. Other larvae in the same situations are those of a common black weevil, they are similar to those of the Bronze Beetle in shape and size, but may be distinguished by Iho absence of legs. "The larvae of the latter species have a series of characteristic golden hairs vent-rally, and a shiny prothoracic shield jllSt behind thei head, differing from voting grass grubs in these respects. The 'winter is passed in the larval stage and larvae may bo found in all phases of development during the cold weather. They hibernate in the autumn and remain in earthen, cells from one to five or six inches below the surface. In the early spring they become, active again. When fullgrown they once more form cells in which they pupate. The pupal period lasts about three weeks after which the. adult beetle emerges and is ready to begin its depredations above ground. A certain amount of experimental work has been carried out as regards spraying for controlling the adult, but as yet'there are no results to justify tin; recommendation of any chemical for this purpose. "This summer we hope to carry out spraying on a large scale, but biological studies are, of course, fundamental and had to be dealt with first of all. The most important means of control is that of clean farming, in the, removal of all extraneous growth in and about the orchard. For example, blackberry, is often left along the sides of ditches running through the orchards; it is a favourable food-plant of the beetle and the larvae cajj be found in such situations if nowhere else in the; orchard: Rank grass and scrub are also selected as breeding grounds. In the orchard itself constant cultivation is 7 most valuable. During the winter the ground under the trees should bei kept as free from grass and weeds as possible, this helps to check the larvae considerably. Even more important is the practice of constant and thorough cultivation when the beetle is on the wing. "In the laboratory it was found that the females refused to oviposit in freshly disturbed soil, and Mr Kidtl, of Greytown, tells me that the infestation in his orchard has been greatly reduced in the last, five or six years by his harrowing regularly once a week during Notvember and December; orchards that do not suffer from the beetle should be cultivated with as much care as those that do as it, is much easier to keep thebeetle out of the orchards than to eradicate it when once it has become established.

"We hope In find a spray that will poison Hie adults, such treatment combined with cultural methods may one day be successful in removing the Bronze Beetle from its placet in the front ranks cf our insect pests." At the conclusion of the addresses given by Mr Bigg on orchard manuring and by' Miss Lysaght on the bronze beetle many questions! were asked by growers concerning both subjects. A vote of thanks to the Cawthron Institute and the lecturers was carried by acclamation on the motion of Mr Brunt, chairman, and Mr Dicker.

Professor Easterfield responded On he half of the Cawthron Institute.