RAGWORT AND GORSE.

Auckland Star, Volume LXI, Issue 62, 14 March 1930, Page 16

RAGWORT AND GORSE.

CONTROL BY INSECTS. t DEFINITE PROGRESS MADE. CAWTHRON INSTITUTE WORK. (By Telegraph.—Own Correspondent.) WELLINGTON, this day. Definite progress has been achieved in devising measures to check the ravages of two weed pests of the Dominion. The Hon. H. Atmore, Minister in charge of the Department of Scientific Industrial Research, has obtained very satisfactory reports regarding the control of ragwort and gorse.

The results of extended investigations with the cinnabar moth on the control of ragwort which has been undertaken by the Noxious Weeds Control Research Committee, under the chairmanship of Professor Kirk, now indicate that the moth has become acclimatised in the Held in an additional number of districts throughout the North Island during the present season. Towards the end of last season, when the moth satisfactorily passed all drastic tests imposed upon it before being set free, eggs were placed in four ragwort areas of the North Island. The emergence of moths from these and their attack upon ragwort plants in the immediate vicinity was entirely satisfactory. Accordingly, this year a much larger number of distribution points was selected, and the work has been attended with similar success. Narrow Range of Breeding. So far it has been found that moths do not spread for more than half a mile from where they hatch. Consequently, it will be necessary for farmers and others interested to secure supplies of eggs from distribution centres and place them ia any patches of ragwort dotted about their farms. This process is a comparatively simple one, as the eggs are attached' in dense clusters to the underside of ragwort leaves. All that the farmer need do is to remove a number of leaves or a whole ragwort plant, and place it in the midst of a patch of fresh-growing weed. From this point the moth will gradually spread throughout the patch.. Another important point is the liability of the cinnabar moth to be attacked and parasitised by insect enemies. Therefore, in order to give it the best chance possible of doing its work, it is desirable that its numbers should be vastly and rapidly increased before the numbers of the parasitical insects increase to any extent. The moth itself is readily identified, being dark in colour, with conspicuous crimson red markings on its wings. Damages, but Does Not Destroy. While all the evidence goes to show that the Cinnabar moth is capable of seriously injuring ragwort, there is no proof that it actually will serve to exterminate the pest. It is recommended therefore that there should be no slackening off in other known methods of dealing with ragwort, and farmers are requested not to relax their efforts to attack and weaken the vitality of the plant by preventing its flowering and seeding. The Cinnabar moth may, however, prove a very great ally of the farmer in any steps taken to reduce the damage and loss caused by ragwort. The work of distribution and supply of the moth to all localities where its assistance .is urgently required will be one of considerable magnitude, and farmers are asked to give the organisation upon the shoulders of which the duty nt distribution will devolve, every assistance and support once the work is put in hand, which it is anticipated will be towards the end of this year.

A Gorse Control Insect. An insect that serves to control the ?pread of gorse in other countries i» apion ulicis, a highly-specialised specie?, which confines its activities solely to gorse. The insect is a weevil which attacks the immature pods of gorse, depositing eggs therein, and the wryae in growing live upon the developing seeds. By this means seed formation in the gorse pod is prevented. The plant itself remains uninjured. Dr. David Miller, director of the noxious weeds control -research scheme, has experienced considerable difficulty in acclimatising this species to New Zealand. The mortality occurring in imported specimens has been very high, and the vitality of those that survive has been so reduced that their rate of breeding in New Zealand has_ been remarkably slow. Difficulty also is experienced by reason of the fact that the flowering period of gorse in New Zealand is different from that in the countries from which the insect is being introduced. Recently, however, suitable "cages" have been devised, which have allowed some of the apion consignments already imported to breed and multiply, and in consequence there would appear to be every reason for hoping that some progress will soon be made and that the successful acclimatisation of another useful insect species has been achieved. It is well to remember that the difficulties experienced in this ease, though serious, have not been more so than those that attended earlier endeavours to introduce the humble bee.

The fact that the apion restricts its activities so exclusively to gorse will enable the quarantine, which is at the present time being maintained, to be lifted at an early date, so that it may be liberated in limited numbers of gorse areas. A course similar to that now proposed with the cinnabar moth could then be followed, viz., the first liberation centres could be used to provide further supplies of insects for distribution in those districts where gorse is a considerable menace.