RAGWORT AND CORSE

Ashburton Guardian, Volume 50, Issue 130, 14 March 1930, Page 8

RAGWORT AND CORSE

CONTROL INVESTIGATION. DEFINITE PROGRESS MADE. (Special to the "Guardian.") WELLINGTON, Match 18. Definite progress has been achieved in devising measures to control two ot the weed pests of the Dominion, Ihe Hon H. Atmore (Minister in charge ol the Department of Scientific and Industrial Research) has obtained very satisfactory wfjorts regarding the control of ragwort and gorse. These reports state that the results of extended investigations with the Cinnabar moth on the control of ragwort which have been undertaken by the Noxious Weeds Control Research Committee under the chairmanship of Professor Kirk, now indicate that the moth has become acclimatised in tne field in an additional number of districts throughout the North Island during the present season. Toward the end of last season, when the moth had satisfactorily passed all the 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 points were selected, and the work has been attended with similar success. .However, owing to the heavy the moths imported from Great Britain during the past year, the number of eggs distributed—about 200,000—was much less than was anticipated. All consignments of moths received . from overseas have first to be bred in the insectaries at the Cawthron Institute, Nelson, in order to obviate any possible chance of introducing any other forms of harmful insects or parasites th,at may prey on the cinnabar moth itself. This quarantine is a very necessary safeguard. In the future it is hoped to make use of all of the distribution centres where the moth at present is established to supply numbers of eggs to all the ragwort infested * areas of the Dominion, and, if their wintering is successful, this should be possible next season.Narrow Range of Breeding. So far it has been found that the 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 the distributioh centres ajjd to place them in any patches of ragwort dotted about thenfarms. This process is a comparatively simple one, as the eggs are attached in dense clusters to' the undersides ot ragwort leaves. All that is necessary to do is to remove, a number of leaves or a whole ragwort plant and place it in the midst of a patch of freshly growing weed. From this point the moth will . gradually spread throughout the\pateh of weeds. Another important point that must be borne in mind is the liability of the cinnabar moth to be attacked and parasitised by insect enemiesf 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 of parasitical insects increase to any extent. The moth itself is readily identified, being dark in colour with conspicuous, crimson-red markings on its wings. While all 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 this pest, which, during recent years, has grown to such a great in seriousness. It is recommended, therefore, that there should be no slackening off in other known methods of dealing with ragwort. Farmers are requested not to relax their efforts to attack and weaken the vitality of the plant b\ preventing its flowering and seeaing. The Cinnabar moth may, howeyer, prove a very great ally of the farmer in any steps taken to reduce the damage and loss caused by ragwort. The work of the distribution and supply of moths to all localities where assistance is urgently required will be one of considerable magnitude. Farmers are asked, therefore, to give the organisation, upon the shoulders ot which the duty of distribution will devolve, every assistance and support once the work is put in hand, which, it is anticipated, will be toward the end of the present year. A Gorse-control Insect.

An insect that serves to control the spread of gorse in other countries is Ap.ion ulicis, a highly specialised specie's which confines its activities solely to gorse. The insect is a weevil which attacks the immature pods of gorse, depositing its eggs therein, the larvae from which, in growing, live upon the developing seeds. By this means seed formation in the gorse pod is prevented. The plant itself, of course, remains uninjured. Dr. David Miller (Director of the Noxious Weeds Control Research scheme 1 ) has experienced considerable difficulty in acclimatising this species in New Zealand. The mortality occurring in the 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 im-5 ported to breed and multiply. In consequence there would appear to be every reason for hoping that some progress will soon be made and that successful acclimatisation of another useful insect species will be achieved. The difficulties experienced in this case, though not serious, have not been more so than those attended earlier earlier endeavours to introduce the humble bee. The fact that the Apion restricts it« activities so exclusively to gorse will enable the quarantine, which is at present being maintained upon it, and which necessitates its being reared in the more or less unnatural conditions of special cages, to be lifted at an early date, so that it mav be liberated in a limited number of gorse areas where its reproduction naturally should lie more rapid than it is at present. 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 as a noxious weed of farm lands.