THE WHITE BUTTERFLY

Evening Post, Volume CXIX, Issue 86, 11 April 1935, Page 23

THE WHITE BUTTERFLY

CONTROL BY PARASITES

PATIENCE NEEDED

. The white butterfly at' the present time may be found in most parts of the North Island, and is also beginning to make its presence felt in parts of the South Island.

During the past year the Department of Agriculture bred up large quantities of parasites in order to start colonies in those parts where the butterfly is present and where no; parasites had previously been liberated. The butterfly first became prevalent in HaWke's Bay, and it was in this locality that the natural enemies were first liberated. In January and February of 1933 the first consignment of Pteromalus puparum was liberated at Maraekakaho, near Hastings. In the 1934 season further supplies of this parasite Were liberated at Maraekakaho, and towards the latter part of this season field investigations indicated that the parasite was spreading rapidly from the initial point of liberation and was commencing to exercise a fair amount of, control. Field investigations for the current season indicate that the work of the parasite is outstanding' in that the Hawke's Bay infestation at the time" of writing has been reduced to such an extent that comparatively few butterflies are seen, though no doubt they exist in fair numbers in restricted area's. In other parts of New Zealand, notably from Wellington right along the coast to New Plymouth, the butterfly has been able to multiply unchecked and consequently large areas of crops are being destroyed, and many in this area are beginning to wonder whether the parasite is of any value. It must be understood clearly that, on account of the enormous population of butterflies, some considerable time must elapse before the parasite begins to overtake its host, since apart from a few that were liberated around Palmerston North. Marton, and Fordell, no individuals of P. puparum were distributed in the Wellington and Taranaki districts before the current season. • "

Some farmers seem to be under the impression that all that is necessary is to obtain parasites from the Department of Agriculture and liberate them on the crops, and that by soms magic the butterfly will disappear. Unfortunately this does not happen, and it is only after the parasite has had sufficient time to breed and multiply into large numbers that the effect of its presence will be properly felt.

During this season the' Department, from its comparatively small stocks of material, can hope to establish initial parasite colonies only, from which it is" confidently expected the parasites will spread successfully, and, after a seasori or so, breed in sufficient quantities to exert the control desired. Up to the present 550,000 parasites have been sent out. Large colonies of these httye been distributed on crops which it was felt were suitable from the point of view of parasite-establish-ment. .

In Hawke's Bay during two Iseasons two colonies of ten thousand parasites were liberated in the one locality,.and a good control is being obtained. Many-more colonies greater than this number have been liberated over other parts of the North Island generally, so that it is reasonable to expect that towards the end /of next season, or soine,time in.the season foX lowing, a satisfactory degree! of control will be obtained ,in infested areas generally. Too hasty judgment on the efficiency of the; parasite should"' be avoided, since experience in Hawke's Bay leads one to expect confidently that the same satisfactory control as In Hawke's Bay will be eventually secured in other areas where the parasite becomes established. •