WHITE BUTTERFLIES ON THE WING

Manawatu Times, Volume 63, Issue 212, 8 September 1938, Page 10

WHITE BUTTERFLIES ON THE WING

Parasite Control Last Season Not Satisfactory OTHER PBBTS MUST ALSO BE BLAMED FOR CROP LOSSES Whito butterflies have already put in an appearance in Manwawatu, causing farmers and market gardeners to wonder if there is to bo a repetition during the coming season of the wholesale destruction of crops that was exjperienced last summer and autumn. According to the annual report of the Department of Scientific and Industrial Research, it is anticipated that 100,000 parasites will be distributed in the coming season by officers of the Department of Agriculture. The allocation to the different districts will be made after consideration oi: the abundance of the butterfly in each district, the importance of the cruciferous crops and the number of parasites which have previously been liberated in each district. The report adds that there is a widespread disposition to consider that the damage to crops is in direct proportion to the numbers of butterflies flying over them. The damage is frequently confused with that caused by the diamondoack moth. The indubitable butterfly damage, which is usually most pronounced around the margins of crops, is not a fair indication of tbo actual damage over the w’holo crop. In addition, the parts which rainfall and soil play in the production of good crops is frequently disregarded and the whole blame for poor crops placed on the insect pests. “Notwithstanding this, the parasite control of tbo whito butterfly last j season has undoubtedly not been satis-, ; factory,” the report adds. “The butterfly has been abundant in Hawke’s Bay, Manawatu and South Canterbury, and considerable damage has resulted to the crops in the first two districts at least. Field collections show that there is a ! very high rate of parasitism of pupae in late summer from all these districts. The past season has been decidedly abnormal. From November onwards the mean monthly temperatures have been several degrees abovo normal, a.nd this condition rvould have the effect of accelerating tho development of tho whito butterfly to such an extent that the parasite was unable to overtake it until late in tho season. It remains to be seen whether the parasite will give a satisfactory control in more normal seasons. At present wo have no reliable information on tho factors which favour the butterfly or militate against tho success of the parasite, but a study of tho problem is now being made,’'