WHITE BUTTERFLY

New Zealand Herald, Volume LXXV, Issue 22984, 11 March 1938, Page 12

WHITE BUTTERFLY

ATTACKS BY PAEASITE

ACTIVITIES NOW INCREASING EARLIER CHECK OVERCOME [BV TELEGRAPH —OWN CORRESPONDENT] PALMERSTON NORTH, Thursday The silent warfare waged between the white butterfly and the parasite which was imported to counteract its activities has appeared throughout the latter part of tho summer to have resulted in a victory for tho butterfly, but according to observations carried out by Mr. C. .T. Hamblyn, fields superintendent of the Department of Agriculture, the tide is rapidly being reversed. About throe weeks ago in the Mount Stewart district it was possible to collect largo quantities of butterfly chrysalids front posts and battens from fences around swede and rape crops, said Mr. Hamblyn. If the parasite had not been present * these would within a few days have hatched out as adult butterflies ready to play their part in multiplying the pest. The parasite was present and could be seen at work laying eggs in these chrysalids, but considerably over 50 per cent of the chrysalids had not been attacked. An inspection mado a few days ago revealed a vastly different state of affairs, he continued. The parasite had apparently increased remarkably in numbers and it was estimated that up to 90 per cent of the chrysalids had been attacked. Unaccountable Lapse "It is more than probable," said Mr. Hamblyn, "that throughout the southern half of the North Island where the white butterfly is continually reported to be doing considerable damage to crops of the turnip family, tho parasite is present and the same state of affairs as was found in the Feilding district applies. This being so, it is not likely that further liberations of relatively small numbers of tho parasites would do any good at this stage. Farmers interested are well advised to make a small collection of chrysalids, place them under glass, and watch for the proportion of parasites to butterfly hatching out. "The failure of tho parasite Ito overtake tho butterfly in the early part of tho season cannot as yet be accounted for. The possibility of this, parasite actually being reduced by a parasite of its own has not been overlooked by Mr. J. Muggeridge, entomologist at the Cawthron Institute, where the work of breeding the parasite is being done, but up to the present nothing of this nature has been found. Check to Parasite

"It would appear that the exceptional weather of last sunwter and autumn gave the parasite a greater check than the butterfly, and from the very small numbers at the beginning of the season it has some time to increase to the extent of overtaking the butterfly, which has had everything in its favour for some months.

"In all cases where the contirol of an insect pest is mintained by a parasite," Mr. Hamblyn concluded, "there is a fluctuation in the efficiency of the control to the extent that occasionally the pest increases enough to do considerable damage."