PESTS & PERIODS

Wairarapa Times-Age, 5 April 1938, Page 6

PESTS & PERIODS

SPREAD OF WHITE BUTTERFLY.

DR. MARSDEN ON FACTORS OF VARIATION.

■ “The increase in numbers of the white butterflies this season conforms with an almost periodic characteristic of pests which become established in this country,” said Dr. E. Marsden, secretary of the Department of Scientific and Industrial Research, in a press interview. “Further, there is little doubt that white butterflies are blamed for much of the .damage done by the black diamond moth. We are not seriously alarmed about the white butterfly at present. We need more information, however, on the relation of the rate of increase of both the white butterfly and its parasite to climatic factors. It is perhaps unfortunate that, so far, we have no other parasites available that would attack the pest at the egg or the caterpillar stage.” Dr. Marsden added that the prolonged warm summer had particularly favoured the breeding of the white butterflies and was. undoubtedly. one of the principal reasons for the increase in numbers noticed. Again, the flight range of the butterfly and the parasite were probably different, which meant that butterflies could escape beyond the field of operation of the parasite. “If, from a knowledge of the effect of climatic factors, we could predict prolific seasons for the pest, then we could arrange for increased distribution of the parasite,” Dr. Marsden said.