THE ÜBIQUITOUS BLACKBERRY.

Marlborough Express, Volume XLVI, Issue 264, 7 November 1912, Page 6

THE ÜBIQUITOUS BLACKBERRY.

CONTROL BY AN INSECT.

Darners whose lands have become overrun with the death-defying blackberry will be particularly interested m an article published by Mr A. H. Cockayne, Government Biologist which article gives a ray of hope to those who have for years been battling to keep the pest in check. Up till quite recently, says Mr Cockayne, the blackberry was singularly free from the attacks of any natural enemy that might be of value m its control. For a number of years past several parasitic fungi, notably orange rust (Caeoma nitens), .have been noted as occurring sporadically, but in no cases have their effects justified the opinion that any of them would prove efficacious as control agents. ~ During the past two years, however, a hitherto rare native moth, "Carposina adreptella," belonging to the Tortrix group, has been found attacking the young vshoots of the blackberry. The immense numbers in which this moth has been present, and the really effective .work that it has already accomplished, indicate that it may prove an exceedingly valuable agent in controlling the spread of the blackberry.

At first sight its mode of attack might lead one to think that its action would have but little permanent benefit. The eggs of the moth are laid in the leaf-bases of the young shoot or in the bud itself. The larvse, after hatching rapidly, penetrates the soft tissue, and bore through the pith for a distance of perhaps two inches. This is followed by the complete death of the terminal shoot. The blackberry spreads extensively by means of pendent branches, which, when they reach the ground, root and give rise to new plants. If a blackberry has the terminal portions of these branches destroyed before they reach the ground the power to spread vegetatively is entirely eliminated, and the plant remains small in size, and will not be able to coalesce with its neighbors and form a dense, close thicket. This is exactly what is occurring wherever "Carposina" has attacked the plants, and, moreover, affected plants appear to be losing their power of producing flowers and fruit to anything like the same extent as unaffected ones. Mr Cockayne believes that "Carposina" also attacks the young flower-buds before they expand, but this •is a point that has not been yet investigated. The extraordinary part of the work of "Carposina," and one hard to believe, is that this moth should for so many years occupy such an unimportant uosition in our fauna, and that within the space of two seasons it should become one of our commonest insects. The number of the larvze present on a single large blackberry bush is almost inconceivable, and Mr Cockayne has seen whole areas of this weed with nearly every terminal bud eaten out and destroyed. The distribution of the moth is very widespread, and in every district the Biologist examined the effects of its work have been most noticeable. If it continues to extend there is not the least doubt, he adds, that it will completely prevent the blackberry from spreading vegetatively. Present indications point to its causing a great diminution in the amount of seed produced.