PEST WEEDS

Manawatu Herald, Volume XLVIII, Issue 3594, 3 February 1927, Page 4

PEST WEEDS

METHODS OF CONTROL

“As a result of my studies and inquiries in American and Europe I feel able to state definitely that there is a very good prospect of either partial or complete control of a number of pest weeds in New Zealand without exposing the country to any serious danger in other directions.” ! The above statement was made by Dr. A. Tillyard, biologist of the Cawthron Institute, Nelson, in the course of his report to the Government on the result of his observations and researches abroad bn the subject of noxious weeds and the problem of controlling them. THE BLACKBERRY.

Dr. Tillyard recommends the introduction of certain European and North American beetles which attack the blackberry. As he has not been able to find any insect so far which was effective in attacking the flowers and fruit, the main weight of the attack must therefore be directed towards the destruction of the crowns and stems, with a subsidiary attack on the food supply of the plant by the destruction of the leaves. He pointed out that insect control of the blackberry earned with it also a menace to the raspberry unless a certain amount of watchfulness was exercised. GORGE.

The problem ic'onf routing Dr. Tillyard in the discovery of some method of preventing the seeding of gorso (thereby controlling it) without killing the plant was a special one. An insect Which would eat out the pods without previously destroying the blossom was highly desirable'. Such insects occurred in many areas in England, chiefly on the commons. He therefore recommended the introduction from England of the apion ulieis, a tiny weevil doing much damage, but whose larva fed inside the green pod and destroyed a very large percentage of the seeds. In-his opinion this one insect should suffice for the complete control of gorse in New Zealand. RAGWORT.

Although there were insects which attacked ragwort vigorously and to a large extent successfully in England, some difficulty was likely to be encountered in acclimatising them in the Dominion. FOXGLOVE. Scarcely any insects were known to feed upon the foxglove, a very poisonous plant, which was likely to become a bad pest in hilly country in various parts of the Empire, including portions of New Zealand. A small moth, however, attacks the flowers, and the larva later bores into the seed capsule and prevents seeding to a large extent. Provisional permits have been issued for the introduction of these insects. CONVOLVULUS.

Although at present there seems to he no prospect of control of convolvulus (by general opinion of botanists in England and New Zealand, soon to become a very serious

menace) by means of insect enemies the subject is by no means exhausted. THE EARWIG. Dr. Tillyard was hopeful of controlling the earwig pest by the introduction of a parasitic fly from abroad. For the control of aphids on pine, spruce and oak,'an attempt was being made to introduce several species of green lacewings. One large consignment had already been received from Canada, and appeared likely to become acclimatised. HORNTAIL. The question of controlling horntail (which appeared to be rapidly spreading in New Zealand) by the introduction of parasitis insects in infected wood was discussed by Dr. Tillyard with Dr. Howard in America, with Danish entomologists, and with Professor Handlirsch, of Vienna, and may be put into practice during the next year or two.