Import to help control gorse

Press, 7 February 1986, Page 18

Import to help control gorse

By

OLIVER RIDDELL

An immigrant may soon be “invited” into New Zealand to help control gorse. It would be studied first at a quarantine station to ensure it would do the job set out for it.

Gorse flourishes over much of the country, but particularly on the marginal hill-country which is expensive to keep in production and where farmers have been hardest hit by the recession in meat prices without many options for diversification. Millions of dollars are spent every year on trying to control gorse This has only mixed success because of its extreme vigour and its ability to compete wUh other Plants. Because of increasing costs of rnntrol. the entomology division of tfce D.S.I.R- has been

ing a programme aimed at biological control of gorse. About 10 insects that could act as control agents have been identified and extensive tests of three of these are now nearly completed. The D.S.I.R. acknowledges that it is not possible to predict the degree of control which any mite could achieve if introduced, but it hopes' that any introduction would be at least partially successful — either by thinning the density of stands or controlling gorse in certain conditions. One important result would be to reduce the amount of herbicide spread — particularly 2,4,5T. Application of this costs millions of dollars a year fsnd

creates problems of spray drift into gardens and crops, as well as affecting animals and people. It contains the contaminant dioxin and New Zealand is the only country in the world where it is still made. There are two other points in any gorse eradication programme by mites:— 1. Imported insects have not evolved with New Zealand plants and have not had the chance to interact with them.

2. Throughout much of the country gorse canopies provide the environment for native bush to regenerate. The Nature Conservation , Council wants an environmental S

impact assessment before insects are introduced, specifically on possible inter-actions with native plants. Also, gorse establishes itself quickly on unstable, eroded, or burned hillsides. It has had an important role in preventing erosion, giving stability, and also improving the quality of the soil. If effective biological control were not followed quickly by regeneration of shrubs and trees, then the loss of the gorse would have major effects on soil stability and water protection.

Bees use gorse as an early-

season source of pollen. Reducing gorse flowering in some parts of the country would be significant for some apiarists. The .implications of biological control g-of gorse are wide-reaching.