General Discussion

ANONYMOUS. Could you tell us more about the heat effect of the protective bands on the trunks of the plantings?

JOLLY. I believe in trials carried out by the Plant Materials Centre, tin sleeves were found to "cook" the live pole plantings and they simply would not grow.

WODZICKI. Are you looking for a species or variety of tree that would be very unpalatable to possums, that would show less damage from them?

JOLLY. I think the Plant Materials Centre has explored the ground very thoroughly. You need a pole 3 m high that will sprout from the top so that stock cannot reach the foliage. Also you need a plant that will strike easily in tough country from such a long pole. Your choice of suitable species is limited and you come back to poplars and willows every time. The alternative is to retire land and there is probably more retirement going on in North Island hill country now than there was in the past.

FITZGERALD. The Plant Physiology Division of DSIR have been working on meristematic tissue and have developed a polar strain highly resistent to Melampsora. Unfortunately it is highly palatable to possums. I gather they are going on to try and find a strain resistent to both possums and Melampsora.

WODZICKI. How does the frequency of damage by possums to plantings vary - have you considered the matter quantitatively?

JOLLY. Most of the poles were planted in mudstone country across the central and eastern part of the North Island - from Wanganui to the Rangitikei and Manawatu catchments, then north up the east coast from Wairarapa to East Coast-Poverty Bay. The damage has been pretty bad in all the catchment districts involved. It does vary locally, in that you tend to get less damage further away from normal possum habitats; conversely in Wairarapa tussock country, lacking in scrub or forest, we found significant damage despite low numbers of possums. There is also a seasonal component - spring is probably the main period of attack, after the leaf emergence.

WARD. You have mainly referred to poles. Does this mean the damage occurs only over the first 2 or 3 years, or is it only critical then? If you can nurse your pole through this early period of establishment can it then hold its own?

JOLLY. The damage is critical over the first three to four, possibly five, years but it continues in older trees too.

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BROCKIE. Dr Gibb has suggested it might be possible to incorporate a poison into a sticky glue and simply paint this in a band around a pole. As the animals climb up and down, the poison is transferred to the fur and when the possum later grooms itself the poison takes effect.

JOLLY. Yes, Dr Spurr also had the same idea. There is the prospect of applying 1080 as a gel onto the top of the pole above the height the stock can reach. I would like to do trials on this aspect.

COLEMAN. A suggestion that the N.Z. Forest Service use 1080 gel on the bark of some forest trees was turned down for on smooth-barked trees, at least, the life of the 1080 gel would be very short indeed.

ANONYMOUS. Would a band of sticky paper wrapped round the trunk be quite an effective deterrent?

JOLLY. The problem is it would have to cover every pole, which themselves cost $1.20 each now, so the catchment boards are not prepared to add to their labour costs unless satisfied it would be worthwhile. I think you need to draw the possums to a particular site and try and kill them there.

SPURR. The Plant Materials Centre has worked on repellents, ranging from rotting seaweed to mechanical devices, but so far they have turned out nothing really effective.