You haven't said how old it is and where planted etc. But in general principle, when you plant a new cane, ideally in the autumn or early winter, you cut it right down, so that it will produce new canes the next year. These are the ones that grow and produce fruit. Some people even stop the first canes producing fruit so that the plant will grow more vigorous. After that, you cut down canes immediately after fruiting which allows the new canes formed each season to ripen and mature. (For summer raspberries).
With autumn raspberries, you cut the old canes which fruited the previous autumn, the next spring. Then the new canes which grow that year produce fruit in the autumn.
Do you mean that something is eating or destroying your canes? Or did you want advice about how to cut them?
If the latter, you cut them as low to the ground as possible. If your plant was put in last autumn, there should be several new green canes now which you leave to ripen and fruit next year. (summer varieties)

I bought and planted it Oct 2009 ,planted in full sun,The canes were short,now longer green and producing fruit,shall i cut them in Oct?.

Not quite sure I understand. Have they produced fruit at all this year, apart from the one fruit you said in the question? If the canes growing now are the ones which have just grown since the spring, then leave them. Cut out any canes which grew last year and you kept through the winter. The old canes should have dark green or brown stems where they have ripened while the new canes should be green.
If the green canes which have just grown start fruiting in late summer and early autumn, then you have autumn raspberries. If they don't, leave the green canes in place over winter and they will fruit next summer.

It is fruiting now,shall ileave this new growth on the plant over winter? thanks.

The new growth should come up from the ground next to the current fruiting plant. These are the new canes you keep and you cut down the ones which have fruited.

Thank you Bertie.