testing factor effects in glm

Dear All,

I'm using a glm to analyse the effect of year on a 
variable with poisson distribution. Using the summary() I 
can test whether years are different from each other, but 
how can I test whether year has an overall effect on my 
respons variable? My guess is that by a Wald-test, but I 
don't know how exactly.

Could someone give me advice?

Many thanks,
Istvan