This is not usually the case. However, it is possible that the insect diapausing at some stage and at onset of suitable conditions, population build-up takes up. Thus the outbreaks in in patches and limited area first and then spreads in subsequent generations. This happens in many other forest insect pests. However, details of the insect pest will help in further discussions. 

Many tree feeding Lepidoptera lay their eggs in batches; these egg batches as subject to attacks by egg parasites (usually wasps and flies); when populations of these parasites fail locally, usually due to some local reason in a small area, larvae from most of the Lepidoptera eggs emerge and an outbreak begins; If they manage to reach adulthood and the egg parasite populations have still not recovered, the next generation begins to spread and then you have a population outbreak.

Of course, there are other reasons for outbreaks, but this is one of the potential scenarios. it might help to know the species you are referring to.

Dear Peter,

This might explain the initial stages of outbreaks of insect defoliators in eucalyptus plantations in Brazil.

Regards,

José Zanuncio