At this time of year we always have problems with these Fig Tree Beetles, Poneridia semipullata. which completely denude the trees in just a few days. The larvae and the adult beetles both cause damage and the groweth cycle of the trees is severely set back
One solution is to use a spray designed to destro lawn beetles. We prefer not to go down this road, but our tests with organic sprays such as detergent or garlic sprays are proving these to be very hit and miss, certainly not doing much to the adult beetle. This approach might prove effective on larvae, however this year we didn't spot the larvae early enough.
The fig trees are espaliered so at this this stage it seems that the best way is to brush the beetles off into a bag and squash them. Simple and very effective. Being espaliered trees we should also be able to spot emerging problems and take action before these issues become a problem. Regular attentiveness and an intimate familiarity with the seasonal cycle is essential.