The fruit-fly damage in the Upper Jordan Valley is limited to the southern belt of Citrus plantations ; further north the fly's activity remains, so far, restricted. There is a permanent fluctuation in the fruit-fly's population density according to ecological conditions, which may change from year to year. This fluctuation is of an irregular character. In years of severe infestation the damage attains 10–15 per cent. of the total crop ; there are seasons, however, when the damage is practically negligible. There is constant danger in the fruit-fly situation, because this fly is able within a short time to increase immensely its population density, if environmental conditions are suitable.

The number of hosts is relatively small in the Jordan Valley ; the Citrus plantations supply sufficient food during 7–8 months, and there is a relatively long summer quiescent period (about 2 months) with an extremely low fruit-fly population ; during the remaining period figs, grapes and other occasional plants serve as hosts.

The fruit-fly is spread chiefly by mechanical agents (wind and transport of infested fruits).

There are 8 generations during the year in the Jordan Valley.

There are two peak infestation periods (October and April-May) and two quiescent periods (winter and late summer).

Fruit-fly control under present cultural conditions should be confined to peak infestation periods only, as unfavourable climatic conditions are responsible for an extremely high mortality of fly later in the winter and in summer.