Olive Fruit Fly - Environmental Needs

Environmental Needs

The development cycle is closely linked to environmental conditions, in particular the climate and the state of the olives. Knowing these parameters, together with the monitoring of the population, is needed to implement effective pest management programs.

The climate influences the cycle, especially with the temperature and less humidity. The duration of each stage is summarized below:

The duration of young larva therefore varies from a minimum of 20 days to a maximum of 5 months in the overwintering generation.

Temperature has an important role on the viability and rhythms of reproduction. Temperatures above 30°C cause resorption of ovarian follicles by reducing the fecundity of females; a female lays two to four eggs on average per day in summer and 10-20 eggs in autumn. Persistent temperatures above 32°C for several hours a day also cause mortality of over 80% of the eggs and larvae of that age.

Low temperatures, therefore, have very limited effects because its activity is undermined by temperatures below 0°C. Given ordinary climatic conditions, low temperatures and harsh winters clearly interfere with population dynamics only in the northernmost areas of olive vegetation.

In general, the optimum temperatures for oviposition and larval development are between 20 and 30°C, together with a need for humid weather.

The second controlling environmental factor is the obvious characteristics of the olives and the phenological stage of the plant. Females receive sensory stimuli to denote the degree of receptivity of the olive, a phenomenon that allows them to choose the olive; before oviposition, the female first “analyses” the size, colour and odour and, it seems, the presence of certain bacterial species. They are especially frequent in summer, caused by the females with a sterile puncture to test the receptivity of the olive. The ethology of the fly has been paid particularly regard in recent years when analysing study control methods based on the use of prior insect repellents (copper, kaolin, etc.).

Larval development is instead influenced by the consistency of the pulp and especially the size of drupe. In table olives, in fact, mortality of the larva is lower in summer because they can escape the lethal effects of high temperatures by migrating deeper. The consistency of the pulp is instead an intrinsic characteristic. Not even susceptibility of olive fruit fly attacks make much difference according to cultivar.