Somewhat is already know about D.suzukii overwintering in invaded areas, but what about aestivation? In South Mediterranean areas trap captures usually disappear (or almost disappear) during summer months.
Where is the fly? Anyone has recorded local migrations or refuge areas as was reported for Lepidoptera?
What do you think? Thanks in advance
The conclusion we came to while monitoring for D. suzukii was that during the summer months, traps were not as attractive as the fruit that was readily available, giving the impression that the flies were not present (this was monitoring done in blueberry fields using apple cider vinegar; this may not be the case with other baits/lures that have proven to be more attractive).
Samantha, Konstantinos, thank very much for your opinions.
We are using both ACV and a more efficient commercial bait in our traps. During summer, in our sampling sites harvest is full, no fruits are available... it is expected that the bait works.
As you know summer migration from lower to higher localities was described in Japan for D.suzukii... but we don't have high altitude sites in our area (Southwesten Spain).
Our suspicion is that during summer such a type of local migrations can occur, and that humid habitats such as watercourses, streams... can act as refuge in the harsh conditons of the Andalusian summer. We would like to know if such a possibility has been considered elsewhere.
Captures in traps are resumed in the sampling sites from the end of summer (september onwards), once again no fruits are available.
In Oregon where our sampling occurred, fruit was present both in the field and in the bordering vegetation (wild blackberries). However, we were able to correlate higher trap numbers with higher humidity levels when we did have fly captures. It is certainly possible they are migrating to microclimates that are more optimal to their survival.
Similarly to Samantha's comment we got higher catches in rainy summer of 2014 compared to dry summer of 2015, when the population build up occurred late in summer/early autumn. However, perhaps also the greater availability of rotting fruit and harvest leftovers in early autumn are connected to the fly's late population build up.
We got usually very dry summers. The resources for feeding and breeding are limited, and concentrate in wet habitat patches (ravines, temporary watercourses, etc.). A common plant in these places is the bramble (R.ulmifolius).D.suzukii uses this plant as host. Thus, it's possible that these patches work as "cores" for the dispersion, and the build up of population during the autumm. Would be applicable the metapopulation concept to the D.suzukii population dynamics?
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