# Spatial Dynamics of Olive Fruit Fly Adults in the Framework of a Monitoring Trap Network
## 4 Discussion  
Our experiment was designed to highlight what happens to the part of the population that is not caught by the baited traps that are set according to the indications provided for routinely monitoring activity. We focused our experiment on the critical period of the year when infestation can be a disaster for olive production and wet traps with trophic attractants, such as McPhail traps, are shown to be less efficient in the monitoring of flies [15]. Some differences among countries are related to the length of the period covered by the experiment, spanning from 40 days in Greece and Tunisia to 90 days in Lebanon, and are mainly related to the different levels of the sampled population, which influenced the presence of adults in the field at different periods of time. The yellow sticky panels, which we used in our experiment, have been previously employed as monitoring traps in several countries [11; 23; 24] and as smart devices [18; 25]. When activated with ammonium carbonate, they provided similar catch levels that were found in recent comparison tests with McPhail traps, which have long been considered the reference trap for _B. oleae_[26]; however, when not activated, the performance was significantly worse than McPhail traps [15] due to short-range attraction. Yellow sticky panels have been selected in our experiment because they can be used with or without an attractant substance. In this second case (UT), only visual cues acted in attracting flies, shortening the range of attractivity by sampling flies almost only to the tree they are applied to [27], making it possible to deploy a denser grid of UTs in between BTs. From this point of view, although the density of UTs was high, interference was minimal, because we respected a distance of at least 20 m. In addition, visual traps are not affected by temperature and humidity and attract both sexes, resulting in a more accurate sampling of the host tree population [27]. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Site** & \multicolumn{4}{c}{**Infestation**} & **Fruit Load** \\ \hline  & 17 Oct & 2 Nov & & & \\ \hline
**Greece** & 0.23 \(\pm\) 0.03 & 0.23 \(\pm\) 0.03 & & & 35.58 \(\pm\) 4.93 \\ \hline  & 23 Sep & 28 Oct & & & \\ \hline
**Italy** & 0.2 \(\pm\) 0.03 & 1.8 \(\pm\) 0.52 & & & 61.79 \(\pm\) 11.68 \\ \hline  & 29 Ago & 12 Sep & 26 Sep & 10 Oct & 24 Oct & 7 Nov & \\ \hline
**Lebanon** & 1.3 \(\pm\) 1.8 & 1.5 \(\pm\) 2.5 & 0.8 \(\pm\) 2.2 & 1.16 \(\pm\) 2.5 & 0.71 \(\pm\) 2.11 & 6.7 \(\pm\) 17.1 & 62.33 \(\pm\) 18.7 \\ \hline  & 21 Sep & 8 Oct & 22 Oct & 5 Nov & 19 Nov & \\ \hline
**Spain** & 2.2 \(\pm\) 0.49 & 4.0 \(\pm\) 0.93 & 9.9 \(\pm\) 1.66 & 18.4 \(\pm\) 2.21 & 28.3 \(\pm\) 2.29 & 23.9 \(\pm\) 0.72 \\ \hline  & 27 Jun & 4 Jul & 11 Jul & 28 Jul & \\ \hline
**Tunisia** & 1.5 \(\pm\) 1.91 & 1 \(\pm\) 1.15 & 0 \(\pm\) 0 & 0 \(\pm\) 0 & & 65.45 \(\pm\) 16.93 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Active infestation (%) and final fruit load, expressed as mean\(\pm\) SE, recorded in the five experimental sites. In our experiment, the few BTs that were used turned out to be aggregation hot spots in the maps, as was to be expected, considering the greater attractivity of BTs compared to UTs. Our results clearly showed that BT and UT adult and female captures per sampling date were found to be correlated for Spain and Lebanon but not in the cases of Greece, Italy and Tunisia. These consistent results indicate that when the population has been established and new adults emerge within the grove due to the larval population, such as in Spain and Lebanon, then more similar numbers in BTs and UTs are recorded; however, without damage, i.e., in Italy, Greece or Tunisia, the adults that enter the grove or are flying in the grove are actively looking for food and may be more attracted to the BTs.