A Preliminary Survey of Olive Grove in Biskra (Southeast Algeria) Reveals a High Diversity of Thrips and New Records

SIMPLE SUMMARY: The diversity of thrips from olive trees in Algeria is unknown. According to the Ministry of Agriculture, thrip species have caused economic damage to the olive yield in the region of Biskra throughout the history of this crop, although the thrips pest species was unknown. To solve this question, we studied the thrips composition of one olive orchard over three years and the seasonal abundance of the species responsible of the damage of the olives in relation to the phenologic development of the olive tree ABSTRACT: This study was conducted to determine Thysanoptera species composition associated with olive trees, fruit injury, fluctuations in the abundance of the most phytophagous species relative to the phenological stages of the olive tree, and the temporal variations in the species Neohydatothrips amygdali in relation to environmental variations in Biskra province between 2018 and 2020. The olive orchard chosen for this study is located at the Experimental Station of the Technical Institute for the Development of Saharan Agriculture (ITDAS) in El Outaya (Biskra, a Saharan region of Algeria). Five trees were sampled each week, and thrips were collected by shaking 20 twigs (4 twigs per tree). Identification of thrips species was based on morphological characters of adults. Microscopic observation of the collected thrips specimens made it possible to report nine thrips species. Among them, four are reported for the first time in Algeria. Three taxa, namely Haplothrips tritici, Neohydatothrips amygdali, and Frankliniella occidentalis constituted the eudominant groups, representing 28.65%, 27.98%, and 23.39% of total specimens collected during the study, respectively. Thrips injury appeared as scaring and silvering of the fruit. The most abundant species was H. tritici, but N. amygdali was most common in the last two years of the survey. The influence of phenological stages of olive trees on the total number of H. tritici and F. occidentalis was significant. The highest numbers were recorded in flowering stage. The highest number of N. amygdali had two peaks: April (2020) and May (2018, 2019), as well as September (2020) and October (2018, 2019), when temperatures fluctuated between 20 °C and 30 °C. N. amygdali was totally absent during the other months (in winter and summer). During the three years of investigation, N. amygdali reproduced by thelytoky, with only females present.