Detection of adaptive genetic diversity and chemical composition in date palm cultivars and their implications in controlling red palm weevil, Rhynchophorus ferrugineus Oliver.

This study, about RPW and date palms, is under the scope of date palm bioecology and nutrition (nutritional ecology) which includes the integration of several areas of research such as date palm biochemistry, genetics, and RPW infestation behavior through various date palm cultivars. Date palm (Phoenix dactylifera L.; Arecaceae) production is under threat from the red palm weevil (RPW), Rhynchophorus ferrugineus Oliver. A better understanding of genetic diversity within date palm cultivars can be useful for its implementation within the insect IPM program in the future. Three indices, namely simple-sequence repeats (SSR) markers to elucidate genetic diversity, chemical components, and a natural infestation index of RPW, were used to evaluate the resistant or susceptible date palm cultivars in Qassim. Based on a field survey of RPW infestation within 79 date palm farms involving 11 cultivars at Qassim, the sensitivity and resistance cultivars were determined. The resistant date palm cultivars were Nabtat Ali, Shakrah, red Sukary, and um Kobar which had the lowest degree of RPW abundance %. Values of the essential minerals, nitrogen, phosphorus, potassium, and calcium within the date palm cultivars were also estimated. RPW abundance % was negatively correlated with the calcium content of date palm cultivars. The principal component analysis (PCA) revealed that the calcium content and RPW abundance % were highly affected by the cultivars. SSR markers of the date palm cluster tree divided genotypes into two main groups at similarity coefficients between 0.56 and 0.91. The 1st group included; Nabtet Ali, Red Sukary, Um Kobar, and Shakrah with similarity coefficients between 0.56, this group was the most resistant cultivars. Therefore, SSR markers were able to characterize and resolve genetic diversity in date palm cultivars for RPW resistance. When SSR markers coupled with higher calcium (Ca) content can efficiently replace indices in characterizing resistant date-palm genotypes with a high confidence level. Integration between date palm genetic diversity, chemical structures, and RPW infestations rates promoted the understanding of the interplay between the diversity of RPW management (short-time scale), and the resistance genes, plant nutrition, and dynamics of the diversity of RPW through domestication and diversification (long-timescale). Therefore, our results may lead to a change in RPW control strategies by switching to using safe alternative pesticide control methods (Resistant cultivars of date palm), which are underestimated and may reveal the impact of low-cost, but highly effective agricultural practices in the field of date production in the world. Understanding the genetic structure and calcium content of date palm cultivars mechanisms could help to predict date palm resistance against RPW populations in the new IPM strategy in RPW control.

Monitoring of infestation percentages of the invasive red palm weevil, Rhynchophorus ferrugineus (Coleoptera: Curculionidae), and management tactics: a six-year study.

Red palm weevil (RPW), Rhynchophorus ferrugineus (Olivier) (Coleoptera, Curculionidae), is a devastating invasive pest, that invaded Saudi Arabia's date palms in 1987. Evaluation of the infestations and the efficacy of both preventative and control treatments have been studied from 2015- 2020 in Qassim. The results indicated that the number of infested date palms varied according to the years and locations. The infested date palm trees percentage was relatively high in 2016 (2.24%) and 2017 (3.19%), then gradually decreased to reach its lowest in 2020 (0.73%) due to the management protocol applied by the Ministry of Environment, Water, and Agriculture. Furthermore, the infested palm trees' percentage varied among the eight study locations, reaching the highest percentage in location G (SA7) with a general average of 4.31%. While in the other locations, the general infested percentage average was very low when compared to location G (SA7) with 1.21 and 0.47% in locations A (SA1) and H (SA8), respectively. The effectiveness of control methods increased sharply from 52.141% in 2015 to 90.0% in 2020 with a general average of 72.73%. The quarantine and management protocols of R. ferruginous applied in Qassim decreased the number of palm infestations. Contrary, the intensive use of insecticide in the last two decades promoted genetic mutations within the Rhynchophorus, which led to the emergence of a new species R. bilineatus. This leads to increase pesticide pollution, and control costs and the insect becomes more resistant to pesticides.