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This study was carried out to determine the lethal effect of the entomopathogenic fungi, Beauveria bassaina Vuell. on eggs, young and old nymphs of the whitefly, Bemisia tabaci Genn. Mortality percentage was significantly differed based on stage of B. tabaci and conidial concentrations of B. bassina. Average of the infection level to insect was very low particularly in eggs with only 4.49%, even with higher conidial concentrations (6 x 10(6) conidia mL(-1)). Whereas, it was higher with 1st and 2nd instars (42.045%) and 3rd and 4th instars (35.93%). Three parameters was assessed with B. tabaci eggs, namely; egg infection, egg hatchability and crawlers emergence. Egg mortality percentages averaged 1.2, 4.27 and 8.0% with fungal concentration 2 x 10(6), 4 x 10(6) and 6 x 10(6) conidia mL(-1), respectively. Daily infection percentages were varied depend upon the conidial concentration where the highest infection rate of eggs was occurred with 6 x 10(6), followed by 4 x 10(6) conidia mL(-1). Egg hatch was very high, while the mortality among the emerged crawlers was neglectable compared with the check. Efficiency of B. bassaina on whitefly nymphs also was varied based on the insect instar and fungal concentration. Mortality percentages were obviously higher to young nymphs (1st and 2nd instars) than to older ones (3rd and 4th instars). The results indicated that nymphs were highly susceptible to fungal treatment compared with eggs. Additionally, pathogenicity and virulence of B. bassaina against B. tabaci immatures was not indicated by LC50 only, but also, by the time in days (LT50) required to achieve 50% mortality of an insect.

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.

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Promising bioactivities of silver nanoparticles SNP urged researchers of different specialties to evaluate their field-respective activities. Bioactivity towards agricultural pests were the subject of limited publications. In the current study, SNP were synthesized and miticidal activity was evaluated towards old world date mite Oligonychus afrasiaticus (McGregor) (Acari: Tetranychidae) and an associated predatory mite Neoseiulus barkeri Hughes (Phytoseiidae). Under laboratory conditions, SNP displayed significantly higher activity towards O. afrasiaticus (LC50 was 39.7 µg/mL) than N. barkeri (LC50 was 1587.9 µg/mL) which accounts for about 40 folds of selectivity against the pest. SNP exhibited ovicidal activity against laid eggs of O. afrasiaticus (LC50 was 67.8 µg/mL). In field, SNP (at 216 µg/mL) achieved slightly higher efficiency than in laboratory study, 86.5% of population reduction of O. afrasiaticus was achieved and only 18.5% of N. barkeri population was affected. SNP suppressed hatching of 57.1% of laid eggs of O. afrasiaticus. Residues of silver were determined using ICP-OES spectrometry. Initial residues reached 1.83 µg/mL after application then declined with time passing. Estimated daily intake (EDI) reached 1.28 µg/kg/day, calculated for the highest residues obtained and the highest consumption rate of date in the world. Hazard index (Hi) was 0.17 in average. The obtained level of residues appeared to be safe in terms of acute and chronic toxicity references.

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The date palm fruit stalk borer, Oryctes elegans, is widely distributed in Saudi Arabia. Undetected and untreated infestations by this pest result in severe losses. Light trap studies to investigate seasonal population fluctuations of O. elegans were conducted in Al-Rajhi Endowment date palm plantation in Al-Qassim, Saudi Arabia, by installing three modified Robinson mercury-vapor light traps in 3 different equidistant sites. The investigation revealed that light trapping is an effective tool for the monitoring and forecasting of O. elegans infestations. The highest activity of O. elegans was witnessed from April to July, during which period 65% of adults captures were made. Peak monthly activity was observed during June, when 19.4 % and 22.2% of the catches were made during 2003 and 2004, respectively. No beetle activity was observed during January and February. The highest number of beetles (56.6% of the population) was recovered in the site with relatively old and tall palms (more than 18 years old and averaging 7.5m in height). The site with shorter and younger palms received 29.6% of the beetles, whereas the uncultivated site had the lowest number of beetles (13.8% of total).