The miticidal activity of silver nanoparticles towards date palm mite (Oligonychus afrasiaticus (McGregor)): efficacy, selectivity, and risk assessment / A atividade miticida de nanopartículas de prata sobre o ácaro da palmeira, Oligonychus afrasiaticus (McGregor): eficácia, seletividade e avaliação de risco

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.

Bioatividades promissoras de nanopartículas de prata (SNPs) incitaram pesquisadores de diferentes especialidades a avaliar suas atividades em campo. A bioatividade contra pragas agrícolas foi objeto de publicações limitadas. No presente estudo, SNPs foram sintetizadas, e a atividade miticida foi avaliada em relação ao ácaro Oligonychus afrasiaticus (McGregor) (Acari: Tetranychidae) e um ácaro predador associado, Neoseiulus barkeri Hughes (Phytoseiidae). Em condições de laboratório, SNP apresentou atividade significativamente maior para O. afrasiaticus (LC50 foi de 39,7 µg/mL) do que N. barkeri (LC50 foi de 1.587,9 µg/mL), o que representa cerca de 40 vezes de seletividade contra a praga. O SNP exibiu atividade ovicida contra ovos postos de O. afrasiaticus (LC50 foi de 67,8 µg/mL). Em campo, o SNP (a 216 µg/mL) alcançou eficiência ligeiramente maior do que em estudo de laboratório; 86,5% de redução populacional de O. afrasiaticus foram alcançados e apenas 18,5% da população de N. barkeri foram afetados. O SNP suprimiu a eclosão de 57,1% dos ovos postos de O. afrasiaticus. Os resíduos de prata foram determinados usando espectrometria ICP-OES. Os resíduos iniciais atingiram 1,83 µg/mL após a aplicação e depois diminuíram com o passar do tempo. A ingestão diária estimada (IDE) atingiu 1,28 µg/kg/dia, calculada para os maiores resíduos obtidos e a maior taxa de consumo de tâmaras do mundo. O índice de risco (Hi) foi de 0,17 em média. O nível de resíduos obtido mostrou-se seguro em termos de referências de toxicidade aguda e crônica.

The miticidal activity of silver nanoparticles towards date palm mite (Oligonychus afrasiaticus (McGregor)): efficacy, selectivity, and risk assessment.

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.