Persistence and dissipation kinetics of trifloxystrobin and tebuconazole in onion and soil

The persistence and dissipation kinetics of trifloxystrobin and tebuconazole on onion were studied after application of their combination formulation at a standard and double dose of 75 + 150 and 150 + 300 g a.i. ha^?1. The fungicides were extracted with acetone, cleaned-up using activated charcoal (trifloxystrobin) and neutral alumina (tebuconazole). Analysis was carried out by gas chromatograph (GC) and confirmed by gas chromatograph mass spectrometry (GC-MS). The recovery was above 80% and limit of quantification (LOQ) 0.05 mg kg^?1 for both fungicides. Initial residue deposits of trifloxystrobin were 0.68 and 1.01 mg kg^?1 and tebuconazole 0.673 and 1.95 mg kg^?1 from standard and double dose treatments, respectively. Dissipation of the fungicides followed first-order kinetics and the half life of degradation was 6–6.6 days. Matured onion bulb (and field soil) harvested after 30 days was free from fungicide residues. These findings suggest recommended safe pre-harvest interval (PHI) of 14 and 25 days for spring onion consumption after treatment of Nativo 75 WG at the standard and double doses, respectively. Matured onion bulbs at harvest were free from fungicide residues.     

Simultaneous detection and degradation patterns of kresoxim-methyl and trifloxystrobin residues in citrus fruits by HPLC combined with QuEChERS

This study aimed to investigate the residues, kinetics and dissipation patterns of kresoxim-methyl, (E)-methoxyimino[α-(o-tolyloxy)-o-tolyl]acetate, and trifloxystrobin, methyl(E)-methoxyimino-{(E)-α[1-(α,α,α-trifluoro-m-tolyl)ethylideneaminooxy]-o-tolyl}acetate”. A simple and sensitive liquid chromatography-ultraviolet detection (LC-UV) method combined with the ‘Quick Easy Cheap Effective Rugged and Safe' (QuEChERS) protocol was developed to quantify the levels of kresoxim-methyl and trifloxystrobin residues in citrus. More than 97% of the kresoxim-methyl and trifloxystrobin deposists gradually dissipated from the citrus peels within 15 days. The half-lives of kresoxim-methyl and trifloxystrobin in the peels were in the ranges of 2.63–2.66 d and 3.12–3.15 d, respectively, and the pattern of decline in the peels followed first-order kinetics. The kresoxim-methyl and trifloxystrobin residues in the pulp dissipated below the detectable level of 0.01 mg kg^?1 after 9 days. Kresoxim-methyl and trifloxystrobin were easily decomposed (T_1/2 < 30 d), and the observed dissipation patterns could support the application of these two fungicides in the postharvest storage of citrus fruits.     

肟菌酯对环境生物急性毒性及安全性评价

本试验通过研究肟菌酯对10种环境生物急性毒性效应,以期评价其对环境生物的毒性风险。结果表明,肟菌酯对日本鹌鹑(Coturnix coturnix japonica)的经口毒性7 d-LD50和短期饲喂毒性8 d-LC50分别大于2.00×103mg a.i.·kg-1bw和5.00×103mg a.i.·kg-1饲料,意大利蜜蜂(Apis mellifera L.)接触与经口毒性48 h-LD50分别为大于100μg a.i.·蜂-1和95.3μg a.i.·蜂-1,家蚕(Bombyx mori)96 h-LC50为1.61×103mg a.i.·L-1,蚯蚓(Eisenia foetida)14 d-LC50大于100 mg a.i.·kg-1干土,赤眼蜂(Trichogramma japonicum)24 h-LR50为0.337μg a.i.·cm-2,羊角月牙藻(Pseudokirchneriella subcapitata)72 h-EC50为5.80×10-3mg a.i.·L-1,大型溞(Daphnia magna Straus)48 h-EC50为1.72×10-2mg a.i.·L-1,斑马鱼(Brachydanio rerio)96 h-LC50为5.40×10-2mg a.i.·L-1,非洲爪蟾(Xenopus laevis)蝌蚪96 h-LC50为8.95×10-2mg a.i.·L-1,土壤微生物28 d硝酸盐转化速率差异小于25%。因此,根据《化学农药环境安全评价试验准则》毒性等级划分标准,肟菌酯对鸟、蜜蜂、家蚕、蚯蚓等陆生生物为低毒,对水生生物的绿藻、大型溞、斑马鱼、非洲爪蟾蝌蚪均为高毒或剧毒,而对天敌赤眼蜂属高风险,故在田间使用过程中应采取措施降低其对水生生物以及天敌昆虫赤眼蜂急性毒性风险,以免造成危害。