Residues and Persistence of Neem Formulations on Strawberry after Field Treatment

Abstract

Azadirachtoids were determined by liquid chromatography/mass spectrometry (LC/MS) in five methanolic seed extracts of the neem tree and in a commercial formulation. On average, seed extracts contain azadirachtin A (10.9%), azadirachtin B (3.5%), nimbin (10.4%), and large quantities of salannin (19.0%). The composition of the commercial formulations may present different azadirachtoids contents depending on the natural extracts used in the preparation. Because these compounds may also show insecticide activity, the efficacy on field of these formulations may be very different. Photodegradation of pure azadirachtoids was also studied. Azadirachtins and related compounds are very sensitive to sunlight, degrading rapidly, with half-lives of the order of 11.3 h for azadirachtin A and 5.5 h for azadirachtin B and few minutes for the other limonoids compounds studied. The residues of azadirachtins and the main constituents, e.g., salannin, nimbin, deacetylnimbin, and deacetylsalannin, of the neem seed extract were determined on strawberries after field treatment using two different formulations. This residue study on strawberry was carried out to assess not only the azadirachtin content but also the main azadirachtoids contents. Three days after field application at five times the dose recommended by the manufacturer, residues of azadirachtin A and B were 0.03 and 0.01 mg/kg, respectively, while residues of salannin (LOQ 0.01 mg/kg) and nimbin (LOQ 0.5 mg/kg) were not detectable.

Evaluation of neem-based nanoformulations as alternative to control fall armyworm

“…This occurs because azadirachtin and related compounds undergo very rapid degradation. Caboni et al (2006) extracted some limonoids from methanolic extracts of neem seeds and exposed them to sunlight; the halflives calculated for azadirachtin, 3-tigloylazadirachtol, nimbin and salanin were 11.34, 5.52, 0.30 and 0.09 hours, respectively. Our bioassays showed that the effect of neem was neither maintained nor increased over time with nanoformulations.…”

Azadirachtin on Oligonychus yothersi in yerba mate Ilex paraguariensis

“…In addition, the action of neem products decreases with time, which is attributed to environmental factors mainly temperature, sunlight UV radiation and rain (CABONI et al, 2006;BERNARDI et al, 2012;SCHLESENER et al, 2012). The short residual action of the product should be compensated with reapplication at 7 days intervals (CABONI et al, 2006;BERNARDI et al, 2012), which was also observed for the yerba mate crop.…”

Efeitos do nim sobre tetranychus urticae Koch (Acari: Tetranychidae) e os predadores Phytoseiulus macropilis (Banks) e Neoseiulus californicus (Mcgregor) (Acari: Phytoseiidae)

“…Entretanto, EFEITOS DO NIM SOBRE Tetranychus urticae KOCH (ACARI: TETRANYCHIDAE)... existem outras substâncias presentes no óleo de nim que causam efeitos importantes para a regulação da população, como é o caso dos terpenos nimbina e salanina. Esses dois compostos também são responsáveis pela diminuição na fecundidade, repelência e esterilidade dos ovos (CARBONI et al, 2006). Persistência biológica sobre T. urticae Nas avaliações de 0; 24 e 48h, com transferências de T. urticae em 0; 24 e 48 HAP, foram verificadas diferenças significativas do produto Azamax ® (0,5 e 1,0%) em relação à testemunha.…”

“…De acordo com Carboni et al (2006), essa rápida degradação pode ser consequência da fotodegradação e da temperatura. As azadiractinas A e B, expostas ao sol, degradam em aproximadamente 11,34 e 5,52 h, respectivamente.…”

“…Porém, com a adição de estabilizantes nas formulações, pode-se aumentar o tempo de persistência do produto a campo. Carboni et al (2006) testaram duas formulações à base de nim. A formulação "A" apresentou um decréscimo de mais de 60% de azadiractina A em frutos colhidos, somente no primeiro dia após a pulverização.…”