Toxic effect of commercial formulations of neem oil, Azadirachta indica A. Juss., in pupae and adults of the sugarcane borer, Diatraea saccharalis F. (Lepidoptera: Crambidae)

ABSTRACT: To evaluate the toxic effect of commercial formulations of neem oil, Azadirachta indica A. Juss, pre-pupae (PP), young pupae (YP) and old pupae (OP) of Diatraea saccharalis F. (Lepidoptera: Crambidae) were sprayed with the diluted extract in distilled water at concentrations of 0.0, 0.3, 0.5, 1.0 and 2.0%. The neem extract caused concentration-dependent effects on mortality of pupae, and the pupae that failed to emerge in adults had multiple abnormalities. The longevity of pupae that emerged in adults (YP and OP group) did not differ from the control group. The abnormalities found in adults were related to mortality in all treatments, except at the concentration of 1.0%. Fertility was assessed according to the oviposition of adult females from the YP group that showed no abnormalities, through the evaluation of the number of deposited eggs and the rate of undeveloped eggs. The results showed a reduction in the number of eggs laid and an increase in the percentage of undeveloped eggs. These results show that neem oil has a high potential to control the toughest stage of the sugarcane borer and also reduces the further development. Therefore, commercial formulations of neem oil have a toxic effect on pupae and adults of D. saccharalis.

摘要：为评估印楝（Azadirachta indica A. Juss）油商品制剂的毒性效应，本实验以蒸馏水将印楝提取物稀释为0.0%、0.3%、0.5%、1.0%及2.0%的浓度梯度，对甘蔗螟虫（Diatraea saccharalis F.，鳞翅目：螟蛾科）的预蛹（pre-pupae, PP）、初蛹（young pupae, YP）及老熟蛹（old pupae, OP）进行喷雾处理。印楝提取物对蛹的死亡率表现出浓度依赖性效应，未成功羽化为成虫的蛹存在多种畸形表型。成功羽化为成虫的初蛹组与老熟蛹组成虫的寿命与对照组无显著差异。除1.0%浓度组外，各处理组中成虫出现的畸形均与死亡率相关。针对无畸形表型的初蛹组雌成虫，本实验通过统计其产卵量与未发育卵占比评估其繁殖力，结果显示其产卵量显著降低，未发育卵占比显著升高。上述结果表明，印楝油可有效防控甘蔗螟虫最难防控的虫态，同时抑制其后续生长发育。综上，印楝油商品制剂对甘蔗螟虫的蛹及成虫阶段均具有毒性效应。