Study suggests excess nitrogen contributes to insecticide resistance

Chinese researchers point out that excessive application of nitrogen (N) fertilizer to corn plantations increases the tolerance of corn larvae. Spodoptera litura to multiple insecticides. The work relates the high concentration of the macronutrient to the increased activity of detoxification enzymes in the larvae and the thickening of their cuticle, contributing to greater resistance to chemical products.

According to an article published by the scientists, their bioassays indicate that the application of high levels of N to corn plants significantly increased the tolerance of corn larvae. Spodoptera litura to insecticides such as methomyl, lambda-cyhalothrin and chlorpyrifos. The activity of detoxification enzymes, such as GST, CarE and P450, was significantly higher in larvae fed on corn plants with high N concentration.

RNA-seq analysis showed that several genes related to GST and cuticle were induced in larvae fed with high-N corn. RT-qPCR analysis confirmed the induction of four GST genes and the cuticle-specific gene LCP167. Furthermore, injection of dsRNA specific for GSTe1, GSTs5, and LCP167 increased mortality of methomyl-treated larvae by about threefold compared to dsGFP-injected larvae.

Furthermore, electron microscope observations revealed that the cuticle of larvae fed high-N corn was thicker. These results suggest that excessive use of nitrogen fertilizer intensifies insecticide resistance in lepidopteran pests.

It is important to remember that nitrogen, in correct doses, is essential for the metabolism and development of plants.

The work was developed by researchers Jie Wang, Zhihui Lu, Lin Hu, Runbin Zhong, Cuicui Xu, Yurui Yang, Rensen Zeng, Yuanyuan Song and Zhongxiang Sun.

His article can be read at doi.org/10.1016/j.pestbp.2024.106002