Effects of silicon application in corn on Spodoptera frugiperda (J. E. Smith).
Objective: To study the effects of feeding exogenous silicon-applied corn on the growth and development of Spodoptera frugiperda(J.E. Smith), and to explore the change of defense enzyme activity of S. frugiperda after feeding siliceous corn to provide a theoretical basis for the study of silicon application to improve plant resistance to pests. Method : Using S. frugiperda collected in Zhangzhou, Fujian as the research material, different concentrations of silicon fertilizer were applied to corn [(1)control(CK) group 0 g Si/kg soil,(2)5-time silicon treatment group(3.85 g Si/kg soil) and (3)10-time silicon treatment group(7.70 g Si/kg soil)]. First, observed the effects of silicon application on the growth and development of corn, and then larvae of the newly hatched S. frugiperda were put to the maize plants treated with different silicon treatments, and recorded the insect weight, body length, development period, pupation rate, pupa weight and emergence rate every 7 d after the larvae grew to the third instar, and used the kit to determine the superoxide dismutase (SOD), catalase (CAT) and polyphenol oxidase(PPO) in corn before and after being eaten by S. frugiperda. Result: Short-term application (21 d)of silicon increased the plant height and stem circumference of corn, and significantly promoted the growth of stem circumference of corn (P < 0.05, the same below). Feeding exogenous silicon application on corn affected the growth and development of S. frugiperda. The larval weight of 10-time silicon concentration on corn on the 21st day of the experiment was the lightest, only 0.2023 g, which was significantly lower than that of the CK, and the development period prolonged 26.02% compared with the CK, the emergence rate significantly decreased by 27.78%. The SOD, CAT and PPO activities in unfed corn plants were the highest treated by 10 times silicon application after corns were treated with different silicon concentrations. SOD and PPO activities were significantly higher than CK and 5-time silicon application,SOD, and CAT activity had no significant difference among the three treatments(P > 0.05, the same below). 24 h after the corn being fed, SOD activityamong the three treatments had no significant difference, but CAT and PPO activities in 10-time silicon application were the highest, and significantly higher than CK and 5-time silicon application. Correlation analysis showed that the three defensive enzyme(SOD, CAT and PPO)activities of corn leaves were negatively correlated with the body weight of S. frugiperda, that was, the higher the defensive enzyme activity, the lighter the weight of S. frugiperda. Conclusion: Exogenous application of silicon fertilizer can increase the activity of defensive enzymes(SOD, CAT and PPO)in corn, thereby enhancing the defense ability of corn against S. frugiperda.