| In recent years,the planting area of facilities vegetables in Yan ’an area has been expanding,mainly planting cruciferous vegetables.Due to the lack of scientific production awareness of farmers,serious diseases and pests occurred,especially Plutella xylostella(L.),an important pest of cruciferous vegetables,seriously hindered the development of facility vegetables.Studies have shown that the unique phenotypic plasticity of diamondback moth enables it to respond quickly to changes in the external environment,which brings severe challenges to its control.In order to investigate the effects of HighVoltage Electrostatic Fields(HVEF)stress on the growth,development and reproduction of diamondback moth,and to understand its biochemical basis.In this study,the interaction between vegetable seeds and its important pest was studied from three aspects: the indirect effect of HVEF treatment on diamondback moth,the direct effect of direct stress on the population of diamondback moth,and the selection pressure of double stress(HVEF direct stress on eggs and feeding of leaves treated with the same intensity and time dose).The results are as follows:1.HVEF treatment promoted seed germination and indirectly affected the fecundity of diamondback mothAfter HVEF treatment with an intensity of 5.0 k V/cm,the germination potential of the seeds could be improved,and the germination potential of the 20 min treatment group was the highest,and the fecundity of P.xylostella after feeding on the HVEF-treated leaves was significantly affected.Under all treatment times,the early stage and spawning period of diamondback moth were extended.Spawning days showed an increasing trend when the treatment time was shorter than 10 min,but the spawning days showed a decreasing trend when the treatment time was longer than 10 min.The average daily egg production and average single female egg production of diamondback moth decreased gradually with the extension of treatment time,but showed signs of recovery at 60 min.By measuring the physiological and biochemical indexes of the fourth instar larvae of diamondback moth:malondialdehyde(MDA)level was the highest at 20 min,mainly because the activity of superoxide dismutase(SOD)increased in the body,but the activity of peroxidase(POD)and catalase(CAT)did not respond,resulting in the accumulation of hydrogen peroxide in the body,causing oxidative damage,and further affecting the fertility of the moth.2.Multiple generations of HVEF directly stress the eggs of diamondback moth had adverse effects on its growth,development and reproduction,and there was a cumulative effectAfter the same day eggs were treated with 5.0 k V/cm HVEF for several generations,the pupation rate and emergence rate of P.xylostella first decreased and then increased.The survival rate of specific age stage showed that short-term HVEF stress had no significant effect on the survival rate of the moth,but the survival rate would gradually decrease after long-term stress,and the development cycle was significantly extended at the 5th generation.In addition,exposure of diamondback moths to HVEF after multiple generations had adverse effects on their fertility.Compared with the first and third generations,the 5th generation had the most significant effect on fecundity,and 10 min treatment time was the key time dose in all generations.HVEF also had a significant effect on life table parameters,in which 10 min stress time had a greater inhibitory effect on these parameters.The results of antioxidant enzymes showed that SOD and CAT played a synergistic role in removing reactive oxygen species in vivo under this stress.However,at10 min,POD activity was inhibited and MDA content was much higher than that of other treatment groups,indicating that this treatment had a toxic effect on insects.3.HVEF dual stress had adverse effects on diamondback mothUnder the double stress,the reproductive parameters of the female adults of diamondback moth were significantly inhibited,mainly reflected in the prolongation of the laying stage.Although the laying period and laying days increased,the laying amount showed an opposite trend,thus decreasing the population number.Correspondingly,the reproductive parameters of diamondback moth,especially the average single female laying amount and average daily laying amount,changed significantly.Further investigation of the physiological mechanism showed that the activity of SOD and CAT was significantly increased,but POD activity was significantly decreased,indicating that SOD and CAT had a synergistic effect in scavenging free radicals.The variation of MDA levels was consistent with the reproductive parameters of diamondback moth.The effects of dual stress on MDA levels of diamondback moth showed a trend of first increasing and then decreasing.In conclusion,the direct or indirect stress of HVEF mainly caused direct damage to the antioxidant protective enzyme system of diamondback moth,and then adversely affected the population dynamics of diamondback moth.These results provide experimental data for the feasibility of developing pollution-free control technology of diamondback moth by HVEF treatment,and also provide theoretical basis for formulating control strategy of diamondback moth under new electric field environment. |
