| Food security is closely related to the national economy and people’s livelihood,and the occurrence and harm of pests are important issues that threaten the safety of grain storage at all levels.Due to the resistance of pests to commonly used pesticides and the increasing requirements for the safety of stored grain,developing green and safe stored grain insecticides is currently an important task in maintaining the safety of stored grain in China.This study investigated the toxicity of three plant essential oils and ozone on the lesser grain borer(Rhyzopertha dominica),and explores the development direction of plant essential oils and ozone as stored grain insecticides.The daily grade essential oils of mugwort,clove,and citronella have strong repellent and contact killing effects on the bark beetle,but their fumigation toxicity is weak.Ozone has similar physical characteristics to phosphine in terms of volatility and diffusion,and has the quality of being an excellent fumigant.Low concentration ozone fumigation not only has no negative impact on grain,but also has the effect of improving grain processing quality.Therefore,the use of ozone as a fumigant for grain storage has good development prospects.In order to scientifically and reasonably use ozone fumigants,this article studied the sublethal effect of ozone on Rhyzopertha dominica.After fumigation with 170 mg/m3 ozone for 30 minutes,60 minutes,and 120 minutes respectively,the average lifespan of the pests was shortened from(62 ± 5.6)days in the control group to(39.7 ± 4.5)days;The ability to exercise decreases,and the capture rate of food traps decreases sequentially with the prolongation of ozone treatment time;The decrease in egg production indicates that short-term ozone fumigation has adverse effects on the population of the bark beetle,and the number of offspring may decrease.After fumigation with sub lethal time of ozone(LT10=120 min),the specific activities of antioxidant enzymes in the body of the pest-total superoxide dismutase T-SOD and catalase CAT were significantly reduced,indicating that the ability of the pest to eliminate oxygen free radicals was reduced under ozone stress.Ozone treatment significantly increased the MDA content of malondialdehyde in the bark beetle,indicating oxidative damage to the pest cells.The changes in these indicators may be the physiological and biochemical reasons for the adverse effects of short-term ozone fumigation on the growth and development of pests.The changes of gene expression in the insect pests after fumigation with ozone sublethal time(LT10=120 min)were analyzed at the transcriptome level.There are 330 genes upregulated and 311 genes downregulated in the insect body.The differentially expressed genes may be related to the process of insect epidermal formation,specifically related to the breakdown and metabolism of chitin;In addition,two genes related to the aging process were upregulated in expression.QPCR confirmed 11 differentially expressed genes,two of the three downregulated genes were associated with the NADPH oxidase system,and the remaining one was related to energy metabolism.These may be the molecular level reasons for the adverse effects of ozone fumigation on the growth and development of pests.Based on the characteristics of plant essential oils and ozone,as well as their fumigation toxicity to bark beetles,we suggest that plant essential oils with high safety levels can be developed as sustained-release microcapsules as repellents for stored grain pests in farmers,households,and food processing sites.Ozone sublethal time fumigation of bark beetles has adverse effects on their parents.In order to further investigate whether the long-term effects of ozone can cause pest resistance and resurgence,further research is needed on the population size,growth and development,and physiological and biochemical effects of offspring,in order to provide scientific basis for the rational use of ozone. |
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