| Tetranychus cinnabarinus(Boisduval)is one of the important pests on strawberries(Fragaria × ananassa Duch.),mainly gathering on the back of leaves and petioles on both sides of leaf veins to form a network of filaments.It uses its mouth to puncture and suck plants,causing premature plant senescence and reducing strawberry yield and quality.In order to reduce the harm of spider mites,a large amount of chemical pesticides have been applied in production.Although the goal has been achieved to some extent,the long-term excessive use of chemical pesticides has brought serious environmental pollution,increased pest resistance,and decreased safety and quality of strawberries.At the same time,it poses a threat to human health.Therefore,it is of great significance to develop new green prevention and control technologies for spider mites and improve the safety and quality of strawberries.This study used strawberry plants as experimental materials to study the occurrence dynamics and control methods of Tetranychus cinnabarinus.The research results provide theoretical basis and technical reference for clarifying the occurrence dynamics of spider mites and using purple light to control the population of Tetranychus cinnabarinus.The main research findings are as follows:1 To understand the occurrence of the natural population of Tetranychus cinnabarinus,a systematic study was conducted on the migration pattern of Tetranychus cinnabarinus from overwintering sites to strawberries in early spring.The occurrence patterns of strawberry cinnabar leaf mites vary in different facilities.In a glass greenhouse in Yangzhou,Jiangsu Province,Tetranychus cinnabarinus can occur throughout the entire growing season of strawberries.When the temperature is low at the end of February,it can overwinter on strawberry plants.In early March of the following year,with the temperature rising,Tetranychus cinnabarinus population rapidly increases.On April 7th,the insect population reached its peak,with the highest insect population reaching 74.13 heads per leaf.In the strawberry greenhouse covered with a single layer of film,Tetranychus cinnabarinus mainly overwinter under the soil,with a small amount overwintering on weeds.Starting from February 27th,the population of spider mites steadily increased.After spring,with the rise of temperature,the population of spider mites rapidly increased.It reached its peak on March 16th,with the highest number of insects reaching 40.33 per compound leaf.Tetranychus cinnabarinus that overwinter in the soil in winter are mainly distributed at 0-15 cm below the soil,with a maximum depth of up to 20 cm,with the highest number occurring in the 5-10 cm soil layer.After the temperature rises in early spring,Tetranychus cinnabarinus migrates upwards and the number of immigrants gradually increases.The migration of Tetranychus cinnabarinus often occurs at night,with the highest migration occurring from 18:00 to 6:00 the next day.There are also significant differences in the number of Tetranychus cinnabarinus occurring on different weeds,with significantly higher numbers occurring on Dachao Cai,Zeqi,and Baogai Grass compared to other weeds.2.Using the relationship between RGB and virtual wavelength,simulate colors of different wavelengths on a computer and screen for light wavelengths that have repellent effects on the Tetranychus cinnabarinus.Research has found that the selection rate of Tetranychus cinnabarinus for purple light is relatively low.In the range of 400-440 nm,spider mites have the lowest selection rate for purple light at a wavelength of 410 nm,only 3.89%.The results showed that purple light with a wavelength of 410 nm had a good repellent effect on Tetranychus cinnabarinus.Subsequent experiments all used purple light with a wavelength of 410 nm.3.The control effect of purple light on Tetranychus cinnabarinus was studied under potted and greenhouse production conditions.The results showed that purple light irradiation had a good repellent effect on Tetranychus cinnabarinus.After 7 days of purple light irradiation,the corrected population reduction rate of Tetranychus cinnabarinus reached 69.33%.Placing a purple light strip in the greenhouse strawberry field resulted in a rapid decrease in the population of Tetranychus cinnabarinus on strawberries,and the number significantly decreased with the extension of lighting time.During the peak period,the number of Tetranychus cinnabarinus on strawberries decreased by 58%compared to the control.There are significant differences in the population size of Tetranychus cinnabarinus under different time periods of purple light irradiation,with the strongest repellent effect of purple light irradiation from 18:00 to 24:00 on Tetranychus cinnabarinus.4.Purple light treatment has a significant impact on the growth and development of Tetranychus cinnabarinus.With the prolongation of daily light treatment time,the developmental period of Tetranychus cinnabarinus from egg to adult gradually extends.After 8 hours of daily light treatment,the developmental period of Tetranychus cinnabarinus from egg to adult is 28.01%longer than the control.The intensity of purple light and environmental temperature are positively correlated with the migration of Tetranychus cinnabarinus.Under the same irradiation time,the greater the intensity of light,the greater the migration of Tetranychus cinnabarinus:An appropriate increase in temperature can increase the migration population of Tetranychus cinnabarinus,and the migration population of Tetranychus cinnabarinus is significantly higher at night than during the day.5.Purple light treatment has a significant impact on the morphological indicators,nutrients,resistant biomass,and resistance related enzymes of strawberry leaves.After 28 days of purple light irradiation,the single leaf area,fresh weight,and stomatal length of strawberries increased by 3.44%,11.36%,and 3.73%respectively compared to the control,but there was no significant difference in stomatal density.Purple light irradiation on strawberry leaves can significantly increase the content of chlorophyll,proline,free protein,total phenols,and flavonoids in the leaves,but the content of soluble sugar and proline will decrease with the extension of light time.After 28 days of light irradiation,the content of proline and soluble sugar in the leaves decreased by 7.48%and 14.07%,respectively,compared to the control.The activities of peroxidase,catalase,superoxide dismutase and ascorbase peroxidase in strawberry leaves were significantly increased by purple light irradiation,and the four enzyme activities reached the maximum value at 21 days of purple light irradiation,respectively 101.68%,60.97%,29.84%and 136.62%higher than the control.Purple light irradiation can significantly increase the content of free protein,soluble sugar,and ascorbic acid in strawberry fruits.After 28 days of illumination,purple light irradiation can significantly increase the content of free protein,soluble sugar,and ascorbic acid in strawberry fruits by 73.67%,102.56%,and 133.04%,respectively.However,there was no significant difference in the total phenolic content of strawberry fruits.6.Further analysis of the changes in secondary metabolites in strawberry leaves under UV irradiation using GC-MS revealed that 15 new secondary metabolites appeared in strawberry leaves after UV irradiation,including 5 benzene compounds,3 alkanes,3 lipids,2 alcohols,and 2 olefins.Among these substances,the relative content of terpineol increased most significantly,and increased with the extension of light time,reaching 0.26%after 28 days of light exposure.After purple light irradiation,the content of 19 compounds in strawberry leaves showed an upward trend with increasing light time,including 5 phenolic compounds,5 ketone compounds,3 lipid compounds,2 olefin compounds,2 aldehyde compounds,1 alkane compound,and 1 alcohol compound.Methyl salicylate,2-nonone,and 2,4-dihydroxyacetophenone showed the most significant increase compared to the control,with an increase of 12.71,3.35,and 2.45 times after 28 days of light exposure,respectively.After purple light treatment,the content of 14 compounds in strawberry leaves showed a decreasing trend with increasing light time,including 4 alcohols,4 esters,3 alkanes,2 amino acids,and 1 ene compound.Purple light irradiation can cause the downregulation of alcohol compounds in strawberry leaves,and with the extension of purple light irradiation time,the content of alcohol compounds shows a downward trend. |
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