| The lemon industry in Tongnan District,Chongqing has experienced rapid development due to the region’s mild annual average temperature(17°C),slightly acidic soil,convenient irrigation conditions and excellent geographical location.However,the frequent outbreak of Panonychus citri has become a major obstacle to its development,exacerbated by new climatic conditions,cultivation systems and management practices.Currently,little is known about the occurrence patterns of P.citri and its ability to tolerate extreme climates in large scale growing condition.Furthermore,many growers lack the monitoring and early warning techniques,resulting in poor timing for pest control.Meanwhile,inaccurate use of pesticides has led to fast resistance development of P.citri,as well as poor control effectiveness,high control costs,and excessive pesticide residues.To address these issues,this study investigated the occurrence patterns of P.citri in Tongnan and developed intelligent monitoring technology based on damage rate identification,as well as a rapid field selection technology based on convenient bioassay.The main findings of this study are as follows:1 Field investigation on occurrence patterns of P.citriA systematic investigation was conducted to study the occurrence patterns of P.citri in three plots of lemon orchard,Yahe Village,Baizi Town,Tongnan District,Chongqing.The number and distribution of eggs and adults of P.citri were studied from November 2020 to October 2022.The results indicated that eggs and adults of P.citri exhibited two peaks every year,in March-April and September-November.The population density was significantly higher on the blade-face of lemon leaf compared to the blade-back.The spatial distribution of P.citri varied with seasons,with higher population density observed in the upper part of the canopy during peak periods,followed by the middle part.Postpeak,the distribution shifted to the middle and lower parts of the canopy,influenced by temperature and agricultural measures.Regression analysis revealed a strong correlation between the population dynamics of P.citri and temperatures in the Tongnan area.In order to further investigate the impact of the temperature of P.citri,female adults were collected during seasons and subjected to low,medium,and high temperatures.The results showed that the mites collected from winter showed higher tolerance to low temperatures and lower tolerance to high temperatures,whereas the opposite trend was observed for summer collected mites.Meanwhile,the mites collected in spring exhibited a certain tolerance in both high and low temperatures.2 Intelligent monitoring technology for P.citri based on damage quantificationDamage areas caused by mite infestation on citrus leaves was recorded by using image analysis software such as Image J Fiji and Ilastik,which established a regression equation between the leaf damage and the number of mites.A quantitative analysis method for citrus mites was then developed based on this relationship,which was subsequently verified through reverse testing.An intelligent monitoring technology as wechat apps of P.citri was also established using image recognition algorithms and by mobile phone cameras to capture photos of P.citri-damaged leaves under different conditions.Field experiments confirmed that the results of this technology were consistent with the actual occurrence of P.citri in the field.Therefore,this technology provides an accurate and smart mean of monitoring the occurrence of P.citri.3 Rapid acaricide selection technology of P.citri in fieldThe resistance of citrus to P.citri in Tongnan area was monitored using bioassay and resistance target detection.The results from the bioassay revealed that the Tongnan population exhibited high resistance to pyridaben.In addition,through target mutation detection,a histidine(H)at position 107 in the mitochondrial complex electron transport(MET1)target gene was found to be mutated into arginine(R).In line with principles of rational and scientific pesticide use,a rapid acaricide selection technology for P.citri was developed based on the bioassay method of leaf impregnation.This technology enables more efficient and accurate field pesticide screening in compared with traditional bioassay.In summary,this study focused on P.citri and focused on the investigation of the occurrence of mites on lemon in Tongnan.The population dynamics and climate factors were analyzed,which in together elucidated the occurrence of P.citri in lemon orchard in Tongnan.Based on information,intnelligent monitoring technology was developed based on the damage spot caused after mite feeding,meanwhile,a fast acaricide selection method was optimized for filed application based on the traditional acaricide bioassay.These two methods provide alternative approaches for sustainable mite control,which are useful in filed application. |
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