Sublethal Effects Of Fenoxycarb And Novaluron On Diaphorina Citri Kuwayama

As one of the most widely distributed economic crops in China,citrus occupies a major position in the composition of our country’s agricultural industry.The Diaphorina citri Kuwayama,as the main natural carrier of Huanglongbing（HLB）,has brought a huge impact on my country’s citrus industry.Since there is no direct and effective control method for Huanglongbing,the prevention and control of Diaphorina citri Kuwayama is of great significance to the construction of my country’s citrus industry.At present,the control of Diaphorina citri Kuwayama still relies on chemical insecticides.However,due to the single and large amount of medication,chemical insecticides have brought hidden dangers in various aspects in actual use,such as causing environmental pollution and causing the death of non-target organisms,resulting in excessive residues of agricultural products,etc.Moreover,in the field,after insecticide spraying,the concentration of insecticides usually decreases to a lower dose that is insufficient to directly kill the target pest due to abiotic factors such as light and rain,which leads to the formation of sublethal effects.This study was carried out at the National Navel Orange Engineering Technology Research Center with specific research content.The indoor populations of Diaphorina citri Kuwayama were used to investigate the indoor virulence of two insect growth regulators（fenoxycarb and novaluron）on Diaphorina citri Kuwayama at various ages using different bioassay methods.Based on the indoor virulence measurements,we determined the sublethal doses and further investigated the sublethal effects on F₀ and F₁generations of Diaphorina citri Kuwayama;we used transcriptomic techniques to explore the resistance-related genes induced by the agents in response to Diaphorina citri Kuwayama.The main results were as follows:1 Toxicity determination and sublethal dose determination of two insect growth regulators to Diaphorina citri KuwayamaThe results of laboratory toxicity tests showed that the two insect growth regulators had good toxicity to Diaphorina citri Kuwayama psyllid eggs and nymphs of all ages.Among them,under the treatment of immersion method,the toxicity of fenoxycarb to Diaphorina citri Kuwayama in the egg stage was lower than that of novaluron,the LC₅₀ value of which was 34.947 mg/L,and the LC₅₀ value of novaluron was 52.343 mg/L.Under spraying treatment,the two pesticides had certain toxic effects on Diaphorina citri Kuwayama nymphs of different ages.Fenoxycarb had the strongest killing effect on 1st instar nymphs,with an LC₅₀ value of 1.921 mg/L,and the toxicity of fenoxycarb decreased with increasing age,and its LC50 value against 4th instar nymphs was 35.465 mg/L.Similarly,the toxicity of novaluron to nymphs decreased with increasing age,the LC₅₀ value for 1st instar nymphs was 2.374 mg/L,and the LC₅₀ value for 5th instar nymphs was 54.728 mg/L.Under the drip method,the two pesticides had certain toxic effects on the 5th instar Diaphorina citri Kuwayama nymphs,and the toxicity of fenoxycarb to the 5th instar Diaphorina citri Kuwayama nymphs was lower than that of novaluron,and the LD₃₀ value was 1.270 mg/L.The LD₃₀ value of fluorourea is 0.586 mg/L.2 Effects of sublethal concentrations of two insect growth regulators on life table parameters of Diaphorina citri KuwayamaThe life table parameters of the F₀ generation were significantly affected by the two insect growth regulators at different sublethal concentrations.The net value-added rate（R₀）and the average generation period（T）of the F₀ generation citrus psyllid population were significantly improved,and the intrinsic growth rate（r_m）and weekly growth rate（λ）were both reduced.The sublethal doses of the two insect growth regulators had a stimulating effect on the F₀ population of Diaphorina citri Kuwayama.The LD₃₀ of the two insect growth regulators coulds ignificantly prolong the nymph stage of the F₁ generation of Diaphorina citri Ku wayama,16.43 days and 18.11 days,respectively.The LD₁₀ of the two insect growth regulators had no significant effect on the nymph stage of the F₁ generation of Diaphorina citri Kuwayama.The life table parameters of the F₁ generation were significantly affected by the two insect growth regulators at different sublethal concentrations.The net value-added rate（R₀）and the average generation cycle（T）are significantly reduced,and the intrinsic growth rate（r_m）and cycle growth rate（λ）are significantly increased.The sublethal doses of the two insect growth regulators could delay the population expansion of citrus Diaphorina citri Kuwaya ma F₁ to a limited extent.3 Transcriptome analysis of 5th instar Diaphorina citri Kuwayama nymphs under sublethal dose stress of two insect growth regulatorsTranscriptome sequencing was performed on a total of 12 samples of the Diaphorina citri Kuwayama control group,the fenoxycarb LD₃₀ treatment group,and the novaluron LD₃₀ treatment group.Comparing the Unigenes obtained in databases such as GO,COG,and KEGG,it was finally found that 20191 Unigenes were functionally annotated.A total of 3173 differentially expressed genes were analyzed,of which 2484 were differentially expressed between CK and FXN treatments,1765 were up-regulated and 719 were down-regulated.484 were annotated in the COG database,1445 were annotated in the GO database,and 1193 were annotated in the KEGG database;there were 745 differential genes between CK and BYW treatments,448 were up-regulated and 297 were down-regulated,and there were 448 genes that were up-regulated and 297 down-regulated in the COG database.176 were annotated,498 were annotated in the GO database,and 390were annotated in the KEGG database.Among the differentially expressed genes,there were 40 genes related to CYP450 enzymes,13 genes related to GST enzymes,and 15genes related to CCE enzymes.