| Tomato leaf mold is one of the important diseases of greenhouse tomato in northern China.It is caused by the infection of Passalora fulva(Cooke)U.Braun & Crous(syn.Cladosporium fulvum),which mainly damages tomato leaves and can infect tomato stem,flower and fruit,and cause great economic loss to tomato production.At present,mainly through chemical agents for the control,registration for the control of tomato leaf mold fungi are mainly thiophanate-methyl,azoxystrobin,flusilazole,orthocide,polyoxins,kasugamycin,etc.But it has been reported in Shanxi,Hebei,Liaoning and other areas of P.fulva have different degrees of resistance for carbendazim,flusilazole,diethofencarb,mancozeb and other commonly used fungicides.It has been reported that hexaconazole and fludioxonil have a good inhibitory effect on tomato leaf mold,but no systematic study has been reported.In this paper,the susceptibility of 126 strains of P.fulva to carbendazim and flusilazole in Shandong was determined by mycelial growth rate method,the resistance frequency and resistance level were evaluated.The inhibitory activity,the mode of action and the field control effect for P.fulva of hexaconazole and fludioxonil were studied,and the adjuvants were screened that have synergistic effect to fungicide.It provided a scientific basis for guide the tomato leaf mold control.The main results are as follows:1.The resistance frequency of 126 P.fulva strain in Shandong was 95%,and the high resistant strains accounted for 77.5%,the sensitive strains accounted for only 5%,the resistance level of the resistant strains was high.The EC50 values of more than 70% strains were over 1000 ?g/m L,and their accurate EC50 values and complete inhibitory concentrations were not determined.The frequency of resistance to flusilazole was 67.39%,the frequency of high resistant strains was 47.83% and the sensitive strains accounted for 32.61%.2.The inhibitory activity of hexaconazole on the mycelial growth and germ tube elongation was 0.67 ?g/mL and 2.58 ?g/m L,respectively.The inhibitory activity for spore germination was the lowest.The EC50 values were in the range of(0.1692~47.0336)?g/mL of hexaconazole for 126 strains P.fulva strain in Shandong,and the mean value was(4.6840 ± 0.7099)?g/mL.The sensitivity frequency was not normal distribution,which can not be used as a sensitive baseline for tomato leaf mold.The EC50 values of 45.05% were concentrated in(0~4.0)?g/m L,9.91% strains had EC50 value greater than 10 ?g/m L,the maximum EC50 value is the minimum EC50 value 277.98 times.Linear correlation analysis showed that there was cross resistance between hexaconazole and flusilazole.The results of field experiment showed that the final control effect of hexaconazole 33.75,67.5 g a.i./hm2 on tomato leaf mould was 64.38% and 77.32%,respectively,which was significantly higher than that of the control agent thiophanate-methyl 540 g a.i./hm2.Therefore,hexaconazole can be used to control tomato leaf mould.3.The inhibitory activity of the fludioxonil on the mycelial growth and germ tube elongation was 0.35 ?g/mL and 0.26 ?g/m L,respectively,and the inhibitory activity on spore germination was poor.The EC50 values were in the range of(0.1604~1.6889)?g/mL of fludioxonil for 126 strains P.fulva strain in Shandong,and the mean value was(0.6448 ± 0.0348)?g/m L.The sensitivity frequency was normal distribution,which can be used as a sensitive baseline for tomato leaf mold.Linear correlation analysis showed that there was no multiple resistance between fludioxonil and flusilazole.The results of field experiment showed that the final protection control effect of fludioxonil 40.5 g a.i./hm2 on the tomato leaf mold was 66.89% and 60.40%,which was significantly higher than that of the control agent thiophanate-methyl 540 g a.i./hm2 control.4.There was additive effect when the mixture of hexaconazole and fludioxonil with 5:1,4:1 and 3:1.There was synergistic effect when the mixture of hexaconazole and fludioxonil 2:1,1:1,1:2,1:3,1:4,1:5,the synergic ratio was 1.76,1.82,2.23,2.01,2.13,2.05,respectively.The synergistic effect of mixture hexaconazole and fludioxonil 1:2 was the most obvious,and the synergic ratio was 2.23.The results of field test showed that the control effect of the mixture of hexaconazole and fludioxonil with 1:2 60.79 g a.i./hm2 was significantly higher than that of hexaconazole 67.5 g a.i./hm2.5.The control effect of cross-layer translocation of hexaconazole 33.75 g a.i./hm2 was 76.68%,and the control effect of transverse translocation was 19.30%.There was significant difference between cross-layer translocation and transverse translocation control effect,indicating that hexaconazole had better cross-layer translocation.The control effect of cross-layer translocation and transverse translocation of fludioxonil 40.5 g a.i./hm2 was 27.79% and 15.82%,respectively,which indicated that the uptake translocation was not observed.6.The effects of different adjuvant on the surface tension of the solution and the contact angle on the surface of the target were investigated.The optimum additives of S903 and AEO-5 were screened.In the field experiment,it was found that the addition of 0.05%,0.1% S903 and AEO-5 had synergistic effect on hexaconazole and fludioxonil.The synergistic effect of fludioxonil 40.5 g a.i./hm2 + 0.1% S903 was the strongest and the synergistic effect is 1.40.The control effect of hexaconazole 33.75 g a.i./hm2+(0.05%,0.1% S903)and(0.05%,0.1% AEO-5)were 73.95%,81.09% and 71.81% and 79.27% respectively,which were higher than that of hexaconazole 33.75 g a.i./hm2.Hexaconazole 33.75 g a.i./hm2 + 0.1% S903 was the most effective,the synergistic ratio was 1.18;The control effect of fludioxonil 40.5g a.i./hm2 +(0.05%,0.1% S903)and(0.05%,0.1% AEO-5)were 77.13%,80.66% and 70.48% and 77.04%,respectively,which were significantly higher than those of fludioxonil 40.5 g a.i./hm2 single dose of 57.60%.So S903 and AEO-5 can be used as tank adjvants to increase the efficacy of agents in field.However,it was found that the addition of spray auxiliaries had different degrees of phytotoxicity to tomato plants,and increased with increasing concentrations. |
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