| Aphis gossypii is one of the pests that severely damage the yield and quality of Lycium barbarum,but in recent years the extensive use of chemical pesticides has led to environmental pollution and the development of insect resistance,so it is imperative to develop the use of entomopathogenic fungus to control A.gossypii.Lecanicillium lecanni is an important entomopathogenic fungus for pests control,but is susceptible to environmental factors that can lead to compromised efficacy in field applications.Therefore,the development and utilization of dispersible oil suspensions of L.lecanni is of great importance for the control ofA.gossypii of L.barbarum.In this paper,we determined the indoor virulence,greenhouse efficacy,enzyme activity and the effect of temperature and humidity conditions on the efficacy of two dispersible oil suspension agents of L.lecanni on A.gossypii of L.barbarum,and studied the effect of the two formulations on the feeding behavior of A.gossypii after infestation,so as to provide a theoretical basis for the biological control of A.gossypii by dispersible oil suspension agent of L.lecanni.The main experimental findings of this paper are as follows:1.Effect of dispersible oil suspension agent of L.lecanni on the prevention of A.gossypiiThe indoor virulence effect of A.gossypii was determined using the dip method and the greenhouse control effect was investigated using a completely randomized design.The results showed th at the two dispersible oil suspension agents of L.lecanni to A.gossypii and the toxic effect was more obvious with the increase of treatment time,and the highest mortality rate and LC50 of 1.21×105 cfu/mL and 2.08× 105 cfu/mL were observed for A.gossypii after 120 hour of treatment with formulations 1#and 2#,respectively.At the 14th day after field application,there were significant differences between the concentrations of the two formulations,and the best prevention effects were 4×106 cfu/mL and 2×106 cfu/mL for 1#formulation,with lethality rates of 97.89%and 97.87%,respectively.Overall,the toxic effect of 2#formulation is better,and the prevention effect of 1#formulation is better.2.Effect of dispelrsible oil suspension agent of L.lecanni on the enzymatic activity A.gossypiiThe LC50 of A.gossypii at 72 hour after treatment with two dispersible oil suspension agents of L.lecanni was measured by indoor virulence assay,and the changes of protective enzymes(Peroxidase(POD)and detoxifying enzymes(Glutathione-S-transferase(GST),Carboxylesterase(CarE)and Acetylcholinesterase(AChE)activities were determined by biochemical analysis after 24,48,72 and 96 hour of treatment with the two formulations.The results showed that with the increase of treatment time,the GST activity,POD activity and AChE activity in A.gossypii after treatment with two formulations,1#formulation showed a decreasing and then increasing trend,and the CarE activity,POD activity and AChE activity in A.gossypii after treatment with two formulations showed an increasing trend followed by a decreasing trend after treatment with the 2#formulation.POD activity in A.gossypii was induced at 96 hour of treatment and the highest enzyme activity was observed after treatment with 2#formulation,CarE activity was induced and peaked at 48 hour of treatment,and AChE activity was induced and peaked at 72 hour of treatment,and there was no significant difference in GST activity among treatments.Overall,there was no significant difference between the two formulations on GST activity in A.gossypii and the control,indicating that the resistance of A.gossypii to the two formulations was not related to GST and that the 2#formulation produced a greater effect on the remaining enzyme activities in A.gossypii.3.Effect of temperature and humidity on the efficacy of dispersible oil suspension ofL.lecanniThe effect of temperature and humidity on efficacy was determined by incubator-controlled temperature and saturated salt solution-controlled humidity.The results showed that there was a difference in the optimal temperature for the two formulations,the optimal temperature range for the 1#formulation to be effective was 25～28℃,and its corrected mortality rate at 5 days was 96.34%and 94.09%,respectively.The optimal temperature range for the 2#formulation to be effective was about 28℃,and its highest corrected mortality rate was 93.03%.There was no significant difference between the two formulations under the same relative humidity conditions,and their optimum relative humidity was 67%and above after 5 days of treatment,with A.gossypii mortality reaching more than 90%;A.gossypii mortality for both formulations at a relative humidity of about 34%was about 70%.4.Effect of dispersible oil suspension agent of L.lecanni on the feeding behavior of A.gossypiiFeeding behavior of A.gossypii on L.barbarum plants was measured using the stinging potential mapping technique.The results showed that A.gossypii treated with three concentrations of the two dispersible oil suspension agents of L.lecanni produced seven waveforms within a total recording time of 8 hour.They were non-puncturing waveform np,path waveform C,potential drop waveform pd,bast secretory saliva waveform E1,bast passive feeding waveform E2,mechanical hindrance waveform F,and xylem active feeding waveform G.The np and C waveforms of 1#formulation increased with the increase of concentration,and the rest of the waveforms decreased with the increase of concentration,while the np and C waveforms of 2#formulation increased and then decreased with the increase of concentration,and the rest of the waveforms decreased and then increased with the increase of concentration.The length of adult A.gossypii feeding refusal time was in the order of 2#formulation 1×106 cfu/mL concentration,1#formulation 4×106 cfu/mL concentration,2#formulation 4 × 106 cfu/mL concentration,1#formulation 1×106 cfu/mL concentration 2#formulation 2.5×105 cfu/mL concentration and 1#formulation 2.5×105 cfu/mL concentration,which 2#formulation 1×106cfu/mL concentration had the strongest feeding rejection effect on A.gossypii. |
PDF Full Text Request