Effects Of The Low-dose Nematicides On The Behavior Of Ditylenchus Destructor

1. Effect of different type of nematicides on the mortality of Ditylenchus destructor was tested at various temperature and salt solution. The results showed that the mortality of nematodes was enhanced with the increase of temperature when nematodes were exposed in aldicarb and profenofos solution at 28-37℃, and the mortality was not changed significantly with the increase of temperature when nematodes were exposed in emamectin benzoate solution. The main reason of death of nematodes was the increase of salt concentration when the concentration of aldicarb was 25μg/mL and emamectin benzoate was 5μg/mL,15μg/mL. The toxicity of profenofos was significantly increased when nematodes were exposed in 3% or 4% salt solution containing 25μg/mL profenofos.2. Effect of three nematicides on the dispersal activity of D. destructor was tested by using sand columns and 1% water agar plate in vitro. Movement of nematodes was adversely affected by 5μg/mL aldicarb, emamectin benzoate and profenofos, respectively. Both nematodes moved through sand columns soaked with 5×10-3μg/mL aldicarb, emamectin benzoate and profenofos and nematodes moved through sand columns soaked with distilled water after incubated in 10-2μg/mL,10-3μg/mL aldicarb and 10-4μg/mL,10-5μg/mL emamectin benzoate solution, the percentage movement of nematodes was significantly higher (P<0.05) than that of control, the effects shows a hormesis phenomenon. The hormetic effect of nematodes that had incubated in low-dose profenofos on the dispersal was not observed. In water agar plate bioassay, low-dose nematicides could promote the dispersal of nematodes, and the hormetic effect was less than that of sand column assay.3. Effect of different type of nematicides on the chemoreceptor activity of D destructor was tested by using a chemoreception bioassay in vitro. The results showed that Botrytis cinerea and Fusarium semitectum are significantly much more attractive than potato cutting, and nematode have not tendency toward sweet potato cutting. The chemoreception response of D. destructor was inhibited when bioassay was performed in 1% agar plate which contained 5×10-2μg/mL aldicarb, emamectin benzoate and profenofos, respectively. The other experiment, nematodes were incubated in nematicides solution or control solution for 36h, subsequently washed three times each and then for 24h in distilled water. Nematode chemoreceptive response was inhibited ai very low concentration (10-1～10-3μg/ml) of aldicarb, emamectin benzoate and profenofos through the same bioassay methods also. It is worth noting that the tendency of nematodes which tested in agar plate contained 5×10-3μg/mL profenofos or treated with 10-3～10-4μg/mL profenofos was enhanced toward sweet potato cutting. 4. Effect of low dose nematicides on the acetylcholinesterase specific activity of D. destructor was tested. Results showed that AChE specific activity was inhibited when nematodes were esposed in aldicard (10-1μg/mL,10-3μg/mL,10-4μg/mL and 10-5μg/mL) and profenofos solution (10-1μg/mL,10-2μg/mL,10-3μg/mL and 10-4μg/mL) for 24h,; AChE specific activity was no significant difference when esposed in 10-2μg/mL aldicarb and Emamectin benzoate (10-1μg/mL,10-2μg/mL and 10-3μg/mL) solution. But AChE specific activity was enhanced than that of control when nematodes were esposed in 10-4μg/mL Emamectin benzoate, the rate of activity was 25.5%.