Studies On The Occurrence Dynamic And Chemical Control Of Rice Root-knot Nematode Disease In Pingjiang

Rice root-knot nematode,Meloidogyne graminicola,is a parasitic nematode which mainly harms rice and economic crops and was found in Hunan province in recent years.Rice root-knot nematode is considered the most important group of plant-parasitic nematodes due to their wide range of plant hosts and subsequent role in yield losses.In severe cases,the yield of rice can be reduced by up to 80%.With the occurrence of nematode disease in some rice planting areas in Hunan Province,the area is increasing year by year and the damage is getting worse,which seriously affects the rice quality and yield.In 2020,the occurence dynamics,the investigation of host relationship and the control effect of different nematicides were studied,and the following results were obtained:1.In order to understand the occurrence dynamic of rice root-knot nematode in the field,soil and rice samples were collected from May 11 to August 23,2020.The changes of the number of 2nd-stage juveniles(J2),the number of root-knots and eggs were monitored.It was found that the number of J2 appeared 3 peaks in the seeding fields,which respectively reached 250 /100 m L soil at the seedling stage(June 1),239 /100 m L soil at the booting stage(July 12)and 400 /100 m L soil at the yellow maturity stage(August 9).The results of dynamic investigetion on root-knot number of rice showed that the numbers of root-knot in direct seeding field appeared 3 peaks,respectively in front of the tillering stage(June 7)4.7 /strains,jointing stage(July 19)4.6 / strains and yellow maturity stage(August 9)3.6 / strains,before tillering stage(June 7),the average maximum number of rice root-knots,It had great influence on the growth of rice at the seedling stage.After the middle of June,there was no significant increase in the number of rice-root knot until the harvest was at a low level(<4 /plant),which had little effect on the growth of rice.The results of dynamic investigation of egg mass showed that the average egg mass per root-knot increased gradually from before tillering stage(June 7)to booting stage(July 26),and reached the highest(>2000 / root knots)at the booting stage(July 26).The average number of eggs per root-knot decreased slightly before harvest on August 23.2.By field investigation and inoculation in the pots,the host range of rice root-knot nematode were identified.It was showed that Cyperus rotundus,Echinochloa crusgalli,Centipeda minima,Lindernia crustacea,Ranunculus sceleratus were good hosts.In the pot experiment of indoor inoculation of J2 economic crops,7 crops(Brassica oleracea Brassica rapa,Chrysanthemum coronarium,Allium tuberosum,Ipomoea aquatica,Coriandrum sativum,Solanum melongena.)were good hosts.6 crops(Brassica campestris,Allium sativum,Allium fistulosum,Daucus carota,Glycine max.)showed weak host resistance.However,13 crops showed non-host resistance,such as Canavalia gladiata,Arachis hypogaea,Dioscorea esculenta,Lycopersicon esculentum,Capsicum annuum and Luffa cylindrica.3.In order to screen highly effective,low toxic and safe nematicides,41.7% fluopyram SC+35% thiamethoxam FSC,1.18% fluopyram· thiamethoxam GR,10% fosthiazate GR and 0.5% avermectin GR were used to control rice root-knot nematode disease.The treatments were carried out before sowing and after the emergence of seeding.41.7%fluopyram SC+35% thiamethoxam SC,1.18% fluopyram · thiamethoxam GR,10%fosthiazate SC and 0.5% avermectin GR had good control effects on root-knot nematodes,the reduction rates of J2 in soil were 57.6～81.3% and 48.0～65.0%,and the control effects of root-knot index were respectively 58.7～77.7% and 42.7～70.4%.After sowing 20 days,1.18% fluopyram· thiamethoxam GR,10.5% avermectin·fosthiazate GR,0.5% avermectin GR and 10% fosthiazate GR were applied.These treatments all had certain control effect on root-knot nematodes disease,the reduction rates of J2 were 27.6～41.3% and 24.3～34.3%,and the control effects of root-knot index were 25.7～48.7% and 19.2～37.8%,The control effect of 1.18% fluopyram· thiamethoxam GR on the J2 in soil were the highest,and the seed coating of 41.7% fluopyram SC+35% thiamethoxam FSC was the most significant.However,the effect of soil spraying was not obvious after the emergence of disease.The number of J2 in soil was decreased,but the control effect was low.Considering the cost and environmental factors,it is suggested to use 41.7% fluopyram SC+35% thiamethoxam FSC to control rice root-knot nematode disease before rice sowing.