A Greenhouse And Field-based Study To Determine The Distribution Of Dimethoate And Its Control Effect Against Leaf Mite On Cotton By Drip Irrigation

Theroot zone applicationistransported systemic chemical pesticides to soil nearby plant root zone.Theroot zone applicationcan effectively control the chewing mouthparts and piercing-sucking mouthparts pestsin arid or semi-arid areas.In this paper,according to the characteristics of the leaf mites increasingly rampant,greenhouse and field based experiments were carried out to determine the susceptibility of leaf mites to dimethoate and the absorption and distribution of dimethoate in cotton by drip irrigation.The main results showed as follow:1Dimethoate detection method.The dimethoate residue in the cotton roots,stems,leaves and soils was detected by HPLC with a UV detector at 210 nm.Acetonitrile:water(30:70by volume)were used as the mobile phase.For the cotton seeds,acetonitrile:water(20:80 by volume)were used as the mobile phase.2 Dissipation of dimethoate in cotton(root,stem and leaf)by drip irrigation.Resultes showed that in leaves9.00 kg ai/ha group,a high amount of dimethoate(65.62 mg/kg)was found 1 d after treatment followed by a sharp increase of dimethoate amount to reach116.36 mg/kg 3d after treatment and then again a sharp decrease to reach 8.50 mg/kg 14 d after treatment.Eventually,dimethoate amount was reduced to 1.93 mg/kg 30 d after treatment and was not detectable 45 d after treatme nt.In leaves 2.25 and 0.56 kg ai/ha groups,a high amount of dimethoate(17.51 and 9.97 mg/kg)was found 3 d after treatment.In roots 9.00 and 2.25kg ai/ha groups,a high amount of dimethoate(5.08 and5.55 mg/kg)was found 1 d after treatment followed by a sharp increase of dimethoate amount to reach 10.89 and 10.92 mg/kg 3d after treatment.Then dimethoate amount gradually decreased and was not detectable 21 d after treatment in all the three treatments.In stems,1 to 3 d after the treatment,dimethoate amount in 9.00 kg ai/ha group(ranging from 6.25 to 7.01 mg/kg)was much higher than those in 2.25 and 0.56 kg ai/ha group(ranging from 1.13 to 2.69 mg/kg).In young leaves,old leaves and cotyledon,1 to 3d after the treatment,dimethoate amount in 9.00 kg ai/ha group were 32.76~44.16 mg/kg,22.08~47.68 mg/kg and 10.79~24.52 mg/kg.Dimethoate amount in 2.25 and 0.56 kg ai/ha groups,dimethoate amount(ranging from 1.51 to 7.72mg/kg).The sequence of dimethoate amount was young leaves,old leaves>cotyledon.3The control efficiency to mite.In 9.00 kg ai/ha group,the corrected mortality increased from 44.44%at 1 d to 97.73%at 5 d and then gradually decreased.The corrected mortalities maintained above 70%from 2 d to 14 d.In 2.25 and 0.56 kg ai/ha group,the highest control efficiencies were ranging from 44.19%to 60.47%at 7 d.4The effect to Amblyseius cucumeris O udemans..In 9.00,2.25 and 0.56 kg ai/ha groups,1 d after the treatments,the corrected mortalities were 0~3.33%,14 d after the treatments,the corrected mortalities were 0.01%~3.45%.5 The control effect on the leaf mites after applying pesticide dimethoate.5.1The control effect of different amount of dimethoate on mite(soil p H=7.80).Results showed that the use rates of 4.50 and 6.00kg ai/ha gave similar results and the corrected mortalities reached peak(more than 60%)5to 14 d after the treatment.No doubt,9.00 kg ai/ha gave the highest control efficiency with corrected mortality maintaining above 75%from 5 to 28 d after the treatment.5.2 The control effect of different amount of water on mite(soil p H=7.80).Results showed that,in all the three dripping water rates,the highest control efficiency was less than 40%7 d after the treatment when dimethoate was used at normal dose 2.25kg ai/ha.Therefore,double normal dose 4.50kg ai/hawere further tested.Results revealed that the control efficiency in 200.10and 300.15 m~3/ha were similar and there was no significant difference.The corrected mortalities in both treatments increased to 70%at 7 d after the treatment and then decreased.5.3 The control effect of different soil p Hson mite with.Results showed that,in all the three soilp Hs,the highest control efficiency was less than 35%7 d after the treatment when dimethoate was used1.50kg ai/ha at soil p H7.80,however,the highest control efficiencyincreased to 61%and 58%7 d after the treatment at soil p H6.70 and 5.70,respectively.The corrected mortalities in both treatments increased to 80%at 7 d after the treatment and then decreased when dimethoate was used 3.00kg ai/haand double normal dose 4.50kg ai/ha,which might due to the degradation of dimethoate in cotton.The results also revealed that the control efficiency at soilpH(5.70and 6.70)were similar and there was no significant difference.6Dimethoate of cotton seeds and soil residues in harvest period.Results showed that,the maximum residues of dimethoate in soil was0.13 mg/kg and was not detected in all of treatment cotton seeds.