MSc

A study on “Insecticide resistance in spiralling whitefly, Aleurodicus dispersus Russell (Hemiptera: Aleyrodidae) and its management” was done at College of Agriculture, Vellayani and farmer’s field at Kalliyoor during 2018 to 2019. Tokassess thehinsecticide resistance in the fieldhpopulation of spiralling whitefly, A. dispersus and to evaluate the efficacy of new generation insecticides against resistant population of A. dispersus were the objectives of the study.
Bioassaykwas carriedLout to assess the insecticideHresistance in field population of A. dispersus collectedUfromHthree different locations (location ISreekaryam, location II-Vellayani and location III-Kalliyoor) based on the intensity of insecticide application. A series of concentrations of three insecticides viz., quinalphos, fenvalerate and imidacloprid were prepared in aqueous solution and leaf dip bioassay was done using the field population of whiteflies collected from three locations. Results revealedDthatkpopulation collected from location-I (Sreekaryam) was foundhto begsusceptible to insecticides with resistance ratio-1 for all three insecticides, which was considered as reference strain. Population collectedgfrom location-II (Vellayani) showed higher resistance with resistance ratio of 2.60, 2.90 and 1.85 and population from location-III (Kalliyoor) was found to be moderately resistant with resistance ratio of 1.14, 1.62 and 1.28 with respect to quinalphos, fenvalerate and imidacloprid respectively.
Laboratoryyexperiments were conductedutotevaluateethedefficacy ofdnew generationdinsecticides viz. buprofezin 25% SC @ 75 g.a.i ha-1, clothianidin 50% WDG @ 20 g,a.i ha-1, cynantraniliprole 10.26% OD @ 90 gfa.i ha-1, dinotefuran 20% SG @ 25 g a.i ha-1, flonicamid 50% WG @ 75 g a.i ha-1, thiamethoxam 25%WG @ 50 g a.i ha-1 and thiamethoxamt12.6% + lambdadcyhalothrin 9.5% ZC @ 33+15.75 g a.i ha-1against resistant population of A. dispersus in tomato plants. The results revealed that significantly higher mortality was observed in A. dispersus treated with thiamethoxamg12.6% +hlambda cyhalothrin 9.5% ZC @ 33+15.75 g a.i ha-1 (100%),
followed by clothianidin 50% WDG @ 20 g a.i ha-1 (80%) and flonicamid 50% WG @ 75 g a.i ha-1 (66.67%) after 0.75 hours of treatment.
Field experiment was conducted by using tomato plants (var. Vellayani Vijay) at Vellayani from where resistant population was collected with three effective insecticides selected from laboratory along with control. No whiteflies were seen in thiamethoxamt12.6% + lambdatcyhalothrin 9.5% ZC @ 33+15.75 g a.i ha-1 treated plants followed by clothianidin 50% WDG @ 20 g a.i ha-1 (9.20) and flonicamid 50% WG @ 75 g a.i ha-1(11.80) after one day of spraying.
Studies on the dissipation of residues of effective insecticides viz., thiamethoxam 12.6% + lambda cyhalothrin 9.5% ZC @ 33+15.75 g a.i ha-1, clothianidin 50% WDG @ 20 g a.i ha-1 and flonicamid 50% WG @ 75 g a.i ha-1 were conducted in tomato plants at farmer’s field at Kalliyoor. Tomato fruits collected at 0,1,3,5,7,10,15 and 30 days after application of insecticides at recommended dose and results showed that insecticides dissipated within 10 days with half- lives of 4.05, 3.42, 8.92 and 7.82 days respectively. The risk assessment studies also proved the safety of insecticides for the end users.
The present study revealed the development of insecticide resistance in the field population of A. dispersus against fenvalerate and quinalphos. Thiamethoxam 12.6% + lambda cyhalothrin 9.5% ZC @ 33+15.75 g a.i ha-1 followed by clothianidin 50% WDG @ 20 g a.i ha-1 and flonicamid 50% WG @ 75 g a.i ha-1 could be recommended against the resistant population of A. dispersus in tomato. Dissipation and risk assessment studies also supported the result by establishing their safety to consumers. Further studies have to be taken up to develop and popularize Insecticide Resistant Management strategies against A. dispersus by developing Good Agricultural Practices on efficient use of insecticides and to conserve the ecosystem for sustainable pest management.