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T. VENKATRAMANA REDDY*, K.V. HARI PRASAD, M.S.V. CHALAM and K. VISWANATH
Department of Entomology,S.V. Agricultural College, ANGRAU, Tirupati-517502, Chittoor Dt., A.P, India
A field experiment was carried out during Kharif 2018 at dry land farm, S.V. Agricultural College, Tirupati to assess theefficacy of certain insecticides against leafhopper (Orosius albicintus) of sesame. Results on efficacy of certain insecticides against leafhopper, O. albicinctus at 3 DAS revealed that the chemical treatment with pymetrozine @ 0.4 g L-1 showed highest per cent reduction of nymphal population (91.5%) followed by imidacloprid (40 %) + ethiprole (40 %) @ 0.3 g L-1 (73.7 %), acephate@ 1.5 g L-1 (73.1%), dinotefuron @ 0.3 g L-1 (72.1%), diafenthiuron @ 1.3 g L-1 (70.6%), The lowest per cent reduction was recorded in flonicamid @ 0.4 g L-1 (69.3%), thiamethoxam (seed treatment) (25.6 %), imidacloprid (seed treatment) (12.7 %).
Sesamum,leafhopper, efficacy and insecticides
Sesame (Sesamum indicum L.) is one of the old-est oil seed crops and has been cultivated in Asia since ancient times. It is grown in more than 50 countries in the world. At global level, it is cultivated on an area of 7.41 m ha with a production of 2.94 MT of seeds. India, China, Sudan, Mexico, Turkey, Burma and Pakistan are the im-portant sesame producing countries (FAOSTAT, 2017). In India it is cultivated in an area of 1.77 Mha with an annual production of 0.71MT. Though India is the major producer of sesamum, with one third of world’s acreage and approximately a quarter of world’s production, the average productivity of this crop in India is quite low i.e.,
426 kg ha-1 (Indianstat, 2017). Sesame is a short duration crop and is grown mostly under rainfed conditions with poor crop management resulting in low yields. Pests and diseases are another major factor for reduction in yield.As many as 29 species of insect pests attack the crop at different stages of crop growth (Rai, 1976).
Among the pests and diseases, phyllody caused
by phytoplasma is a major potential disease in most sesame growing regions. In warm climates, this disease inflict up to 80 per cent yield loss with a disease intensity of 61-80 per cent (Kumar and Mishra, 1992; Salehi and Izadpanah, 1992). This phytoplasma disease is transmitted by sesamum leafhopper (Orosius albicinctus) (Sahambi, 1966). Manoharan et al. (1997) reported that phyllody disease was transmitted by the Orosius albicinctus as one of most destructive disease limiting the productivity in India and causing up to 55 per cent yield losses. Pesti-cides continue to be one of the most powerful tools avail-able for managing insect vectors and increasing crop yield in majority of the crops including sesame.
A field experiment was conducted at dry land farm, S.V. Agricultural College, Tirupati during summer 2018-2019, to evaluate the efficacy of certain new insecticides against sesamum leafhopper. The experiment was laid out in a randomized block design with nine treatments including untreated control and replicated thrice. The size of the individual plot was 5 m x 4 m, with spacing of 30 cm between the rows and 10 cm between the plants. All the recommended package of practices were adopted in managing crop to maintain a good crop stand. “YLM-66”, a popular sesame variety was sown on 17th August, 2018. Seed treatment was done by measuring known quantity of seed i.e., 50 gms of sesamum seed and mixing them with 250 micro litres of imidacloprid 600FS and 250 micro litres of Thiomethaxom 35FS.Seeds were sown normally in all the plots except in plots receiving seed treatment where the seeds were treated with imidacloprid and thiomethoxam as seed treatment and were sown later. The remaining insecticidal treatments (spray) were given 30 days after sowing to coincide with maximum insect activity. Required quantity of the insecticide was measured and mixed with required quantity of water and stirred well to obtain the desired concentration of spray fluid. In case of wettable powders required quantities were mixed with a little quantity of water and then the remaining quantity of water was added to obtain desired concentration and stirred well. Insecticide treatments included in this experiment were applied with hand held knapsack sprayer at 30 days after sowing. Spraying was done during morning hours by taking care to prevent the drift of the spray fluid reaching the adjacent plots by keeping a screen in between the plots. The sprayer was cleaned with water before changing the insecticide treatment.
Pre-treatment counts were taken as number of nymphs for O. albicinctus on ten selected plants one day before spraying and post treatment counts were taken at 1st, 3rd, 5th, 7th, 9th and 11th day after spraying. Statistical Analysis The per cent reduction of larval population was calculated by using modified Abbots formula as given by Fleming and Retnakaran (1985).
Per cent population reduction =
Test insecticides Details of insecticides used in the experiment are given in Table 1.
Management of leafhopper (Orosius albicintus) one day after spraying
At 1day after spraying, treatment with pymetrozine @ 0.4 g L-1 (67.3%) had given a significant per cent reduction in nymphal population followed by diafenthiuron @ 1.3 g L-1 (57.4%), dinotefuron @ 0.3 g L-
1 (54.9%), acephate @ 1.5 g L-1 (53.3%), imidacloprid (40%) +ethiprole (40%) @ 0.3 g L-1 (50.5%), The lowest per cent reduction was recorded in flonicamid @ 0.4 g L-
1 (49.6%),thiamethoxam (seed treatment) (30.9%), imidacloprid (seed treatment) (28.8%).
The order of efficacy of different treatments was as follows:
T7> T4> T5> T8> T3> T6> T2> T1> T9
Three days after spraying
At 3day after spraying, treatment with pymetrozine @ 0.4 g L-1 (91.5%) had given a significant per cent reduction in nymphal population followed by imidacloprid (40%) +ethiprole (40%) @ 0.3 g L-1 (73.7 %), acephate @ 1.5 g L-1 (73.1%),dinotefuron @ 0.3g L-1 (72.1%), diafenthiuron @ 1.3 g L-1 (70.6%), The lowest – 183
per cent reduction was recorded in flonicamid @ 0.4 g L-
1 (69.3%), thiamethoxam (seed treatment) (25.6%), imidacloprid (seed treatment) (12.7%).
The order of efficacy of different treatments was as follows:
T7> T3> T8> T4> T5 > T6> T2> T1> T9
Five days after spraying
At 5 day after spraying, treatment with pymetrozine @ 0.4 g L-1 (95.8%) had given a significant per cent reduction in nymphal population followed by dinotefuron @ 0.3 g L-1 (87.5%), acephate @ 1.5 g L-1 (84.0 %), diafenthiuron @ 1.3 g L-1 (81.5%), flonicamid
@ 0.4 g L-1 (81.2%), The lowest per cent reduction was recorded in imidacloprid (40%) +ethiprole (40%) @ 0.3 g L-1 (79.6%), imidacloprid (seed treatment) (37.7%), thiamethoxam (seed treatment) (24.4%).
The order of efficacy of different treatments was as follows:
T7 > T5 > T8> T4 > T6> T3> T1> T2 > T9
Seven days after spraying
At 7 DAS, treatment with pymetrozine @ 0.4 gg L-1 (98.7%) had given a significant per cent reduction in nymphal population followed by dinotefuron @ 0.3 g L-1 (92.7%), acephate @ 1.5 g L-1 (91.7%), diafenthiuron @ 1.3 g L-1 (91.2%), imidacloprid (40%) +ethiprole (40%)
@ 0.3 g L-1 (90.9%). The lowest per cent reduction was recorded in flonicamid @ 0.4 g L-1 (90.3%), thiamethoxam (seed treatment) (23.6%), imidacloprid (seed treatment) (23.5%).
The order of efficacy of different treatments was as follows:
T7 > T5> T8> T4> T3> T6 > T2> T1> T9
Nine days after spraying
At 9 DAS, treatment with pymetrozine @ 0.4 g L-1 (83.5%) had given a significant per cent reduction in
nymphal population followed by acephate @ 1.5g L-1 184
@ 1.3 g L-1 (70.5%), imidacloprid (40%) +ethiprole (40%)
@ 0.3g L-1 (67.0%).The lowest per cent reduction was recorded in flonicamid @ 0.4 g L-1 (66.8%), thiamethoxam (seed treatment) (27.6%), imidacloprid (seed treatment) (25.5%).
The order of efficacy of different treatments was as follows:
T7> T8> T5 > T4> T3 > T6> T2> T1> T9
Eleven days after spraying
At 11 day after spraying, treatment with pymetrozine @ 0.4 g L-1 (73.5%) had given a significant per cent reduction in nymphal population followed by acephate @ 1.5 g L-1 (66.8%), dinotefuron @ 0.3 g L-1 (65.0 %), diafenthiuron @ 1.3 g L-1 (63.8 %), imidacloprid (40%) +ethiprole (40%) @ 0.3 g L-1 (60.3%). The lowest per cent reduction was recorded in flonicamid @ 0.4 g L-
1 (60.1%), thiamethoxam (seed treatment) (26.9%), imidacloprid (seed treatment) (25.6%).
The order of efficacy of different treatments was as follows:
T7> T8> T5> T4> T3> T6> T2> T1> T9
The results of the experiment are in line with Seni and Naik (2017) who conducted a field experiment on brown plant hopper in paddy with the treatments thiamethoxam 25 WG @ 37.50 g a.i. ha-1, lamda cyhalothrin 5 EC @ 30 g a.i. ha-1, pymetrozine 50 WG @
150 g a.i. ha-1, buprofezin 25 SC @ 250 g a.i. ha-1, imidacloprid 40+ethiprole 40% w/w@ 80 WG @ 100 g a.i. ha-1, dinotefuran 20 SG @ 40 g a.i. ha-1, acephate 75 SP @ 564 g a.i. ha-1,untreated control. All the treatments were effective for hoppers management than control. The overall data revealed that the pymetrozine 50 WG @ 150 g a.i. ha-1 recorded higher per cent reduction of hoppers and higher grain yield than the other treatments in rice crop.
However for observations taken after 3 day af-ter spraying no significant differences were observed among different foliar insecticidal treatments but seed treatment with imidacloprid and thiomethoxam had ex-hibited significantly lower nymphal reduction as compared with other foliar spray treatments.
This could be due to the fact that the neonicotinoids such as imidacloprid and thiamethoxam as seed treatment protect the crop from sucking insects up to 25-30 days after treatment and the efficacy reduces with passage of time. Iqbal et al. (2013) reported that the application of insecticide (imidacloprid 20% SL, acetamiprid 20% SL, thiamethoxam 25 WG and acephate 75 SP) sprays immediately enhanced the mortality of the sucking insect pests on mungbean, Vigna radiata (L.). Whereas, seed treatment with imidacloprid + detergent did not show distinctive effect on the pest population. Imidacloprid and thiamethoxam were found to be the most effective insecticides against sucking pests followed by acetamiprid.
By the end of last observation (i.e., 11 DAS) the crop has reached an age of 45-50 days and though there were differences in the nymphal population of leafhopper, the per cent phyllody disease in all the experimental plots have reached to the stage of 85-90 per cent and we were unable to establish any correlation between vector population and per cent disease incidence of phyllody.
No correlation between insect vector population and that of percent disease incidence of phyllody have been reported by several workers. Sellammal et al. (1973) who observed no clear relationship between phyllody incidence and leaf hopper population. The authors opined that it is likely that a single inoculative vector may spread the disease to varying number of plants and hence no significant correlation could be exhibited between leafhopper population and per cent disease incidence of phyllody.
As the per cent disease of phyllody have reached to the maximum level we were unable to undertake any spray and also data on yield and the experiment was terminated.
CONCLUSIONS
In the present investigation pymetrozine treated plots showed significantly higher nymphal population re-duction as compared with other treatments especially at 3 days after spraying. Pymetrozine suppresses the stylet penetration of sucking insect pest especially homopter-ans hence leading to starvation and death (Kayser et al., 1994).
