Globally India is the largest producer of black gram, accounting for more than 70% of production followed by Myanmar and Pakistan (Bharathi et al., 2025). Blackgram is referred as the “king of the pulses” due to its delicious taste and numerous other nutritional qualities (Vadivel et al., 2023). It is rich in nutritional quality with 24-27% protein, 1% fat, 57% carbohydrate, 3.8% fibre and 4.8% ash. It is grown in both summer and winter seasons (Mohanlal et al., 2023). Furthermore, it is fed to milch cows in particular as nutrient-rich fodder. Among the states, A.P. is leading in production with 3.62 lakh tonnes. Average price of blackgram in A.P. during august 2025 is Rs. 6704/- per quintal. Increasing price pattern of blackgram in the open markets during recent years couldn’t give happiness to our farmers as they were struggling to secure the yields. The prime reason for this is sucking pest complex which acts as vector of deadly viral diseases like YMD (yellow mosaic disease) and bud necrosis. The symptoms of GBNV in the field have been thoroughly documented. Necrosis and chlorotic rings emerge after young quadrifoliate leaves first show minor chlorotic patches. The primary defining feature of wet and post-rainy seasons is terminal bud necrosis. Common secondary signs include distortion of leaflets, axillary branch growth and stunting. Early infection causes bushy, stunted and early-death plants. Only a few branches exhibit symptoms if the plants are more than a month old. The only way of managing this problematic viral menace in blackgram is through the management of its vector i.e. Thrips significant yield loss may occur If not properly managed at an early stage of the crop. In order to mitigate this menace, several insecticides as seed treatment, foliar sprays in combination were studied to know their efficacy in the management of thrips and also benefit cost ratios. Choosing an appropriate, cost effective insecticide is always challenging for the farming community.

This experiment was conducted during 2019-2022 at Agricultural College Farm -Bapatla, Guntur, A.P., laid out in RBD (randomized block design) with fifteen (15) treatments including untreated check, replicated thrice with a plot size of 12 m² to study the efficacy of insecticides as seed treatment and foliar sprays for the control of thrips in blackgram (LBG 752). The insecticide treatments were mentioned in the Table 1. The experimental field was kept unsprayed up to 15 DAS and later protected through blanket sprays using suitable pesticides to control other pest and diseases. Foliar application of selected insecticides was given at 30 DAS, 45 DAS and 60 DAS during morning hours. Data on pest population was recorded one day before spraying as pre treatment count and at 1, 3, 7, 10 days after spraying as post treatment count. The observations were recorded from 10 randomly selected plants in each plot leaving the border rows. Second and third sprays were given at 15 days interval to allow subsequent population buildup in the experimental plots.  Per cent population reduction was calculated by using modified Abbot’s formula (Flemming and Ratnakaran, 1985).

The total number of diseased plants in each plot was counted at 15 days interval i.e. 15, 30, 45 (after 1^st spray), 60 (after 2^nd spray), 75 (after 3^rd spray) days after sowing. PDI was calculated by using the following formula:  

Upon harvest, the mean seed yield of treatments recorded per plot (kg/plot) was converted to kg/ha and subjected to ANOVA to test the significance of treatments. The incremental cost-benefit ratio was calculated to find out the most economical management method.

 
Data viz., mean number of thrips per plant, percent reduction in the population of thrips over untreated check, mean per cent bud necrosis disease incidence and yield data was subjected to ANOVA after using suitable transformations. The mean comparisons were made by least significant difference (LSD) (Duncan, 1951).

Cumulative efficacy of insecticides during rabi 2019-2020
 
Table 1 indicates that T₅ was found superior with lowest mean number of thrips per plant (0.22) and it was on par with T₁₁, T₈, T₁₄, T₉, T₃ and T₇ with 0.31, 0.51, 0.63, 0.80, 1.08 and 1.38 respectively. Highest mean per cent population reduction over untreated control was recorded 89.37 in case of T₅ followed by T₁₁(80.91). Present findings pertaining to efficacy of Imidacloprid and thiamethoxam were in accordance with Radhika et al. (2018a) who reported that Imidacloprid 70 WS at 5 g kg^-1 was found most effective with 2.67 thrips per six leaves among the tested insecticides followed by thiamethoxam 25 WG at 3 g kg^-1 with 2.80 thrips per six leaves as seed treatment in blackgram during rabi 2017-18 in Hyderabad.  The results regarding the efficacy of spinosad were in line with findings of Surbhi et al. (2018) who reported that insecticidal spray of spinosad 45 SC @ 0.0135 % was found effective with lowest number of thripsi.e. 0.28 thrips/leaf on greengram with highest seed yield in thiamethoxam 25 WG @ 0.10% + spinosad 45 SC @ 0.0135 % treatments with 1066 kg ha^-1 followed by Imidacloprid 30.5 SC @ 0.12% + spinosad 45 SC @ 0.0135% with 1025 kg ha^-1.
 
Mean PDI of bud necrosis during rabi 2019-2020
 
Overall mean per cent bud necrosis disease incidence (Table 2) was lowest (3.24) in T5 and it was on par with T₈(3.45), T₁₁(3.78), T₁₄(3.95), T₃(4.66), T₉(4.70). Table 3 pertaining to ICBR, T5has recorded the highest grain yield i.e. 1414 kg ha^-1 with ICBR 1:4.80 followed by T₁₁ (1:4.47), T₉ (1:3.25) and T₃ (1:2.99). The results regarding the efficacy of Fipronil 5SC spray @ 50 g a.i ha^-1 can supported by the findings of Radhika et al. (2018a) who reported that Fipronil 5% SC @ 1 mL L^-1 at weekly intervals against sucking pests in blackgram saved 269 kg ha^-1 pod yield with an avoidable yield loss of 26.16 per cent.




 
Cumulative efficacy of insecticides during Kharif 2020-2021
 
Data in Table 4 reveals that T₅ has recorded 0.38 mean number of thripsplant^-1 and it was statistically at par with T₈ (0.42), T₁₄ (0.47), T₁₁ (0.54 ), T₃ (1.04) and T₉ (1.21). Highest population reduction over control was found in T₈ (86.67 per cent) followed by T₅ (86.62), T₁₁ (85.21), T₁₄ (82.69). These results are in accordance with Reddy et al., (2020) who reported that Imidacloprid 17.8 SL (20.54%) was the most effective treatment in controlling the sucking insect pests in blackgram during kharif 2017. Results pertaining to efficacy of Fipronil can be supported by the findings of Singh et al., (2019) who reported that Imidacloprid (0.005%) and Fipronil (0.01%) proved to be the most effective next to acetamiprid (0.004%) against sucking insect pests in greengram during kharif season.


 
Mean PDI of bud necrosis during kharif 2020-2021
 
Among the treatments (Table 5), T₅ recorded least mean bud necrosis per cent disease incidence i.e. 5.19 and it was at par with T₁₁ (5.64), T₃ (5.94) T₁₄ (6.13), T₉ (6.39), T₈ (6.64). Ruth et al., (2016) reported that seed treatment with Imidacloprid @ 5 g kg^-1 seed. + neem seed kernal extract @ 5% + spinosad 0.3 mL L^-1 were found superior in controlling the viral diseases in tomato during kharif 2009. Whitefly and thrips population were low and were 1.18/plant and 0.51/plant, respectively after post treatment. Least incidence of bud necrosis disease was recorded i.e. 6.60, 9.93 and 14.88 at 30, 45 and 60 days after planting in the same treatment plots. Table 6 pertaining to ICBR indicates, T5 has recorded highest grain yield i.e. 1372 kg ha^-1 with ICBR 1:3.73 followed by T₁₁ (1:2.93), T₃ (1:2.64) and T₉ (1:2.28). Similarly, Sujatha and Bharpoda (2017) who reported that higher incremental cost benefit ratio (ICBR) 1:7.81 was obtained in the treatment thiamethoxam 25 WG (0.01%) in greengram during kharif 2015.




 
Cumulative efficacy of insecticides during rabi 2020-2021
 
Results tabulated in Table 7 indicates that T₅has recorded least mean number of thrips (0.37 plant^-1) and it was statistically on par with T₁₁ (0.42), T₈ (0.66), T₁₄ (0.81), T₉ (1.19), T₃ (1.34). Population reduction over untreated control was 89.48, 89.22 and 82.42 per cent in T₁₁, T₅ and T₈ respectively found effective among the treatments. Present findings pertaining to Spinosad are in accordance with Sharanappa et al. (2020) who reported that the overall mean per cent reduction of thrips population after imposing first, second and third spray was highest in Spinosad 45 SC (88.15%) followed by Fipronil 5 SC (87.24%) and found significantly superior than rest of the treatments in capsicum during rabi season. Present findings about Fipronil are in line with Swathi et al., (2018) who reported that acetamiprid 4% + Fipronil 4% @ 2 mL L^-1 found effective against thrips by reducing 70.81% thrips population next to thiacloprid 21.7 SC @ 0.0325% with 74.80% reduction of thrips population over untreated control in rice fallow blackgram during rabi 2017-18.


 
Mean PDI of bud necrosisduring rabi 2020-2021
 
Table 8 indicates that T₁₁has recorded least mean disease incidence (1.28) and it was statistically on par with T₈ (2.15%), T₉ (2.16%), T₁₁ (2.64 %) and T₅ (3.05%). Present findings are in line with Swathi et al., (2018) who reported that flonicamid 50 WG @ 0.0325% found effective against the population of whitefly by reducing 72.19 % and lowest per cent YMV disease incidence (17.66%) followed by acetamiprid 4% + Fipronil 4% @ 2 mL L^-1 (64.94%) and thiamethoxam 25 WG @ 0.005% (62.21%) which were on par with each other in rice fallow blackgram during rabi 2017-18. Table 9 about ICBR reveals that T₅has recorded highest grain yield i.e. 1439 kg ha^-1 with ICBR 1:4.45 followed by T₁₁ (1:3.97), T₃ (1:2.19) T₉ (1 2.10). Even though the treatments viz. T₈, T₁₄ found effective, their ICBR found low (1:1.58 and 1:1.23, respectively) due to high input cost. The present findings are in line with Darshan et al., (2018) who reported that Imidacloprid 17.8 SL @ 0.005 per cent found most effective with lowest population of thrips (1.30) and found on par with thiamethoxam 25 WG @ 0.008 per cent (1.33) and acetamiprid 20 SP @ 0.004 per cent (1.36). The maximum yield was obtained in plots treated with thiamethoxam 25 WG @ 0.005% (701 kg ha^-1) against control plot (400 kg ha^-1) in mothbean during rabi season. Swathi et al., (2018) also reported that the highest seed yield was gained from the plots treated with thiamethoxam 25 WG @ 0.10% + spinosad 45 SC @ 0.0135% with 1066 kg ha^-1 in rice fallow blackgram during rabi 2017-18.

Always it is challenging to manage or mitigate the viral diseases in field crops as they cant be controlled directly using therapeutic pesticides. One must understand the exact vector(s) responsible for their spread. In case of GBNV in blackgram obviously its Thrips, a cryptic, minute, complex Thysanopterans. This study aimed at suitable and cost-effective seed dresser and an insecticide for the management of Thrips directly and bud necrosis indirectly. Even some treatments found suitable for this task can be placed at second due to their input cost especially treatments contain Spinosad and flonicamid. This study also observed that similar treatments performed in a different way across the  seasonsand which has no significance.

The present study was conducted by the corresponding author during doctoral degree programme.
 
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The views and conclusions expressed in this article are solely those of the authors and do not necessarily represent the views of their affiliated institutions. The authors are responsible for the accuracy and completeness of the information provided, but do not accept any liability for any direct or indirect losses resulting from the use of this content.
 
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The authors declare that there are no conflicts of interest regarding the publication of this article. No funding or sponsorship influenced the design of the study, data collection, analysis, decision to publish, or preparation of the manuscript. Informed consent All animal procedures for experiments were approved by the Committee of Experimental Animal care and handling techniques were approved by the University of Animal Care Committee.