Pigeon pea (Cajanus cajan L.) is an important pulse crop of the tropics and subtropics, particularly in India, where it contributes significantly to dietary protein and soil fertility. Despite India being the largest producer of pigeonpea, its productivity has remained a persistent concern. Pigeon pea occupies about 4.5 M ha in India, with an annual production of 3.66 M tonnes and an average productivity of 824 kg/ha. In Telangana alone, the crop is cultivated in 2.28 lakh ha, producing 2.06 lakh tonnes annually (Anonymous, 2022). Both biotic and abiotic constrain pigeonpea productivity. Among biotic factors, insect pests pose the most serious challenge in increasing the production and productivity under subsistence farming conditions of red gram, irrespective of agro ecological zones. More than 300 species of insect species have been reported infesting the pigeonpea, although only a few are considered economically significant. The pod borer complex, comprising Helicoverpa armigera and Maruca vitrata during flowering and pod formation, along with the pod fly (Melanagromyza obtusa) and pod sucking bugs at pod maturation represents the major bottleneck in achieving potential yields. Infestation of reproductive parts directly translates into severe grain yield losses, with annual losses estimated at 2.5-3.0 M tonnes of pulses due to insect pests (Rabindra et al., 2004). Specifically, pod borers such as M. vitrata and H. armigera can inflict 60-90% yield loss (Lal et al., 1992).
       
Farmers largely depend on agrochemicals to manage pod borers, often adopting calendar based applications and indiscriminate insecticide use. Such practices not only escalate the cost of plant protection and reduce profitability but also result in poor pest control, resistance development in H. armigera and environmental concerns. These limitations underscore the need for rational and sustainable management strategies. Scheduled application of insecticides, wherein sprays are aligned with crop phenology and pest dynamics offers a more targeted and effective approach. Therefore, the present study was undertaken to evaluate the efficacy of sequential insecticide applications against pod borers in pigeon pea under the field conditions of Telangana.

A field experiment on schedule application of insecticides against pod borers in pigeonpea was conducted during Kharif 2022, 2023 and 2024 at the Experimental Farm (D Block) of the Regional Agricultural Research Station (RARS)-PJTAU, Warangal, Telangana (GPS 18°00'38.5"N 79°35'45.3"E). The study was laid out in a randomized block design (RBD) with ten treatments each replicated thrice. The sequential treatments are:
T1: Bt var. kurstaki @2.5 g /L- Chlorantraniliprole@0.3 ml/L- Lufenuron@1.2 ml/L.
T2: Bt var. kurstaki @2.5 g /L- Flubendiamide@0.2 ml/L- Lufenuron@1.2 ml/L.
T3: NSKE 5% @50 g/L- Chlorantraniliprole@0.3 ml/L- Lufenuron@1.2 ml/L.
T4: NSKE 5%@50 g/L - Flubendiamide @0.2 ml/L- Lufenuron @1.2 ml/L.
T5: Indoxacarb@ 0.8 ml/L- Chlorantraniliprole@0.3 ml/L- Lufenuron @1.2 ml/L
T6: Indoxacarb@ 0.8 ml/L- Flubendiamide@0.2 ml/L- Lufenuron @1.2 ml/L
T7: Lambda cyhalothrin@1.0 ml/L- Chlorantraniliprole@0.3 ml/L- Lufenuron@1.2 ml/L.
T8: Lambda cyhalothrin@1.0 ml/L- Flubendiamide@0.2 ml/L- Lufenuron@1.2 ml/L.
T9: Untreated control.
T10: Standard check (Neem oil 1500 ppm@5 ml/L +Chlorpyri- phos@ 2.5 ml/L- Chlorantraniliprole@ 0.3 ml/L- Emamectin benzoate@0.4g/L)
       
The pigeonpea cultivar, Warangal Kandi-2 (WRG 255) medium duration was sown at a spacing of 120 × 20 cm following the recommended agronomic practices for the zone except for crop protection interventions. Each treatment plot consisted of four rows of 4 m length. Insecticide sprays were scheduled at the flowering stage with a 15 day interval between successive applications. Observations recorded  include larval density of H. armigera and M. vitrata per plant from randomly tagged three plants per replication, recorded before spraying and at 7 and 10^th days after spray, percentage of pod and seed damage, grain yield (kg/ha), cost: benefit ratio (computed based on treatment wise input costs and yield returns). The data generated on the mean pod borer population in pigeonpea were transformed to a square root transformation and the percent pod damage was transformed to arcsine values for normalization. These values were subjected to statistical analysis using R software to test the level of significance.

Efficacy of sequential application of insecticides against Helicoverpa armigera
 
The cumulative mean incidence of Helicoverpa armigera across different treatments before spraying ranged from 1.71 to 2.40 larvae per plant during the study period (Kharif 2022 to 2024). Differences among treatments were statistically non-significant indicating a relatively uniform distribution of the pest in the experimental field prior to insecticidal application. In contrast, post-treatment observations revealed significant differences in larval populations across treatments at seven and ten days after each spray. The pooled data on insecticidal efficacy indicated that the lowest mean larval count (0.04 larvae/plant) and the highest reduction (94%) over control were achieved in T6 where sequential sprays of Indoxacarb at the flowering stage, Flubendiamide at the pod formation stage and Lufenuron at the pod maturation stage (15-day intervals) were applied. This was followed in effectiveness by T8 (Lambdacyhalothrin - Flubendiamide - Lufenuron) and T2 (B. thuringiensis var. kurstaki - Flubendiamide - Lufenuron (Table 1).    


 
Efficacy of sequential application of insecticides against Maruca vitrata
 
With respect to the incidence of Maruca vitrata, the cumulative mean larval population/live webs of Maruca across treatments before insecticidal application was either 1 or 2 larvae per plant during the study period with non-significant difference among treatments indicating an almost uniform distribution of the pest across the experimental field. However, cumulative post treatment data on insecticidal efficacy revealed significant differences among treatments. The lowest mean number of live webs (0.09/plant) and the highest reduction (88%) over control were recorded in T6 wherein sequential sprays of Indoxacarb at the flowering stage, Flubendiamide at the pod formation stage and Lufenuron at the pod maturation stage (15 day intervals) were applied. This was closely followed in effectiveness by T8 (Lambdacyhalothrin- Flubendiamide-Lufenuron and T2 (B. thuringiensis var. kurstaki-Flubendiamide-Lufenuron. Overall, all insecticidal treatments were found significantly superior to the untreated control, as evidenced by consistently lower M. vitrata populations per plant and higher percent reductions in larval population across treatments (Table 2).


 
Sequential application of insecticides on pod damage by pod borer complex
 
The cumulative pod damage caused by H.armigera, M. vitrata, M. obtusa varied significantly across the different insecticidal treatments. All treatments significantly reduced the pod and grain damage compared to the untreated control. The cumulative mean (%) pod damage by H. armigera ranged from 3.49 to 8.90 while that of M. vitrata ranged from 2.32 to 6.62. Similarly, damage caused by M. obtusa varied between 7.32 and 18.99 across the treatments. Among the evaluated treatments, T6 (sequential sprays of Indoxacarb at the flowering stage, Flubendiamide at the pod formation stage and Lufenuron at the pod maturation stage emerged as the most effective against all three pod borers recording the lowest pod damage (3.49% by H. armigera, 2.32 by M. vitrata and 7.32 by M. obtusa. In contrast, the cumulative pod damage inflicted by pod sucking bugs ranged between 6.87 and 17.71, with the T7 treatment (sequential sprays of Lambda cyhalothrin at the flowering stage, Chloran-traniliprole at the pod formation stage and Lufenuron at the pod maturation stage) performing best against these pod bugs (Table 3).


 
Seed yield and economics
 
The cumulative grain yield data revealed that all insecticidal treatments recorded significantly higher yields than the Untreated control. The mean grain yield across the treatments varied from 1400 to 1763 kg/ha as against 1068 kg/ha in the control indicating the superiority of stage specific sequential interventions in enhancing productivity. Among the treatments, T6 (sequential sprays of Indoxacarb at 0.8 ml/L at the flowering stage, Flubendiamide at the pod formation stage and Lufenuron at the pod maturation stage) produced the highest yield (1763 kg/ha) corresponding to a 65% increase over the untreated control. This was followed by T8 (Lambda cyhalothrin-Flubendiamide-Lufenuron) and T2 (B. thuringiensis var. kurstaki -Flubendiamide-Lufenuron), which also recorded significantly higher yields than the control (Table 3).
       
The comparative economic analysis of sequential insecticidal sprays against major pests of pigeonpea over three years indicated that the benefit: cost (B:C) ratio ranged from 2.00 to 2.99 across treatments. The highest B:C ratio (2.99:1) was achieved in plots treated with sequential sprays of Indoxacarb at 0.8 ml/L at flowering, Flubendiamide at pod formation and Lufenuron at pod maturation. In terms of profitability, net returns over control varied from INR 34,961 to INR 76,879 per hectare. The maximum net return (INR 76,879/ha) was recorded in the Indoxacarb-Flubendiamide-Lufenuron treatment, followed by INR 71,599/ha in the Lambdacyhalothrin-Flubendiamide- Lufenuron treatment. These findings clearly establish the economic superiority of sequential spray schedules involving newer insecticides, particularly Flubendamide based combinations, in managing pigeonpea pod borers
       
The sequential application of insecticides against pod borers and pod-sucking bugs in pigeonpea is crucial due to their overlapping generations, peak activity during flowering and podding and their high potential to cause severe yield losses. Time specific sprays synchronize control measures with the most vulnerable stages of pod borers ensuring continuous protection of flowers and pods. Moreover using insecticides with different modes of action in a sequential manner enhances efficacy and delays resistance development in pest populations. Hence, careful selection and rotation of active ingredients with diverse modes of action are critical within an Integrated Pest Management (IPM) framework (IRAC, 2019; Bassi et al., 2016).
       
The present study on the cumulative efficacy of sequential insecticide applications against the pod borer complex and pod sucking bugs in pigeonpea revealed that sequential spraying of Indoxacarb at flowering, Flubendiamide at pod formation and Lufenuron at pod maturation was most effective in suppressing  H. armigera, M. vitrata and  M. obtusa. For pod-sucking bugs, the sequential application of Lambdacyhalothrin at 1 ml/L at flowering, Chlorantraniliprole at pod formation and Lufenuron at pod maturation was found to be the most effective ultimately resulting in the highest grain yield. Indoxacarb applied at the flowering stage of the crop effectively controlled both eggs and early larval instars of pod borers due to its dual contact and stomach action with ovicidal properties thereby preventing larval establishment in flowers and young pods. Flubendiamide applied at pod formation effectively managed mature larvae by disrupting calcium homeostasis in muscles leading to rapid feeding cessation and mortality. Since this coincided with peak pod borer activity its application protected developing pods from severe damage. At pod maturation, Lufenuron, an insect growth regulator (IGR) and chitin synthesis inhibitor effectively suppressed late instar larvae and pod fly by disrupting moulting and pupation thereby preventing pest carryover.
       
These findings are in close agreement with earlier reports highlighting the efficacy of stage-specific sequential sprays in reducing pod borer damage and improving yield. Bantewad et al., (2018) reported that Chlorantraniliprole followed by Flubendiamide and Dimethoate significantly reduced pod fly populations at 3, 7 and 14 days after spraying. Our findings also corroborate the results of Dabhi et al., (2015), who reported that Indoxacarb 15 EC @ 73 g a.i./ha was most effective in controlling pod borers in pigeonpea, while also resulting in significantly higher yields (1753 and 1652 kg/ha in two consecutive years). Similarly, Mamta et al. (2021) reported that the foliar application of the broad spectrum insecticide Indoxacarb 14.5 SC for the management of pod borer, Helicoverpa armigera in green gram resulted in a 35.1% increase in green gram yield. Veeranna et al., (2024) reported that Thiamethoxam 25 WG @ 0.4 g/L + jaggery @ 5 g/L and Flubendiamide 480 SC @ 0.3 ml/L reduced pod fly populations and pod damage while recording the highest grain yield (1582 kg/ha) and the best cost: benefit ratio (1:2.39), when they sprayed at pod formation stage of the crop. The present findings are also similar to findings of Taggar et al. (2021) who reported that the spray of Chlorantraniliprole 18.5 SC @ 150 ml/ha followed by flubendiamide 480 SC @ 125 ml/ha registered significantly the lowest pest population and pod damage. Similarly Khinchi and Kumawat (2021) reported that the chloran-traniliprole 18.5 SC was found most effective @ 200 ml/ha for suppression pod borer, H. armigera and pod fly, M. obtusa. Dodia et al., (2009) reported flubendiamide as the most effective treatment with 5.98% pod damage due to pod borer complex followed by Emamectin benzoate (6.35%). The sequential use of Indoxacarb, Flubendiamide and Lufenuron also represents a resistance management strategy as they belong to different chemical groups with distinct modes of action. This sequential rotation of insecticides with different modes of action effectively reduces pod borer damage while delaying resistance development.

The sequential application of insecticides in pigeonpea proved highly effective in suppressing the pod borer complex viz., H. armigera, M. vitrata, M. obtusa and pod sucking bugs while ensuring higher grain yields. Application of Indoxacarb at 0.8 ml/L at flowering, Flubendiamide at 0.2 ml/L at pod formation and Lufenuron at 1.2 ml/L at pod maturation showed highly effective against pod borers, whereas Lambda cyhalothrin at 1 ml/L at flowering, Chlorantraniliprole at 0.3 ml/L at pod formation and Lufenuron at 1.2 ml/ L at pod maturation were found most effective in controlling pod sucking bugs. These results emphasize the importance of stage specific mode of action based insecticide rotation in reducing pest pressure, minimizing yield losses and delaying resistance development. Thus, sequential insecticide applications represent a rational, sustainable and integral component of integrated pest management (IPM) approaches in pigeonpea.

The present study was supported by the Professor Jayashankar Telangana Agricultural University, Hyderabad and the Indian Council of Agricultural Research (ICAR), Government of India, under the AICRP on Pulses program
 
Disclaimers
 
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.

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.