Efficacy of different treatment schedules against black flies in citrus ecosystem

Introduction

Citrus is one of the most prominent fruit crops globally, originating from Southeast Asia and belonging to the family Rutaceae and subfamily Aurantiodeae. Over time, citrus cultivation has expanded widely and today thrives in tropical and subtropical climates. India stands as the sixth-largest producer of citrus fruits worldwide, following Brazil, China, the USA, Spain, and Mexico. Among the fruit crops cultivated in India, citrus ranks third after mango and banana. Among citrus fruits, sweet orange (Citrus sinensis L. Osbeck) is highly prized for its appealing taste, nutritional value, and commercial importance. It is extensively cultivated in India, particularly in states such as Andhra Pradesh, Maharashtra, Telangana, Karnataka, Punjab, and Rajasthan. According to recent data, India has approximately 200.7 thousand hectares under sweet orange cultivation, producing around 3.4 million metric tonnes with an average productivity of 6.8 MT/ha. Despite its nutritional and economic value, sweet orange production is frequently threatened by insect pest infestations, which lead to significant quantitative and qualitative losses. A wide range of pests attacks citrus crops, but among them, blackfly (Aleurocanthus woglumi), thrips (Scirtothrips dorsalis), aphids (Toxoptera aurantii), and leaf miner (Phyllocnistis citrella) are considered major pests in Jalna district. The citrus blackfly, (Aleurocanthus woglumi), is a destructive pest that can reduce yields by up to 80%, especially under severe infestations. It extracts sap from leaf tissues and secretes honeydew, which facilitates the growth of sooty mould, impairing photosynthesis and reducing fruit quality (Bhut & Jethva, 2017) [3] . It also contributes to "Kolshi" disease in oranges (Rajak & Diwakar, 1987) [7] . Nowadays, insect pests are becoming a major constraint in sweet orange cultivation, significantly reducing both yield and quality. Among them, sucking and chewing pests are of prime concern due to their direct damage as well as their role in disease transmission. Therefore, it is essential to gather comprehensive information on the pest complex associated with sweet orange, especially under the changing climatic conditions of the region.

Materials and Methods

The present investigation therefore was undertaken to evaluate the effective control measure to tackle the prevailing pest problems with harmonious way. For evaluation of safer molecules seven treatments was imposed in three replications with untreated control. A single plant of sweet orange was selected for each treatment under Randomized Block Design (RBD). The treatment was imposed at vulnerable growth stages, viz., pre-flowering, flowering, fruiting, and observing the ETL of pest. The observations were recorded at 1day before 1 st spray and 3, 7 and 14 days after subsequent sprayings. The data generated was exposed to appropriate statistical analysis recommended by (Gomez and Gomez, 1984).

Results and Discussion

This trial was conducted to evaluate the efficacy of seven treatments (T1-T7) against thrips in pomegranate fruit crop. Each treatment involved three sequential sprays and observation on thrips populations were recorded at 3, 7 and 14 days after each spray. Below are the mean thrips counts for each spray and the overall pooled mean efficacy. [6] reported that imidacloprid 17.8 SL at 0.005% concentration achieved a 76.77% reduction in citrus blackfly populations 14 days after application in sweet orange orchards. This performance was comparable to thiamethoxam (79.54%) and slightly lower than acephate (81.25%), indicating imidacloprid's effectiveness in managing citrus blackfly infestations. These findings concur with Tarale et al. (2024) [8] , whose 2023-24 Akola field trials showed that chemical control using Imidacloprid (0.5 ml/L) achieved the greatest reduction in citrus blackfly (Aleurocanthus woglumi). [6] reported that acetamiprid 20 SP at 0.01% concentration effectively managed citrus blackfly populations in sweet orange orchards, contributing to improved fruit yield and quality.

Second Spray Application

The study highlighted acetamiprid's role as a valuable tool in integrated pest management strategies for citrus blackfly control.

Third Spray Application

Pooled Mean Analysis

The pooled mean, representing overall efficacy across all three spray applications and observation periods. Treatment T6 (Thiamethoxam drenching followed by Acetamiprid and Chlorantraniliprole sequence) demonstrated the best pooled (8.91 black flies per 15 cm twig). Treatment T5 sequence) achieved the second-best result with 9.64 black flies and indicated effectiveness of this systemic insecticide rotation. Treatment T4 (Buprofezin-Azadirachtin-Bt combination) recorded 10.49 black flies per 15 cm twig, while T1 (Azadirachtin-bioagent sequence) showed 10.50 black flies. Treatment T2 (sticky traps-NSKE-bagging approach) resulted in 10.84 black flies and T3 (botanical sequence with Bt) recorded the highest among treated plots with 12.25 black flies per 15 cm twig, suggesting that purely botanical and biological approaches may require extended periods or supplementary applications for optimal efficacy. The untreated control T7 maintained the highest pooled mean of 38.21 black flies per 15 cm twig.

Conclusion

In the first spraying, Thiamethoxam 25% WG (drenching) was the most effective in controlling blackflies, followed by Imidacloprid 200 SL and Buprofezin 25% SC, which also gave good suppression. Azadirachtin 1% EC (10,000 ppm) showed moderate results. Sticky traps (yellow and blue, 4+2 per plant) provided limited physical control, while Sweet flag (Acorus calamus) powder was the least effective during this round. During the second spraying, Acetamiprid 20% SP recorded the highest reduction in blackfly population, followed by Azadirachtin 1% EC, which offered moderate control. NSKE 5% gave partial results, and Lecanicillium lecanii showed the lowest effectiveness in this application. In the third spraying, Cyantraniliprole 10.26% OD was found to be the most effective treatment against blackflies. It was followed by Beauveria bassiana and the practice of bagging and destruction of infested fruits. Bacillus thuringiensis var. kurstaki 5% WP showed moderate suppression. Chlorantraniliprole 18.5% SC was less effective, and it ranked lowest in performance during this spray.

References

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