Evaluation of biorationals against Myzus persicae Sulzer (Aphididae: Hemiptera) on broccoli under net house

Introduction

Broccoli (Brassica oleracea var. italica) is a popular and nutritious vegetable crop that belongs to the family Cruciferae. It is known for its green, flowering heads and is widely cultivated in many parts of the world. Broccoli is a particularly rich source of vitamin C and vitamin K (Nagraj et al., 2020) [8] . Broccoli crop production involves several key aspects, including cultivation practices, growth requirements, and pest management. Like other cruciferous crops, insect pests cause damage to broccoli and play a major role in reducing the yield. The peach-potato aphid, Myzus persicae Sulzer, is one of the most important pests of economic crops. This pest damages plants both directly, by consuming nutrients and water, and indirectly, by transmitting plant viruses. With resistance to more insecticides than any other herbivorous insect pest, it holds the unenviable title of being highly resistant. Due to the development of its resistance to chemical pesticides, it is necessary to find other control options (Ali et al., 2023) [3] . Keeping in view the economic and nutritive importance of broccoli and adverse effects of synthetic insecticides on human health and environment, the non-synthetic natural pest control approaches seem to be the novel alternatives of chemical insecticides. Biorationals like azadirachtin, pongamia, Lecanicillium muscarium, Beauveria bassiana, Metarhizium rileyi, M. anisopliae, spinosad were selected as safer alternatives for effective control of M. persicae, in order to support sustainable production with least environmental pollution.

Material and Methods

The study was conducted in net house at Hi-tech Horticulture Unit, University of Agricultural Sciences, Dharwad following randomized block design with 8 treatments and 3 replications during Rabi season 2022-23. Raised beds of 100 cm width and 15 cm height leaving 50 cm path between the beds were prepared. Broccoli seedlings (Green magic) were procured from nursery. The seedlings of 30 days old were transplanted in zigzag manner with a spacing of 45 cm × 45 cm in two rows in plot size of 10 m length and 1 m width. All the recommended agronomic practices were carried out during the experiment including plant protection measures except for the M. persicae. Treatment details: The treatments listed below were targeted against M. persicae. The required quantity of spray solution was calibrated and treatments were imposed using a knapsack sprayer. Need-based application was carried out when pests reached peak level or ETL. Observations recorded: Observations were recorded from randomly selected five plants from each treatment and replication and were tagged. Pre-treatment observation was recorded a day before treatment (DBT) imposition and post treatment observations were recorded on 1, 5, 7 and 10 days after treatment imposition (DAT), respectively. The aphid population was counted from 1 cm 2 leaf area from three leaves of each selected plant.

Statistical analysis:

The number in reduction of pest population over control due to biorational treatments was calculated at the different time intervals. The data so obtained were subjected to ANOVA (Randomized Block Design) after following transformation (√x +0.5) values (Square root transformation). The significance of the difference among the treatment combination means were determined by Duncan's Multiple Range Test (DMRT) at 5% level of probability. Software like Microsoft excel and WASP 2.0 were used for aforesaid analysis.

Results

The study was carried out to evaluate efficacy of different biorationals against M. persicae on broccoli. The observations of M. persicae on broccoli before and after first spray are presented in Table-2. Aphid population was found non-significant, indicating uniform distribution of population in all the treatments at 1 day before spray (DBS). At 1 day after spray (DAS) the treatments viz., azadirachtin 3000 ppm @ 3 ml/l was found significantly superior over remaining treatments by recording least aphid count of 14.89 per cm 2 , which was at par with spinosad 45 SC @ 0.2 ml/l and pongamia oil @ 3 ml/l recorded 14.94 and 15.00 aphids per cm 2 and were significantly superior over L. muscarium, B. bassiana, M. anisopliae and M. rileyi respectively. Same trend was observed at 5, 7 and 10 DAS. Azadirachtin showed 56.85% reduction over control after 10 DAS which was followed by spinosad 45 SC, pongamia oil, L. muscarium and others. All the treatments showed significant increase in yield over control. Azadirachtin 3000 ppm @ 3 ml/l recorded the highest yield of 12.32 tones per hectare and was superior over all the treatments followed by spinosad 45 SC @ 0.2 ml/l and pongamia oil @ 3 ml/l recorded 11.40 and 10.28 tones per hectare respectively. However, entomopathogens were also recorded comparable yield ranging from 8.15 to 10.09 tonnes per hectare.

Discussion

Broccoli (Brassica oleracea var italica L.) is a popular exotic and nutritious vegetable belonging to the family (Brassicaceae). Renowned for its densely packed green heads made up of compact flower buds, broccoli is grown for its consumable florets and stems, boasting a wealth of essential vitamins, minerals and dietary fiber. To cater to both domestic demands and exports, it holds significant cultivation importance, often raised in protective environments like net houses. The research aimed to develop strategies for controlling M. persicae using environmentally friendly approaches. The findings of this investigation are discussed and analyzed in relation to existing scholarly resources. Among all the treatments azadirachtin 3000 ppm @ 3 ml/l was found significantly superior (63.92% reduction over control (ROC)) over remaining treatments in controlling aphid population and was at par with spinosad 45 SC (58.74% ROC). The next best treatment was L. muscarium, (49.25% ROC) and was found superior over other entomopathogens. Azadirachtin was highly effective in controlling aphid population under net house, it is recommended mainly for sucking pest. This compound has been shown to be an antifeedant and insect growth regulator.

Azadirachtin is a complex compound and its exact mode of action is still not fully understood. It is insect antifeedant at high concentrations and growth inhibitor at low concentrations to all the test insects if applied topically or by feeding (Mordue and Blackwell, 1993;Seymour et al., 1995;Abudulai et al., 2003) [7, 11, 1] , due to its insecticidal nature azadirachtin was superior over all treatments in controlling aphids. Spinosad 45 SC @ 0.2 ml/l which is mainly recommended for defoliators also could control aphid population to some extent but it followed the azadirachtin. In second spray L. muscarium got superior over pongamia, since entomopathogens takes time to multiply and establish first and control later, hence delayed response of L. muscarium was observed. At 1 DAS slight reduction in pest population in treatments comprising of entomopathogens was noticed, it might be due to spray action. Research work is supported with following studies, (Shinde et al., 2010) [12] , found that L. muscarium (Zimm.) is a promising microbial biocontrol agent with a broad host range. Numerous studies have documented the natural infection of various insect pests by L. muscarium, with a notable prevalence among sucking insects like M. persicae and pests from the Homoptera, Hemiptera and Thysanoptera orders. Survival and fecundity and the effect of secondary metabolites of L. muscarium and B. bassiana on Aphis gossypii was evaluated by Gurulingappa (2011) [6] . L. muscarium and B. bassiana are important entomopathogens of A. gossypi. Their capacity to colonize crop plants is also becoming widely recognized, both fungi significantly reduced the rate and period of reproduction of A. gossypii.

(Akbar et al., 2010) [2] , evaluated effect of biosal 10 EC, a neem formulation against aphid, Myzus persicae (Sulzer) (Aphididae: Hemiptera), on cabbage biosal performed well with 59.77% reduction. B. bassiana was more effective against M. persicae with a 40% reduction on broccoli, B. bassiana is also important for reducing the risk of pesticide resistance and maintaining environmental sustainability