Evaluation of Different Treatments on the Management of Black Gram Powdery Mildew Disease Caused by Erysiphe Polygoni (De Candolle)

Introduction

Black gram (Vigna mungo L.) is one of the most important short-duration pulse crops grown in India. The pulse ‘Black gram’ plays an important role in the Indian diet, as it contains a high amount of protein and it is a supplement to a cereal-based diet. The green pods are eaten as a vegetable and they are highly nutritious. Black gram is rich in easily digestible protein 25.21 per cent, contains about 58  per cent of carbohydrate, 2 per cent of fat, 0.273 mg of vitamin B1, 0.254 mg of vitamin B2, 1.447 mg of Vitamin Niacin, 138 mg of calcium, 379 mg of phosphorus, 7.57 mg of iron per 100 gram of seeds (USDA National Nutrient data base). Since it serves as a cheaper source of protein for the poor, it is rightly called the “Poor man’s meat” and can also be used as green manure.

Black gram originated from South Asia, later it has been in cultivation in many parts of Asia, Australia, West Indies, South and North America, and tropical and subtropical Africa. In India, it is primarily grown in Madhya Pradesh, Maharashtra, Orissa, Andhra Pradesh, Uttar Pradesh, and Tamil Nadu. Asia alone contributes about 90% of the world’s total black gram production. In India, black gram is cultivated around an area of 4.6 m ha with a total production of 24.5 lakh t and productivity of 543 kg ha^-1 whereas, in Tamil Nadu, it holds an area of 3.7 lakh ha with a production of 2.7 lakh t and productivity of 650 kg / ha.¹

In the case of its vast growing area and production, its productivity is low due to various biotic and abiotic stresses.² Among all the fungal diseases, powdery mildew caused by Erysiphe polygoni is the major one. The pathogen was reported by de Candolle and found to be one of the most economically important diseases in black gram which occurs at the later stages of the crop growth causing high yield loss.

Powdery mildew is usually noticed in 45 days old crops in black gram.³ In the powdery mildew disease white, powdery patches appear on leaves and other green parts and later become dull in color. These patches gradually increase in size and become circular, covering the lower surfaces as well. Severely affected parts become shriveled and distorted. In severe infections, the foliage turns yellow, causing premature defoliation. Powdery mildew results in qualitative and quantitative loss of grains. The reduction in photosynthetic activity and physiological changes takes place leading to 40-90% yield loss depending on the stage and the occurrence of the disease.⁴

Many systemic and non-systemic fungicides were reported to manage the powdery mildew of black gram. However, the application of chemicals causes environmental pollution and is injurious to the soil ecosystem. The information on the efficacy of new generation fungicide, botanical and organic amendment against powdery mildew of black gram is insufficient. Hence bio-control agents and botanicals are used against E. polygoni.

In the present study to screening the efficacy of different treatments to management of black gram powdery mildew under pot and field trial.

Materials and Methods

Experimental details

Management practices were carried out against E. polygoni in black gram variety ADT-3. The leaf extract and A. quisqualis were prepared as per the recommended dosage. The treatments were sprayed on all aerial parts of the plant using a hand sprayer. The first spraying was taken up before the initial appearance of the disease in the crop i.e., 43 DAS and further spray was given at 10 days intervals on 53 DAS.² The pot trial and field trial was conducted with nine treatments including control. The cultivation practices have been carried out following righteous procedures uniformly.

Layout (Experimental farm, Annamalai University)

Season	:	Kuruvai
Design	:	RBD
Replications	:	3
No. of. pots	:	27
Duration	:	70-75 days
Variety	:	ADT-3

Field layout

T2	IRRIGATION CHANNEL	T7	IRRIGATION CHANNEL	T8
T5		T6		T2
T4		T1		T9
T8		T9		T3
T1		T2		T5
T9		T5		T1
T3		T4		T7
T6		T8		T4
T7		T3		T­6

 Treatment details

T1	:	Ampelomyces quisqualis @ 0.5% on 43 DAS
T2	:	Ampelomyces quisqualis @ 0.5% on 53 DAS
T3	:	Rhizophora apiculata @ 15 ml on 43 DAS
T4	:	Rhizophora apiculata @ 15 ml on 53 DAS
T5	:	T1 + T2
T6	:	T3 + T4
T7	:	T5 + T6
T8	:	Azoxystrobin @ 0.1%
T9	:	Control

Since, Azoxystrobin is effective against powdery mildew disease, it is used as standard check for further studies. In case of compatibility, in vitro study is tedious since it is an obligate parasite. Hence, field study was carried out and both bio-agent and botanical were found to be compatible as they showed significant better result in combined application than individual.

Observations on powdery mildew incidence

Observations were made on the prevalence and severity of powdery mildew at different stages to record the prevalence of disease after 1^st spray and 2^nd spray.

Statistical analysis

Statistical evaluation was done using the analysis of variance (ANOVA) followed by the Duncan’s Multiple Range Test (DMRT). The statistical significance was expressed at p≥ 0.05. Here we used Replicator software and Wasp software for statistical analysis.

Result and Discussion

Evaluation of different treatments on management of black gram powdery mildew disease (Pot trial & Field trial)

A pot trial was conducted to evaluate the efficacy of bio-agents, botanicals and fungicides against powdery mildew of black gram during 2022 with bio-agent, botanical and a fungicide. Observations on per cent disease index was recorded. In the present investigation, Azoxystrobin 25% SC @ 0.1 % was found to be effective against E. polygoni. The fungicide recorded PDI of 19.30 per cent after 1^st spray and 9.37 per cent after 2^nd spray followed by foliar application of A. quisqualis @ 0.5% on 43 DAS + A. quisqualis @ 0.5% on 53 DAS + R. apiculata @ 15% on 43 DAS + R. apiculata @ 15% on 53 DAS with PDI 23.25 per cent after 1^st spray and 14.63 per cent after 2^nd spray. The untreated plants showed higher PDI of 51.76 per cent to 67.47 per cent (Table 1).

Table 1: Evaluation of different treatments on management of blackgram powdery mildew disease (Pot trial)

Treatment number	Treatment	Disease Index (%)			Disease control (%)
		After 1st spray	After 2nd spray	Mean	After 1st spray	After 2nd spray	Mean
T1	Ampelomyces quisqualis @ 0.5% on 43 DAS	36.17e (36.95)	30.71e (33.63)	33.44	30.11	54.48	42.19
T2	Ampelomyces quisqualis @ 0.5% on 53 DAS	41.90f (40.32)	36.39f (37.08)	39.14	19.04	46.06	32.42
T3	Rhizophora apiculata @ 15% on 43 DAS	45.42g (42.35)	41.48g (40.07)	43.45	12.24	38.52	25.24
T4	Rhizophora apiculata @ 15% on 53 DAS	49.31h (44.58)	45.35h (42.31)	47.33	4.73	32.78	18.60
T5	T1 + T2	27.45c (31.58)	20.48c (26.89)	23.96	46.96	69.64	58.22
T6	T3 + T4	32.90d (34.98)	25.62d (30.39)	29.26	36.43	62.02	49.13
T7	T5 + T6	23.25b (28.81)	14.63b (22.47)	18.94	55.08	78.31	66.62
T8	Azoxystrobin  @ 0.1%	19.30a (26.04)	9.37a (17.81)	14.33	62.71	86.11	74.35
T9	Control	51.76i (45.99)	67.47i (55.21)	59.61

*Figures in parentheses are arc sin transformed value

A field trial was conducted to evaluate the efficacy of bio-agents, botanicals and fungicides against powdery mildew of black gram during 2022 with bio-agent, botanical and a fungicide. Observations on per cent disease index was recorded. In the present investigation, Azoxystrobin 25% SC @ 0.1 % was found to be effective against E. polygoni. The fungicide recorded PDI of   15.50 per cent after 1^st spray and 6.98 per cent after 2^nd spray followed by foliar application of A. quisqualis @ 0.5% on 43 DAS + A. quisqualis @ 0.5% on 53 DAS+
R. apiculata @ 15% on 43 DAS+ R. apiculata @ 15% on 53 DAS with PDI 19.95 per cent after 1^st spray and 9.06 per cent after 2^nd spray. The untreated plants showed higher PDI of 48.17 per cent to 64.37 per cent (Table 2).

Similarly, among various fungicides evaluated, Penconazole 10% EC @ 1 ml per litre of water is the minimum dose required for effective management of urdbean powdery mildew with disease incidence 10.51 per cent.⁴ Taqat 7 WP was found to be significantly effective for managing black gram powdery mildew with disease incidence 1.48 per cent due to the presence of triazole and hexaconazole components than other fungicides like Tridemorph, Karathane.⁵

An experiment was conducted to assess the efficacy of bio-control agent, botanical and a fungicide.² The mean per cent disease incidence ranged from 15.80 to 47.70 in different treatments. The maximum reduction of disease incidence was recorded in wettable sulphur 0.25% (15.80%) followed by carbendazim 0.1% (58.91%) and castor oil 1% with A. quisqualis (48.53 per cent).

A field experiment was conducted for testing fungicides and botanicals at IGKV, Raipur during rabi, for the management of powdery mildew of black gram.⁶ Five treatments are tested viz., neem leaf extract @ 3%, eucalyptus leaf extract @ 3%, neem oil @ 3%, Trichoderma harzianum @ 3% and Pseudomonas fluorescence @ 0.2% against garden pea powdery mildew.⁷

Table 2: Evaluation of different treatments on management of blackgram powdery mildew disease (Field trial).

Treatment number	Treatment	Disease Index (%)			Disease control (%)
		After 1st spray	After 2nd spray	Mean	After 1st spray	After 2nd spray	Mean
T1	Ampelomyces quisqualis @ 0.5% on 43 DAS	36.17e (36.95)	30.71e (33.63)	33.44	30.11	54.48	42.19
T2	Ampelomyces quisqualis @ 0.5% on 53 DAS	41.90f (40.32)	36.39f (37.08)	39.14	19.04	46.06	32.42
T3	Rhizophora apiculata @ 15% on 43 DAS	45.42g (42.35)	41.48g (40.07)	43.45	12.24	38.52	25.24
T4	Rhizophora apiculata @ 15% on 53 DAS	49.31h (44.58)	45.35h (42.31)	47.33	4.73	32.78	18.60
T5	T1 + T2	27.45c (31.58)	20.48c (26.89)	23.96	46.96	69.64	58.22
T6	T3 + T4	32.90d (34.98)	25.62d (30.39)	29.26	36.43	62.02	49.13
T7	T5 + T6	23.25b (28.81)	14.63b (22.47)	18.94	55.08	78.31	66.62
T8	Azoxystrobin  @ 0.1%	19.30a (26.04)	9.37a (17.81)	14.33	62.71	86.11	74.35
T9	Control	51.76i (45.99)	67.47i (55.21)	59.61

*Figures in parentheses are arc sin transformed value

Conclusion

Among the various treatments tested, Azoxystrobin 25% SC @ 0.1 % was found to be effective against E. polygoni in both pot and field trial. However, the synergistic effect of A. quisqualis and R. apiculata was significantly reduced the disease incidence and considerably improve the biometric of blackgram. Thus, it may be consider as an effective bioproduct for the successful management of blackgram powdery mildew disease for future concern instead toxic chemical pesticides.

Acknowledgement

Sincere thanks to Directorate of Research, Annamalai University, Tamil Nadu, India.

Conflict of interest

I am to state that authors of this study have no conflict of interest.

Funding Sources

This study was not funded by any organization. 

References

1. FAOSTAT (Food and Agriculture Organization Corporate Statistical Database) (2020) Food and Agriculture Organization Statistics. https://www.fao.org/faostat/en/#data
2. Jayasekhar M., Ebenezar E. G. Management of powdery mildew of black gram (Vigna mungo) caused by Erysiphe polygoni. Agric Sci Digest; 2016; 36:72-74.
3. Abbaiah K. Development of powdery mildew epidemics in urdbean in relation to weather factors. Indian J. Pulse Res; 1993;6:186-188.
4. Balol G., Math G., Mogali S., Kumbar B., Revadi N. Chemical management of powdery mildew caused by Erysiphe polygoni DC on urdbean and its economic analysis. Int J Chem Stud; 2020;8(6):256-259.
   CrossRef
5. Sharma R. L., Mishra T., Bhagat R., Swarnkar V. K. Field evaluation of different fungicides against rust and powdery mildew disease of blackgram (Vigna mungo L.). Int J Agric Sci; 2017;13:249-253.
   CrossRef
6. Prakash P. K.  Environmental relationship of powdery mildew of black gram, its management and documentation of powdery mildew fungi in Chhattisgarh. M.Sc. Thesis, Indira Gandhi Krishi Vishwavidhalaya, Raipur (Chhattisgarh);2016
7. Vivek Mishra.,  Lal A. A., Simon S. Efficacy of botanicals and bio agents against powdery mildew disease of garden pea (Pisum sativum L.).  Journal of Pharmacogn Phytochem; 2017;6(4):1125-1126.
   CrossRef