Diseases of Field Crops Diagnosis and Management

Volume 2: Pulses, Oil Seeds, Narcotics, and Sugar Crops

J. N. Srivastava, A. K. Singh, J. N. Srivastava, A. K. Singh

• Publisher: Apple Academic Press
• Year: 2020
• ISBN:
  9781000439113
• Edition: 1
• Topic: Biological Sciences
• Subtopic: Horticulture
• Index: Biological Sciences

Plant diseases cause yield loss in crop production, poor quality of produce, and great economic losses as well. Knowledge of the perpetuation and spread of the pathogens and various factors affecting disease development is an important need. Disease diagnosis is the prime requirement for determining preventive or curative measures for effective disease management. This new 2-volume set, Diseases of Field Crops, helps to fill the need for research on plant diseases, their effects, how they spread, and effective management measures to mitigate their harmful consequences.

The volumes in this set showcase recent advances in molecular plant pathology and discuss appropriate diagnostic techniques for identification of causal agents and diseases, providing the information necessary to establish management strategies. The chapters in these two volumes include detailed description of symptoms, causal organisms, disease cycles, epidemiology, and management techniques of economically important diseases. The volumes explore existing strategies and offer new methods that can be used in an integrated manner and with a comprehensive approach for the management of major diseases of the field crops. Also taken into consideration is the impact of global climate change on the spread and severity of plant diseases.

This volume covers pulses, oil seeds, narcotics, and sugar crops. Each of the chapters focuses on one crop, with a detailed account of symptoms, causal organisms, disease cycles, epidemiology, and management of the diseases caused by fungi, bacteria and viruses. Some crops discussed include green gram, chickpeas and peas, lentils, soybeans, groundnuts, sunflowers, sugarcane, tobacco, and others. Volume 1 focuses on cereals, small millets, and fiber crops.

CHAPTER 1

Current Status of Bengal Gram Diseases and Their Management Strategies

K. K. SHARMA¹ and ASHISH KUMAR ²

¹ Ballowal Saunkhri, Tehsil-Balachaur, SBS Nagar–144521, Punjab, India, E-mail: [email protected]

² JNKVV, College of Agriculture, Rewa, Madhya Pradesh, India

Chickpea (Cicer arietinum L.) is the second most important pulse crop after beans (Phaseolus vulgaris), which is widely cultivated in India. It fixes atmospheric nitrogen and belongs to family leguminaceae (Ferguson et al., 2010). This crop is cultivated under rainfed conditions in Asian, African, American countries, etc. (Sharma et al., 2015). The global area under cultivation was estimated about 12.14 million hectare with an annual production of 11.30 million tonnes (FAOSTAT, 2012). In India, area under this crop was maximum and estimated about 8.32 million hectares giving 7.70 million tonnes of production annually (FAOSTAT, 2012). It can be grown as a main sole crop or mixed with cereals in heavy and other types of soils, respectively. The chickpea grown with limited irrigation gives good returns although, it is preferably cultivated in the area with low-rainfall during Rabi season. Though, significant yield losses have been estimated in chickpea caused by several diseases like wilt, ascochyta blight, dry root rot, collar rot, botrytis grey mold, wet root rot and chickpea stunt, but few of them cause severe losses in chickpea growing areas while others remain as minor in occurrence. Considering the economic importance, major diseases are discussed along with their management practices.

1.1 MAJOR DISEASES

1.1.1 ASCHOCHYTA BLIGHT

1.1.1.1 ECONOMIC IMPORTANCE

In India, this disease appears frequently in states viz., Madhya Pradesh, Haryana, Himachal Pradesh, Bihar, Northwestern part of U. P., and Punjab. The credit goes to Butler for its description first time in 1911 in country when it appeared in Punjab, Bihar, and Jammu in epidemic form.

1.1.1.2 SYMPTOMS

The pathogen attacks on all above ground plant parts which are diagnosed generally at the late vegetative to near blooming. On leaf, the lesions are circular to elongated, sunken brown spots appear with darker margin and grayish center. On stem and pods, black and dotted pycnidial bodies can be seen in the form of concentric rings. Shoot terminals are especially liable to attack. When the lesions girdle the stem, speedy death of the stem portion above the point of girdling can be seen.

The patches of plants exhibiting wilting symptoms clearly visible in the field with the advancement of disease, which cover the entire, field subsequently (Bashir and Malik, 1998). When infection occurs at flowering or pod formation stage, it may form unhealthy pods with distorted seeds without showing any observable symptom. Moreover, infected pods may not able to produce seed at all. Under condition of heavy rains couple with favorable temperature, whole crop in the field may be killed quickly (Figure 1.1).

FIGURE 1.1 Symptoms of aschochyta blight in chickpea.

1.1.1.3 CASUAL ORGANISM (ASCHOCHYTA RABIEI)

Fungus produces hyaline to brown, septate mycelium. Pycnidia are spherical to globular with a clear ostiolar opening. Single celled or bicelled pycnidio-spores (conidia) are hyaline, oval to oblong, straight or slightly Curved with assize of 9–20 x 3–6 micron which are produced on small conidiophores. The perethecia are globose, dark colored, 100 to 140 micron in diameter and contain asci which are typically 8 spored. The ascospores hyaline, thin walled, ellipsoid, and two celled.

1.1.1.4 FAVORABLE CONDITIONS

Hot and moist weather, temperature between 20 and 25°C with 60% relative humidity (RH) and dense crop cover favor the speedy spread and development of the disease (Pande et al., 2009). Rapid development of the disease also co-related with high rainfall during flowering.

1.1.1.5 DISEASE CYCLE

The fungus is externally and internally seed-borne in nature and perpetuates as pycnidial bodies on diseased crop residue which is left in the fields after harvesting. The fungal spores and hyphae both remain on soil and seeds may also provide primary inoculum. The air-borne pycnidiopores (conidia) causes secondary infection. About 6% infection from seed is quite enough to create epidemics under favorable conditions. The primary inoculum multiplies on hypocotyle, epicotyle, and near the stem base followed by the spreading on aerial parts. Dissemination of pathogen occurs through conodia and wind borne rain splashes, by contact between leaves through insects and animals fields.

1.1.1.6 MANAGEMENT

For the effective management of the ascochyta blight, integrated strategy, i.e., field sanitation, cultural, monitoring of crop, use of resistant varieties, application of chemical fungicides and biological approaches is successful. Farmers always use disease free healthy seeds and sow the seeds up to 15 cm or deeper in soil. Remove or destroy blight-infested crop residues after harvest. Bury the infected crop debris by plowing deep in the soil. Intercropping with the cereals such as chickpea-barley is the most suitable combination for reducing the diseases.

Since this fungus is externally and internally seed born, fungicidal treatment with carbendazim 50 WP + thirum 75 DS @ 2 g/kg seed of the seeds is very significant for the management of the disease. Treating the seeds in hot water at 52°C for 10 min was also found very effective to reduce the level seed borne inoculum. Growers should apply the mancozeb @ 3 g/l on the crop immediately after appearance of initial symptoms of the disease. Under the conditions like repeated rain with heavy dew, a preventative spray of chlorothalonil at the rate of 1 kg/ha should be applied 7 to 10 days before flowering whereas the same fungicide should also be sprayed at flowering under dry conditions. Spray the crop with carbendazim at the rate of 500 g/ha is advised at 7 to 10 days after spray of chlorothalonil. Under favorable weather conditions for disease, growers should continue successive sprays of aforesaid fungicides at 10 to 14 days during the major bloom and pod fill period. Farmers should grow resistant/tolerant varieties like Gaurav (H75-35), PBGI, GNG146, BG261, GNG469, GL 23094, GL 260584, GL 26069.

1.1.2 BOTRYTIS GREY MOLD (BGM)

1.1.2.1 ECONOMIC IMPORTANCE

Botrytis grey mold (BGM) is reported from worldwide and but it is quite serious disease in countries namely India, Nepal, Pakistan, Australia, Argentina including some parts of Bangladesh (Nene et al., 2012). This disease appear regularly every year in moderate to severe form in North-Indian states. It develops rapidly and spread widely under conducive weather which may cause up to 100% yield losses

1.1.2.2 SYMPTOMS

The all the above ground parts, leaves, flowers, pods, branches, and stems are atta...