Cotton (Gossypium spp.) is one of the most important economic products of the group of fibers due to volume and value of production. It provides employment and sustenance to a population of nearly 42 Million people, who are involved directly or indirectly in cotton production, processing, textiles and related activities. Looking to the experiment, different fungicides were evaluated in cotton crop under field condition against the boll rot and different diseases. Total seven treatments including control were evaluated in this trial from which, treatment T4 (25.17 PDI) and T5 (28.83PDI) recorded minimum Bacterial leaf blight infection in comparison to the treatment T7 i.e., control (53.67PDI). The lowest boll rot incidence was observed in the treatment T4 (13.67 PDI). The highest seed cotton yield was recorded in the treatment T4 (2401.67 kg/ha), respectively.

Cotton, Gossypium spp, Treatment, Disease, Fungicide, Control.

Cotton (Gossypium spp.) is one of the most important economic products of the group of fibers due to volume and value of production. Its cultivation is also of great social importance, due to the number of jobs generated directly or indirectly. Cotton is a tropical and subtropical crop. For the successful germination of its seeds, a minimum temperature of 15oC is required. The optimum temperature range for vegetative growth is 21 - 27oC. It can tolerate temperatures as high as 43oC, but does not do well if the temperature falls below 21oC. During the period of fruiting, warm days and cool nights with large diurnal variations are conducive to good boll and fibre development. The fiber, the main product of cotton has many industrial applications. Examples are manufacturing of yarn for weaving of various kinds of fabrics, cotton batting for hospital use, felt clothing, blankets and upholstery, photographic films and plates for radiography among others (Richetti and Melo Filho 2001). The fibres can be made into a wide variety of fabrics ranging from lightweight voiles and laces to heavy sailcloths and thick-piled velveteens, suitable for a great variety of wearing apparel, home furnishings, and industrial uses. Cotton fabrics can be extremely durable and resistant to abrasion. Cotton accepts many dyes, is usually washable and can be ironed at relatively high temperatures. It is comfortable to wear because it absorbs and releases moisture quickly. When warmth is desired, it can be napped, a process giving the fabric a downy surface. Nonwoven cotton, made by fusing or bonding the fibres together is useful for making disposable products to be used as towels, polishing cloths, tea bags, tablecloths, bandages, and disposable uniforms and sheets for hospital and other medical uses Weigmann (2023).

Cotton, derived from the Arabic word 'quotn' (Lee and Fang 2014)  belongs to Gossypium genus, which was also derived from the Arabic word 'goz', meaning a soft substance (Gledhill, 2008). Cotton is a unique natural fiber producing most common fiber crop of the world, which provides humanity with cloth and vegetable oil, medicinal compounds, meal and hull for livestock feed, energy sources, organic matter to enrich soil, and industrial lubricants (Abdurakhmonov, 2013). Cotton is grown worldwide for its natural fiber and oil. Cotton seed contain 30 per cent starch, 25 per cent oil and 16.20 per cent protein. It is also being used in the manufacture of medicinal supplies, tarpaulin, cordage and belting. The cotton hulls serve as roughage for livestock and the fuzz (short seed hair) is used in the manufacture of papers, plastics, carpets, rayon, explosives and cotton wool (Prasad, 2015). Based on archeological evidence, humans utilized cotton fiber from at least more than four to seven thousand years ago, and cotton started to be grown as a fiber crop around three thousand years ago (Lee and Fang 2014); (Fang and Percy 2015). 

The cotton seed is rich in oil, with approximately 18 to 25 per cent, and contains 20 to 25 per cent of crude protein. The cotton seed meal is a by product of oil extraction, and is used in animal feed because of its high protein content, approximately 40 to 45 per cent. The seed coat is used to make certain types of plastics and synthetic rubber (Carvalho, 1996). The cotton seed after the removal of the plume, is commonly used as ruminant feed. It is considered a palatable food, with characteristics of dietary fiber with high levels of energy and protein (Savastano, 1999). Cotton, one of the world's leading agricultural crops is plentiful and economically produced, making cotton products relatively inexpensive. 

The genus Gossypium includes five 52 chromosome species (2n=4x=52) that arose some 1-2 million years ago (Cronn et al., 2002) through allotetraploidization between the extinct representatives of A and D cotton genomes. Cotton is grown on around 32-36 million-hectares area of tropical and northernmost agricultural latitudes in over 80 countries of the world (Abdurakhmonov et al., 2011) ; (Kumar et al., 2006) to fulfill the current global needs of humanity for the natural fiber. 

In India, there are ten major cotton growing states which are divided into three zones viz., North zone, Central zone and South zone. North zone consists of Punjab, Haryana, and Rajasthan. Central zone includes Madhya Pradesh, Maharashtra and Gujarat. South zone comprises Andhra Pradesh, Telangana, Karnataka and Tamil Nadu. Besides these ten States, cotton cultivation has gained momentum in the Eastern State of Orissa. Cotton is also cultivated in small areas of non-traditional States such as Uttar Pradesh, West Bengal and Tripura.

The most common cotton diseases reported in India are Wilt (Fusarium oxysporum f. sp. vasinfectum (G.F. Atk.) W.C. Snyder & H.N. Hansen), Root rots (Rhizoctonia bataticola (Taubenh.), Verticillium wilt (Verticillium dahliae Kleb.), Anthracnose (Colletotrichum gossypii Southworth. or C. capsici (Syd.) Butler & Bisby), Grey mildew (Ramularia areola G.F. Atk.), Blackarm (Xanthomonas campestris pv. malvacearum (Pammel) Dowson), Leaf blight (Alternaria macrospora Zimm), Leaf curl (Cotton leaf curl virus), Corynespora leaf blight (Corynespora cassiicola (Berk. & M. A. Curtis) C. T. Wei, Boll rot and physiological disorders as Para wilt, Leaf reddening and sometimes leaf elongation etc. The bacterial blight is the most wide spread and destructive disease reported to cause yield losses of about 10 to 30 per cent (Kalpana et al., 2004); (Sandipan et al., 2016). Losses due to Alternaria leaf spot (26.6%) however, Alternaria alternata has the potential to cause yield loss up to 30% under severe infection (Olmez et al., 2023), grey mildew (29.2%) and Myrothecium leaf spot (29.1 %) have been reported. Moreover, sometimes Myrothecium leaf spot, caused by the fungus Myrothecium roridum Tode, was responsible for losses of 50 per cent in the town of Balsas in Maranhão and also been reported in the state of Mato Grosso. The symptoms of the disease can appear on the leaves and cotton bolls (Suassuna et al., 2006).  Cotton bolls rot can cause 20-30 per cent losses in productivity, (Iamamoto, 2007). Boll rot is considered as the most destructive one. In the USA, at least 170 microorganisms are capable of causing cotton boll rot (Guthrie et al., 1994). According to Hillocks (1992) a great number of microorganisms were isolated from cotton bolls rot and these pathogens can be divided into three groups: those capable of penetrating intact bolls, those which are introduced by insects and those are introduced after the bolls are damaged by insects or after the suture of the boll lobes are broken. Most of the agents that cause cotton bolls rot penetrate through wounds from insect or pests and / or rupture of the division through the lobes of the bolls. However, primary infection of boll, when the pathogen penetrates directly into the healthy boll is common in areas with high humidity or in those where the crop has dense vegetative growth.

According to Belot & Zambiasi (2007) there are many pathogens that can cause boll rot such as Alternaria spp., Ascochyta gossypii, Aspergillus flavus, Aspergillus niger, Bacillus pumilus, Colletotrichum spp., Diplodia gossypina, Erwinia aroideae, Fusarium spp., Lasiodiplodia theobromae, Myrothecium roridum, Pantoea agglomerans, Phoma exigua, Phomopsis sp., Phytophthora spp., Rhizoctonia solani and Xanthomonas axonopodis pv. malvacearum. And sometimes, saprophytic and/or opportunistic fungi detected and associated with cotton boll rots were Botrytis spp, Cephalosporium sp, Cercospora spp., Cladosporium sp., Curvularia sp, Epicoccum sp, Graphium spp., Mucor sp, Nigrospora sp., Periconia sp., Trichotecium sp and Rhizoctonia sp. Zancan et al. (2013). Various symptoms may be due to the existence of a complex of pathogens. Commonly, the bolls are soft and blackened and in some cases, arise from lesions in both the apex and at its base. Fructifications in various colors, from white to purple are also verified. Sclerotium rolfsii is identified as one of the causes of boll rot in Bangladesh (Shamsi and Naher 2014). Hence systemic explorations by using different fungicides on cotton disease including boll rot were carried out. Keeping in view, an experiment based treatment is planned for the effectual management of the boll rot and cotton disease.

External boll rot: Generally, this external boll rot complex occurs during the boll maturity and bursting stages. It is caused by several fungal and bacterial pathogens and saprophytic fungi depending upon climatic conditions and insect-pest infestation (Mirzaee et al., 2013). Continuous cloudy weather, rain shower, warm weather and high relative humidity are conducive to external boll rots. (Photograph: a, b, c, d, e, f, g and h)

Internal boll rot: It can be caused single or a combination of bacteria and fungi. Bacterial seed and boll rot was first recorded in South Carolina, USA in 1999. In India, Erwinia aroideae was associated with boll rot of green bolls in cotton. Pantoea ananatis, Pantoea anthophila and Pantoea agglomerans causes disease symptoms in a wide range of economically important crops including plantation crops. Early disease diagnosis is very complicated, the boll seems to be healthy as no symptoms appear on the outer surface of the boll. The disease can only be observed when bolls are cross-sectioned or opened. The putative internal boll rots of green bolls are incited by opportunistic, facultative anaerobic bacterial phytopathogens of the family Enterobacteriaceae and some endophytic fungi. After flowering, disease organisms may invade the developing ovary (boll) via wounds associated with insect feeding, especially stink bugs and drizzling rains (Ehetisham-ul-Haq et al., 2014). However, the developing boll is susceptible to these piercing/sucking insects for only about the first 3 weeks. The immature seeds, fibers and lint in locules of immature unopened green bolls initially appear discolored, light yellow, pink-red to brown coloured with a slimy presence.  The first report of occurrence and association of phytopathogenic bacteria Pantoea dispersa, a member of the Enterobacteriaceae family as a potential and principal pathogenic agent causing inner cotton (G. hirsutum L.) boll rots in Maharashtra state, India (Nagrale et al., 2020; Photograph a, b and c).

The experiment was laid by dibbling method with the following experimental details (Table 1 and 2). All the recommended agronomic practices were followed for raising the good crop. In each net plot of each treatment randomly tag 5 plants and score 4 lower, 4 middle leaves and 2 upper leaves of each plant/bolls in terms of 0-4 grade and work out PDI as mentioned below by using 0-4 scale as given by Sheo Raj and Verma (1988) and then these grades were converted into per cent disease incidence (PDI) by using the formula given by Wheeler (1969). (Bacterial leaf blight) and similar formula was used by Sandipan et al. (2022). 

The fungicides were used as per the above treatment two foliar sprays were applied at 15 days interval, first from the initiation of the disease and second after the interval of 15 days from the first spray.

Table 1: Experimental detail as below.

Table: 2 Treatment details.

For, Boll rot disease

For, Bacterial leaf blight (BLB) disease

For, Alternaria (ALS), Cercospora, Corynespora leaf spot (CoLS), Myrothecium (MLS), Grey mildew and Rust disease

It is the standard methodology of AICRP on Cotton and similar disease scale was used by Sandipan et al. (2022).

Phytotoxicity Test. Observations on leaf injury, vein clearing, necrosis, epinasty and hyponasty is taken after 7 days of first spray and second observation after 7 days of second spray of application of the fungicides.

The field experiment was conducted during Kharif 2022 at Main Cotton Research Station (MCRS), Surat (Gujarat). The results presented in the Table 3 and Graph 1 revealed that the out of seven treatments including control, treatment T4 (25.17 PDI) and T5 (28.83PDI) recorded minimum Bacterial leaf blight infection in comparison to the treatment T7 i.e. control (53.67PDI) in RCH 2 BG II hybrid but in comparison to bactericide it is less effective to control Bacterial leaf blight disease (Table 3 and Graph 1).

The lowest boll rot incidence was observed in the treatment T4 (13.67 PDI) and T5 (14.67 PDI) treatment as compared to the control T7 (26.83 PDI) Table 3 and Graph 2.

The highest seed cotton yield was recorded in the treatment T4 (2401.67 kg/ha) and treatment T5 (2223.67 kg/ha), respectively (Table 3 and Graph 3).

Comparison of the efficacy between the fungicides used in different treatments at Surat centre indicated that treatment T4: Fluxapyroxad 167g/ litre + Pyraclostrobin 333g/ litre SC @ 0.6g/ litre of water first spray at the time of initiation of the disease and second after 15 days was found little bit effective in reducing the Bacterial leaf blight infection in comparison to other fungicides and boll rot infection effectively and increases the seed cotton yield in RCH 2 BG II hybrid cotton followed by treatment T5: Metiram 55% + Pyraclostrobin 5% WG @ 2g/ litre of water.

Table: 3 Statement showing the per cent disease intensity of Bacterial leaf blight (BLB), Boll rot and seed cotton yield in different fungicides against cotton disease 2022-23.

* Figure in the parenthesis are Arc sine transformed values

Graph 1: Per cent Disease Intensity (PDI) of Bacterial leaf blight (BLB).

Graph 2: Per cent Disease Intensity (PDI) of Boll rot.

Graph 3: Seed cotton yield.

Table 4: Phytotoxicity effect of fungicides on cotton during Kharif, 2022 (7 days after 1st spray).

Table 5: Phytotoxicity effect of fungicides on cotton during Kharif, 2022 (7 days after I1st spray).

Prashant B. Sandipan, P.S. Patel, R.K. Patel and M.C. Patel  (2024). Effect of Different Fungicides Against the Boll Rot and Foliar Disease of Cotton under South Gujarat of India. Biological Forum – An International Journal, 16(5): 85-91.