The following points highlight the six major diseases of kodo millet. The diseases are: 1. Head Smut 2. Rust 3. Ergot or Sugary Disease 4. Udbatta Disease 5. Bacterial Leaf Streak 6. Phanerogamic Partial Root Parasite.
Kodo Millet: Disease # 1. Head Smut:
Head smut caused by Sorosporium paspali was first reported from Queensland, Australia. Subsequently the disease has been reported from Eastern and Southern Asia. In India, the disease is reported from Bihar, Madhya Pradesh, Karnataka, Andhra Pradesh and Tamil Nadu.
At present, the disease is endemic in all the kodo millet growing areas of the country, its occurrence and severity vary with the place, environment and host variety. Viswanath (1992) reported 30 to 40 per cent loss in grain yield due to this disease.
Jain and Yadava (1997) observed that loss in yield increases linearly with the increase in disease incidence and estimated a loss of 13.15 to 32.98 per cent at 13.95 to 40.15 per cent smut incidence in few varieties.
The disease manifests itself at the time of flowering. Infected plants remain stunted and almost all the panicles in the infected plants are transformed into a long sorus ranging from 2.1 to 14.6 cm long and 0.1 to 0.6 cm broad. In early stage, a cream coloured thin membrane covers the sorus.
Sometimes the sorus remains enclosed in the boot leaf and does not emerge fully. The sori destroy the whole inflorescence except the fibro-vascular bundles. At maturity, the membrane burst and exposes the black mass of spores. Ahmed (1991) also observed necrotic streaks on the boot leaf covering infected panicles.
The disease is mainly seed borne. Seedling infection takes place by penetration of germ tube through the cell wall. After entering the seedling, the hyphae spread inter and intra- cellularly and become systemic. It enters the meristematic tissues and finally infects the ear.
Management:
As the disease is seedborne, seed treatment with chemicals like, Carboxin, Carbendazim, Mancozeb, Chlorothalonil and Thiram were found effective in controlling the disease. Seed treatment with 1.5 per cent copper sulphate and copper carbonate at 6g/kg of seed is equally effective.
In addition to chemical control use of resistant genotypes GPLM 78, 96, 176, 322, 364, 621, 641, 679 and 720 can also help in minimizing the damage.
Kodo Millet: Disease # 2. Rust:
Rust caused by Puccinia substriata was first recorded on kodo millet from Kanaighat in Sylhet and from Kumaon hills of Uttarakhand as Uredo paspali-scrobiculata. Afterwards the disease was also recorded from Coimbatore in India and Ceylon. Both the uredial and telial stages were recorded and it was renamed as Puccinia substriata.
The erumpent, oval, brown uredia are formed on the upper surface of the leaf blade and on the leaf sheath. The brown coloured telia are formed on the under surface of the leaf blade and on the leaf sheath during December-February in Coimbatore conditions.
They remain covered by the epidermis for a long time. Under sheltered conditions, uredia are present throughout the year on grass hosts and from where they disseminate to the main cultivated crop.
Management:
Eradication of the grass hosts is partly useful in reducing the primary inoculum of the disease but so far no significant work has been carried out on control aspects.
Kodo Millet: Disease # 3. Ergot or Sugary Disease:
The disease caused by Claviceps paspali was first recorded from Burma (Myanmar). In India the disease was first reported from Kodaikanal in South, Assam in the North and Gwalior in Madhya Pradesh. Consumption of mature sclerotia causes paralysis and death in cattle, horses and sheep.
The disease manifests itself at the time of panicle emergence. Generally individual spikelets are affected but sometimes majority of the spikelets in the panicle may also be affected. The most peculiar external sign of the disease is the exudation of pearly drops of honeydew oozing out of the infected spikelets that indicates the ‘sugary or honeydew’ symptom.
The droplets are soon hardened into reddish brown crusts. A plectenchymatous mass of fungal growth replaces the ovary. As the panicle matures, dark grey sclerotia or ergot replace the kernel which is the most conspicuous symptom of the disease.
Management:
Removal and destruction of infected panicles and eradication of the alternate hosts can minimize the primary inoculum.
Kodo Millet: Disease # 4. Udbatta Disease:
In India, Butler and Bisby (1931) first reported the disease. Subsequently, it was recorded from Koraput and Kalahandi in Orissa and Jabalpur in Madhya Pradesh during 1966 and 1974, respectively.
The affected panicles are transformed into a compact agarbatti like shape, hence the name “Udbatta”. Butler and Bisby (1931) reported that the disease is caused by Ephelis japonica P. Henn. However, Ephelis oryzae Syd. (Teleomorph: Balansia oryzae sativae Hoshioka) was also recorded on the same host by Mohanty and Mohanty (1957) from India.
Management:
Management practices which are helpful in preventing the disease viz.; removal and burning of affected panicles, keeping the bunds free from weeds that serve as collateral hosts and pre-sowing seed treatment with Carbendazim at the rate 4g/kg seed may be followed.
Very little information is available on the resistance sources against this disease. Pall and Nema (1976) screened fifty genotypes of kodo millet at Jabalpur (Madhya Pradesh) under natural conditions and recorded IPS 45, 196, 342, 365, 368, 387, 140 and Niwas 1 as highly resistant.
Kodo Millet: Disease # 5. Bacterial Leaf Streak:
In India, bacterial leaf streak caused by Xanthomonas sp. was first reported from Jabalpur, Madhya Pradesh. Though considerable quantitative yield losses due to this disease has been reported, so far this disease is not noticed in any other kodo millet growing areas of the country.
The disease manifests itself as pale yellow streaks measuring 0.5 to 1.0 mm running parallel to the veins of leaf. Later, the streaks enlarge to 1.0 to 1.5 mm X 3-4 cm lesions, which ultimately turn brown. In severe infection, the entire leaf withers away. The leaves may be shredded along the length. Streaks may also be formed on shoots and peduncle of panicles.
Management:
Two foliar sprays of Streptomycin sulphate at the rate 300 ppm, first just after the appearance of disease and subsequently after 15 days interval are effective against the disease along with 2.5 fold increase in yield. Varieties JK 41, JK 62, CO 2, CO 3, T 1 and IPS 14 have been reported to be resistant against the disease.
Kodo Millet: Disease # 6. Phanerogamic Partial Root Parasite:
Witch weed (Striga spp.) has a very wide ecological range and have been reported on kodo millet plants. In India, it is reported to occur in Andhra Pradesh, Karnataka and Madhya Pradesh. Yadava and Jain (2006) reported 42.4 to 65.8 per cent loss in yield per plant due to infestation of Striga densiflora in Kodo millet.
The infestation of Striga species appears in the field after emergence of Striga plants from the soil. The under-ground portion of Striga plant remain attached to the roots of host plant by houstoria, from which the parasite absorbs water and nutrients. The attacked plants are stunted with poor aerial growth and bear lanky panicles. If the infestation occurs in early stage, the plants may dry up before flowering.
Management:
Weeding or hand pulling of Striga plants before flowering is the cheapest and effective method for its eradication. Improved varieties viz; JK 41, GPUK 3 and GPUK 5 were found to be least affected with the parasite. Application of nitrogenous fertilizers also reduces the infestation of Striga species.