September 26, 2005
From: The Tribune Online Edition, 21 Sep 2005 [edited] <http://www.tribuneindia.com/2005/20050921/main8.htm>


Farmers' hopes of harvesting a bumper crop of paddy [rice] and cotton are turning sour in Punjab and Haryana. They are desperately trying to protect their crops from attacks from various pests and diseases by increasing the frequency of pesticide sprays.

However, many farmers, who had transplanted paddy early, seem to be fighting a losing battle because of an extensive attack of flag smut. The cotton crop, which was in good shape earlier, was set back in the past week.

During a visit to various affected villages, farmers said that in certain areas the damage to paddy and cotton would be up to 35 per cent.

However, officials of the Agriculture Department do not agree with such an assessment. Officials of the Department and Punjab Agricultural University accept the damage to crops but are not prepared to quantify it yet. They say that pest attacks pests are "below the estimated threat level [ETL]", a parameter fixed by them in this regard. Incessant rain has caused widespread damage to both paddy and cotton crops in Ropar, Patiala, Sangrur, Mansa, Bathinda, Sirsa, Hisar, Fatehabad and other parts of the 2 states.

On paddy, leaf roller, flag smut, and bacterial leaf blight are more pronounced. The cotton crop, which is by and large free from the American bollworm, is facing an attack by other pests. Moreover, inclement weather has caused large-scale deflowering of cotton plants and rotting of their bolls.

Mr Gurdial Singh, Joint Director, Agriculture Department, said the paddy crops of those farmers who had sown non-recommended varieties had been hit by blight and smut. The only apparent solution at this stage is to drain the water from the paddy fields.

Farmers have been partially successful in controlling pest attacks on cotton with pesticide sprays. But flag smut is causing panic. It has already caused huge damage to the paddy crop in the Samana-Patran-Moonak-Jakhal-Ratia belt.

"Rain has dashed our hopes. We were expecting very good returns from paddy and cotton crops this year. However, the returns will be much lower than what we had estimated 2 weeks ago", says Satvir, a farmer, who has taken land on contract in Gular village to transplant paddy. His fields are under extensive attack by flag smut, blight, and the leaf roller.

Mr Harpal Singh of Chohat, near Samana, says farmers in his village have found flag smut on their paddy crop, too. "We have been able to manage blight and the leaf roller but the blackening of grains seems to be unpreventable", he adds. " Everything was fine with the paddy 2 weeks ago", he claims. Mr Tejinder Singh, a farmer of Rao Majra village, near Patiala, says he has transplanted paddy on 72 acres. He complains about of the smut attack, and believes that by the time the crop is harvested, its quality will have deteriorated and it will be difficult to dispose of it.

[Byline: Sarbjit Dhaliwal]

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ProMED-mail
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[Bacterial leaf blight [BLB] of rice is caused by _Xanthomonas oryzae_ pv. _oryzae_.[Xoo] and Kernel smut (_Neovossia horrida_ [= _Tilletia barclayana_]) are significant pathogens of rice. They have reduced Asia's annual rice production by as much as 60 percent. In Japan, about 300 000 to 400 000 hectares of rice were affected by BLB in recent years. 20-50 percent yield losses have been reported in severely infected fields. In Indonesia, losses were higher than those reported in Japan and in India, millions of hectares were severely infected, causing yield losses from 6 to 60 percent. Removal of weed hosts, rice straws, ratoons (sprouts from the root or crown), and volunteer seedlings is important to reduce infection.
Maintaining shallow water in nursery beds, providing good drainage during severe flooding, and plowing under rice stubble and straw following harvest are also useful management strategies. Proper application of fertilizer, especially nitrogen, and proper plant spacing are recommended for management of BLB.

Planting resistant varieties is the most common and effective approach to management by farmers in Asia. When different strains of bacteria are present, it is recommended to grow resistant varieties possessing field resistance genes. Let the paddy go to fallow and allow it to dry thoroughly. Seed treatment with bleaching powder (100 micrograms/ml) and zinc sulfate (2 percent) reduce bacterial blight. Control of the disease with copper compounds, antibiotics, and other chemicals has not proven highly effective.

Kernel Smut (_Tilletia barclayana_ [Tb]) - rice

Tb infects developing flowers of the rice plant, growing within the embryo "milk" until the kernel enters the soft dough stage. At this time, the vegetative hyphae of Tb turn into dark black teliospores that replace the internal rice kernel contents. The teliospores absorb moisture during the night and early morning hours and the black spore mass often exudes from the rice flower during the morning. As the spores dry, they are blown around the field and contaminate other plant parts, the soil and harvesting equipment.

Tb is ubiquitous in mid-southern USA rice soils, where the teliospores can survive for more than 2 years. When the field is planted to rice again, teliospores float to the surface of the irrigation water and eventually germinate, producing primary sporidia. The primary sporidia have not been observed to fuse, as is the case in _Tilletia_, but do produce 2 types of secondary sporidia. The allantoid-shaped secondary sporidia are easily airborne and probably are responsible for most infections. Only a few florets per panicle are infected in most fields, but the disease has caused up to 10 percent yield loss and reduced head rice yield by 6 percent in certain highly susceptible cultivars under favorable conditions.

The cultivars 'LaGrue', 'Francis', 'Banks', 'Cocodrie', 'Priscilla' and 'Cypress' are considered susceptible to very susceptible, especially under conditions where excessive rates of nitrogen fertilizer have been applied.
Heavily "smutted" rice cannot be parboiled, since it results in a grey product, so mills routinely discount for "smutty" rice. While teliospores contaminate rice seed and are moved geographically with them, seed treatments do not affect the disease, since it is primarily soilborne once established. Kernel smut is favored by extended periods of cloudy weather during heading, high humidity, long dew periods, and frequent but very light rainfall. Excessive nitrogen use at preflood and late planting strongly favor kernel smut development.

Heavy rainfall during heading can reduce the disease. Kernel smut can be minimized by early planting, use of recommended nitrogen rates, and propiconazole fungicide applied preventively during the booting stage.

Links:
<http://www.ricejournal.com/backissues/april2000/story2.asp>
<http://www.apsnet.org/education/feature/BuntSmut/>
<http://www.publish.csiro.au/paper/AR9730219.htm>
<http://www.ipmcenters.org/pmsp/pdf/SouthRice.pdf>
<http://www.knowledgebank.irri.org/diseaseDiag/print.doc>
- Mod.DH]