Scientists from the University of Delaware, USA, have recently uncovered critical information about the effect that deadly rice blast fungus has on rice plants, which could lead to more effective effective control measures in the fight against this disease. The team found that Magnaporthe grisea, the fungus responsible for rice blast, causes an increase in the production of abscisic acid in the plant on infection. Abscisic acid is a stress hormone usually released during times of drought to prevent the plant from losing water through holes in its leaves. However, it has been found that this hormone also causes a reduction in the disease fighting mechanisms of the plant.
The first factsheet of the month for 2016 ‘Blast in Paddy‘ contains information on the current methods of control used to manage rice blast in rice, or paddy as it is sometimes known. This Pest Management Decision guide was written by Mr G. Sudhakar from the M S Swaminathan Research Foundation (MSSRF), India.
Contributed by Heng Chunn Hy and Ho Chea, General Department of Agriculture, Phnom Penh, Cambodia
Hy Broey, a farmer from Choeung Tik Khor village in Prey Veng Province, Cambodia, came with her problem to the plant clinic. She had many problems in rice planting and production, especially during the tillering stage. By attending plant clinics in her village she has learned how to solve her agricultural problems.
Mr Tep Say, the plant doctor, had identified the problem and told her that it was caused by stem borer. He showed her the affected part: dead hearts or dead tillers that can be easily pulled from the base during the vegetative stages. Also, during the reproductive stage, the plants were showing whiteheads: emerging panicles were whitish and unfilled or empty. He showed her tiny holes on the stems and tillers. He told her that she should synchronize planting, and use a recommended resistant variety. During the harvesting she should cut rice near the stem base in order to remove and kill all larvae and pupae. She should also try to conserve predators and try to catch the adult stem borer moths. If she removes all the affected plants, and only if the insect still persists, she can spray a named insecticide in order to kill the insect.
Later the plant doctor also visited the farmer’s field and gave her IPM recommendations. He told her and her husband not only to rely on chemical control but also include cultural practice to improve crop yields, and to protect the environment, thus allowing the natural enemies like dragonflies to breed and help control the adult stem borer moth.
The plant doctor had a follow-up visit to the farmer to see the implementation of his advice. After attending the plant clinic, Hy Borey and her husband changed their habit of only relying on chemical sprays and practised with IPM technique as provided by the plant doctor. They got good results and harvested a good crop. At the harvesting time the farmer was very happy since she got a better yield. Before visiting the plant clinic she got only 2.5 ton/ha but this year after visiting the plant clinic the yield had increased to 3.7 ton/ha. Before visiting plant clinics, she sprayed pesticide 3 times per season for management of pests but after visiting the plant clinic she learnt to apply the IPM method to control insects and diseases, and no more spraying of chemicals was required in this season. She was very happy and thanked CABI’s Plantwise plant clinic program for the support to help farmers in Prey Veng, and other provinces as well.
Rice is the most important crop in the Greater Mekong sub-region of Southwestern China, Laos and Myanmar, providing food, work and income for a diverse range of people living all along the Mekong river. However, the yield of this crop in the Mekong region is still missing the mark in terms of potential, partly as a result of the millions of tons of rice that are lost to pests, including insects, diseases and weeds. Unfortunately, in trying to resolve this, the excess use of pesticides in previous years has caused problems of its own with increasing pesticide resistance and damage to farmer health and the environment. Continue reading →
Example of Ecological engineering in Vietnam (Photo credit: Dr HV Chien)
The rice ecosystems are inhabited by more than 100 species of insects. Twenty of them can cause potential economic losses. With the change in the climatic factors and modern cultural practices adopted for production a drastic change has been caused in the pest scenario in the recent past. Besides stem borer, gall midge, brown plant hopper and green leafhopper which were the major problems in past, several other relatively minor pests such as leaf folder, armyworms, cut worms etc. have gained importance. In a study conducted by the International Rice Research Institute (IRRI), it was found that, on average, farmers lose 37% of their rice yield to pests and diseases, and that these losses can range between 24% and 41% depending on the production situation (http://irri.org). All the pests are generally kept under check by their natural enemies (parasitoids and predators) by feeding on them. The food web of their relationships prevents the explosion of their populations and keeps them under economic thresholds mimimising the pesticide use.
Last week, Nature published an article on the story of rice, from a wild grass to the stable crop we know today. Rice is one of the most important crops in the world as it forms the basis of the diet of a large portion of the human population. Due to the high importance of this crop, there is a vast amount of research that goes into ensuring the world’s rice production is as efficient and sustainable as possible.
Like all crops, rice is affected by a range of pests including insects, pathogens, weeds, nematodes and birds. One of the most damaging pests for rice in Asia is the Brown Planthopper (BPH). This pest not only feeds on rice plants, but also transmits grassy stunt virus and ragged stunt virus which cause stunting and reduce productivity. There are chemicals that will control this insect pest but it is important to note that this isn’t always the best method of control, due to the effect on natural enemies that feed on BPH. There are a range of non-chemical options that are effective at preventing and controlling BPH including the use of resistant varieties and avoiding excessive urea application to the field.
To find out more about BPH and its management, read this month’s Plantwise Factsheet for Farmers which was written by staff from Shushilan, an agroecology and rights-based NGO situated in South West Bangladesh. Please note this factsheet is also available in Bengali.
As the last part of our data management trip, Claire and I headed to Bangkok for the 11th and 12th of September. We joined a group of plant doctors and farmers at the plant clinic/rally in Nong Kung village, Suppaya district, Chainat province. We saw a demonstration on biocontrol, looked through pamphlets and information available to farmers about crop problems, and discussed the rice harvest which was currently taking place. In the backstopping training at the Rice Department, the participants shared their concerns and plans for future data management in Thailand.
Vargur is a small village in the Tamil Nadu state of India where paddy is grown on a large scale. The plant clinics in this region are very popular with farmers. For plant doctor Sarangpani it was a usual day, anticipating the regular crowd of paddy farmers in his plant clinic. He enjoyed this interaction with them, especially after improving his pest diagnostic and advisory skills through training provided by Plantwise and research non-profit M S Swaminathan Research Foundation (MSSRF). His rich experience as a farmer in the past had now translated into service for his community through these regular plant clinics.
Though ‘samba,’ or long grain rice season was usually quiet, this time Balchander and many farmers like him had a different story. The farmers had been seeing white spots on the young leaves of their paddy plant, which began to turn to grey-green in couple of days, bringing them increasing worry. It was time for plant doctors like Sarangpani to take immediate action to try and help Balchander and his neighboring paddy farmers.