Recommended Price K 3.30 (incl. VAT) Copies of this toktok and further information can be obtained from: National Agricultural Research Institute Vanilla Diseases: Shoot Blight (Anthracnose) National Agricultural Research Institute Wet Lowlands Islands Programme Lowlands Agricultural Experiment Station LAES Keravat Information Centre P.O. Box 204 Kokopo East New Britain Province Papua New Guinea Telephone: (675) 983 9200 / 9145 Facsimile: (675) 983 9129 Email: outreach.k@global.net.pg narilli@global.net.pg NARI TOKTOK KER020E December 2003 12 1
THE INSTITUTE The National Agricultural Research Institute (NARI) was established by an Act of the National Parliament of Papua New Guinea in July 1996 as a publicly funded, statutory research organisation, to conduct applied and development oriented research on food crops, alternative food and cash crops, livestock and resource management issues. Besides applied and adaptive research, NARI is responsible for providing authoritative technical, analytical and diagnostic services and up-to-date information to the entire agriculture sector in PNG. The major targets are the smallholder semi-commercial farmers in the country. The mission of NARI is to contribute, through applied research and technical services, to the development of the agriculture sector and realisation of the national goals by identifying, adapting and transferring agricultural technologies and information, so as to: Enhance the productivity, efficiency and sustainability of the smallholder agriculture, and Improve farmer income, food security and welfare of Papua New Guineans and the nation. Use correct vanilla pruning techniques. Very dense vanilla plants can also provide conditions suitable for the growth of the disease. Old vines should be removed after the beans have been harvested and any weak, diseased or dying vines removed regularly. Keep the plant size to maximum of about 20 looped vines. Remove and destroy diseased parts. Remove and burn diseased vines. Spores ( seeds ) produced from diseased vines can be easily spread to adjacent healthy leaves and stems or even to another planting in the same block. Remove weeds from the base and around vanilla plantings. Make sure the weeds between the rows are kept low by slashing. Hand-weed in and around the mulched area. This will help to keep the vines healthy and less susceptible to shoot blight. The removal of weeds also improves the airflow around the vanilla. This toktok was written by Pere Kokoa, NARI Wet Lowlands Islands Programme in June 2003. The material presented is based on the best information available at the time of printing (November 2003). Farmers should contact their nearest DAL/DPI office or NARI for further information. 2 11
The recommended practices by NARI are: Always use clean and disease free planting materials. Check planting materials for signs of shoot blight on leaves and stems. You can use a small sharp knife to trim off leaves and stems that are affected by the disease. Burn the infected plant parts. The knife should be washed between plants (preferably in bleach) to remove any disease on it. Farmers are advised to obtain planting materials from vanilla blocks, which are well managed and maintained. Use correct plant spacing. Proper spacing is very important. If the spacing is too close, it will be difficult to maintain the shade at the correct level. Close plant spacing will also limit the airflow through the vanilla and the leaves will remain wet for longer after rain which favours the growth of shoot blight. Use correct support tree pruning techniques. Correct pruning is very important because too much shade provided by the support trees creates an environment suitable for the growth of shoot blight. The support tree should reduce the amount of light reaching the vanilla to not more than 50% of the full sunlight. 10 Vanilla Diseases: Shoot Blight (Anthracnose) The Disease Shoot blight is the most important disease of vanilla in Papua New Guinea. It is caused by the fungal disease Anthracnose. Shoot blight has been recorded in most coastal provinces of PNG. It attacks the leaves, stems and beans of vanilla plants. Many vanilla farmers in the country may have seen the damage caused by shoot blight but do not know what causes it. The early signs of anthracnose are the appearance of small dark brown or black spots on leaves, stems and/or beans. As the disease progresses, the affected plant parts shrivel and turn brown or black. If a spot develops around the stem, the portion above the diseased area becomes rotten and eventually will turn dark brown and dies. The dead tip may remain attached to the living stem for sometime and will eventually fall off, leaving a blunt terminal tip. This is called shoot blight. In some cases the death of the vine end may trigger flowering of that particular vine. Sometimes creamy to pink or black spots can be seen on old dead parts. 3
Infection and Spread Both commercial vanilla species (Planifolia and Tahitensis) are affected by shoot blight. The disease can be spread within the block or to other vanilla blocks by rain splashes, wind or on tools such as bush knives, if in direct contact with an infected vine. Control It is recommended that farmers control shoot blight by good management of their vanilla blocks. The incidence and severity of the disease is higher in plantings with poor management. The disease is a bigger problem in vanilla which has heavy shade and moist conditions. Therefore, correct support tree and vanilla vine pruning, plant spacing and weed management are important. Following the NARI recommended crop management practices for growing vanilla (described in previous NARI vanilla toktoks) will generally control shoot blight and should be followed no matter if the disease is a problem or not. Even heavily disease infected vanilla blocks can be rejuvenated and become productive if the correct management practices are carried out. 4 9
The Effect of Shoot Blight on Vanilla If not managed, shoot blight can cause severe damage to vanilla vines which will result in reduced bean production. Shoot blight causes the loss of immature beans when vines that bear beans are infected and die. Shoot blight also reduces the size of the vanilla plant as vines die off. This will reduce the amount of beans in the following harvest. Other effects of the disease are the loss and the poor quality of planting material and the danger of spreading shoot blight to new planting sites if infected vines are used as planting material. It has been observed that some farmers harvest immature beans from diseased vines or even collect beans from the ground after they fall off a diseased vine. NARI does not recommend this practice as these beans will produce very poor quality vanilla that can not be sold. 8 5
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