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National Agricultural Research Institute

NARI TOKTOKKER020E

December 2003

RecommendedPrice K 3.30(incl. VAT)

Vanilla Diseases: Shoot Blight(Anthracnose)

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Copies of this toktok and further informationcan be obtained from:

National Agricultural Research InstituteWet Lowlands Islands Programme

Lowlands Agricultural Experiment StationLAES Keravat

Information Centre

P.O. Box 204Kokopo

East New Britain ProvincePapua New Guinea

Telephone: (675) 983 9200 / 9145Facsimile: (675) 983 9129

Email: outreach.k@global.net.pg narilli@global.net.pg

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THE INSTITUTE

The National Agricultural Research Institute (NARI) wasestablished by an Act of the National Parliament of Papua NewGuinea in July 1996 as a publicly funded, statutory researchorganisation, to conduct applied and development orientedresearch on food crops, alternative food and cash crops,livestock and resource management issues. Besides appliedand adaptive research, NARI is responsible for providingauthoritative technical, analytical and diagnostic services andup-to-date information to the entire agriculture sector in PNG.The major targets are the smallholder semi-commercial farmersin the country.

The mission of NARI is to contribute, through applied researchand technical services, to the development of the agriculturesector and realisation of the national goals by identifying,adapting and transferring agricultural technologies andinformation, so as to:

• Enhance the productivity, efficiency and sustainabilityof the smallholder agriculture, and

• Improve farmer income, food security and welfare ofPapua New Guineans and the nation.

This toktok was written by Pere Kokoa, NARI Wet Low-lands Islands Programme in June 2003. The material pre-sented is based on the best information available at thetime of printing (November 2003).

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· Use correct vanilla pruning techniques. Verydense vanilla plants can also provide conditionssuitable for the growth of the disease. Old vinesshould be removed after the beans have beenharvested and any weak, diseased or dying vinesremoved regularly. Keep the plant size tomaximum of about 20 looped vines.

· Remove and destroy diseased parts. Removeand burn diseased vines. Spores (‘seeds’)produced from diseased vines can be easilyspread to adjacent healthy leaves and stems oreven to another planting in the same block.

· Remove weeds from the base and aroundvanilla plantings. Make sure the weeds betweenthe rows are kept low by slashing. Hand-weed inand around the mulched area. This will help tokeep the vines healthy and less susceptible toshoot blight. The removal of weeds also improvesthe airflow around the vanilla.

Farmers should contact their nearest DAL/DPIoffice or NARI for further information.

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Vanilla Diseases:Shoot Blight (Anthracnose)

The Disease

Shoot blight is the most important disease ofvanilla in Papua New Guinea. It is caused by thefungal disease Anthracnose. Shoot blight hasbeen recorded in most coastal provinces of PNG.It attacks the leaves, stems and beans of vanillaplants. Many vanilla farmers in the country mayhave seen the damage caused by shoot blightbut do not know what causes it.

The early signs of anthracnose are theappearance of small dark brown or black spotson leaves, stems and/or beans. As the diseaseprogresses, the affected plant parts shrivel andturn brown or black. If a spot develops aroundthe stem, the portion above the diseased areabecomes rotten and eventually will turn darkbrown and dies. The dead tip may remainattached to the living stem for sometime and willeventually fall off, leaving a blunt terminal tip. Thisis called shoot blight.

In some cases the death of the vine end maytrigger flowering of that particular vine.Sometimes creamy to pink or black spots can beseen on old dead parts.

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The recommended practices by NARI are:

· Always use clean and disease free plantingmaterials. Check planting materials for signs ofshoot blight on leaves and stems. You can use asmall sharp knife to trim off leaves and stemsthat are affected by the disease. Burn the infectedplant parts. The knife should be washed betweenplants (preferably in bleach) to remove anydisease on it. Farmers are advised to obtainplanting materials from vanilla blocks, which arewell managed and maintained.

· Use correct plant spacing. Proper spacing isvery important. If the spacing is too close, it willbe difficult to maintain the shade at the correctlevel. Close plant spacing will also limit the airflowthrough the vanilla and the leaves will remain wetfor longer after rain which favours the growth ofshoot blight.

· Use correct support tree pruning techniques.Correct pruning is very important because toomuch shade provided by the support treescreates an environment suitable for the growthof shoot blight. The support tree should reducethe amount of light reaching the vanilla to notmore than 50% of the full sunlight.

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Infection and Spread

Both commercial vanilla species (Planifolia andTahitensis) are affected by shoot blight. Thedisease can be spread within the block or to othervanilla blocks by rain splashes, wind or on toolssuch as bush knives, if in direct contact with aninfected vine.

Control

It is recommended that farmers control shootblight by good management of their vanillablocks.

The incidence and severity of the disease ishigher in plantings with poor management. Thedisease is a bigger problem in vanilla which hasheavy shade and moist conditions. Therefore,correct support tree and vanilla vine pruning, plantspacing and weed management are important.

Following the NARI recommended cropmanagement practices for growing vanilla(described in previous NARI vanilla toktoks) willgenerally control shoot blight and should befollowed no matter if the disease is a problem ornot. Even heavily disease infected vanilla blockscan be rejuvenated and become productive if thecorrect management practices are carried out.

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The Effect of Shoot Blight on Vanilla

If not managed, shoot blight can cause severedamage to vanilla vines which will result inreduced bean production.

Shoot blight causes the loss of immature beanswhen vines that bear beans are infected and die.Shoot blight also reduces the size of the vanillaplant as vines die off. This will reduce the amountof beans in the following harvest.

Other effects of the disease are the loss and thepoor quality of planting material and the dangerof spreading shoot blight to new planting sites ifinfected vines are used as planting material.

It has been observed that some farmers harvestimmature beans from diseased vines or evencollect beans from the ground after they fall off adiseased vine.

NARI does not recommend this practice asthese beans will produce very poor qualityvanilla that can not be sold.

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