1
point
Leaf spot in secondary Oil palm nursery

Oil palm    Eluru,Andhra pradesh,India

My name is nagaraju and I am from Andhra Pradesh, India. I have some leaf spots on the oil palm in our nursery and I want to know what it is. Please help me find out the cause and tell me how to prevent this disease



Posted by: nagaraju a (2 points) nagaraju a
Posted: April 6, 2014


Thuan_attapeu commented,

over 6 years ago.



Answers

2
points
Your Oil Palm has leaf spot. This is a general term for a condition that can have many causes.

The disease can be caused by Fungi, Water Moulds and in one case a bacteria
Acidovorax, Annellophora, Bipolaris, Botrytis, Cylindrocladium (=Calonectria), Cercospora, Colletotrichum, Exserohilum, Gliocladium, Pestalotia, Pestalotiopsis, Phaeotrichoconis, Phytophthora, Pseudocerspora, Stigminaitalic

Acidovorax belongs to the Kingdom Bacteria. Phytophthora belongs to the Kingdom Stramenopila. The remaining pathogens belong to the Kingdom Fungi.

The condition, leaf spot is found throughout the world. It is possible that in your area only a few of teh agents cause the disease.

It is really important to stress that you cannot decide on what is causing this without a closer examination with a microscope.

Here is some text from an excellent resource (which is in the public domain and which I credit below)
"Despite the many pathogens that cause leaf spots and leaf blights, the initial symptoms are very similar.

Initial leaf spots are usually round to oval in shape and vary in color from yellow to brown to black. The initial size may be as small as a pin point. Some leaf spots initially appear as water-soaked lesions (Fig. 1). At some point during disease development, leaf spots will have a contrasting colored edge or halo - e.g., brown spot with a yellow halo, tan center with brown edge or gray center with black edge and a yellow halo (Figs. 2-4). All color combinations are possible. As the leaf spots expand in size, the shape and coloration may change (Fig. 5). As the disease progresses, leaf spots often coalesce (merge together) to form large areas of blighted tissue (Fig. 1), hence, the term leaf blight. If the disease continues to develop, leaflets or the entire leaf may die prematurely.

Any age leaf can be affected by leaf spots, and there usually is no distinct pattern to the spotting . Leaf spot diseases may occur at any stage of palm growth, but are a more serious problem of seedling and juvenile palms because they have fewer number of leaves or the leaves are smaller in size than in a mature palm.

One should not guess as to the identity of the pathogen based on the leaf spot symptom observed. Identification is based on observation of the pathogen spores, either directly on the leaf tissue (Fig. 6) or in culture after isolating from the leaf tissue".
Broschat, T. K., M.L. Elliott, I. Maguire. 2010. Symptoms of Diseases and Disorders. In A Resource for Pests and Diseases of Cultivated Palms. University of Florida, Identification Technology Program, CPHST, PPQ, APHIS, USDA; Fort Collins, CO. [April 6th 2014]


One of the authors of the above text, Dr Monica Elliot wrote this about control in Nurseries

"In a nursery situation, severely diseased leaves should be pruned and destroyed to reduce spores available to infect healthy tissue. If the palm is small with only a few leaves, eliminate the palm completely."
She was speaking about Pestalotiopsis diseases (Fungus) but it would apply to all the fungal/water mold described above as watering and humid conditions promote their spread.

And also here

"While fungicides may be useful to prevent further spread of the disease, they are merely a supplement to water management, sanitation, injury prevention and good palm nutrition. Fungicides alone will not solve the problem. It is critical to understand that fungicides do not cure the leaf spot or petiole blight already present. Once a leaf spot or petiole lesion occurs, it will remain for the duration of the life of that leaf. Fungicides are used to prevent further spread of the disease by protecting leaf tissue that has not been infected by the fungal pathogen.

In the nursery situation, prune severely diseased leaves prior to fungicide application. These leaves need to be removed anyway, and this will reduce the amount of fungicide used in the process. In the landscape situation, unless the leaf spot disease is severe, leaf pruning is not recommended unless the palm is free of nutrient deficiencies. In general, nutrient deficiencies are far more debilitating to the landscape palm than leaf spot diseases."

Questions for you
Please can you send images of the surrounding plants?
Do you have many insects (damage by insects spreads disease)
Do you water from above? (It is best to water directly onto the ground, at the base)
What time of day do you water?




Posted by: David Hughes (54 points) David Hughes
Posted: April 6, 2014




1
point
I agree with much that has been reported above concerning pruning of diseased leaves and removal of the whole plant if all the leaves are already affected. I advise strongly that the pruned leaves and infected whole plants are destroyed or buried and not left in the rows or at the nursery edges where these prunings are a source of infection spread when the leaf spot fungi produce large numbers of spores during senescence of the plant material.
Importantly, in a nursery situation good spacing is essential to allow free air circulation so as to reduce a moist and humid micro-climate. Watering from the base is much better nursery practice as the foliage is not wetted. Good air circulation prevents water sitting on the leaves for long periods of time. Wet leaves allow the leaf-spot fungal spores mentioned above, an opportunity to germinate and infect young tender oil palm leaves.
It is also important to make sure that any fertiliser applications are timely and of the correct application rate. Too much or too little fertiliser can predispose the oil palm seedlings to leaf-spot fungus infection.
It is not necessary to use fungicides in the nursery if good sanitation and hygiene are practised and most of the usual leaf spot fungi do not respond well to fungicide application so this is a waste of money, will not have the outcome you want and is adding unnecessary chemicals to the environment.


Posted by: Barbara J. Ritchie (5 points) Barbara J. Ritchie
Posted: April 9, 2014




0
points
i think it's fungus cause by Curvularia or Helminthosporium. you need to spray with Maneb or Thiram, . may be cause by the herbicide if you have used in the main nursery. you need to put enough fertilized.
this pictures are the oil palm 10 months old in my nursery


Posted by: Thuan_attapeu (5 points) Thuan_attapeu
Posted: April 27, 2014




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