Wednesday, July 6, 2011

culling

CULLING
Only the best palms should be sent to the field. So, good and prompt management of pest and disease cannot be over emphasized. In addition, very important aspects is the ability to identify rogues and runts at an early stage.
FUNCTIONS
a. To allow only normal healthy seedlings to grow.
b. To remove all runts, abnormal and unproductive seedlings.
c. To supply the best quality palm available for field planting.

Pre- nursery
 Twisted shoot.  Planting of germinated seeds was not correctly done. This  is not genetic in origin as it can be attributed to germinated seeds having been planted upside down.  Such plants have coiled leaves and twisted stem.

  Grass leaf.  Also termed "narrow leaf".  Seedlings have narrow and erect grass-like leaves.
  
 Rolled leaf.  The leaf lamina is rolled along its vertical axis, giving the appearance of a spike.
 Collante is the term applied to seedlings that display marked constriction around the central part of the lamina which prevents full leaf expansion.  It can be genetic, or may be induced.  
Natural collante of genetic origin normally develops at an early stage of seedling development and affected seedlings never fully recovers.  Induced collante symptoms may appear within a few weeks after germination or transplanting, sometime after a period of normal growth.  Any pathological or environmental factor (especially moisture stress) which impairs root development may predispose seedlings to collante.  Maintenance of a satisfactory soil moisture status, by regular watering, should result in recovery of seedlings with induced collante symptoms.



As differentiation of seedlings with natural or induced collante
symptoms is difficult in the early stages of nursery development, culling should be delayed until seedlings are about six months old, by which time those with induced collante symptoms will display evidence of recovery.  


 Crinkled leaf. 
As mild cases of leaf crinkling generally recover with improved watering,  these should not be culled. Only severe and persistent cases should be discarded.
 Chimaera  The entire leaf or sections of the leaf are pale or bright yellow in colour in comparison to the normal dark green colour of the leaf tissue. The intensity, distribution of the discolouration may vary.


Main nursery
 Retarded development. (Runt)   This is sometimes shown by seedlings which are morphologically similar to palms of the same age.  Such seedlings are liable to remain stunted and will yield badly.  
 Barren or sterile form.  The fronds grow at an abnormally acute angle so that the palm has a very upright and rigid appearance.
 Flat top form.  Newly - produced fronds are progressively shorter so that they do not project beyond the older fronds.

 Limp or flaccid form.   The fronds and leaflets are very flaccid.  The whole palm has a limp appearance and may appear quite short. 








 Juvenile form.   The frond has a compressed appearance due to very close spacing of pinnae along the rachis.








 Wide internodes.  This condition may occur due to etiolation in closely spaced nurseries.  However, in adequately spaced nurseries genetic abnormalities may also occur - such as pinnae spaced wide apart, thus giving the seedling a very open habit.  Only the genetic abnormalities should be discarded ,and remedial measures should be considered if over-crowding is implicated.








 Narrow pinnae insertion.   This is a common characteristic of seedlings which are abnormal in their general morphology.








 Accute pinnae insertion. Seedlings with abnormally acute pinnae insertion. ie. pinnae are borne at a very acute angle to the rachis








 Short Internodes. Pinnae are very closely spaced along the rachis. Fronds appear compressed














 Short, broad pinnae.  This symptom often occurs in combination with short internodes and pinnae points are usually quite blunt













 Chimaera. It can also appear at this later stage of nursery development. This should be rejected for field planting  

1 comment:

  1. So much useful info can be gained from your blog.. Thanks for the info...

    ReplyDelete