We decided to visit the Rennel Island
because of the variety called “Rennell Island Tall” which is world-renowned.
Our objective was to assess sourcing of new planting material from the island.
The former Yandina Research centre sent
this variety to many countries. Rennell Island Tall is conserved in at least 10 countries and serve
(or served) as parent for many hybridization programs: Fiji, Samoa, Solomon;
Vanuatu, Côte d’Ivoire and the Philippines continue to use it for production of
hybrid or synthetic varieties. According to M. Foale, the The pure variety can only be found around the Tengano Lake, now classified as world heritage.
Following the disappearance of
its Research centres, and taking into account the recent rhinoceros beetle problem, it seems that (as of 2018) the
Ministry of Agriculture of Solomon does not have any more a source of Rennell Island
Tall in Guadalcanal.
The coconut grove in Rennell Island
appeared in a very poor sanitary status. During our visit, we estimated that
more than 60% of the palms were improductive, due to various attacks of pests
(insects and rats), putative disease, and mineral deficiencies.
 |
| Frequent aspect of palms in the Rennell with almost no fruit |
Around the airport and along the road to the lake, coconut palms are suffering from mineral deficiency, and in our opinion, the most important is chlorine deficiency. Palms should receive some salt and the production will increase. The second most important deficiency seems to be magnesium, but conducting foliar diagnosis analysis would help to confirm this opinion.
We strongly recommend a pest and disease
specialist to visit the Rennell Island and make conclusion about the new
putative disease and the insects involved in reducing production. Before
that, it seems risky to source again planting material from Tengano Lake.
|
 |
| Foliage attacks |
Villagers attributes most of the production loss to a rat recently introduced by logging activity, but we do not share this point of view. In many other countries, we saw massive rat’s attacks. In this case there are plenty of small coconut typically eaten by rats remaining in the ground. In Rennell we observed only a very few of these nuts on the ground. There are plenty of foliage attacks probably caused by insects but we did not have the opportunity to go further in their recognition – we searched without success brontispa sp.
In some islands of the Tengano lake, we saw
something looking like a coconut disease. Within a 2-3 years period, the stems
of the palms reduce from normal size to approximately 10 cm wide, the crown
considerably reduces, finally become yellow and the palms dye. It is a kind of slow
foliar decay reminiscent of some phytoplasma-induced diseases in Sri Lanka and
India. One might think that this is a phenomenon related to the rising waters, but
some close islands that seems to be exactly in the same situation continue to
host normal coconut palms. According to the villagers, this phenomenon is quite
recent and appears less than five years ago. Back to Honiara we had some
discussion with Simon Iro, who think it could be linked to rare mineral deficiencies,
some essential trace elements missing, slowly killing the palms. In this case, identifying the missing trace element by foliar diagnosis would be of crucial importance: by applying a few grams of adapted fertilizer per palm, farmers will avoid their palms to dye, and will at least double the yields.
In Niu Pani, we also saw two close palms of very different stature and color, and showing exactly the same symptoms: production of a large number of flowers of which none develop into fruits. It could be caused by an insect or another pest eating the floral organs (pistils) and preventing pollination to occur. Villagers are speaking about two beetles, one very big eating the roots of the coconut palm, and one smaller who may damage the flowers, but we did not had the opportunity to see these insects.
We decided to visit the Rennel Island
because of the variety called “Rennell Island Tall” which is world-renowned.
Our objective was to assess sourcing of new planting material from the island.
