To Combat

‘Nutfall’

Remarkable Use of Solomon Is.

Ant

Honiara, Sept. 12.

SUCCESSFUL research by scientists into the nutfall disease which causes serious losses in British Solomon Islands coconut plantations has recently been concluded.

Lever Bros, sent Mr. Leach, plant pathologist, from England to the Solo mons, to reopen investigations made by scientists before the war. The Fiji Gov ernment co-operated by sending Mr.

O’Connor, Government Entomologist, with Mr. Leach.

The present research team confirmed earlier scientific opinion that the nutfall trouble is caused by an insect, Ambly pelta, which feeds in the same manner as a mosquito, and pierces the young coconuts to suck their juices. Injury to the young coconut is caused by a toxic fluid which the insect injects while it feeds; the damaged area turns brown and soft; and the nut falls prematurely.

Maturing nuts are also damaged, though these do not fall.

Messrs. Leach and O’Connor conduc ted their investigations in plantations which, before the war, were almost entirely ruined by nutfall. They found that these estates, once kept clean and tidy, were now overgrown with vines and small shrubs, and that the coconut trees, though some of the old coconuts were heavily marked with Amblypelta scars, had recovered and were bearing very large crops of healthy nuts.

Pre-war, scientists discovered that the large yellow ant, Oecophylla, was pre sent on nearly every good bearing tree, and that it disturbed and attacked the sucking bug. This ant builds its nest out of leaves, preferably at the top of a tree, and comes down the tree to cover a wide area in its search for food.

The recent research disclosed that this yellow ant is attacked by two other species of ant, neither of which will harm the sucking bug, Amblypelta. One of these enemy ants (Pheidole) nests in the base of the coconut trees, and the other (Iridomyrmex) in depressions in the trunk and in the crown of the palm.

In plantations where only the ant living at the base of the tree was present, it was found that the overgrown state of the plantations had resulted in the yellow ant being provided with natural bridges from the ground to the upper trunk of the tree, so that it was not subject to the attack of its enemy at the tree base.

Transplanted colonies of the yellow ant readily made their way up and down the trees against which coconut fronds had been placed for their use, and the yellow, ants were also observed to be travelling along the natural vines which have sprung up near the trees.

Palms examined six weeks after a col ony of ants had been introduced and pro vided with artificial bridges were already bearing healthy young nuts.

Messrs. Leach and O’Connor were not able, in the time available, to find any way of countering the second variety of ant (Iridomyrmex) which destroys the yellow ant. Iridomyrmex is found all the way up the trunks of trees, and at their tops.

In plantations affected by Ambly pelta and therefore subject to nutfall, where Iridomyrmex is present, it is con

sidered that the yellow ant cannot be successfully established, unless Irido myrex is previously eliminated from the palms. Further work may show that this ant could be destroyed by reasonably economical methods.

In the meantime, dusting or spraying, for direct control of Amblypelta, appears to be indicated.

However, in plantations affected by Amblypelta, where only the ant (Phei dole) which nests at the base of a palm is present, nutfall should be a thing of the past, provided that coconut i)lanta tions are not kept too clean, and that provision is made for the yellow ant to bypass Pheidole.

Areas in the BSIP mainly affected by nutfall before the war, were the islands of Guadalcanal, Malaita and Nggela. It was then estimated that an average yield of only 2 cwt. of copra to the acre could be produced in affected areas; while in the unaffected Russell Islands Group the average yield was 15 cwt. of copra per acre. Copra is at present returning about £4O gross per ton to the Solomon Islands producer, and increased production is badly needed to alleviate the world-wide shortage of fats.