Browsing by Author "Williams, J.M."

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Rat Damage to Coconuts in Fiji Part 1 Assessment of Damage
    (1974) Williams, J.M.
    The amount of rat damage to immature coconuts was assessed by two methods. The first involved fortnightly recordings of all coconuts produced, including those rat damaged, at representative sites for up to three years. The second method attempted to utilise decay characteristics of rat damaged coconuts as a basis for projecting spot counts of damaged coconuts to long term estimates of damage. Damage was concentrated on coconuts aged three to six months with most of the damage being inflicted by Rattus rattus. Damage varied considerably from month to month with seasonal trends in damage being apparent at only one site. Rats clearly favoured particular palms in all plantations, resulting in over 75% of the damage being confined to 30% of the palms. Those selectively attacked were randomly distributed within the survey plots and did not produce significantly fewer harvustable coconuts than those palms seldom attacked. Tall palms, i.e. over 15m incurred less damage than those under 10 m. Decay characteristics of rat damaged coconuts proved to be of limited value as a basis for projecting spot counts to long term losses, but counts of green damaged coconuts accurately reflected the previous 33—35 days damage. Overall production losses (derived after adjustments for known palm compensation for damage) were relatively low; being 2.7, 2.0 and 1.3 nuts per palm per year during 1970, 1971 and 1972.
  • Thumbnail Image
    Item
    Rat Damage to Coconuts in Fiji. Part II Efficiency and Economics of Damage Reduction Methods
    (1975) Williams, J.M.
    The effectiveness and economics of two commonly recommended methods of reducing rat damage to coconuts were examined. Three replicated trials were used to investigate the effectiveness of a 30 cm wide aluminium band placed around the palm trunk 3.5—4.5 m from the ground. On palms only 9—10 m high these bands did not effectively reduce rat damage as senile fronds frequently bridged the bands, providing rats with access to the palm crowns. Bands did prevent damage on tall palms (over 15m) since no bridging by fronds occurred. A poison trial indicated that rat damage could be almost eliminated in a mature plantation for up to three months following one application of 3 kg/ha warfarin bait. This confirmed work carried out in Jamaica and the Gilbert and Ellice Islands. The cost of control by the two methods was assessed in relation to four copra values and it was concluded, in view of the relatively low levels of rat damage that prevailed, that neither form of control would be worthwhile until the value of copra exceeds F$150 per tonne and in the case of banding would only apply in the limited number of situations where bands are really efficient.