Browsing by Author "Morgan Williams, J."

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    The Effect of Artificial Rat Damage on Coconut Yields in Fiji
    (1974-09) Morgan Williams, J.
    In all cases assessed yield loss from rat damage in coconut plantations has been based on counts of immature damaged nuts, it being assumed that yield loss was directly proportional to the number of nuts attacked. Insect attack on coconuts and other crops has indicated that compensation for pest damage can occur, hence counts of immature damaged coconuts were unlikely to be directly related to yield loss. A trial involving artificial rat damage at four intensities was therefore established to investigate the relationship between damage and yield. Several possible compensatory modes were investigated and two responses were noteable: 1. The number of female flowers increased in response to the loss of immature coconuts but this compensatory response could not influence the number of harvestable nuts until 23—24 months after damage started, since this represents the time lapse from flower formation to nut maturity. 2. There was no apparent decrease in the number of harvestable nuts produced by the highest levels of artificial damage and it was postulated that there could be a decrease in late immature nutfull caused by factors other than rat attack, since the flower responses were ineffective within the two years. In addition it was found that coconuts favoured by rats contained 23.9—29.2% of the dry matter of mature coconuts, suggesting that 70—75% of the material resources that would have been expended on the coconuts lost could be deployed in replacements. It was concluded that the upper limit of compensation was probably 75% of the number of nuts damaged but because none of the compensatory responses are fully understood it was considered that 50% compensation would be a realistic level. Counts of immature damaged nuts should therefore be halved to represent yield loss