Spread of bunchy top disease in established banana plantations

Abstract

The spread of bunchy top disease by the banana aphid was studied in two established banana plantations, in the presence and absence of roguing operations for disease control. The probability P of a new infection occurring x metres from an estimated source of inoculum was described by a special case of Pearson's gamma probability function

Px = exp( – x / x) ÷ x,

where the mean distance between all of 178 new infections and their estimated sources of inoculum was x = 17.2 m, irrespective of roguing. All except two of the new infections occurred within five standard deviations (5x = 86 m) of the source as predicted, with nearly two-thirds within 20 m. The results were confirmed by successfully predicting the number of new infections that were encountered within 10 m of sources of inoculum in five other banana plantations. The results are discussed in relation to quarantine measures aimed at limiting the spread of disease in established plantations.