Biological and ecological factors affecting populations of the sugarcane moth-borer, Diatraea saccharalis (Lep.: Pyralidae) Barbados, W.I.
The introduction and establishment of Apanteles flavipes (Cam.) and Lixophaga diatraeae (Tns.) in Barbados for the control of Diatraea saccharalis (F.) on sugar-cane has substantially reduced the level of joints bored and sugar lost. Concurrently with the introduction of the parasites some cultural practices have also changed (especially pre-harvest burning and the predominance of some cane varieties), and the author discusses the relative importance of the parasites and these changes in effecting the reduction of joints bored from 16 to 5%. In paired-field comparisons, it was concluded that burning allowed a rapid build-up of the pest with initially poor control by the parasites. However, an analysis of the overall population changes during the non-burning periods indicated that the period during which pre-harvest burning was common was correlated with an additional reduction in joints bored. The discrepancy between the small-scale investigation and the large-scale experience may be coincidental but it may also illustrate the danger of extrapolating from paired-field comparisons to a larger scale. The evidence indicates that the 2 parasites have brought about a reduction of about 10% in joints bored. Changes in varieties may have accounted for 1-1.5% of the increased level of joints bored since 1974. Large-scale pre-harvest burning may have effected a reduction in the number of joints bored of 1.5-2%.