Abstract:
Sugarcane White Leaf Disease (WLD) is one of the major threats to the cane sugar industry
in Sri Lanka and Deltocephalus menoni (Hemiptera: Cicadellidae, Deltocephalinae) is the only
locally-identified vector of this phytoplasma disease. In Sri Lanka, screening of sugarcane varieties for WLD resistance is done by field evaluation of them considering the natural infection
levels of WLD. It is a lengthy, tedious and expensive process. This study was conducted at the
entomology laboratory and the research farm of the Sugarcane Research Institute (SRI), Uda
Walawe with the objective of finding the potential of using vector performance on sugarcane
varieties to evaluate varietal reaction to WLD. Level of WLD infection by D. menoni on eight
sugarcane varieties and two wild relatives under natural environment and the behavioural characteristics of D. menoni; aggregation, amount of feeding amount of feeding, fecundity, nymphal
development and adult longevity on the same varieties were studied. Variations between varieties and correlations between level of WLD infection and insect behavioural characteristics
were studied. The level of WLD infection and behavioural characteristics of D. menoni were
significantly varied with sugarcane varieties. Significant and positive correlations observed for
aggregation, amount of feeding and adult longevity of the vector. Correlation coefficient between natural infection of WLD and insect aggregation was 0.59 (n = 90, p = 0.001). It was
0.73 (n = 90, p = 0.001) for amount of feeding and 0.71(n = 90, p = 0.001) for adult longevity.
Amount of feeding correlated with insect aggregation (r = 0.54, n = 90, p = 0.05) and adult
longevity (r = 0.71, n = 90, p = 0.001). As aggregation, feeding and adult longevity of vector
directly correlate with the natural infection level of sugarcane WLD, there is a potential of using
these behavioural characteristics at the primary stages of variety evaluation process for WLD
reactions. It makes the screening process timely and cost effective.
