Effects of lethal bronzing disease, palm height, and temperature on abundance and monitoring of Haplaxius crudus

Insect vector feeding preference plays an important role in pathogen transmission. Study of phytoplasma-induced plant traits on vector preference may provide important insights into controlling economically important plant diseases caused by phytoplasmas. This study aims to examine the effects of 16SrIV-D phytoplasma infection of palms on associated planthoppers and leafhoppers (Order Hemiptera: Suborder Auchenorrhyncha) population abundance. The 16SrIV-D phytoplasma causes lethal bronzing disease (LBD) that results in economic losses to palm industries. The numbers of auchenorrhynchans collected during one-year weekly surveys using yellow sticky card traps in LBD disease area were analyzed. The total number of Haplaxius crudus, which was the most abundant auchenorrhynchan and is a potential vector of LBD, was 4.5 times greater on LBD-infected than non-infected palms. Other auchenorrhynchans showed no difference between LBD-infected and non-infected palms or were greater on non-infected than infected palms. Further analysis examining impacts of LBD infection of palms, temperature, and palm heights on H. crudus abundance revealed significant interactive effects among these factors. At the low temperature, H. crudus was more abundant on shorter palms than taller palms; however, H. crudus was more abundant on taller than short palms at the median and higher temperatures. These results indicate the preferential response of H. crudus to LBD-infected palms over non-infected palms and further suggest the involvement of multiple biotic and abiotic factors shaping vector preference. The interactive effects of LBD, temperature, and palm heights suggest that vector monitoring and disease management should be optimized according to seasonal variation in temperature.