Development of an expert system for fire blight management in Pennsylvania, and the role of aphids and copper in blight management

In the process of defining and building the knowledge base for the Fire Blight Management Expert System, two researchable questions arose from gaps in the literature: whether copper micronutrients could be used for controlling shoot infections and whether aphids were important vectors of the fire blight bacterium.; Single Sorba-spray Cu treatments of 31 ppm copper resulted in a slight suppression of lesion length in shoots of 'York Imperial' after artificial inoculations with Erwinia amylovora. Multiple applications of Sorba-spray at 62 ppm resulted in phytotoxicity to fruit and foliage of 'York Imperial'. Although slight suppression of blight was observed in two of three seasons when tested on 'York Imperial', no blight suppression was noticed under very favorable blight conditions and when Sorba-spray was tested on a very susceptible cultivar. Sorba-spray copper holds little promise as a commercially viable control option for fire blight shoot infections.; Aphids were unable to vector the fire blight in the conventional manner of acquisition, migration and injection as demonstrated in the paired shoot test and in membrane feeding tests conducted in the field. In agreement with previous research, aphids in these tests were not able to introduce enough bacteria to cause infection. Two years of field data suggest that several hundred to several thousand bacteria need to be introduced in order for blight to develop. Increased efforts to control aphids in apple orchards with fire blight are therefore not warranted.; The Fire Blight Management Expert System, FBMEX, provides the user with decision-support for fire blight management in all phases of the production cycle, and serves as a reservoir of disease- and management-specific information. FBMEX reports of high risk days agreed well with observations of blight severity in validation orchards. FBMEX is the first system to formally incorporate the concept of orchard risk in fire blight management decision making, delivering decision support at a level greater than mathematical or qualitative methods could independently.