Fire Blight Disease of Apple: A Growing Concern for Commercial Apple Production

Fire blight, caused by the bacterium Erwinia amylovora, is a severe disease that affects apple trees globally. The disease can cause significant losses to commercial apple production, resulting in substantial economic impacts. In the United States alone, fire blight has been responsible for millions of dollars in losses each year.

One of the characteristic symptoms of fire blight is the formation of bacterial ooze on the surface of infected tissue, which turns brownish due to necrotic lesions. The bacteria can also enter plants through natural openings or wounds, and infect flowers, leaves, shoots, fruits, and rootstocks. Infected tissues may develop cankers on perennial parts and a typical shepherd's crook shape at the terminal branches.

The accurate and timely detection of fire blight is crucial to deploy effective measures to reduce epidemics in commercial apple orchards. However, the choice of diagnostic assay depends on various factors such as time, sensitivity, and specificity required for detection and management. Grower surveys and comparative cost-benefit analysis have shown that immunoassay kits are less expensive, easier to use, and require less technical expertise compared to Loop Mediated Isothermal Amplification (LAMP) and quantitative Polymerase Chain Reaction (qPCR).

Recent studies have tested various diagnostic assays, including commercial lateral flow immunoassays such as AgriStrip and Pocket Diagnostics kit, LAMP, and qPCR. The results showed that the qPCR assay was able to detect bacterial cells up to 10^-3 cfu/ml with high specificity for Erwinia amylovora. However, the LAMP assay had lower specificity and showed positive tests for other bacteria.

In contrast, the AgriStrip and Pocket Diagnostics kits were able to detect actively growing bacteria up to 10^6 cfu/ml. These results highlight the importance of choosing the right diagnostic assay for effective management of fire blight in commercial apple production.

Fire blight remains a serious threat to commercial apple production worldwide, emphasizing the need for continued research into accurate and timely detection methods. Accurate diagnosis is essential to deploy appropriate measures to reduce epidemics and prevent significant economic losses. By understanding the characteristics of fire blight disease and its diagnostic assays, growers can take effective steps to manage this devastating disease and protect their apple crops.

Fire blight disease of apple