Correlation between field disease and latent infection by Glomerella cingulata of strawberry plants as revealed by a simple diagnostic method using ethanol immersion

Leaves of strawberry plants growing in fields were collected and assayed by ethanol immersion treatment (SDEI) to detect latent infection by Glomerella cingulata and Dendrophoma obscurans. SDEI revealed that 83% of the plants in growers fields were latently infected by G. cingulata and 58% by D. obscurans. In such fields, only 0.8%–2.5% of the plants later became wilted or died because of G. cingulata. When the latently infected plants from naturally infested fields were kept under optimal conditions for disease development for 5 weeks, 70.0%–83.3% of them wilted or died from G. cingulata. However, only 5.6%–6.7% of the plants diagnosed by SDEI as being without latent infection wilted or died. The results indicate the importance of selecting healthy plants, suggesting that SDEI is an effective method for detecting latent infection and reducing losses from G. cingulata.