Relationships of environmental factors and inoculum levels to the incidence of postbloom fruit drop of citrus

Postbloom fruit drop, caused by Colletotrichum gloeosporioides, and environmental variables were monitored in three citrus (Citrus species) orchards from 1989 to 1991. In a navel orange orchard near Arcadia, the incidence of blossom blight was up to 30% in 1989 and up to 75% in 1991, but was less than 10% in other years and at other sites. The area under the curve for blossom blight was related positively to the number of persistent buttons (calyxes and floral disks) and related negatively to fruit counts (.)