The following plant disease highlights have been compiled from samples submitted to the University of Kentucky Plant Disease Diagnostic Laboratory from January 3 to January 31, 2023. Although a few agronomic and greenhouse vegetable samples were received during this period, the majority of diagnostic samples for the first month of 2023 were ornamental crops, including both greenhouse ornamentals and landscape plants.
Samples included Trichoderma ear rot on corn; Pythium root rot on arugula and bok choy; foliar injury from greenhouse air quality problems on tomato; nutrient deficiency/high pH problems and powdery mildew on calibrachoa; Pythium root rot on pansy and petunia; thrips injury on oxalis; chilling injury and red thread disease on bluegrass; Botryosphaeria canker on arborvitae; hemlock borer injury on hemlock; black root rot on holly; and winter injury/winter desiccation on arborvitae, boxwood, and holly.
Red thread (Figure 1) made an early appearance this year due to warmer-than-typical temperatures in January. This disease may be eye-catching but rarely requires management in home lawns; for information on management of red thread in sports turf, refer to UK Extension publication Chemical Control of Turfgrass Diseases (PPA-1).
By Julie Beale, Plant Disease Diagnostician, and Sara Long, Plant Diagnostic Assistant