Page 58 - Free State Spring 2023_WEB

TOTAL PLANT MANAGEMENT (Continued)

At all the sites, the cultivar ‘Aroma,’ had heavy downy
mildew symptoms by mid-August.
Salisbury - In Salisbury, plants were evaluated for
resistance on September 15 and September 29. ‘Emerald
Towers’ and ‘Aroma’ had poor resistance to DM,
‘Obsession’ and ‘Thunderstruck’ had good resistance,
and ‘Devotion’ and ‘Passion’ had good to excellent
resistance. (see chart bottom page 57)

Westminster and Brookeville - Harvest at these sites
was every two weeks in July, August, and mid-September,
cutting stems to 4” from the soil line. Bunches varied from
4 – 7 stems per plant at each harvest. At farm markets,
these bunches could easily fetch $5 - $6 per bunch.
The first harvest occurred July 15, 2021, and continued
on two-week intervals through mid-September. In
mid-September, as temperatures cooled, harvest was
extended to every four weeks. By early October, the ‘Emerald Towers’ with damage, 9/8, CMREC
cultivars ‘Devotion,’ ‘Obsession,’ ‘Prospera,’ ‘Passion’ and cultivars remained free of disease for the duration of
‘Thunderstruck’ all started to produce flowers. ‘Everleaf the trial.
Emerald Towers’ started to produce flower heads in late
September. The Everleaf Emerald Towers plants stopped Summary
producing marketable foliage by early September. Red Overall, over the last three years of trials, ‘Devotion,’
Opal was planted at these two sites and showed no ‘Passion,’ ‘Prospera,’ and ‘Amazel’ showed the highest
symptoms of downy mildew throughout the study. We resistance to downy mildew. ‘Thunderstruck’ and
continued to harvest all of the cultivars until Oct 29, 2022, ‘Obsession’ showed moderate resistance but still had
at the Westminster site. symptoms. ‘Emerald Towers’ showed very little resistance,
Downy mildew was detected on Sept 11 on ‘Aroma’ basil, if any, and had the lowest yields. ‘Red Opal’ performed
with 10% of foliage infected. By Sept 23, all of the ‘Aroma’ well with resistance to downy mildew at two sites. Lemon
plants were dead. ‘Passion’ had under 5% of the foliage basil grown at two sites was decimated by downy mildew
infected with downy mildew on Sept 11, but the plants by September. A
continued to grow and produce foliage.
At the Brookeville site, on September 18, we detected Stanton Gill, Extension Specialist in
downy mildew on ‘Aroma,’ lemon basil, and ‘Passion’ IPM for Greenhouses and Nurseries,
basil plants. The ‘Aroma’ and lemon basil plants were University of Maryland Extension
thoroughly covered in downy mildew within two weeks. And Professor, Montgomery College,
The ‘Passion’ basil showed 20 -30% of the foliage infected; Germantown Campus, Landscape
though the plants continued to grow, they did not have Technology Program
marketable foliage. ‘Prospera,’ ‘Obsession,’ ‘Devotion,’ sgill@umd.edu
‘Thunderstruck’ and ‘Opal’ were free of downy mildew https://go.umd.edu/ipmnet
until heavy frost in early November ended the trial.
David Clement, Extension Specialist in Plant Pathology,
Finksburg - The first symptoms of downy mildew
appeared on ‘Aroma’ and ‘Emerald Towers’ on August 19. University of Maryland Extension, HGIC
The disease progressed rapidly in these two cultivars, and Suzanne Klick, Lead Technician, University of Maryland
by September 9, all had severe symptoms. The remaining Extension, CMREC
‘Devotion,’ ‘Passion,’ ‘Thunderstruck,’ and ‘Obsession’

58 SPRING 2023 • Free State News