Abstract
Sugar beet is harvested in the Imperial Valley of California from April through July. Daily
high temperatures often exceed 110-115 degrees F in late June and July. The extreme heat,
in combination with saturated soil conditions due to furrow irrigation, creates favorable
conditions for the development of late rot in sugar beet fields. Late rot is a complex of two
or more pathogens that can rapidly deteriorate a sugar beet root. Pythium aphanidermatum
and Phytophthora drechsleri are the two primary soil-borne pathogens contributing to late
root rot losses in fields. Late rot complex reduces the sucrose and purity content of the
sugar beets, which leads to processing difficulties and losses. Imperial Valley sugar beet
varieties have varied tolerance to late rot infection. Furrow irrigation is the predominant
irrigation type for sugar beet production in the Imperial Valley. Trials were established
to explore if the combination of variety tolerance and irrigation type can reduce late rot
development and increase yields during the final month of the harvest season. Trials were
established during the 2022-2023 and 2023-2024 growing seasons at the Imperial Valley
Research Center near Brawley, CA. The trials were randomized complete block designs
with a split-plot arrangement. Irrigation type (sprinkler vs. furrow) was the whole plot,
and variety (tolerant vs. susceptible) was the subplot. The trials were planted in early October
and harvested in early August. In both seasons, root yield and extractable sucrose per
acre were greater, and the percent rot was lower with the use of a tolerant variety. Sucrose
content was greater with the use of sprinkler irrigation in both seasons. The trial is being
repeated for the 2024-2025 growing season.