The current
Texas Cooperative Extension recommended system for the control of
the spinach white rust disease consists of the following:
- follow a 3 – 5 year crop rotation
- plant a resistant variety
- apply metalaxyl (Ridomil) in-seed furrow at planting
- Initiate a foliar fungicide spray schedule when the first 12 + continuous
hours of leaf wetness occur after 30 – 35 days from seedling
emergence.
The suggested foliar fungicide spray schedule should include two applications
of Amstar (formerly Quadris) rotated with one application of copper
fungicide. It is a must that a fungicide of different chemistry than
Amstar, a strobilurin, is used to prevent resistance buildup to Amstar.
The copper compounds offer only marginal efficacy against white
rust. Therefore, for the past five years, the Texas Cooperative Extension,
Wintergarden Spinach Improvement Team (Marcel Valdez, Kenneth White,
County Extension Agents for Zavala and Uvalde Counties respectively
and Drs Larry Stein and Frank Dainello, Extension Horticulture Specialist)
have been attempting to find a good rotation product for use with
Amstar. During this period the team has evaluated 16 compounds at
various rates and application schedules for efficacy against white
rust. Results of these evaluations have shown that the most effective
compound against white rust has been Cabrio. Unfortunately, Cabrio
is also a strobilurin product and cannot be used with Amstar. In addition,
Cabrio has not yet received a label for use on spinach. However, several
other compounds have been found to offer promise as a potential rotation
product for use with Amstar; Zoxium, Prophyte, and KP485. Continued
evaluation of these compounds will be conducted during the coming
spinach season. If these compounds continue to offer a consistently
high level of control of white rust, efforts will be undertaken to
obtain a label(s) for their use in a spinach disease control system.
