Prothioconazole/Trifloxystrobin

Ms. Karen Cain 12.
ECOLOGICAL EFFECTS ASSESSMENT:
The following assessment was produced by the Department’s Bureau of Habitat
(BOH) within the Division of Fish, Wildlife, & Marine Resources:
Both active ingredients in Stratego YLD Fungicide have been reviewed previously by
BOH, trifloxystrobin most recently in May 2010 and prothioconazole in May 2009.
USE PATTERN:
Stratego YLD Fungicide is a broad spectrum fungicide for use on corn (sweet, pop, and
field varieties) and soybeans. Applications of 4-5 fl oz. (4.65 fl oz. upper limit on soybeans) per
acre (/A) are made using water as the carrier.
On sweet corn sequential applications are not allowed. Each Stratego YLD application
must be alternated with a fungicide with a different mode of action. No more than 20 fl oz. /A
may be applied per season.
On field corn and soybeans two sequential applications are allowed before rotating to a
different mode of action. The retreatment interval is 7-14 days for field corn and 10-21 days for
soybeans. No more than 10 fl oz./A may be applied to field corn per season. The seasonal limit
for soybeans is 13.95 fl oz/A.
The label allows aerial, ground, and chemigation applications.
Application rates for both Stratego YLD active ingredients individually are lower than
those reviewed previously. The total seasonal maximum Stratego YLD combined ai application
rate is lower than previously reviewed trifloxystrobin rates. It is 0.1 lb ai/A higher than the
maximum previous prothioconazole rate reviewed.
EXPOSURE MODELING & RISK ASSESSMENT:
Terrestrial- Standard BOH post application food-item residue exposure modeling for
birds and mammals showed no potential for acute or chronic toxicity. These two groups are not
discussed further.
Aquatic- Application of Stratego YLD directly to the surface of a water body, the
condition by which aerial application threat is evaluated, results in trifloxystrobin concentrations
that far exceed lethal values. As described in previous trifloxystrobin reviews, trifloxystrobin is
a rapidly lethal aquatic toxin. While its half-life in water is relatively short at 14.4 hours, the
very high toxicity, rapid lethality, and resulting multiples of LC50s far outweigh its short resident
time. Therefore, aerial applications of Stratego YLD pose an unacceptable risk to aquatic nontarget
organisms.