Post-shucksplit applications of Bravo WeatherStik for cherry leaf spot control
Growers can use Bravo WeatherStik past the typical shucksplit timing on mechanically harvested tart cherries only.
Editor’s note: To use Bravo WeatherStik post-shucksplit, growers must go online to the MDARD website and sign the training affidavit every year. Please see #11 on the use restrictions list below.
Because of fungicide resistance issues and the season-long challenge of controlling cherry leaf spot (Blumeriella jappii), growers can use the fungicide Bravo WeatherStik past the typical post-shucksplit timing on mechanically harvested tart cherries. The old Bravo label prohibited this fungicide from use past shucksplit, but with new residue information provided by Michigan State University Extension, this label has been changed to provide Michigan tart cherry growers with an additional tool for controlling cherry leaf spot.
In 2011, MSU’s John Wise worked with the Michigan cherry industry and Syngenta to determine the levels of residues of chlorothalonil, the active ingredient of Bravo, on machine-harvested cherries that had spent time on a cooling pad. This situation simulates what a grower would do in the “real world” – harvest tart cherries into water and place on a cooling pad for a time period before delivering fruit to the processor. The study confirmed that when tart cherries were harvested and handled in water, they had less chlorothalonil residue than fruit not harvested in water.
As a result of this work, the Michigan Department of Agriculture and Rural Development granted a Section 24 (c) special local need registration for allowing use of Bravo WeatherStik past the old shucksplit timing on mechanically harvested tart cherries that are handled in water. However, to ensure that post-shucksplit applications do not result in illegal residues (less than 0.5ppm), there are use restrictions that growers must follow:
- The minimum pre-harvest interval (PHI) is 21 days.
- Cherries must be mechanically harvested.
- Cherries must spend at least two hours on the cooling pad.
- The initial flow rate on the cooling pad must be eight to 10 gallons of water per minute (gpm). After this period, the flow rate can be reduced to 4 to 6gpm.
- Rinse water generated during the cooling process must not drain or channel toward aquatic areas.
- Cherries cannot be used fresh; they must be processed by a commercial processor.
- This special registration is for Bravo WeatherStik only! Even though there are other generics of chlorothalonil available, this label applies only to Bravo WeatherStik.
- This special registration cannot be used on cherries harvested dry for the juice or other markets; fruit must be harvested in water and cooled on a cooling pad.
- Cooling pad rules need to be followed explicitly — the MSU data that were collected specified fruit would be on a cooling pad for two hours, so the resulting regulations were based on this information. Even if a grower cools cherries for a shorter amount of time, this time specification is important to follow to remain in compliance.
- Growers should check with their processor if fruit is to be harvested in a special manner (e.g., dry) if the grower wants to take advantage of this special registration.
- **Important step!! Growers that want to use this special registration must go through a training affidavit online at the MDARD website and complete steps 2 and 3. If a grower participated in this special use label last year, they WILL HAVEto go through the training affidavit process again due to some language issues on the 2012 affidavit. The new affidavit will be available on the MDARD website by May 24, 2013. The language of the Bravo WeatherStik label states that to use this product post-shucksplit, a grower must sign this affidavit EVERY YEAR. Therefore, if growers that did or did not go through the online training process last season must do so this year if Bravo WeatherStik will be used post-shucksplit. If growers do not have access to a computer, please call Nikki at 231-946-1510 for assistance.
To reiterate, growers need to follow these steps to ensure they will be in compliance of this special use label. Cherries that are harvested 21 days after the last application of Bravo WeatherStik will have illegal residues — growers must follow the label carefully to ensure the residues on fruit are reduced to a legal level (less than 0.5ppm). Illegal residues would violate federal law and would have serious consequences for the grower, processor and the Michigan cherry industry as a whole.