What is the fine-grained topic of the following text: Western Growers represents more than 3,000 shippers in California and Arizona and is a proponent of the California Leafy Greens Handler Marketing Agreement, which would require all signatory leafy green handlers to only purchase product from growers who adhere to the voluntary agreement’s Leafy Greens Good Agricultural Practices. Only return the topic.
California Leafy Greens Handler Marketing Agreement Advocacy by Western Growers