Yes, a single rainfall or sprinkler irrigation of 0.5 inches or more is necessary to activate Gallery 75 DF Specialty Herbicide.
There are 16 oz in a pound of Gallery 75 DF Specialty Herbicide.
Gallery 75 DF Specialty Herbicide is a pre-emergent herbicide that can be applied to established cool and warm season turfs. It should be applied separately from Prodiamine or other pre-emergent herbicides.
We do carry a product by Fertilome that contains Gallery, it is called the Ferti-Lome Broadleaf Weed Control with Gallery and is a granule. It is currently the only "generic" isoxaben that we carry.
Gallery 75 DF Specialty Herbicide has a 3 year shelf life if stored away from extreme temperatures in the original container.
It is important to apply pre-emergents like Gallery 75 DF Specialty Herbicide just before the soil reaches 55+ degrees, right before the seeds begin to germinate in the soil. For warm season grasses, this is typically around February-March. You may contact your county extension office for the specific time frame to apply in your county and also visit our Lawn Care Schedule Guide for more information.
Chamberbitter (also called mimosa, gripeweed, niruri) germinates when temperatures are warm, around 70 degrees F. You would need to apply Gallery 75 DF at the rate of at least 1 lb per Acre (0.38 oz per 1,000 sq ft) to prevent this weed from germinating. You can reappyl at 60 day intervals as needed, as long as you do not exceed 4 lbs per Acre per year, per the product label. The only temperature restriction we would recommend is that you should not apply pre-emergents when the ground is frozen, near freezing temperatures, or water-logged. So if you make a February or March application, then you could reapply at least 60 days from that.
Another great tool to help prevent this weed in ornamental beds is to keep a 2-4" layer of mulch in the beds to prevent these seeds from being able to germinate. Here are some articles with additional relevant tips and information:
You should irrigate areas that have been treated with Gallery 75 DF Specialty Herbicide with about ½ in. of water within 24 hours of application.