Yes, Certainty Herbicide is labeled to control both rescuegrass and poa annua.
You may notice signs of the poa trivialis dying (discoloration-yellowing or browning) within 2-3 weeks after you have applied Certainty but it is normal not to see anything for at least a month. Per the product label, you can make an additional application 4 or more weeks after the initial application as needed. Best results are obtained when target weeds are actively growing & not disturbed by mowing for at least 2 days before and 2 days after application. Warm, moist conditions following application will accelerate activity; cold, dry conditions will delay activity. Drought stressed weeds are less susceptible.
The small scoop for Certainty is .16grams and the large .8grams. Depending on what you are treating for and what type of turf you are treating for would make the difference in how many scoops you would use per gallon water. On page 2 of the Product label you will find the mix chart.
Certainty Herbicide should be applied when weeds are actively growing and temperatures are between 65-85 degrees.
Certainty Herbicide is safe to use around pets as long as it is used according to the directions on the product label. You do want to keep pets and people out of the area while the product is being applied and until it is completely dry. Once everything is dry, it is fine for everyone to return to the area.
Certainty Herbicide is safe for mondo grass, but it is not labeled for oxalis. We would recommend a product like Monterey Weed Whacker, which is labeled for both oxalis and dandelion, and is safe to apply to established mondo grass.
When treating with Certainty Herbicide it can take time to see results based on the weather. Per the product label: Time to Symptoms: This product is absorbed by both the roots and the foliage of plants and rapidly inhibits the growth of susceptible weeds. Susceptible weed growth stops within 24 hours of treatment even though visual symptoms are slow to develop. Susceptible weeds usually show yellowing or browning within 2 to 3 weeks. Warm, moist conditions following application will accelerate herbicidal activity. Cold, dry conditions will delay herbicidal activity. Weeds stressed by drought are less susceptible to this product.
Per the Certainty Herbicide product label for dallisgrass suppression, you would use 1.25 oz per acre. This would be mixed in 10-50 gallons per acre. The amount of water you use will vary as the water acts as the carrier. For smaller areas, you would use 5 small (or 1 large) scoop per 2 gallons of water to cover 1000 sq ft. At this rate one bottle will cover one acre. Please refer to the product label for complete instructions for treatment and tank mixing recommendations.