It is best to apply Trimec 992 when the weeds are no too wet from any rain or dew so that the product can be applied to the leaves and not drip off easily from being wet already. You should apply when rain is not expected within 24 hours after application as well.
When using Trimec 992 Broadleaf Herbicide the tempuratures would need to be above freezing, and the weeds would need to be actively growing in order for the product to work effectively. Most post-emergent herbicides such as Trimec will be most effective when temperatures are around 65-80 degrees.
Trimec 992 Broadleaf Herbicide is mixed at 1.5 fl oz per gallon of water. It will take 4 pints to treat an acre. Herbicides do not give a water amount. They only tell you how much of the product to apply over 1000 square feet. The amount of water is dependent on how ever much water it takes for you to walk 1000 square feet. Whether you place the amount of product per 1000 square feet in a gallon of water or 10 gallons of water, it does not matter, just as long as that amount of product is distributed over the 1000 square feet.
Trimec 992 Broadleaf Herbicide has a higher percentage of active ingredient than the Trimec Classic Broadleaf Herbicide. Neither will harm your lawn when used as directed on their product labels, and both are good for ground ivy. The rates vary depending on your lawn type and for the Classic it is 0.75 - 1.5 oz. per 0.5 to 6 gallons of water per 1,000 sq. ft.