For foliar applications of trees, shrubs: 1.6 oz (1 packet) of Merit 75 WSP (75% imidacloprid) per 300 gallons of water. Please refer to the product label for complete application instructions.
The best time to treat with Merit will depend on the type of insect that you are treating for and the region that you live in. We recommend contacting your local cooperative extension office to ask about insecticide timing for the pests in your region. These offices are an invaluable resource when dealing with pests and most have a master gardener and an entomologist on staff to answer pest insect questions. It is also a great idea to read through the Merit product label as the manufacturer may have provided information on the best time to treat for a particular insect.
We would recommend using Domnion 2L. It is labeled for use on trees for emerald ash borers as a preventative and a curative. This only needs to be done once a year. The mixing ratio is 0.1 to 0.2 fl oz per inch of the trunk diameter. This needs to be mixed in at least 5 gallons of water and poured around the roots of the tree.
When applying Merit 75 WSP as a soil drench applications to trees for Japanese Beetles, Leaf Beetles and other listed pests, it is applied at 1.6 oz (1 packet) Merit 75 WSP per 24 to 48 inches of cumulative trunk diameter.
As far as we know there are no known insecticides that will work on Ground Pearl. Ground Pearl is a type of hearty armored scale, and other than natural enemies like ants, no true solution is available. The best solution to try is to reduce plant stress by following recommended fertilizing and irrigation recommendations to enable turfgrass to tolerate the damage. You may also want to contact your local Cooperative Extension office to see if they have any recommendations.
Merit 75 WSP is labeled to treat grubs in turgrass and would be safe to use around ornamentals such as roses, but it will not kill the adult insects. Merit 75 WSP is diluted at a rate of one 1.6 oz packet per 300 gallons of water for ornamental treatment. If you only have a few plants, then you may want to consider using a product that is more specifically for roses, such as Bonide Systemic Rose and Flower. Monterey Rose and Flower Spray Plus can be used for adult insects on the plants.