2 arborists have told me the rate should be higher for larger trees; I treat a 47" dbh green ash with a 2.5% solution of Dominion. One of the benefits of buying Dominion Imadicloprid (21%), beyond the cheaper price, is you can vary the solution rate to fit the tree / shrub. Also, for small oaks / chestnut trees with thin bark, it would be very easy - and effective - to use a small tank sprayer to complete a bark drench application (spray the trunk of the tree from 4.5' -dbh down to the ground. Uptake might be faster than a soil drench. Either a soil drench or bark drench would work ... eliminating any issue with Japanese beetles. Don't know if it would help with gall wasps on small oaks.
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