Are your roses getting brown patches in them already? Don't reach for the pesticide to control Japanese Beetles as they are not to blame...yet! In the really early season of the year, there is another insect that is hard to see that causes damage to the leaves. It can be severe at times where there will either be lots of brown spots or holes. This damage is caused by the Rose Slug Sawfly.
Rose Slug Sawfly
This insect is really small and can be easily overlooked as its coloration will be similar to the leave itself. The insect will feed on the underside of the leaf in early stages of life. When young, its mouth is too small to be able to chew all the way through the leaf. That is why the damage can appear to be browned spots at first (they leave only the epidermis tissue of the leaf) that may later fall out as it dries to become a hole in the middle of the leaf. As they get older and larger, the insect can start actually removing all layers of the leaf much like a Japanese Beetle would damage it.
What To Do
When the damage is minor, let them have their fill. That is at least the most environmental solution to the problem or go find them (Good Luck! They camouflage well!) and pick them off. If their damage become severe, they are pretty easy to control with carbamate (Sevin) or bifenthrin (Talstar). There may be other products available as well. Please do be bee-conscious and do not apply when the plants are flowering as it might cause bee death! More information can be found at: http://www.ppdl.purdue.edu/ppdl/weeklypics/6-7-10.html