Small Black Critters Chewing Leaf Holes

Q. For the past three years these little black critters have chewed holes in the leaves of my Mexican Primrose. What are they and how can I get rid of them permanently? Since Mexican Primrose is not a food crop, I sprayed them with Ortho’s Home Defense, but that may not be the best solution.

BB sized holes in grape leaves from flea beetle feeding

A. Thanks for telling me the insecticide you used but legally you are not supposed to use an insecticide unless the label states it can be used for that purpose. The active ingredient of the insecticide might work on flea beetles but unless there is a given rate of application on the label, then the rate to apply is not known. The rate of application can mean the difference between control or no control.

Mexican Primrose and Flea Beetle Damage

            Mexican Primrose is notorious for flea beetle damage in the spring and sometimes fall months. Knowing which flea beetle is yours is the first step in getting permanent control. If you elect to go down this path, take five or six flea beetles in a vial of alcohol to the Nevada State Department of Agriculture and ask their entomologist in Reno to identify the type of flea beetle. Once the flea beetle is properly identified, methods of permanent control can be discussed. There is quite a bit of literature on permanent control without chemicals.

Flea beetles are quite small

            As far as I am concerned, flea beetles are vagabonds and become a problem frequently during the spring, and sometimes fall months. Mark your calendar because they will come near the same date in the spring most years. This date signals you to start looking for them or their damage and apply the proper control measure.

Heavy flea beetle damage on grape leaves

            Flea beetles last about three weeks and they are gone. They can cause a lot of damage in a noticeably short time. If you see damage during the fall months, mark your calendar. Watch for holes in the leaves that signal their feeding has begun. They hide out on the bottom of leaves so you must spray “up” as well as over the top.

Pesticides and Controlling Flea Beetles

            Conventional insecticides used for controlling flea beetles include Sevin (active ingredient of carbaryl) or one of the pyrethrins (look for something ending in -thrin in the active ingredients). These must be applied each season you see them. Once damage is done, cut the plant back to get rid of the ugly parts, fertilize, water, and let it regrow.