It may seem early, but this month is a good time to start thinking about garden pests, specifically the cucumber beetle. I had never heard of a cucumber beetle before moving to Northern California. When I first saw them in the garden, I thought they were cute little bugs, similar to ladybugs. In fact, they are the opposite. Ladybugs eat aphids; cucumber beetles nibble petals and leaves, leaving tiny holes in nearly everything.
Because they are strictly plant feeders, cucumber beetles are capable of causing widespread damage in a short amount of time. Leaves often develop a skeletonized appearance, with most of the soft tissue eaten away, leaving only the veins. I do not know of many other common garden pests here that leave plants looking quite like that.
Part of what makes cucumber beetles so frustrating is how well they suit our climate. Our mild weather lines up perfectly with their life cycle and feeding habits. They never experience a population reset because we do not have extended periods of frost, which is why their numbers compound year after year. Organic sprays often fail against cucumber beetles for several reasons. Many organic products work by direct contact or ingestion, but cucumber beetles have a hard outer shell that limits absorption. They also tend to drop off or fly away when disturbed, reducing contact time with sprays.
I eventually found a sticky lure trap specifically made for cucumber beetles. Over the years, these traps have become increasingly difficult to find, and the price is steep, about twenty dollars for two lures. I need at least four lures in my garden, and replacing them every two weeks quickly becomes cost-prohibitive. I scoured the internet for alternatives, and after testing this method last season, I can confidently stand by its effectiveness.
Items for Lures
Making the Traps:
1. Choose a yellow plastic cup. The brighter, the better. Cucumber beetles are strongly attracted to yellow, which is why commercial traps use bright plastic housings to attract them.
2. Coat the outside of the cup with Tanglefoot. This sticky horticultural glue is traditionally used to keep crawling pests off fruit trees, and Harmony Farm Supply usually keeps it stocked. Apply a thick, even layer around the outside of the cup, stopping about a half inch from the top so you can still handle it. Alternatively, coat the cup once it is already in place in the garden.
3. Place a cotton ball soaked in clove essential oil inside the cup. Cucumber beetles find the scent irresistible. The oil lures them close enough to investigate the trap, where they get stuck. I also put another layer of Tanglefoot inside the cup, almost up to the cottonball. This provided one more area to trap them.
Fresh Lure
4. Attach the cup to a stake, tomato cage, or nearby structure. I have had great success punching a hole in the rim of the cup and tying it onto trellis panels, but a simple stake works just as well.
5. Check and refresh as needed. When the cup becomes covered in beetles, replace it.
The earlier I place the lures, the faster I can get ahead of the population. This method occasionally harms beneficial insects, but it is rare, usually one or two bees per lure. This low impact is one reason this has been a successful strategy for controlling cucumber beetles.
Happy Gardening!