Question of the Week – Yellowmargined Leaf Beetle

What is this critter hanging out on sweet alyssum?

This is an adult yellowmargined leaf beetle (YMLB), which is well-known (notorious?) to many of our smaller and low-input brassica farmers, as it is very difficult to manage without conventional insecticides. It is a specialist herbivore of plants in the Brassicacea family and is a key pest of some organic brassicas in the southern US, such as mustards, turnips, Napa cabbage, mizuna, and other asian greens. So why do we keep finding them in sweet alyssum flowers?

Sweet alyssum (Lobularia maritima) is also in the Brassicaceae family. Sweet alyssum flowers are known to benefit many natural enemies, especially hoverflies (Syrphidae), whose larvae are voracious predators of aphids and other small insects and mites, but it’s also important that we research and understand all possible benefits and drawbacks. 

Through ongoing work by my Ph.D. student Pragya Kiju we have found that sweet alyssum appears to be highly attractive to YMLB and we keep finding it in sweet alyssum plots during her field research trials. What this means for pest management is not known, but we are hopeful that YMLB’s attraction for alyssum can be exploited for developing new management strategies, like trap cropping. I have submitted research proposals recently to investigate this further and develop sustainable tactics that our brassica farmers can easily implement. 

This week’s question is from Tom Bilbo, Extension Vegetable Entomologist.