Every year brings its own trials. This year, the Mexican bean beetles have been ferocious. At the Plant-a-Row-for-the-Hungry garden, we tried spraying with Neem, but that didn’t seem to bother the beetles at all. At home, I’ve just been smashing them, one beetle (or larva) at a time, but the beetles are winning. This is what most of the leaves on my pole beans look like:
And this is the adult form of the critter that is turning the bean leaves into lace:
The adult beetle looks enough like a ladybug (it is even in the ladybug family!) that most people would think it’s a good guy. They would be wrong.
When the beetles are mature, they lay eggs, clusters of yellow dots. At some point, these eggs will hatch.
When the eggs hatch, what comes out doesn’t look at all like a beetle. It is a fuzzy yellow larva. The larval stage of this beetle is heck on the leaves of bean plants. When I was looking for larvae to photograph, I couldn’t find any young ones. These (below) have gone, I think, into the pupa stage.
When the pupa completes its development, it breaks out of its husk (like cicadas do) in the more familiar beetle form. There is an empty husk on the upper leaf in the picture below.
The big question is what to do about all these beetles. I am thinking about pulling up all the pole bean plants, but I still have cowpeas growing in another part of the garden. I am concerned that, without the pole beans around, those cowpeas will look a lot more tasty; right now, the cowpeas are bean-beetle free.
I have read that adult beetles overwinter in leaf litter, so I am definitely going to be turning the garden’s soil some this winter, to make sure that remaining adults are exposed to whatever cold we have this year— but last year we had a very cold winter; I am not sure how so many beetles survived!