Battles with the bean beetle

I have always loved growing green beans.  They grow easy, produce a ton, my kids happily eat them raw daily, and they preserve great as dilly beans –  what’s not to love?

I first planted beans 2 years ago at Radix, when we built the first raised beds up on the hill.   I watched them grow big and vibrant and beautiful.  Then I noticed some insects hanging around – they looked like ladybugs but were a little more on the orange side than red.

Oh man.  Within weeks my pole beans were devastated – the leaves looked like lace and there were fuzzy yellow bugs everywhere.  I ripped them out and bagged them up and left it all in the sun to cook the bugs – but it was too late.  My bush beans went down next.

According to Barbara Ellis and Fern Marshall Bradley in the Organic Gardener’s Handbook of Natural Insect and Disease Control (one of my favorites!  Garden Insects of North America by Whitney Cranshaw is another…) I had met the Mexican Bean Beetle – Epilachna varivestis.  

“Adults overwinter in leaf litter in nearby field; in spring, females lay eggs on beans.  Eggs hatch in 5-14 days, larvae feed 2-4 weeks, then pupate on leaves.  One to 3 generations per year.

Control: Plant early season bush beans to avoid main beetle generation; plant soybeans as trap crops, destroy them when infested with larvae; handpick larvae and adults daily in small bean patches; cover plants with floating row cover until plants are large enough to withstand damage; attract native predators and parasites by leaving flowering weeds between rows or by interplanting flowers and herbs; dig in crop residues as soon as plants are harvested; release spined soldier bugs to control early generation; release parasitic wasps when weather warms; spray weekly with neem or pyrethrin.”

Eggs

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Baby larvae on bottom

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Leaf damage

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Last year, I set out on a determined watch. I am loathe to spray and hurt beneficial insects, so instead I monitored the plants and squashed every adult, larvae, and eggs that I found. I also planted flowers around, and we have flowering weeds in our ‘urban meadow’ right next to the beds.

I spent LOTS of time checking the underside of leaves, and smashing.  All 3 smash with a very satisfying bright yellow liquid.   A couple came for a tour that had gardened at a community garden in Troy, they emphathized and shared that they used to joke about their ‘yellow thumbs’ instead of green.  It was a long battle, and I’m not sure if I won by the end of the summer.  I harvested many beans, and killed many bugs, but there were SO MANY larvae!

This year, because I was so busy with other things, I was late planting my beans.  I have been monitoring them as they’ve grown, and haven’t found too many beetles or larvae or eggs.  There is the evidence of their presence, but their numbers appear to be reduced.

Possible reasons for what feels like success at this moment are:

  • planting late – maybe they set up shop on the earlier beans at the community garden on the next block instead?
  • deterred by the many daikon radishes and mustards that volunteered around the beans (we reused dirt from the micro green trays to top off the raised beds)
  • a rainier year meant healthier, hardier plants
  • this was a bad year for the bean beetle… or
  • I write too soon?

Anyone have any thoughts or experiences?

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