I have planted green beans three times because I have an
annual problem of the leaves either being completely chopped off or they
appear lacy and nearly gone. I have seen slug slime, so that may be some
of the problem, but what does the lacy leaf indicate? I also have a lot
of “potato bugs” or “sow bugs,” could that be the problem?
According to The Organic Gardener’s Handbook of Natural Insect and
Disease Control edited by Barbara Ellis (Rodale, 1996), lacy leaves on
your bean plants might be the work of Mexican bean beetles. Parasitic
wasps (Pediobius foveolatus) can be used to control the Mexican bean
beetle. As a last resort, you can spray or dust your plants with
pyrethrin. See links here:
From the Connecticut Agricultural Experiment Station
From the University of California
Large holes in the leaves may be caused by other beetles as well, such as
the cucumber beetle, which can be managed by protecting your plants with
row cover like Reemay. If damage is severe, you can use pyrethrin or neem
spray.
Small holes in the leaves may be the work of flea beetles, and the
management is the same as above.
The chopping off at ground level sounds like it could be the slugs eating
shoots as they emerge, or climbing up the plant and eating it down to the
ground. It could also be the result of cutworms. Look for these at dusk, and look during the day at or just below the soil surface. I manage these
pests by looking for them frequently, and squishing them or cutting them
in half with my pruning shears.
I had never heard of sow or pill or potato bugs (isopods) being a
vegetable pest, but apparently they do have that potential if the
population is large enough. See the discussion among gardeners on Houzz.
You might try fooling the pests by planting your beans in a different
location, especially a raised bed.