There is a whole array of insect pests who live to eat your bean plants. They attack quickly and can make a defoliated mess of your plants if left unchecked. Luckily, it is possible to mount an organic defense against them. Here are the keys to protecting
the bean citizens of your garden kingdom:
Identify which pests are attacking your beans
Learn what organic controls exist for the pests that
are plaguing you
Use your control strategies as early in the growing
season as you can, before the bean-eating insect troops
have mounted a full scale invasion in your garden.
Many of the pests devouring your beans are likely to be beetles.
Mexican bean beetles, bean leaf beetles and both striped and
spotted cucumber beetles love to feast on bean plants. Other
bean-eating insects include cowpea curculios, cutworms, bean
weevils, leaffooted bugs, leafhoppers and stinkbugs.
Some of these pests, such as the bean weevil, spread to your
garden on infected seed. Others, such as the Mexican Bean
Beetle, travel to your garden from nearby bean, alfalfa. corn or
clover fields. No matter how these pests get into your garden,
once they've moved in, they won't want to leave. Because many of
these pests spawn several generations of offspring per year,
your best bet to keep from being overrun with them is to keep
their populations in check. Your bean plants can tolerate some
insect nibbling but can't survive a full-on attack.
Who's the Bean Eater in My Garden?
Mexican Bean Beetle -- common in all parts of the US
except the Pacific coast, 1/3'' long, wing covers have 8 black
spots, lay their orange eggs on the underside of leaves in
clusters of 40 or more (be sure that the eggs belong to Bean
Beetles, not ladybugs which are their close cousins)
Bean Leaf Beetle -- prevalent in the Southeastern and
Midwest US, lay their eggs in the soil, 1/4'' long, may or may
not have spots, drop to the ground when disturbed
Striped Cucumber Beetle -- 1/4''long, yellowish green
with 3 black stripes
Spotted Cucumber Beetle (AKA Southern corn rootworm) --
1/4'' long, yellowish green with 12 spots on its back.
Cowpea curculio -- adults are shiny, black and 1/4''
long. Larvae are yellow maggots that are often found in the bean
pods. Most common in the Southeastern US.
Bean Cutworm -- common in Western and Midwestern US. The
cutworms are tan with a darker, faint diamond shaped pattern on
Bean Weevil -- dark grayish-brown, with grayish yellow
hairs and dark bands across back. 1/10 '' long and has six
Leaffooted bug and Stinkbugs
-- shield-shaped 1/2-3/4''
long. Can be green or brown and may have stripes.
I know who the trouble maker is. How do I get rid of him?
Now that you know what's causing your problem, what's an
effective, organic way to get rid of it or to help your plants
cope with the onslaught? Part of the answer is that keeping your
garden tidy by removing weeds, tall grasses and crop residues in
and around it will eliminate some breeding sites for pests. Many
of these pests have natural predators which will feed on them,
thus reducing their numbers. Specific management practices such
as matching planting dates with seasonal low points in pest
populations or by using row covers to keep pests can help too.
Here's some information that will help you thwart the pests that
are bugging you!
Mexican Bean Beetle -- The Pediobius wasp is a natural
predator of Mexican Bean Beetle larvae.
Bean Leaf Beetle -- A floating row cover can be used to
keep these pests away from young plants. Bean Leaf Beetles can
be hand-picked off plants if you have a small garden.
Mid-afternoon is often the best time to do so.
Cucumber Beetle--Natural predators include soldier beetles, tachinid flies and braconid wasps. Planting your beans later in
the season when they will germinate and establish more quickly
can help you fight this bad bug.
Cowpea curculio -- Natural predators include tachinid
flies and ants. Keeping late-season plantings away from the
sites of earlier plantings will keep the cowpea curculio's
population from snowballing as the season wears on.
Bean Cutworm -- try using Bt to control this caterpillar.
Bean weevil -- heat treat seeds that you suspect are
infected or buy seeds that you know are weevil free.
Leaffooted and stink bugs -- populations of these pests
are highest in late summer to early fall. Work around their
schedule by growing early crops. Take away their home and
breeding sites by keeping weeds under control. Some common
species of birds feed on stinkbugs.
Now you know more about these bean-eating pests and how to
defeat them. Be persistent and you will have victory (and green
beans for dinner!).
For further reading
Pictures of assorted bean pests
Goosefoot in my Garden
It's Easy to Grow
How Does Your Garden Grow
Part One: Getting to Know Your Soil