Concurring Cucumber Beetles – Organically

Had a client ask me yesterday about Cucumber Beetles so thought I’d write up this post so you can all benefit form the information too.

I admit, of all the bug type critters I have dealt with in my gardening endeavors, these little buggers have been the hardest to deal with and some of the most prolific. I also admit, I have stopped growing cucumbers because of them.   With those caveats, let look at why these critters are such a challenge.

First, there are two types, striped (Acalymma vittatum/A. trivittatum) and spotted (Diabrotica undecimpunctata howardi Barber).  This can be confusing, with some folks thinking they are dealing with something other than cucumber beetles.  So, yes, both of these are cucumber beetles:

Spotted and striped cucubmer beetles.

Cucumber beetles attack, yes, cucumbers, but also other members of the Cucurbit plant family that includes summer squash (and zucchini), winter squash and melons.  I have also found that they love, I mean LOVE, Amaranth, both the ornamental and grain type, so we strictly avoid growing all types of Amaranth.  They will really love to eat your Cleome, so we have stopped growing those beauties as well.  They have also been known to munch on beets, beans, peas, sweet potatoes, okra, corn, lettuce, onions, and various cabbages although, gratefully, I have not had them go for these other crops.

These little critters do munch on your plant leaves, but the main issues is that they transmit bacteria that cause Fusarium or Bacterial Wilt and this is what will often kill the plant first.  Adult cucumber beetles can severely defoliate plants and scar fruit. Adults generally reach their peak activity in morning and late afternoon and are fast and pretty hard to catch.  If you do catch them, they have very hard shells so are hard to squish. Don’t try and put them down to step on them like you might a worm, as they’ll fly before you can get them.  If you are able to catch them, put them in soapy water.  All that said, this is not the best way to deal with them.

Cucumber beetle damage

As with handling any pest predation, a good Integrated Pest Management (IPM) strategy that includes more than one option works best. All the products on this list are OMRI rated for organic use. Not sure what that means, check out this video.

Ways to concur cucumber beetles:

  1. Row cover or growing in completely protected culture in a high tunnel or greenhouse.  I recommend this at the beginning of the season to give your plants a good head start. This client, Kathleen, did this and I am sure this is why her plants have done as well as they have. She also used..
  2. Neem oil spray. Neem can be effective here as it is a wide spectrum killer.  It is also effective against fungal diseases, which is an added benefit. When sprayed on garden plants, it does not leave a lasting residue because it washes away with rain and is broken down by ultraviolet rays. It can kill some beneficial bugs if they are directly sprayed. Most of Neem’s action is from critters biting leaves that have been sprayed with it. Your beneficial insects are carnivores, eating those other bugs who are eating your food.  
  3. Kaolin Clay, or Surround. We love this stuff and use it often. The product name is Surround, which is made from a specially modified Kaolin clay. This forms a barrier that protects plants from many pests. We spray it on and it makes a white barrier not only repels bugs, but causes them irritation, confusion, and is an obstacle for feeding and egg-laying. We have found it very effective against deer too!  The deer look at those ‘white plants’ and don’t think are food.  Like the Neem, you have to keep applying it after rains and as new green growth appears.
  4. Cleaning up. Cucumber beetles will overwinter eggs in the mulch under your plants.  If you have had an infestation, remove all the mulch from the area and don’t even compost it.  Dispose of it off property or burn it, depending on your location. Then you can apply ..
  5. A spray containing Spinosad, like Monterey Garden Insect Spray used to drenchto the soil tokill the larvae before they pupate in the soil can be effective to avoid further infestation in following seasons.  I should mention here, I only see these critters in the warm summer months.
  6. Beneficial insects. Ladybugs, Green Lacewing, Spined Soldier Bugs and Assassin Bugs will all feed on various life stages of cucumber beetles. Attracting and keeping these garden helpers in your garden will not only help keep the cucumber beetle population down, but many other less desirables from eating your food. A few good plants to start with are: yarrow, sunflowers, dill, cilantro and parsley. Makes sure you let the dill, cilantro and parsley go to flower.  
Assassan bug eating a spotted cucumber beetle

7. You can also buy cucumber beetle lures and use these with yellow sticky traps. The lure is effective for 45 days. If the trap becomes covered with insects or other debris before that time, remove the lure and attach it to a fresh trap. One advantage is that these are not a spray and therefore you run less risk of killing other critters you would rather not kill. I confess I have not tried these although it seems a reasonable thing to try and I might get some for the cucumber beetle population currently in my garden. If anyone uses these, let me know how they worked for you.

8. The last option in this article is adding a Heterorhabditis bacteriophora beneficial nematodes to your soil. Nematodes occur naturally in our soil, but we might not have the ones that really like beetle, and specifically cucumber beetle larvae.

So to wrap up, here is my recommended IMP strategy if you have a cucumber beetle infestation:

  1. Spray Neem to get the population down.
  2. Put out lures and traps for adults you have missed or that continue to hatch.
  3. Depending on how diseased and chewed up your plants are, remove them off site or burn them.
  4. Remove all the mulch under where the plants were and spray Monterey Garden Spray heavily into the soil.

Next spring:

  1. Apply beneficial nematodes to your soil.
  2. Use row covers for young plants.
  3. Apply Surround as your plants grow.
  4. Put in plants that attract beneficial insects.

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Have an awesome day and good luck with those cuke beetles! – Debby

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