Grow Guide: 7 Organic Ways to Defeat Cucumber Beetles

2

The first time I saw these guys wandering around our outdoor plants I thought, “Aww, yellow lady bugs, how cute!” Man, was I wrong. While they might try to disguise themselves as beneficial ladybugs, these yellow scoundrels will chomp their way through your garden in no time.

While they may seem like a simple pest, these beetles are surprisingly stubborn. But we’re all about organic cannabis cultivation at Marijuana.com, so while there may be chemical pesticides out there that will eradicate cucumber beetles, those same pesticides will also kill everything they touch, throwing off the balance of the ecosystem and creating a worse problem in the long run.

There are two kinds of cucumber beetles, ones that are spotted (Diabrotica) and ones that are striped (Acalymma). Both are members of the Chrysomelidae family. I’ve found that the spotted ones seem to be more attracted to cannabis while the striped ones stick to cucurbits (squash, cucumbers, pumpkins, etc.).

Today, we’re going to discuss some organic methods for deterring and eradicating those pesky beetles. We’ll go through some recipes for organic sprays that can be applied directly to the plant’s foliage (only on vegetative plants, it’s never recommended to apply directly on flowers) and we’ll go over some old school organic methods for battling pests.

It’s also important to remember, none of these methods are going to kill ALL the cucumber beetles in your garden — it’s okay to have a couple cucumber beetles wandering around because they will serve as food for some of your beneficial bugs. The goal is to return balance and homeostasis to the garden. There’s always going to be a few “bad guys” but as long as they’re kept in check by a stable ecosystem, it won’t turn into an issue.  

1

Hot Pepper Spray

Hot pepper spray is one of the most effective and inexpensive natural sprays you can make at home. Hot peppers will repel almost all destructive pests from your garden without harming the beneficial insects, including pollinators. Cucumber beetles are particularly sensitive to the capsaicin in hot peppers. You’re going to be working with fresh hot peppers which can inflame your hands, eyes, and throat so be sure to wear gloves, goggles, and tie a shirt or towel around your mouth while you’re creating this potent spray.

Hot Pepper Spray Recipe:

Two cups of hot peppers (habaneros work great)

One tablespoon of cayenne pepper

A bulb of garlic

A couple of drops of natural dish soap (Dr. Bronner’s is my go-to)

Four gallons of water

If you want to make more or less than four gallons, use these ratios to create a larger or smaller batch. Start by chopping up the hot peppers into smaller pieces and place them in a blender or food processor with an entire head of garlic and one tablespoon of cayenne pepper. Be sure to include as many seeds from the hot peppers as possible, that’s where most of the heat resides. Add ½ cup of water and blend. Add this hot pepper mixture to four gallons of water, cover, and let sit overnight. Strain with cheesecloth or fine metal mesh, add a couple of drops of natural dish soap to help the mixture stick to the plants. Thoroughly coat your plants with this spray at dusk. If you’re battling an outbreak of beetles, you may want to spray every couple of days until the problem subsides.

6

Lactobacillus (LAB)

Lactobacillus is a type of beneficial bacteria that can be used to enhance your garden in a wide variety of ways. Think of it like probiotics for your plants — it keeps your plants healthy and strong with near-bulletproof immune systems. When you make lactobacillus serum, you’re breeding and activating effective microbes (EM). It’s easy to make LAB at home with a few kitchen staples like rice and milk. Check out this great step-by-step recipe for lactobacillus serum.

Spraying your plants down with LAB serum is a good habit to start that increases overall health and nutrient uptake of your plants, but it’s also a great preventative measure for pests like cucumber beetles. LAB serum builds up a plant’s biological resistance, making it less vulnerable to infestation and disease.

7
Neem Oil

Neem oil is a go-to pesticide for organic farmers, and while it’s not my personal favorite, it is definitely effective. It’s a systemic pesticide which means the plant uptakes the neem into its system and is released once a pest bites into the plant. The reason why neem oil isn’t my favorite natural pesticide is because the flavor of the neem, while subtle, can stay within your flower all the way up until consumption. This potent pest-repeller is extracted from the fruits and seeds of the neem tree which is native to India. Neem is commonly used by organic cannabis farmers because it kills almost all of the pests that love cannabis — aphids, thrips, mites, fungus gnats, whiteflies, and of course, cucumber beetles.

Unlike many of these natural methods that will deter cucumber beetles, neem oil will kill them on contact. Neem oil is also effective because it kills the larvae and eggs along with the adult beetles. It’s not known to be harmful to birds, worms, or beneficial garden buds such as butterflies, honeybees, and ladybugs.  

Neem oil is easy to find in prepared bottles at your local grow store. Simply spray directly on the plant’s foliage (not while plants are flowering), making sure to coat the undersides of the leaves. Neem should be applied regularly, about every two weeks.

Note: Karanja oil has similar insecticidal properties and can be easily substituted for neem.

3

Diatomaceous Earth

This is the perfect organic option to use when there is serious destruction and you’re looking to go nuclear. If a cucumber beetle family has found a nice habitat with food and shelter, it’s hard to get them to move (plus they’ve already told all their friends about this cushy new neighborhood). So once they have dominated an area, it’s hard to eradicate with sprays unless you are sure to douse every inch of your plant.

This is where diatomaceous earth (DE) comes in! DE is a type of silica created from fossilized exoskeletons of ancient diatoms. Plants love it and pests hate it. To the human eye, it appears to be a fine, white powder, however, under a microscope it looks like a vicious landscape of broken shards of glass. These shards will destroy any pest with an exoskeleton such as cucumber beetles, ants, fleas, etc.

To use, simply throw DE all over your plant (while it’s in vegetative state, of course, never apply DE on a flowering plant). Cover your plants leaves with DE, being sure to spread some underneath the large fan leaves where cucumber beetles like to hang out. There’s no wrong way to apply DE and you can never overdose your plant with it, but you do want to be careful that you’re not disturbing the good bugs that protect your plants from pests. The DE should naturally dissipate over the next couple of days but you can always wash your plant off with water and reapply if need be.

5

Trap Crops

A simple yet effective method, and definitely the most organic one, is to plant trap crops. Essentially, plants you sacrifice to the beetles in order to keep your cannabis safe. It’s a win-win for everyone — the beetles are happy and the farmers are happy. Planting a border of squash, pumpkins, and cucumbers around your cannabis will occupy the beetles and you won’t have to even worry about them chomping at your priority crop.

4
Squish!

If you have a reasonable amount of plants (not a commercial level) sometimes the best option is to go old school and simply squish them by hand. As cannabis growers, we rarely have the opportunity to physically crush our enemy (being microscopic and all) so it is somewhat satisfying and honestly the most effective method. Do your cucumber beetle hunting in the morning when it’s cooler out because they’re much slower and easier to catch — as the day goes on and it gets warmer, the beetles can dodge you.

2

Pyrethrin

Pyrethrin is a natural pesticide that is extracted from the chrysanthemum flower. It is a slightly controversial pesticide in the organic gardening community because while it is natural, it contains neurotoxins that can affect humans and shouldn’t be used in excess. The real danger is not pyrethrin itself but the synthetic versions of pyrethrins that pesticide companies have chemically engineered to be more toxic with longer breakdown times. Pyrethroid and permethrin are both synthetic versions of pyrethrin, so be hyper-conscious about what you’re purchasing and using.

If you’re worried about the misleading labels at the grow store, you can always make a watered down version of a pyrethrin spray at home. Purchase bulk dried chrysanthemum flowers, crush them, and add to water. Let the mixture soak for 24 hours before applying to your garden. You can also get ahead of the pests next year by planting chrysanthemums throughout the garden to act as a natural repellent.

Pyrethrin, in my opinion, should be used as a last resort if the above methods don’t eradicate the problem. It works by debilitating the insect’s nerve system, making them unable to move or fly. This comatose state usually kills the pest within a day or two.

About Author

Allie is a NW-based content curator for Marijuana.com and an organic farmer at TKO Reserve. She has been a professional in the marijuana industry since she was 18 years old, spending the first five years of her career working for Dope Magazine as lead photographer. Allie has worked on mainstream projects such as Idiot's Guide: Growing Marijuana, Branding Bud: The Consumerization of Cannabis and her own self-published book, As The Grass Grows.

2 Comments

  1. Your liberal use of DE in your comment above, although it will get rid of your beetle problem, it also gets rid of your beneficial bugs also. For that reason, I always try to keep my DE very low when I use it since pollinators generally stay high on a plant since they want the blossoms. This is where prevention is so very important. If you can prevent a large outbreak, you don’t have to go overboard in dusting the whole plant.

    • Hi
      I should mention that there are three grades of DE. Food Grade, Garden Grade and Pool Grade. The Pool Grade is dangerous to your health as well as to pets etc. Garden Grade is meant to be used in the garden so it is ok for this purpose but I would prefer to use Food Grade. Also as Kathi points out, DE is not good for any insect including Bees. Also, you mention dusting which is one would think the obvious way to use it but here is a better way, a way you will use99% less DE while being as effective if not more. I would add 1 tablespoon DE to a gallon water. Stir well until it is all dissolved. Then you can spray that only where it is needed. Once it drys, it leaves a thin coating of the DE. The water will not affect the function of the DE. DE comes from dead sea life.
      A much better idea would be to use a refractometer, measure the Brix of the plant in question. If Brix level drop below a certain point (dif for each plant) then you will get pests. Also, compost tea if made correctly will also prevent and or kill most pests.
      My new book is out “Don’t Panic It’s Organic) and I will give the EBook version for free to anyone that asks!

Leave A Reply