Cucumber Beetle Overview
If you planted cucumber last year, you've probably had problems with cucumber beetles eating your crop. Cucumber beetles attack their favorite host plant, cucumbers, and squashes, and they can be a big problem for gardeners.
Cucumber beetles are also called striped cucumber beetles, because they have three white stripes on their black bodies. The initial damage from cucumber beetles is often as small holes in the leaves of the plant. The beetles can eat the entire leaf if left unchecked.
The beetles also spread a bacterial wilt called cucumber mosaic, which can destroy plants. Symptoms of cucumber mosaic include yellowing and browning leaves, stunting of the plant, and off color fruit with sunken spots. Cucumber beetles are small, only about 1/4" long, but can do a lot of damage to crops.
Cucumber beetles lay their eggs at the base of the plant. The tiny white or yellow eggs are squashed between leaves, and can look like tiny green specks.
The eggs hatch in about a week and the tiny, black larvae feed on the roots of the plant, killing it or weakening it.
The larvae form a large ball near the base of the plant, and eventually, the larvae pupate.
The adults migrate to the top of the plant and shed their outer skin, revealing the bright yellow and black exoskeleton that will look like stripes.
Types of Cucumber Beetle
Cucumber beetles are a group of insects with a yellowish to black-and-orange striped shell that sports a pointed projection at the joint where the head meets the wing case. This bug is less than 1/2 inch in length, which gives it great camouflage as it strolls along your zucchini vines. The winged form of the cucumber beetle is also a soft yellowish color with black stripes ” this lasts only a few days until their wings dry out and fall off.
As adults, cucumber beetles go from plant to plant, laying eggs on the undersides of leaves. After about three to four days, the eggs will hatch and after two more days emerge as larvae that resemble tiny alligators.
These larvae are the most voracious stages of the pest's life cycle. The larvae tunnel into the developing cucumbers or squash and leave tell-tale scarring on the fruit's surface.
The larvae will munch their way through a variety of plants including beets, corn, squash, and melons, as well as cucumber or cukes.
Life Cycle of Cucumber Beetles
There is nothing like the satisfaction in seeing and picking your first homegrown cucumbers.
But don’t be surprised if they show up with some guests; you may notice misshaped cucumbers or white dots that don’t wash off the fruit. These white dots are actually eggs laid by the cucumber beetle. You will find three varieties of cucumber beetles that commonly feed on cucumbers, peppers, and squash plants. There is the spotted cucumber beetle, the striped cucumber beetle, and the yellow and black spotted cucumber beetle.
If cucumbers are left on the plant, the eggs will hatch and the larvae will burrow into the cucumber and feed on the soft tissue. They will eventually pupate, and emerge from the cucumber beetles, as adults.
The older beetles will actually lay new eggs on the cucumber or on nearby plants, so you will have several generations throughout the growing season.
Luckily, there are several methods for getting rid of cucumber beetles. The easiest thing to do is remove the larvae before you eat the vegetable. To do this, just pull back the leaves and if you see the larvae, scrape them off.
Another method is to use yellow sticky traps which are easily purchased at garden stores. You will catch the adult beetles and prevent them from depositing their eggs on your cucumber plants.
Common Habitats for Cucumber Beetle
Cucumber beetles are a common garden pest that affects cucurbit vegetables. When mating, cucumber beetles will be found on the undersides of cucumber leaves. In the larval stage they will feed on plant roots. They will also feed on leaves of cantaloupe, watermelon, and pumpkin. The Lifecycle of a cucumber beetle consists of 4 stages: Egg, Larvae, Pupa, and Adult. The entire lifecycle takes 2-3 weeks. Their eggs are laid into the ground on or near the roots of the plant.
As it gets warmer outside, cucumber beetles will begin to emerge. At this time they will start to feed on the leaves of the plant. Adult cucumber beetles only live for about two weeks and during this time they will feed on the plants. They tend to stay in one place on the plant and infest cucurbits. For control to be effective, all 4 stages of the cucumber beetle lifecycle (egg, larvae, pupa, and adults) must be controlled. It is a common misconception that once the cucumber beetles are gone, the problem is gone. This is not true. The eggs that have been laid on the ground will hatch into larvae that will continue to feed on the roots of the plant. To control the cucumber beetle, the eggs need to be controlled.
What Do Cucumber Beetles Eat?
Probably the most annoying thing about cucumber beetles is that they can wreak havoc on your garden. Outlined below are a variety of treatments you can use for this garden pest. But, first things first, let’s discuss what these guys eat.
Cucumber beetles can pick off your entire crop, chewing on the leaves and the plant stem; the leaves turn yellow and wither. You’ll also noticethey like to feast on flowers, aphids, and other insects (all organic food).
The beetles have a yellow/black body with black eyes and antennae, are about an inch long, and their larvae are yellow with dark-brown stripes.
There are two ways to ward off cucumber beetles. The first is the black-colored beetle–its larvae and eggs are black. It is sporadic and does not like marigolds. The yellow beetle, on the other hand, is attracted to either the smell of cucumbers or lemons.
The first thing you want to do is control your plants' spacing. Cucumber beetles tend to travel towards one other place: the cucumber. If you have the cucumber plants scattered throughout your garden, the beetles will end up congregating around them. If you group the cucumber plants in a cluster in just one part of your garden, you increase the chance of keeping them away from your other plants.
How To Get Rid Of Cucumber Beetles
Cucumber beetles are small green insects that prey on cucumbers. They typically hide during the day, then at dusk, they will start eating your cucumber leaves. They lay eggs in the plant, which look similar to aphid eggs. If you see small white balls of eggs on the underside of the leaves, you probably have cucumber beetles.
To get rid of cucumber beetles, you can try:
- Spray them off with a hose sprayer. If you kill them, they are not going to be able to lay more eggs and are one less beetle to eat your cucumber plants. You will need to do this every day for a few days to eliminate them.
- Use neem oil. The cucumber beetles will die after a few days, and it will also kill aphids and other insects in the garden.
- Spray with Pyrethrin. Pyrethrin is one of the most effective but least toxic pesticide sprays. It will kill a number of insects, so mix according to label instructions. You can purchase a Pyrethrin 1-2-3 mix, which makes it quite simple.
- Bt Spray. Bacillus thuringiensis is a specific bacteria that eats cucumber beetle larvae. It stays very active in the soil and will continue to kill other beetles for the next few years.
Organic Cucumber Beetle Control
According to Cornell University, the cucumber beetle prefers to be on the move. Eliminate soft, moist ground cover, woody debris (firewood, shrubs, etc.), weeds, and other debris that would provide shelter for the beetle. The cucumber beetle also needs a nearby host plant to lay eggs, so prune away any plant material that your cucumber or other vegetable plants touch.
This may not be a complete cucumber beetle control plan, but it can reduce the infestation to a minimum. Keep in mind you still have to deal with the larvae, which stage is the most difficult, because many of the products you can use on adults won’t work on the larvae and beetles.
Before you decide to just squash them all, keep in mind that the bees will notice you squishing them and they will make a bigger nuisance of themselves to get revenge. So a cucumber beetle spray of either diatomaceous earth or pyrethrin can be used.
According to the Ohio State University, the best way to deal with a cucumber beetle infestation is to cut away all of the plant material that is touching your cucumbers or other vegetable plant you wish to protect.
Chemical control options to control cucumber beetle infestations include neem oil, which is an oil derived from the neem tree.
Environmental Cucumber Beetle Control
Cucumber beetles and scarabs are definitely your enemy as they feast on your cucumber, zucchini, squash, pumpkin, and melon plants. They know which plants are the best for them to eat and can quickly destroy your plant garden. Although they are not poisonous, they take huge bites out of your plants and they will have multiple root holes all over them .
They are hard to fight and difficult to prevent from invading your garden but you can get control of these beetles by managing the amount of weed growth, which will make them place to hide, and supporting your crops with a healthy dose of organic fertilizer.
Garden plants should be grown thick and close enough together so that it is difficult for beetles to hide. Your garden needs to be healthy and have no dead or dying plants in it, this way it will be easy for the beetles to find food .
Placing a trap under your garden is yet another way that you can get rid of beetles. The beetle trap is made of wood, a flat board and a bucket. The bucket should be about a third full of water and a third full of beer or wine. The bottom board of the bucket should have an X cut out of it so that the beetles fall through the top and lodge into the bottom of the bucket. This also makes it hard for them to escape.
If you happen to get lucky and have a huge explosion of beetles, another recipe is good for them.
Preventing Cucumber Beetles
Using the correct crop rotation is an effective way to control cucumber beetle populations.
Alternating plants with three years between cycles of cucumbers, melons and squash will reduce susceptibilities to cucumber beetles and other plant diseases.
Also, planting trap crops, like buckwheat, between cucumber plants deters cucumber beetles.
As a matter of fact, when properly managed, trap crops can be very effective layers of defense against cucumber beetles.
As much as the traps can protect against early outbreaks, use of neem oil after harvest can prevent the release of beetles from these traps.
In addition, applying neem oil before plants flower can help reduce cucumber beetles, but requires treatment in August or May before expected infestation.
Male cucumber beetles release the first generation of beetles in early June.
When the insect is about 2.5mm long, it emits a repellent pheromone which usually attracts the opposite sex.
An insignificant number survive to adulthood.
Second-generation beetles emerge from mid-July to late-August.
This larvae stage is yellowish green and has three rows of black spots, while the third is dull yellowish green with four rows of black spots.
The females lay eggs on July 20, and the hatchlings molt into tiny larvae about a week later.
Frequently Asked Questions
Are the cucumber beetles only in the garden or can they be in the house too?
Cucumber beetles are only a threat to garden plants. They are isolated pests that are unable to enter the house. If you find one in your home, you can gently pick the beetle up and dispose of it. If they are eating your plants, you don’t have to worry like you do with other garden pests. Cucumber beetles do not have the capacity to fly. They are less likely to spread to your houseplants.
However, your vegetable plants can easily be transported into your house. If you notice cucumber beetles on your plants, you should immediately dispose of them. If any of the beetles have fallen off of the plant, you need to wash them off immediately with warm, soapy water. If you have already washed the plants, you may need to soak them in water for several hours before using them or before eating from them.
Q: These beetles just aren’t going away, no matter what I do.
Any advice?
A: Beyond the common cucumber beetle, there are a couple of other types of cucumber beetle you might see in your garden. (The mottled and striped cucumber beetles are the most common.) You can control them using the same strategies that work for the common cucumber beetle.
The first step in eradicating cucumber beetles from your garden is to figure out where they are coming from. This did not go unnoticed by gardeners. Many gardeners consider cucumber beetles to be the worst type of pest there is. They are responsible for destroying your garden, and in some cases even your fruit and vegetable plants.
Check your garden for areas where weeds are growing. This is the best place to start if you can’t specifically find the source of these annoying pests. If you find weeds that have holes in them and cucumber beetles slowly flying around them, you can be sure that this is where they are coming from. Take these weeds out as soon as possible and remove any debris around your garden.
Now water the areas around your garden plants. This will cause all the beetles to fly away from your plants while they are above the ground. They like to hang around these areas in groups, so it would be easier to find them flying around in the air. This is a good chance to spray the pesticide on them to get rid of them once and for all.
Q: Is there anything else that I can try that you haven’t mentioned yet?
A: It’s true that the most common and effective way to control cucumber beetles is to knock them off plants with a sweep of your hand. But there are a few other things you can try if you want to keep these pesky garden pests at bay.
Spinosad is another organic agent that you can add to your garden to deter pest insects, including cucumber beetles. This anti-fungal, bacteria-derived substance causes vomiting and muscle paralysis in insects that feed on it, which usually results in death. The beetles are expected to transfer the spinosad to their eggs and larvae, too. This pest-fighting product currently appears on the OMRI list as an approved organic pest management method, and you can use it in your vegetable gardens and in other parts of your landscape.