What’s Eating My Cucumbers? Cucumber Pest Control
Although cucumbers have a reputation for being easy-to-grow and prolific vegetables, insects can still take them down. Join farmer Briana Yablonski to learn about some common cucumber pests and how to deal with them.
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Thanks to their prolific nature, cucumbers often get a reputation for being an easy-to-grow plant. Healthy plants can quickly sprawl across your garden and provide you with handfuls of crunchy cucumbers. But when pests attack, the plants can quickly become diseased or experience a decrease in productivity.
If you spot something munching on your cucumber leaves or plants, identifying the critter is your first step. I’ll introduce some common cucumber pests and cover how to prevent and treat them.
General Cucumber Pest Control
Before I cover how to manage and treat some of the most common cucumber pests, I’m going to cover some general practices for keeping these unwanted visitors away.
First, pay attention to plant health. Stressed plants are more susceptible to attack, so make sure the plants receive the water, nutrients, and light they need. Provide these thirsty plants with plenty of water, plant them in a location with full sun, and fertilize well but not too much.
Another way to keep cucumber pests in check is to encourage the presence of natural predators. Insects like ladybugs, green lacewings, hoverflies, and parasitic wasps feed on pests and help keep their populations low.
One way to encourage the presence of these good bugs is by avoiding broad-spectrum insecticides. If you choose to spray for pests, choose a targeted product and spray in the morning or evening when insects are the least active.
Planting an array of flowering plants will also help keep predators around, since many of these critters feed on pollen and nectar. Try planting small flowers like sweet alyssum and dill in with your veggies to provide food for hoverflies and green lacewings.
Common Cucumber Pests
Even if you do your best to keep your cucumbers healthy and attract natural predators, it’s still possible that unwanted insects will appear. Here are some of the most common cucumber pests to watch out for.
Cucumber Beetles
An unwelcome sight to cucumber growers everywhere, these little yellow beetles can cause serious damage. Their chewing can lead to ragged leaves and stems, as well as misshapen fruit. They can also spread diseases like the dreaded bacterial wilt.
There are multiple types of cucumber beetles, including striped and spotted varieties, but all of these insects are around a quarter of an inch long. The striped cucumber beetle (Acalymma vittatum) has black and yellow striped wings, a yellow-orange thorax, and a black head. The spotted cucumber beetle (Diabrotica undecimpunctata) has yellow wings with black spots, a yellow thorax, and a black head.
The adults overwinter in plant debris in warm climates and become active once the weather warms. Although they may not survive the winter in more northern climates, they migrate to these areas in the summer. Once they arrive, they begin feeding on plants.
Eventually, the adults lay their eggs near the base of cucurbit plants. The eggs hatch in a few weeks, and the small worm-like larvae then feed on plant roots. They emerge as a new generation of adults about a month later.
Signs of Damage
The adults chew on cucumber leaves, stems, and fruits. Since the beetles are tiny, they may only eat through the top of the leaves rather than the entire leaf.
Although a few of the pests won’t cause a noticeable impact, large infestations can lead to ragged leaves and/or damaged fruits. However, the pests also transmit bacterial wilt, a disease that can cause plants to suddenly wilt and die. This disease transmission means it’s wise to protect your plants from even a few beetles.
Prevention
The best way to protect your plants from these pests is to physically exclude them from your plants. Covering your cucumbers with row cover or insect netting after planting will do the trick. However, you must remove these covers when the flowers appear, unless you plant a parthenocarpic variety that doesn’t require pollination to set fruit. ‘Telegraph Improved’ is one type of parthenocarpic cucumber.
You can also help limit cucumber beetle populations by applying beneficial predatory nematodes to the soil. These nematodes feed on and kill beetle larvae, but they won’t impact adults that overwinter and/or fly in from other areas.
Control
If you spot a cucumber beetle, there are probably more on the way. You can attempt to squish the adult beetles by hand, but their tendency to quickly fly away makes this tricky. Another option is to spray the beetles with an organic insecticide, like spinosad. Only spray your plants when there are two or more beetles per plant.
If you notice bacterial wilt in one of your plants, pull and dispose of it ASAP. This will help prevent the disease from spreading to other plants.
Aphids
These tiny, soft-bodied insects might not look like major pests, but they can quickly multiply and colonize a cucumber plant.
Aphids come in shades of green, red, gray, black, and brown, but the green peach aphid (Myzus persicae) is the aphid that’s most commonly found on cucumbers. These tiny pests often appear on the underside of cucumber plant leaves or on young, growing tips.
Aphids are less than a quarter of an inch long, so you may need to look closely to spot them. Regularly checking the underside of plant leaves is a good way to catch them early.
Signs of Damage
Aphids feed on plants by piercing their leaves and sucking out the sap. Plants with early infestations rarely show signs of damage, but the leaves may eventually appear spotted or distorted. If the aphids are left untreated, plants can become stunted and weak.
Aphids also release a sticky substance known as honeydew as they feed. This sugary liquid can coat the leaves and lead to the presence of ants and/or black sooty mold.
Prevention
Aphids often occur in gardens, even if you don’t see them. Fortunately, natural predators feed on the pests and keep them from getting out of control. Therefore, encouraging these predators is one way to prevent aphids from becoming a big problem. Planting small flowers like yarrow, fennel, and sweet alyssum can help attract beneficials like hoverflies and parasitic wasps.
Properly fertilizing your cucumbers is another way to limit major aphid infestations. Avoid over applying nitrogen, since aphids reproduce more rapidly when plants have high nitrogen levels.
Control
If you see aphids on your cucumber plants, you can try to spray them off the plants with a blast of water. If this doesn’t work, spray them with neem oil or insecticidal soap while ensuring that you make contact with the pests. Spraying in the early morning or evening is best.
Pickleworms
Although pickleworms (Diaphania nitidalis) are often found on summer squash and zucchini, they can also become pests of cucumber plants. The worms are the larvae of a brown and yellow nocturnal moth that overwinters in warm climates. The moths eventually fly into northern areas where they lay their eggs near host plants.
When the eggs hatch, the small, light yellow larvae feed on cucumber flower buds and fruits, as well as other cucurbits like squash and melons. The larvae molt a few times before they pupate and turn into adults.
Signs of Damage
The most obvious sign of pickleworm damage is small holes in cucumbers, with a jelly-like substance around the outside of the holes. If you cut open the cucumber, you’ll see the larvae and notice a hollow cavity where it’s dined on the fruit. You may also be able to spot the pickleworms eating flowers or buds.
Prevention
Since pickleworms arrive in most climates later in mid to late summer, you can avoid them by planting early-maturing varieties. Covering your plants with row cover or insect netting will also protect them from the moths and prevent worm damage.
If you live in a warmer region, say zone eight and below, the pickleworms may be able to overwinter in your area. Destroying plant material and debris can help kill the larvae and prevent worms from growing the next season.
You can also attempt to prevent infection via trap cropping. Pickleworms prefer summer squash over cucumbers, so planting a squash plant a few weeks earlier than your cucumbers will attract the worms to the squash. Once they take hold of the squash, you can destroy them by removing the infected fruits.
Control
Since pickleworms often enter into cucumbers, it’s too late to treat them by the time you notice them. If you notice the larvae in the flowers, you can spray your plants with Bt to kill the worms.
