7 Cucumber Pests to Watch for This Season
To get the crisp, juicy summer crunch of a homegrown cucumber, scouting for invading insects becomes part of their care. The easy, productive vines are susceptible to common garden pests, as well as cucurbit specialists. Join gardening expert Katherine Rowe in the insects we want around our cucurbits and the cucumber pests to prevent.
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However you pickle or slice them, cucumbers are one of the easiest crops to enjoy fresh from the vine. From heirlooms to modern hybrids, the usually low-maintenance crops offer a productive yield and fit a range of garden scales. Compact, bush types are ideal for small spaces, pots, and areas with short growing seasons, while full-size vines and fruits relish long, hot summers.
Because of their versatility and ease in the edible landscape and on the plate, cucumbers (Cucumis sativus) are a favorite summer selection. They perform best in full sun and organically rich, well-draining soils with even moisture. Setting the vines up for success includes meeting their preferred growing requirements to strengthen their vigor against pests and diseases.
Regular pest scouting is the first step in catching problems early on and in determining a management strategy. Grow companion plants and a diversity of blooming species to attract natural predators and other beneficial insects. They’ll pollinate the vines’ bright blooms while deterring the following common cucumber pests.
Cucumber Beetle
Cucumber beetles are capable of severe damage to cucurbits, especially to young plants. The adult beetles feed on leaves, blossoms, and fruits, while the larvae feed on roots and stems. Their quick feeding damages and kills the specimen in severe infestations. The beetles are also vectors for cucumber mosaic virus and bacterial wilts, which kill infected cucumbers.
There are three main species of cucumber beetles: the banded (Diabrotica balteata), the striped (Acalymma vittatum), and the spotted (Diabrotica undecimpunctata). Each is yellow to yellowish green with distinct markings. The larvae are white to yellow-white and may be below the soil level or boring into stems.
Beetle damage can appear on all parts of the plant, including the cucumbers themselves. Signs include irregular, jagged holes in leaves from their chewing.
Treatment
Hand-pick small populations, which may warrant more than one round a day. Drop them into a bucket of soapy water as you go.
Floating row covers can help while plants are young and block the pests from feeding on tender growth. Remove the covers as the seedlings mature and begin flowering. Remove them during pollination, or try hand-pollination to boost yields.
Pyrethrin sprays, spinosad, and neem oil help treat the cucumber beetle. They’re most effective with regular treatments for transplants and seedlings during beetle activity, though they impact other insects, as well, including pollinators and beneficial predators.
Prevention
Keep the area around cucumbers weed-free to reduce the spread of beetles. Grow flowering perennials like asters, yarrow, and coreopsis, and herbs like dill, parsley, and chamomile that attract tachinid flies, soldier bugs, lacewings, and ladybugs. These natural predators feed on the eggs, larvae, and adult cucumber beetles.
Try planting after the active emergence of the beetles. By mid-June, they’ll emerge and move on to search for hosts. Planting late can help seedlings skip the larval stage.
Squash Bug
The squash bug is a sap-sucking cucumber pest that depletes water and nutrients from leaves. They become speckled and eventually wilt, brown, and drop. Squash bugs (Anasa tristis) are common pests among cucurbits and other vegetables.
The bugs are large, brown-gray insects with flat, winged backs. The nymphs are pale green with black legs and mature to darker gray, and are small and spidery. The adults overwinter in sheltered spaces like under logs, rocks, and debris to begin mating and laying eggs as seedlings emerge. Clusters of eggs in yellow-orange appear on leaf surfaces and undersides.
Treatment
Horticultural soaps and oils and spinosad sprays may eradicate early numbers of nymphs. The adults are tough to control, so catching them in the young phase offers the best success.
Remove eggs and nymphs by hand. Because eggs are difficult to crush, tear off the leaf portion to destroy it.
Adults and nymphs take cover at the soil level under mulch and in hiding places. Place a board, shingle, or piece of cardboard near the stem to draw them to cover. Lift it in the morning to destroy the congregating squash bugs. Remove mulch from the area if populations are high to reduce protective cover.
Prevention
If squash bugs are a problem in your garden, try planting seedlings early in the season to establish before the insects become most active (usually in June).
Clear debris after the final harvest to reduce prime overwintering habitat for adults. Temporary row covers can shield the cucumbers until flowering.
Squash Vine Borer
Squash vine borer, Melittia cucurbitae, is a moth with a bright orange thorax lined with black dots. It flies during the day with a pattern that resembles a wasp and buzzes loudly.
The pervasive pests are found east of the Rocky Mountains and from Canada to South America. They’re not often a problem in the West, but occur in the Midwest, along the East Coast, and particularly in the Southern United States.
Squash vine borers (SVB) rely mostly on squash, pumpkins, and gourds as hosts, though they can be a problem for cucumbers, too. The female borer lays eggs along the stems, especially near the base. The first sign is often sudden wilt, as larvae block the stems from water uptake.
At maturity, they leave the plant and burrow into the soil. They’ll overwinter until the following summer when they emerge as moths, and the cycle continues.
Treatment
Squash vine borers are tough to control, as they travel, they are hard to spot in the larval stage, and can enter plants from different points. The most common and effective way to get rid of the caterpillars is to perform squash vine “surgery.” The procedure involves a small vertical cut along the stem to physically remove the larvae.
For only a few plants, it may be feasible to wrap the stems to block access. Aluminum foil, burlap, or other materials protect stems from the moths.
BT (Bacillus thuringiensis) is a biological control that stops the caterpillars from feeding. BT is a bacterium that disrupts the digestion of SVB larvae and similar pests. If you’ve scouted and discovered a bore hole or damage, inject liquid BT into the localized section with a simple needle. It may work if the borer is still in the vicinity.
BT is only effective against feeding larvae, not eggs, so topical spraying isn’t viable. Spraying also affects the caterpillars we want in our gardens.
Prevention
If you live in a squash vine borer-prone area, a preventative measure is to stop growing the most impacted cucurbits, like summer squashes. Choose those that are resistant to the pest, and grow squash two years on, and two years off.
Covering the lower portion of the stem with soil may help reduce infections. The coverage creates a natural barrier, leaving the adult moth unable to access the main stem. In warmer areas, delay plantings, as the moth tends to move on when temperatures rise.
Spider Mites
Spider mites are sap-sucking pests that live on the undersides of cucumber leaves. Their piercing mouthparts feed on cellular tissue. You may not see the tiny creatures without a magnifying glass, but their telltale webbing gives them away.
Colonies of the insect live around leaf veins and mid-ribs beneath leaves. Females lay eggs, and the larvae quickly feed on sap and tissues. Pale spots appear on foliage. Adults feed and produce tight webs around leaves, stems, and branches.
The foliage shows light yellowing and stippling on the surface and may turn bronze. Leaves become stiff and curl and may prematurely drop.
Treatment
Beneficial predatory insects like ladybugs, lacewings, and predatory mites help control populations. If you detect spider mites, spray the plant with a strong stream of water early in the day to deter and knock insects off the stems. Spraying also rinses dust off plants.
Prune away affected plant parts. Dispose of debris rather than adding it to the compost pile, which can harbor and spread the insects.
A simple horticultural soap or oil like neem rids the plant of severe cases.
Prevention
Spider mites proliferate in hot, dry, dusty conditions. They flock to cucumbers experiencing drought stress. Provide even moisture to avoid dry spells and promote flowering and fruiting. Water fluctuations give spider mites a chance to grow in number and further weaken the crop.
Squash Beetle
Squash beetles (Epilachna borealis) feed on the leaves of cucurbits. The beetles have large black spots on their leaves like lady beetles, and coppery-orange wings.
With squash beetles, you’ll notice chew damage on the leaf surface between the veins. It starts as a semicircle as they carve out their feeding area.
Treatment
Handpick the beetles, larvae (spiny yellow worms), and eggs (orange clusters on the underside of leaves) off the foliage and use the soapy water bucket disposal method. Neem oil helps treat larger infestations.
Prevention
Good garden sanitization helps prevent the adults from overwintering. Clear all debris at the end of the season. Light tillage at the soil surface can reduce their winter habitat.
Floating row covers for seedlings prevent early damage (remembering to remove them during flowering.
Melon Aphids
Aphids are soft-bodied sap suckers that congregate in large numbers on the undresides of leaves. Melon aphids (Aphis gossypii) are yellow to green and pear-shaped. They feed on plant tissues, especially on new shoots.
With an aphid infestation, leaves curl downward and cup before they turn yellow, brown, and drop. They leave behind a sticky honeydew, which often becomes black sooty mold in humid conditions.
Treatment
Opt for the same spider mite treatment with a spray of water to displace the cucumber pests. Aphids reproduce quickly and in high numbers; if the population is large or damage escalates, an insecticidal soap or oil can be effective.
Prevention
Start with the best cultural conditions to ward off susceptibility to aphid damage. Ladybugs, hoverflies, and parasitic wasps are the best natural defense that prey on aphid larvae. Rely on a diversity of flowering plants among the edible landscape for a well-balanced garden system.
Pickleworms
Pickleworms bring disappointment and destruction as they make holes in developing cucumbers and burrow into buds, stems, and flowers. The pickleworm (Diaphania nitidalis) can severely damage plants at their point of entry and may kill the specimen. The fruits rot as a result of their holes.
The caterpillars molt four times, changing their color before they pupate and emerge as brownish-yellow moths. The caterpillars begin yellowish-white, gain red spots after they molt, and lose them in the final round as they turn pale green to copper. Before they pupate, they turn pink to pale green.
Treatment
Pickleworms often die out in cold winters with freezing conditions, but they survive winter in warm, tropical, frost-free climates (like Florida). They migrate north as they emerge, appearing later in the season and damaging the later cucumber harvests.
Spinosad sprays may be effective in weekly intervals during pickleworm activity. Apply them as soon as pickleworms or their indicators appear.
Prevention
Select early-maturing cucurbits to miss the height of the feeding population. For cucumbers, compact varieties are often ready before longer vines. ‘Gemini’ cucumbers show good resistance in field trials, with treatments being more effective than in susceptible varieties.
