Cucumber beetles are major pests of cucumbers, melons, squash, and other cucurbits.
There are three major classes of cucumber beetle in California: spotted, striped, and banded. Banded cucumber beetles are mostly found in southern regions, while striped and spotted cucumber beetles begin emerging in late spring and can have as many as three generations in a single season in the Bay Area.
Cucumber beetle identification
Cucumber beetles are relatively easy to identify. They are small, only one-quarter of an inch long, and they have shiny black heads. The larvae are yellowish with a dark head. Other identifying marks, by species, include:
Cucumber beetle damage
Adult beetles overwinter in the soil and lay their bright orange eggs at the base of host plants. When these eggs hatch, ravenous larvae start feeding on plant roots. Adults will feed on roots, blossoms, leaves, and plant crowns, along with fruit, as they feed. This is especially true for tender, new growth. Cucumber beetles can easily kill seedlings, and they feed on far more than just your cucumbers. Other favorite plants are corn, beans, lentils, roses, and grasses, along with your melon and squash plants. They are also attracted to ripening stone fruit. Holes in leaves may be the first obvious sign of infestation. Cucumber beetles can also carry squash mosaic virus (for up to 20 days after feeding on infected fruit), and bacterial wilt, a fatal cucurbit disease.
Controlling cucumber beetles
Cucumber beetles are difficult to control. Parasitic tachinid wasps provide some assistance, so avoid broad spectrum pesticides, which will kill off your helpers along with the pests. Cucumber beetles prefer cool, moist places, such as under your squash or melon plants after they have been watered. That makes it the best time to look for these pests and squish them as soon as you see them. They can bite, so wearing gloves is a good idea. Since cucumber beetles can fly, battling them is an ongoing process. Regular monitoring is your best defense.
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