The University of California Division of Agriculture & Natural Resources provides excellent information regarding the identification and life cycles of cucumber beetles. "Adult beetles are shiny with black heads, long antennae, and about 1/4 inch long. Larvae are whitish and slender with three pairs of short legs; the head and tip of the abdomen are darker. Adults may be striped or spotted, depending upon species." Adults of the two species are easy to tell apart: the spotted cucumber beetle is somewhat larger and has dark black spots, whereas the striped cucumber beetle has long black stripes down its back. Damage on leaf surfaces can be observed as irregular holes surrounded by brown necrotic tissue.
Beetles overwinter as adults in weedy areas and move into planted fields and gardens as soon as plants start to come up. They lay their yellow orange eggs at the base of plants or in soil cracks. Hatching larvae burrow into the ground seeking out roots, feed for 2 to 6 weeks, pupate, and emerge as adult beetles that attack the aboveground portions of the plant. There are several generations a year.
Recommended controls for cucumber beetles
Each control will have its own set of parameters that will be best suited for individual environments. Certain controls may only be available for commercial application.
Commercial farmers are required to reference their own state laws to ascertain if the recommended controls fall within compliance of their states regulatory guidelines.
A bio-diverse community of predators may be important for biological control of cucumber beetles, rather than relying on any single predator species.
Biological Controls (direct contact is necessary)
Botanical Controls (direct contact is necessary)
CHEMICAL CONTROLS (direct contact is necessary)
MECHANICAL AND PHYSICAL CONTROLS
- Frequent monitoring helps in identifying early infestations. Regularly inspect fan leaves for beetle damage.
- Manual squishing the beetles by hand is very effective but time consuming. TIP: Place one hand underneath the beetle before trying to squish. The beetles can be evasive and often "drop" straight down.
- Delaying outdoor planting until the last week of June can help ensure that large plant stands survive.
- Floating row covers can also be used to exclude the beetles from the plants.
- Perimeter trap cropping can be used to concentrate beetle populations in the border areas.
- Consider providing a habitat for other insects that that feed or prey on cucumber beetles.