Spotted cucumber beetles can be found on cucurbits (squash, cucumbers, pumpkins, melons, etc.). They are less discriminating than their cousins, striped cucumber beetles, feeding on other plants in addition to cucurbits.
Cucumber beetles are found across the United States, Canada, and Mexico.
- Adult spotted cucumber beetles are about ¼ inch long and have a greenish-yellow background with 12 black spots on their wing covers. They have a dark-colored head with antennae and an orangish prothorax (the area directly behind the head). The larvae of each are worm-like, white, dark-headed, and have three pairs of legs.
- Eggs of both species are pale orange-yellow and are laid in groups. Cucumber beetles fly readily, like moisture, and dislike heat.
- Cultivated melon fields are a favorite of this traveling pest, particularly during hot weather and after irrigation.
- Spotted cucumber beetles live through the winter as adults in dense grass or under leaves, emerging in early spring to late summer. They feed on the blossoms of flowering plants, mate, and lay eggs in the soil at the base of host plants. They also lay eggs on non-cucurbit plants such as corn and other grasses.
- Eggs hatch in several weeks; the larvae feed for 2 to 6 weeks underground on plant roots and parts of stems, then pupate in mid to late summer.
- Adults emerge in mid to late summer to feed on blossoms and maturing fruit.
- There is one generation per year.
Damage and Detection
- Cucumber beetle larvae feed on the roots of curcibits which can kill younger plants and/or stunt plant growth. Adult feeding is, however, more damaging to the crop.
- Beetles swarm on seedlings, feeding on flowers, leaves, young shoots, and the fruit itself, often killing plants. Feeding on flowers can reduce fruit production while feeding on stems of young plants weakens the plant, which may be lost unless replanted. Direct feeding on fruits causes unattractive scars and pock marks on the melon or other host, limiting marketability and hence yields. After the skin hardens, melons are less susceptible to attack and damage.
- Often, the cucumber beetles alone will not kill the plants or cause significant damage, but the subsequent spread of disease might. Feeding by adult cucumber beetles can spread bacterial wilt disease among cucurbit plants, even when insect population density is low.
Prevention and Control
- Inspect plants regularly
- Check for cucumber beetles early in the season. Be particularly attentive when plants are seedlings and/or in the early stages of leafing when they can suffer defoliation and bacterial wilt.
- Be watchful until fruiting, as larger plants can also be affected by bacterial wilt.
- Handpick or vacuum beetles as they are detected.
- Maintain a clean garden
- Remove weeds that can act as potential hosts for adults.
- A heavy layer of mulch around established cucurbit plants can discourage egg-laying.
- Remove any infested plant to mitigate the spread.
- At the end of the season, remove garden debris to limit sites for wintering adult beetles.
- Use trap crops
- Use sticky traps to catch cucumber beetles and other pests.
- Once spotted cucumber beetle numbers build up in these traps, treat them with an effective pesticide to minimize further movement.
- Use a physical barrier
- Cover seedlings with row covers during early to mid-June to attempt to keep cucumber beetles away from plants. Remove the barrier when cucurbits start to flower.
- Use Pesticides
- Use pesticides only when necessary, as cucurbits are very sensitive. Usage should be limited to when plants are just beginning to emerge from the soil.
- Choose a pesticide that has a low impact on natural enemies, such as ladybeetles and pollinators. Neem is a plant-based pesticide that prevents insects from feeding.
- Companion planting
- Oregano is a companion to most plants. Plant it close to cucumber plants to repel the cucumber beetle.
- Radishes are an excellent companion to have in the garden as they deter cucumber beetles and rust flies.
- Goldenrod, milkweed, hydrangeas, or catnip attract adult soldier beetles. Soldier beetles feed on many different insects, including maggots, eggs, and soft-body insects. They are particularly fond of cucumber beetles.
- Nasturtium is known to deter whiteflies, wooly aphids, squash bugs, cucumber beetles, and other pests.
- Tansy helps concentrate potassium in the soil, benefiting nearby plants. It also repels cutworms, cabbage worms, squash bugs, cucumber beetles, ants, flies, mosquitoes, and fruit moths.
While every effort has been made to describe these plants accurately, please keep in mind that height, bloom time, and color may differ in various climates. The description of these plants has been written based on numerous outside resources.