Brief Summary: Unmated Adults In Life History

LIFE HISTORY: Unmated adults overwinter in plant debris, crevices of fences and buildings, and other protected sites around woodlands, gardens and agricultural fields. They become active at temperatures above 50 °F and begin to mate in the spring. Eggs hatch in 7-10 days and larvae take about 15 days to complete development to the pupae stage. Pupae live about 7 days before becoming adults. In east central Utah, two summer generations of adults occur.
DAMAGE: Both adults and larvae of the striped cucumber beetle feed on cucurbits with chewing mouthparts. Larvae of the spotted cucumber beetle do not feed on cucurbits but the adults will feed on cucurbit leaves and sometimes soft fruits. This makes the spotted cucumber beetle a less severe
pest of cucurbits than the striped cucumber beetle. Larval root feeding in cucurbits can cause reduced plant stands by stunting or killing the host plant. Larvae can also feed on fruit rinds that are touching the soil. Smooth-skinned cucurbits such as watermelon, honeydew, crenshaw, and casaba are more susceptible to damage. Beetles prefer immature fruit with soft rinds and also feed on stems, leaves, and flowers. Injured stems can break during high winds causing reduced plant stands and runners. Both the spotted and striped cucumber beetles are vectors for diseases as well. The striped cucumber beetle vectors bacterial wilt and squash mosaic virus, while the spotted cucumber beetle vectors bacterial wilt, squash mosaic virus, bean mosaic virus and maize chlorotic mottle machlovirus.
Hosts of the striped cucumber beetle include; roots and fruits of cucurbits (larval) and leaves, stems, blossoms, and fruits of cucurbits, corn potatoes, tomatoes, beans, ripening peach fruits, and others (adult). Hosts of the spotted cucumber beetle include; roots of corn, beans, small grains, and grasses (larval) and leaves and soft fruits of cucurbits, corn potatoes, tomatoes, beans, peach and others (adult).
Early management of cucumber beetles is crucial for commercially produced cucurbits.
Use monitoring to detect adult beetles and estimate their population numbers. Start monitoring when seedlings emerge or after transplanting, and through the fruiting stage.
• Monitor with field scouting. Scout by checking all of the above-ground parts of plant hosts. Newly emerged or transplanted cucurbits should be checked two or three times per week. Scout the field margins in the early season and if adult beetles are detected, scout random locations in the center of fields.

• Monitor with traps. Use cucumber beetle traps with attractive odors (pheromone traps baited with Eugenol or similar compounds, kairomone traps with cucurbit fruit, floral or root extracts) and colors (yellow sticky traps). Make sure you have traps specifically for either spotted cucumber beetle or striped cucumber beetle depending on the species of interest. Lures will be different for each species. Follow the timing and format for field scouting, with early emphasis on field margins.

• Lure beetles away from cash crop with trap crops and baits. Trap crops and baited traps can help lure cucumber beetles away from main crops and help to monitor their
populations.

• Delay planting until beetles have laid their first generation of eggs (late May to mid June). Because of the short growing season in Utah, this is less practical for melon, pumpkin, and winter squash, but could be practical for management in cucumber and summer squash (although delayed planting would eliminate early harvests).

• Use floating row covers or plant fabric. This will keep adult beetles from landing on plants in the spring but will need to be removed during flowering for pollination. This is less practical for large commercial fields but would be practical for home gardens and small commercial fields.

• Use plastic or organic mulches and drip irrigation. This will deter cucumber beetles from laying eggs in the ground near host plant stems and may hinder movement of larvae from roots to fruits to feed. This also reduces soil moisture under fruits and therefore cucumber beetle feeding on fruits. Aluminum coated (reflective) mulches have also been shown to reduce bacterial wilt and virus diseases transmitted by beetles and aphids.

• Avoid planting near other host plants. This includes weeds, grasses and other fruits and vegetables and will help reduce cucumber beetle infestations. See hosts above in the damage section.

• Limit irrigation near harvest. Use irrigation systems that limit the spread of water, such as drip lines. Limit irrigation of any kind, near harvest. Both of these practices will decrease the chance of crop injury from moisture loving cucumber beetles during mid and late summer.

• Destroy crop residues with thorough and deep cultivation after harvest. This will accelerate the decomposition of residues (especially roots and fruits) that may be hosts to overwintering populations of cucumber beetles. Use appropriate tillage practices or cover crops to prevent soil erosion.

• Use bug vacuums to remove beetles. As these large-scale, motorized vacuums can be expensive, this may be more practical for organic farms where cucumber beetle infestations are severe.
Long-term sustainable management of cucumber beetles is achieved by combining cultural, physical, and biological tactics.
When using insecticidal sprays, ensure that they penetrate the crop canopy and contact damaging life stages of beetles. This can be done by depositing spray droplets on the top and underside of leaves, stems, flowers, and fruits and also by drenching the soil surface when larvae are active. Timing of insecticide treatments is critical in cucumber beetle control. Treatments should target susceptible life stages as follows:
• Spring: overwintered adults. Treat before feeding injury is significant and before mating and egg-laying.
• Late spring and early summer: larvae. Treat when eggs hatch and before larvae move to plant roots to feed.
• Mid and late summer: adults and larvae. Treat high number of adults and larvae to prevent feeding damage to leaves, stems, flowers, and fruits.
• Isolated fields during spring or summer: overwintered adults. Despite good early-season control in production areas, adults may move to main crops from nearby infested fields during mid and late summer.
Natural enemies of cucumber beetles include ground beetles, soldier beetles, braconid wasps, tachinid flies, and entomopathogenic nematodes. Nematodes can suppress larvae and pupae in the soil while the others listed attack adults, eggs, and larvae on the soil surface or on plants. Commercial purchase and release of natural enemies has not shown to be effective on cucumber
beetles.