Species

Pale-Striped Flea Beetle (Systena blanda)

Related species

There are many species of flea beetle. They are usually identifiable by the type of host plant they attack. For example, the eggplant flea beetle Epitris fuscula, only feeds on eggplants.

Other common flea beetles include: Crucifer flea beetle (Phyllotreta cruciferae), Horseradish flea beetle (Phyllotreta armoraciae), Potato flea beetle (Epitrix cucumerist), Spinach flea beetle (Disonycha xanthomeles), Striped flea beetle (Phyllotreta striolatae).

The damage caused by the pale-striped flea beetle is similar in appearance to that caused by alfalfa weevil larvae, but is more concentrated at the leaf bases. Also, pale-striped flea beetle damage occurs somewhat later than damage from alfalfa weevils.

Host/site

• The pale-striped flea beetle has the widest host range of all flea beetles including squash, beans, corn, sunflowers, lettuce, potatoes, eggplant, melon, pepper, pumpkin, radish, beets and many weeds.

Identification

Appearance

• Flea beetles are small beetles that jump when disturbed.
• Adults are approximately 3.0-4.3 mm long, shiny, have a pair of pale yellow stripes lengthwise down the back and a stripe on each wing cover. The rear legs are enlarged for jumping.
• Color is somewhat variable.
• Larvae are a whitish color with darker heads that range from 1mm after hatching to 11 mm at maturity.

Indicators

• Typical flea beetle damage occurs in the foliage of young crop plants, and damage usually manifests itself as numerous small shot holes through the leaves. This occurs early in the growing season and can show up soon after transplanting depending on the date.
• Larvae feed on fine roots near the soil surface or occasionally tunnel into larger roots.\
• Damage is usually minor and easily outgrown on established plants.
• When populations are high the shot-holes increase resulting in a lacey, skeletonized appearance to the leaves.

Life cycle

• Flea beetles spend the winter in the adult stage, hidden under leaves, dirt clods, or in other protected sites. They typically begin to become active during warm days in mid-spring but may straggle out over several weeks. Many flea beetles are strong fliers and seek out emerging host plants, which they locate by chemical cues that the plants produce.
• In spring, adults feed on the host plants foliage, which is when the most damage occurs. During this time adult females begin to lay eggs, up to 200, in soil cracks around bases of the host plant
• Eggs hatch within 6-8 days. Larval development usually lasts from 16-20 days under warm conditions. They feed on small roots and root hairs until it forms a small cell in the soil where it pupates for 4-5 days emerging afterwards as adult beetles.
• From the time eggs are laid until they emerge as adults is about 28-54 days.
• Only up to two generations of pale striped flea beetle have been reported per year.

Natural Enemies

The big eyed bug, Geocoris punctipes, feeds on some species of flea beetles, such as the tobacco beetle and possibly the pale-striped flea beetle.

Monitoring

• Flea beetles can move quickly into a garden, so newly planted crops should be scouted for insects or foliage damage every 1-2 days, while plants are small and unable to withstand much damage.
• Beetles can be a continuous problem throughout the season, with younger plants and leafy vegetables becoming the most susceptible to damage. Therefore, monitoring for these pests should begin in the early spring or when crops are first planted.

Action Thresholds

• A home gardener can bear some damage to the crop unless it is a leafy one like mustard greens. On broccoli, cabbage, potatoes, and tomatoes damage can be tolerated as long as the part you harvest is not being damaged.
• On established plants, 10-20 percent destruction of leaf is a good threshold to act.

Cultural and Physical Controls

• Adjusting planting dates to avoid damage by flea beetles might be useful in some situations.
• Thick mulches may also help reduce the number of flea beetles by interfering with activity of the root and soil stages.
• Trap crops work in some situations as well. Plant a highly favored crop to attract flea beetles away from the main crop. Radish, daikon, or mustard can protect other seedling crucifers (e.g., broccoli, cabbage, Brussels sprouts) that are more sensitive to flea beetles. The trap crop may then be harvested or destroyed after the main crop has established itself sufficiently to outgrow flea beetle injury.

Biological Controls

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Chemical Controls

• Horticultural oils and some neem insecticides have some repellent effect on this insect. However ANY use of a spray / pesticide can be harmful to beneficial insects and oils and soaps are hard on aquatic creatures if their habitat gets affected by drift or spills.
• Diatomaceous earth is one of the more effective repellents, applied as a dry powder to the plants.
• Garden insecticides containing carbaryl are often used. This is not recommended as it kills bees.
• Synthetic pyrethrum is also commonly used but is not recommended as it is toxic to humans and others.

References

Cranshaw, W. S. Flea Beetles. 5.592. Colorado State University, Nov. 2006. Web. 26 Apr. 2010. <http://www.ext.colostate.edu/pubs/insect/05592.html>.

Delahaut, Karen. Flea Beetles. Garden Facts. University of Wisconsin, Feb. 2000. Web. 1 May 2010. <www.uwex.edu/ces/wihort/gardenfacts/x1022.pdf>.

Pale-striped Flea Beetle, Systena Blanda (Chrysomelidae). Fact Sheet. Montana State University, 14 Feb. 2008. Web. 27 Apr. 2010. <http://diagnostics.montana.edu/MTAlfalfaSeed/Pests/Pale-stripedFleaBeetle.html>.

Sparks Jr, Alton, and David G. Riley, comps. Flea Beetles. Fact Sheet. University of Georgia, 18 Dec. 2008. Web. 25 Apr. 2010. <http://www.ent.uga.edu/veg/colecrops/fleabeetle.htm>.