The flea beetles are a tribe of small hopping insects called Atlicini, and they're part of the subfamily Galerucinae. Adult beetles chew on the foliage of the plants leaving wounds that resemble gunshot holes. Flea beetles' larvae feed on the roots of short-maturing seasonal vegetables, whereas some species' larvae also feed on the leaves. The presence of shot holes in the leaves spoils the cosmetic look of the foliage in seedlings and young plants that could retard the growth of the plants leading to their physiological death. There are several species of flea beetles, and each of them possesses a selective taste. Some species feed only on tomatoes, potatoes, and other nightshade plants, whereas another group solemnly on crucifers. Another class of flea beetles’ forages on invasive weeds only so intentionally introduced to some US states.
Flea beetles are the most dominant pests on Brassicas throughout the Northern Great Plains of the US. Two species that harm mustards were introduced from Eurasia. i.e., The Crucifer flea beetle and striped flea beetle. The hop beetle is native North American species that exist in low numbers. Moreover, striped flea beetles and more than a dozen other beetle species infest commercial crops and garden plants throughout the Great Plains of the US, including northwestern Minnesota, Montana, North Dakota, and South Dakota. The striped flea beetle was first noticed in Caroline in the early 1800 and is now widely distributed among most Southern and Northern US. The crucifers and horseradish flea beetles are frequent in Northern US, striped and eggplant flea beetles in the eastern US, Potato, and Western Black flea beetles in the Western US, and Tobacco flea beetle in a warmer area of the US.
Adult flea beetles are small and measure about 1/8th of an inch the Spinach beetle which measures 1/4th of an inch. Most beetle species are shiny black, purplish, bronze, brown, and greyish metallic with powerful hind legs modified to hop many inches when disturbed. They can also fly a long distance to invade neighboring fields and gardens. Otherwise, they move when foraging on the plants. The western potato beetle and tuber flea beetle are identical and need microscopic studies to differentiate them. Crucifers flea beetles are black, oval-shaped, and measure as minimum as 1/32th of an inch. Striped beetles contain two yellow stripes on the wings.
Females lay about 25 eggs in the soil in summer. The adults that have overwintered, remain active during the early summer but start dying in mid-summer. The larvae from the freshly laid eggs hatch in about 10-days and feed on the roots. Larval feeding may decrease yield up to 5% or more. Larvae then pass through 3-instars and mature in 25 to 35 days. They make small earthen puparium where they pupate for almost 10-days in the mid-summer. This new generation emerges in late summer and could last for another one and a half months before the fall. In early fall, the mature beetles move to the sheltered locations such as twigs, fallen leaves, and soil clods to overwinter. The crucifer beetles observe only one generation a year while some other species could have up to 2 only.
Adults and larvae possess chewing mouthparts for feeding both foliage and the secondary roots. This multidirectional feeding could damage seedlings, transplants, and cotyledons. Underground feeding sometimes leaves scars on the tubers that reduce the marketability of such products, especially in the case of potatoes, sugar beet, and other tuberous plants. The significant damages may be prevalent in spring when these beetles feed on the foliage of the plants and roots together. Total crops failure may occur if the number of beetles crosses the economic injury level. A shot hole is an example, as any leaf damage can't recover. Some flea beetles also attack the meristems of the plant and break the link between root and stem. High feeding sometimes leads to compromised growth and a reduced number of plants which, may delay maturity and decrease yield altogether.
Since most flea beetles overwinter in plant stubbles, twigs, weeds, and shelterbelts and emerge when the garden temperature reaches about 57°F. Flea Beetles are more active up to 65°F. That is typically a narrow temperature range that allows them to roost on your garden plants. Flea beetles can't be neglected in the landscape and need an effective management solution.
Green Lacewings are a superior class of predatory bugs that invades both adult and larval stages of flea beetles. They’re also highly effective against many soft-bodied insects, crawlers, chewing, and boring pests that invade plants from the cruciferous and Solanaceae family in your garden. Green Lacewing is Chrysoperla rufilabris, also known as 'aphid lions', which retain exceptional host searching qualities with a high dispersal ratio against foliage pests. They are voracious predators of many insect species including, flea beetles and their larvae. Adult lacewing primarily feeds on pollen, honeydew, nectars in the absence of the host.
Green Lacewing eggs may hatch in 5 days, and the best time to release them in the garden is early spring at 57°F.
Bacillus thuringiensis (Bt) is presented in a new formulation method that enhances the efficacy of these spores but makes its application easier for the growers. Also, easier to apply in different growing facilities. BT is for the greenhouses, commercial, and garden plants including, vegetables and fruits. The Dust Flowable formulation contains 54% of Bacillus thuringiensis (Bt) kurstaki, where each pound of the product contains 14.5 billion available spores for applying in the field. This product is OMRI listed and recommended for application in biological pest control. BT is a bacterium that releases Cry proteins, and its ingestion kills flea beetles within 3-days. These proteins are not toxic for humans and mammals as their bodies don't let these proteins to active. The product pack size suits well to the greenhouses and commercial growers.
Add 0.16 to 0.32 ounces per gallon of water and spray thoroughly on the foliage of the plants using a drop-down nozzle in early spring when the temperatures range between 57- 65°F.
Natural Guard Soap Mixes Potassium Salts of Fatty Acids with Spinosad in this ready-to-use product formulation. The mixing ratio remains 0.940% and 0.005% for Potassium Salts and Spinosad, respectively. Spinosad is effective through ingestion and as a contact poison. Its unique mode of action induces excessive excitation in the nervous systems of the insects that compels them to contact muscles speedily which, collapses and paralyzes them. The product application is good in the morning or late evening.
The ready-to-use product is for the effective killing of all insect pests, including adults and larvae of flea beetles.
DEsect- Diatomaceous Earth derives from freshwater resources, and its' mode of action is physical as the passing over pests injure their chitin and die of starvation later. The death occurs due to loss of excess body moisture, leaving no residues that could harm pets and humans around. Moreover, DE products are OMRI listed and a top choice of organic gardeners. DE effectively controls all crawling insects during the entire stages of their development including, both adult and larvae of many flea beetle species.
DEsect- Diatomaceous Earth complies with EPA safety regulations and allows worry-free applications on all edible plants.
Most flea beetle species have developed resistance against synthetic pyrethroids, and especially the neonicotinoids are not recommended for use on edible plants of all types. PyGanic is an OMRI-listed Pyrethrins that derives from Chrysanthemum flowers. Its product concentrate contains 1.40% Pyrethrins but, it's a contact poison and needs thorough coverage to kill flea beetles of all stages. Pyrethrins are effective against many pest species of crawling, chewing, and boring insects that damage most garden plants.
Add between 1 to 1.4 ounces of product concentrate per gallon of water and spray on the top foliage of the plants covering the leaves from both sides.
Check out our other guides on common garden bugs.
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