Aphthona species flea beetles are about the size of flax seed (about 0.10 inches long) and vary in color and shape depending on species.

Biological control of leafy spurge was initiated in the mid 1980s. To date, 10 species of insects have been released in North Dakota for control of leafy spurge, and six have become established. Four of the six established insects are flea beetles, (Aphthona spp.) which have reduced the leafy spurge density more than any other agent.                                   Top

.A. nigriscutis
(brown with a black dot)

A. lacertosa
(black with brown femurs)

Flea beetle life cycle

Aphthona spp. adults emerge from the soil in late spring to early summer. Following emergence adults feed on leafy spurge leaf tissue and mate. Females begin laying egg clusters of three to 15 eggs almost immediately. Egg laying continues every three to five days throughout the adult life stage. Aphthona spp. females produce an average of 220 to 280 eggs over a lifetime. Eggs are yellow and laid on the soil surface or slightly below, near the leafy spurge stem base. Larvae emerge from eggs in 12 to 19 days.

Flea beetles overwinter as second- and third-instar larvae in the soil. Larval feeding begins to decline when soil temperatures fall below 45^o F and resume feeding when soil temperature warms in the spring to above 45^oF.

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Larvae and holes from feeding damage in a leafy spurge root crown.

The longevity of A. czwalinae, A. lacertosa and A. nigriscutis will vary from year to year depending on weather conditions. A hot dry spring and summer will shorten the time adults are present while a cool, wet season will lengthen it. Generally adults live for 1.5 to two months in the field. Most leafy spurge flea beetles have a single generation, egg to adult, each year.

Flea beetles undergo three larval instars. First- and second-instar larvae feed on filamentous and larger leafy spurge roots, respectively. Third-instar larvae feed on the root crown.

Two larvae feeding in a leafy spurge root bud.

Where to release flea beetles

Research at North Dakota State University found flea beetle establishment was best on silt loam, silt clay loam, clay loam and clay soils with an organic matter content of 6 to 9.5 percent. Flea beetles were least productive in fine sand to loamy fine sand soils with an organic matter content of 1 to 3 percent. In addition, the release area needs to be well drained and not subject to frequent prolonged flooding or standing water, which will kill the larvae.

Initial releases have been most successful on south facing slopes, although good success has been achieved on western and eastern slopes as well. On north facing slopes Aphthona spp. requires a longer period to establish at high enough numbers to control leafy spurge. Flea beetles establish best in moderate densities of leafy spurge (60 to 90 stems per square yard) with minimal grass cover and thatch. Establishment in dense leafy spurge stands is often difficult. Release flea beetles on the margins of dense infestations and allow the insect to work into denser stands as the population builds.

Research data is lacking and/or has given inconsistent results concerning the best species to release in a specific area. What is known at this time is that A. lacertosa is more widely adopted to the North Dakota climate and will tolerate a wider range of temperature and moisture conditions than other Aphthona spp. A. nigriscutis generally has done better on higher drier sites with low to moderate stands of leafy spurge. Releasing a mixture of both species in the same location is the best way to determine which Aphthona spp. is best suited for a particular area.                                                                    Top

When to collect and release flea beetles

Aphthona spp. flea beetles generally are distributed through the North Dakota Weed Control Association. Contact the local county weed officer for date, time, and location of flea beetle collection and redistribution programs in your area. Flea beetles are generally collected and redistributed from mid June to early July. Total accumulated growing degree days (AGDD) for sunflower can be used as a guide to determine when to begin scouting for adult flea beetles. Begin scouting for adult flea beetles when the AGDD approaches 1000.

Likewise, the flea beetle population and egg laying by females begins to decline when the AGDD reaches 1600 or more.

Another method to determine when the flea beetle population is near peak abundance is using plant phenology. Growth patterns by various plant species can be used as `indicators' of seasonal abundance of leafy spurge flea beetles. Aphthona spp. are often near peak levels when the prairie wild rose is flowering and strawberries are ready to be picked in family gardens in North Dakota.

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Every 10 ml of flea beetles is approximately 1000 individuals. Redistribute flea beetles to other leafy spurge infestations when 500 to 1000 beetles per five minute sweeping period are collected. Over-harvest of beetles is not possible because many flea beetles fall to the ground prior to being swept or are on the soil surface laying eggs.

Once Aphthona are collected, remove as much trash as possible and place into paper cartons or bags.

The more similar collection and release environments are, the sooner the flea beetles are likely to become established and begin to control leafy spurge.

Keep the containers in the shade and transport the insects in coolers with blue ice. Flea beetle sorters may be used during mass redistributions. Consult your local APHIS representative or weed control officer for availability.

At least 1000 or more insects should be released per location. Often new populations are started with several thousand insects.The higher the release number the faster a population increases. Do not scatter the adults over a large area.

Aphthona flea beetles are very gregarious, and males and females need to be in close proximity. Multiple releases in a large area are better than a single large release. Flea beetle establishment often increases when release points are scattered over a wide area of terrain. It is important to place a permanent marker such as a steel fence post at each release site so the population can be monitored in subsequent years. Adult flea beetles are susceptible to insecticides, so avoid wide scale spraying near a flea beetle population, especially from June through mid August.

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Although flea beetles have become established throughout North Dakota, they have not been successful in all environments. To date approximately 30 percent of the releases have established and the leafy spurge stem density has been reduced. In another 30 percent of the releases the insects have become established but the population density is too low to be effective. In the remaining releases flea beetles have not established.

Unlike herbicides, biological control agents do not provide predictable, consistent levels of leafy spurge control. Often Aphthona spp. take several years to become established and then require several more years to reduce a leafy spurge stand. Wide-scale rapid reduction of leafy spurge infestations are so far the exception, not the rule. Biological control of leafy spurge with flea beetles is not a "quick fix" and a land manager must practice patience when using this control method.

Several options are available for leafy spurge control besides biological control agents, including the use of herbicides, grazing, seeding competitive grasses, and cultivation. Before beginning a leafy spurge control program, consider the best options suited for the situation and utilize more than one. Most successful control programs have used multiple control methods combined over several years.

Herbicides should be used to control leafy spurge patches as they become established and around the perimeter of larger infestations to keep them from spreading while biological control agents become established.