Photo by: Bob Richard, USDA-APHIS-PPQ.
Apthona sp. Larva Beetles:   
By: Lance Briggs, WHS Student.
Scientific name: Aphthona nigriscutis.
Common Name: Black dot leafy spurge flea beetle.
Class, order, and family: insect; Coleoptera: Chrysomelidae (1)
Origin: A. nigriscutis originated from Central, Eastern, and Southern Europe (5). Specifically from Hungary (6).
Overwintering state: These insects overwinter as larvae, living within the leafy spurge roots (1).
Egg stage: Clusters of 20-30 eggs (7) are laid on the stem of the plant at or just below the surface of the soil (1).
Larval stage: A. nigriscusis larvae can be found between July until the next spring. After the larvae hatch, they burrow down into the soil and begin to feed on the new, small leafy spurge roots. This continues to happen until the fall when cold weather sets in and they become dormant again (1).
Pupal stage: Pupation, where the larvae from a pupae and mature into an adult, happens in a soil cell beginning in the late spring and goes into the early summer (1).
Adult stage: Adults are present in fields starting in May to July. Adults are visible to the naked eye (3). They survive and are active from several weeks to several months (2). The beetles are approximately 3 mm to 3.5 mm long and are colored brown or brownish with a black dot on their back behind their thorax (1). Adult females continue laying eggs all through the summer and into the fall, laying up to 400 eggs per year. Surviving adults then die in the fall.
Type of damage to host:
Adult A. nigriscutis insects feed on the leafy spurge's foliage but does not severely impact the plant. The larvae does the real damage feeding on the roots. They destroy the root system of the plant which in turn slowly kills the plant. This beetle feeds on leafy spurge (Euphorbia esula) (1). A. nigriscutis have been documented as feeding on a few closely related species but will not feed on plants outside the genus Euphorbia (1).
The most damage is done by the insect larvae feeding on and in the young roots and root hairs of leafy spurge (6). The larvae destroy the root system, therefore, making the absorption of essential nutrients and moisture to the plant slow down. This slows flowering and retards the plants growth. This also inhibits the plant's ability to make sugars for the root reserves. After a while, the plant will eventually be damaged enough and it will die. A large number of insects in one area can significantly reduce the density of the leafy spurge, which is called putting a "hole in the spurge." (2)
Favorable/Unfavorable release habitats:
This insect prefers dry habitats like sandy swells. They do the best in well-drained soils with less than 3% organic matter (1). They also prefer dry, hot sites on south faced slopes (7). They should be placed in sites that will not be cultivated, mowed, sprayed, burned, heavily grazed, or otherwise disturbed for several years after the release of the beetles. This is so the beetles can get a large population established on the infestation. It takes several years to get the insects established, so on small infestations, chemical or mechanical means of control may be more useful (3). These conditions are restrictive but many sites with these same conditions occur on the Great Plains. Multiple bio-control agents may be needed to effectively control infestations in varied environments (4).
How to collect, transport, and release:
Collection of these insects should be done with a sweep net from July through early August (1) on warm, sunny days (3). 500 or more insects should be collected for each release site. Collection should be taken only from sites that have been established for at least 3 years. This insures that the population is sufficient for collection. After the first year of establishment, collection and redistribution should only be done for a few small sites which may include the same field or at a different location (3).
Transportation is very important when trying to redistribute spurge beetles. They should be collected in a large plastic pale, cloth bag, plastic bag (3), or card board cans (6). Since spurge beetles can jump, climb, and fly, it is necessary to have a tightly sealed container for transport but not air sight. A. nigriscutis should be protected from overheating by transporting the insects in a cooler with ice in the bottom. Never set the insect containers directly on the ice because of the risk of freezing them (3). They can be stored for many days if they are provided cool temperatures and fresh leafy spurge foliage. They can also be kept for an extended amount of time if kept in large cages with leafy spurge at room temperature. Another possibility is keeping them in smaller containers in a cool environment while being fed and exercised occasionally. With these methods, they can be kept for up to several weeks (1). This is not advised because this leaves less insects in the field where they can get to work destroying leafy spurge (2); therefore, it is best that they are released within 48 hours of collection (3).
Releasing the insects should be done by sprinkling the beetles on moderately dense infestations of leafy spurge (1). Areas with many grasshoppers or near large ant piles should be avoided whenever possible (2). Another redistribution method is taking frozen roots of soil containing A. nigriscutis larvae and keeping it frozen until a few weeks when the adults are wanted for a site. After this, remove the excess soil or roots and maintain the insects at room temperatures (6).
How to redistribute once established:
A. nigriscutis have been established in Colorado, Idaho, Montana, Nebraska, North Dakota, Oregon, and Washington (1). The success of these beetles at a site can be assessed by this criteria. 25 spurge beetles should be collected from every 5 sweeps after one year. In two years, there should be a great reduction of flowering from the leafy spurge and there should also start to be a larger weight of grasses and a smaller overall weight of leafy spurge. Beetles in an optimal environment should be ready to collect for redistribution after three years (7).
How and where to purchase:
There are many places to purchase and acquire the insect Aphthona nigriscutis. Arrangements can be made though your local agricultural field man, district agriculturalist (3), county weed districts, commercial growers, or may be obtained at no cost from state weed agencies (2). When public lands are involved, the range management section of the Public Lands Division can be contacted for insects (3).
When the spurge beetles are first released, the leafy spurge density is greatly lessened by these insects; however, roots not attacked are able to send up new shoots (1). It is only after a long period of time with favorable beetle conditions that the leafy spurge can be destroyed and completely eliminated (3).
Aphthona nigriscutis was first released in Canada in 1983. The results were great. It was first released in the United States (1) in Montana in1989 (6). It also received good results there. It has now been established in many states as listed above. Contact a biologic control specialist to see if conditions are right on your land for this insect.
1) Rees, Norman E., et. al., Ed., November 1995 Biological Control of Weeds in the West: Aphthona nigriscutis; Western Society of Weed Science.
2) Pemberton, B.W., Rees, N.E., Last updated March 17, 1998, Aphthona nigriscutis, Cornell University.
3) Cole, D.E., et. al., Last updated June 3, 1996, Control of Leafy Spurge with Spurge Beetles; Alberta Agriculture.
4) Shanower, Thomas, Last updated September 16, 1998, Insect: Aphthona nigriscutis.
5) Petroff, Janet K., et. al., Ed., Leafy Spurge Data Base, USDA Agricultural Research Service, 1994.
6) Rees, N.E, et. al., Ed., Rough draft: Biological Control of Rangeland Weeds in the Northwestern United States; unpublished.
7) Government of Saskatchewan, Last updated January 25, 1999; Farm Facts: Biological Control of Leafy Spurges; Saskatchewan Agriculture and Food and Saskatchewan Rural Development.
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