Frequently Asked Questions (FAQ)

TEAM Leafy Spurge: Working Together to Purge Spurge If you have additional questions or don’t see your question listed here, please visit our feedback page and fill out the form or e-mail us with your question. We'll do our best to get back to you with an answer to your question.

Biological Control


Biological Contol

Q:  Where do flea beetles come from?

A:  Aphthona flea beetles are natives of Europe and Asia, and are widely dispersed across a large geographic area – they’re found as far east as China and as far west as France. There is also a North American leafy spurge flea beetle, but it appears to have relatively little impact on leafy spurge. Ironically, leafy spurge is generally not a problem in its native lands, where flea beetles and other enemies maintain infestations at economically unimportant levels. In fact, entomologists looking for new biocontrol agents overseas often have difficulty finding large patches of spurge.

Q:  Will flea beetles eat crops or other economically valuable plants if they run out of leafy spurge?

A:  No. All imported biocontrol agents, including Aphthona flea beetles, are quarantined and rigorously tested before being imported and released. If any potential for damage to crops or economically important plants is identified during this process, the candidate agent will not be approved or imported. This process has shown that Aphthona flea beetles are very host-specific and feed only on a narrow range of hosts restricted to the spurge family. We will soon have a page giving the step-by-step description of the quarantine and host-specificity testing process so be sure to come back and visit our What's New? page for this and other new pages and updates.

Q:  What about other leafy spurge biocontrol agents?

A:  To date, 15 different insects (including six different Aphthona flea beetles) have been tested, approved and released for biological control of leafy spurge. Significant success at controlling leafy spurge, however, has been achieved by only the A. nigriscutis and A. lacertosa flea beetles. Other insects have either failed to establish populations, or have established limited populations that have not had a significant impact on spurge infestations. Following are brief descriptions for a few of the other leafy spurge biocontrol agents. The long-horned beetle (Oberea erythrocephala) and clear-winged moth (Chamaesphecia spp.) are "stem-miners" that cause damage in two ways: Adults lay eggs in stems, then the larvae hatch and burrow down the stem – weakening the stem and stressing the plant – and into the root crown, where they feed and cause additional damage. Oberea could potentially be important in moist, sandy soils where flea beetles don’t work well. The gall midge (Spurgia esula) is a tiny gnat that lays its eggs in leafy spurge flowers, which produces a gall that prevents seed production. While these agents have generally not produced significant spurge control, their long-term impact is not yet known. It’s possible that some might play important roles in certain situations or when used in combination with other agents. In addition, researchers are always looking for new biocontrol agents, particularly insects that can fill niches or habitats not occupied by agents that are currently available.

Q:  Where do I get flea beetles?

A:  This is a very common question. It’s always best to start looking locally. Flea beetles obtained from local sources won’t have to be stored and transported far, and are more likely to be adapted to local conditions. If you are unable to locate local sources through your county Extension agent or weed officer, contact your state department of agriculture or nearest USDA-APHIS PPQ office. (see our Local Contacts Page)

Q:  Will harvesting flea beetles this year reduce next year’s population, and will it retard leafy spurge repression?

A:  No, and no. There are always plenty of unharvested beetles, and normal population development will continue even with extensive collection efforts. Likewise, harvesting your flea beetles will not impact the population’s ability to repress or control leafy spurge.

Q:  Can flea beetles withstand long, harsh winters?

A:  Flea beetles have proven they can survive the long, harsh winters common in the northern Great Plains by establishing populations and controlling leafy spurge. There is some speculation, however, that a lack of snow cover to provide insulation, combined with extended periods of extremely cold weather, can adversely impact flea beetle populations. Additional research into the topic is needed.

Q:  How large of a patch of spurge is needed for flea beetles?

A:  This is a common, but difficult to answer, question. Flea beetles can establish populations on small patches of spurge (a half-acre or less), but may eliminate such patches and be unable to maintain a population. Generally speaking, a moderate to dense patch of spurge, a half-acre or more in size, is needed to establish AND maintain a population. On a related topic, scattered patches are OK but scattered plants aren’t – flea beetles cannot establish or sustain a population on scattered plants.

Q:  Can I spray over flea beetles with herbicides?

A:  As mentioned in the Biological Control Manual, herbicides and flea beetles can indeed be used together. The key is timing: Fall and early spring applications can enhance population establishment by reducing densities and opening the spurge canopy. However, late spring or summer applications will remove the spurge top growth flea beetles need to complete their life cycle, and should thus be avoided in situations where you are attempting to start or maintain a population.

Q:  Can I spray over flea beetles with insecticides?

A:  Flea beetles are obviously susceptible to insecticides. In some situations, however – a severe grasshopper outbreak, for example – the use of insecticides cannot be avoided. If the use of insecticides at an established flea beetle site is unavoidable, leaving small areas untreated can provide "reservoirs" of flea beetles that will help sustain populations.




Q:  Where can I find good quality sheep to graze leafy spurge?

A:  There are a number of quality livestock auctions in the northern Great Plains that handle large runs of high quality breeding stock. Ranchers interested in grazing sheep as a leafy spurge management tool, however, will likely need to do some planning. For example, it’s much easier to buy sheep in the fall and over-winter them instead of trying to find and buy sheep in the spring. One option is to buy ewe lambs in the fall, over-winter them, graze them on spurge the first year then start a breeding program. County extension agents can sometimes provide information on local sources of sheep, and in some cases, may know of sheep that are already trained. In addition, each state in the northern Great Plains has an Extension sheep specialist who will be able to provide advice and information on your particular state.

Q:  Can you use mature sheep that are intended for the kill market?

A:  Absolutely. Studies show that sheep gain a lot of weight during a season of grazing leafy spurge. In fact, leafy spurge is high in crude protein, is easily digested and provides especially good forage for lactating ewes and lambs.

Q:  Will grazing leafy spurge impact normal sheep functions such as growth, breeding, etc.?

A:  No it will not. In fact, sheep grazing leafy spurge will actually outperform sheep grazing native range. This is simply due to the high quality of forage that leafy spurge exhibits.

Q:  Do I have to completely re-fence my operation, and do I have to use woven wire?

A:  Research studies have found that adding one to two extra wires on a pre-existing 3- to 4- strand barb wire fence will work. It is recommended to use a 5- to 6- strand barb wire fence to successfully keep sheep in. A four to six strand electric fence will also work well. Woven wire is not really needed. It is also recommended that the perimeter fences be the most substantial in your management plan.

Q:  How much of a diet overlap would one expect to see between cattle and sheep, and what stocking rate is recommended?

A:  Dietary overlap of cattle and sheep can be high or low depending upon biodiversity, forage diversity and availability, environmental conditions, and management. The dietary overlap can range from 30% to 70%, however, when grazing cattle and sheep on leafy spurge infested rangeland the dietary overlap has the potential of being low until a significant reduction in leafy spurge occurs. Once this happens, individuals need to consider reducing the number of sheep in order to reduce the competition for desirable, available forage for cattle, yet still be effective in controlling leafy spurge.

Proper stocking rates are essential in gaining control of leafy spurge. It has been found that an average of one to two sheep per acre of leafy spurge for a four-month grazing season is required to maintain acceptable control.

Q:  Do you need to train naive sheep to consume leafy spurge before releasing them out to pasture?

A:  There is some debate on this subject. Many people believe that sheep need to be trained to eat leafy spurge. Research studies have used naive sheep and experienced sheep. From these studies it was concluded that it largely depends on the diversity of the plant community and sometimes the breed of sheep. It has been observed that when a plant community is diverse in broadleaf plants, which are preferred by sheep, there usually is a delay in the sheep selecting out leafy spurge. After this period they develop an acquired taste for leafy spurge and will readily consume it.

Q:  What can one expect to see in the control of leafy spurge using sheep? (example: first grazing season, second, etc.)

A:  Depending on the type of grazing treatment and stocking rate used, you will typically see an increase in leafy spurge densities after the first year. This is not a bad thing. What this is saying is that you have put stress on the plant. The increase in leafy spurge densities is from the adventitious root system, triggered by the grazing to put up more shoots. After the second and third year a reduction should be noticeable. Depending on the management and growing seasons 75 to 85 percent reduction can be expect by years five and six.

Q:  When should I begin grazing sheep on leafy spurge?

A:  Sheep should begin grazing leafy spurge as soon as it reaches 3 to 4 inches in height, typically around the 15th of May. This growth is a key component in the control of leafy spurge. By turning them out when the plant is 3 to 4 inches tall, it will allow the sheep to prevent the majority of the leafy spurge plants from going to seed.

Q:  What do you use for predator control?

A:  There are many techniques that are beneficial. Using dry mature ewes with cow/calf pairs has reduced losses; however, the most common methods of control used today are donkeys, dogs, llamas, and the use of the local USDA Plant and Animal Control division (Government Hunter and Trapper).

Q:  When using a rotational grazing system should I run the sheep together with the cattle or should I graze them ahead of the cattle?

A:  Sheep can be run with the cattle, however, there are some precautions that should be used. Producers that creep feed their calves may want to run the sheep ahead or behind the cattle in the rotation to prevent the sheep from consuming their desired creep feed. Also sheep are sensitive to copper. This may cause a problem in areas were copper is deficient and producers use higher copper content to supplement their cattle. Thus it would be more appropriate to run sheep and cattle independent of each other.

Q:  What would happen if I grazed the sheep for three to four years and removed them, would the leafy spurge come back?

A:  The answer is yes. Within two to three years the leafy spurge will be back to the original density without implementing any other control method. The use of sheep in a long-term management plan is essential. Although you might not see any leafy spurge you still have a viable seed bank and viable adventitious roots.

If you have additional questions or don’t see your question listed here, please visit our feedback page and fill out the form or email us with your question. We'll do our best to get back to you with an answer to your question.




Q: How far into the fall (according to the temperature) can you spray leafy spurge and have good results?

A: The best timing varies by herbicide. Plateau should be applied in mid-September for best results as control may drop 50 percent or more if Plateau is applied in August or October. Tordon plus 2,4-D has a wider application window and can be applied from late-August to early September. Paramount has provided good leafy spurge control even when applied in late October following several hard frosts. Leaf color can vary from green to yellow and red. The key is to make sure the leafy spurge leaves are still firmly attached to the stem so the herbicide can be translocated to the roots. If leaf drop has begun, it is best to wait until the following growing season before applying herbicides for leafy spurge control.

Q: Can I spray over an area that has biocontrol agents?

A: Yes, as long as the herbicide is applied in the fall after the adults have finished egg laying. Avoid herbicide application in June and July when the adults are feeding on leafy spurge. No herbicide used for leafy spurge control directly affects Aphthona spp. adults or larvae.

Q: How much water do I use?

A: Proper calibration of the sprayer and uniform coverage is much more important than spray volume. Typically, applicators using multi-nozzle spray booms apply herbicides at 10 to 20 gallons per acre. Herbicides applied with a single-nozzle back-pack sprayer typically use 60 gallons or more per acre.

Q: When is the best time to spray?

A: Proper timing depends on the herbicide you are using. See the text and flea beetle life cycle chart on page 8.

Q: How long before cattle and sheep are allowed to graze after a chemical application?

A: Tordon and Banvel can be applied even if the pasture has grazing cattle present. However, do not transfer the livestock from treated areas to pastures or cropland with sensitive broadleaf plants for at least 12 months without first allowing seven days of grazing on an untreated grass pasture. Otherwise urine may contain enough herbicide to cause injury to sensitive plants. The waiting period after treatment with Banvel varies from seven to 90 days, so consult the label before using.

Q: How many applications of chemical are recommended if used as an IPM method?

A: The number of applications will vary depending on the success of the other control method used in the IPM program. When used with Aphthona spp. flea beetles, excellent control has been achieved with as few as one application, but sometimes two to three annual applications are needed. If used in conjunction with grazing animals, three annual treatments worked best.

Q: How close can I spray to water?

A: Long residual herbicides such as Tordon and Banvel should not be used within 50 feet or less of a body of water, depending on the terrain. Other leafy spurge herbicides can be used near or in water. See pages 18-19, which describe specific herbicides to control leafy spurge near water.

Q: What size of a leafy spurge patch generally is too big for chemical treatments?

A: This is really dependent on budget (see pages 26-27). Herbicides should be applied around the perimeter of even very large infestations to prevent spread. It is never too early to begin a treatment program, but it can be very costly to start years after the program should have begun.


TEAM Home Page