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ISSUE 6    June 9, 2005


Mosquito activity is on the rise, and will probably increase during the coming weeks as a result of recent rains and warmer weather. Mosquitoes are a major annoyance during outdoor work and leisure activities, and a few species pose human health concerns because they transmit pathogens that cause West Nile virus (WNV) and other forms of encephalitis. The elderly and individuals with compromised immune systems are most at risk. Although over 600 cases of WNV and 5 deaths were recorded in North Dakota in 2003, its incidence was down to 20 known cases and 2 confirmed deaths in the state last year. Western equine encephalitis occasionally pops up in North Dakota and surrounding states on rare occasions. Most cases involve horses, but humans can also become infected. Mosquitoes also transmit WNV and Eastern equine encephalitis to horses, and heartworm to dogs.

Personal Protection. Wear long sleeve shirts and pants outdoors during peak mosquito activity(late afternoon/evening to morning). Repellents are available as sprays, liquids, creams, solids (sticks), and wristbands, and many work well. Wristbands are not as effective as other forms. Choose products that contain one of the following ingredients: 1) diethyl phthalate, 2) diethyl carbate 3) ethyl hexanediol, and N, N,N-diethyl-m-toluamide (DEET). DEET is a very effective repellent. Permethrin-containing repellents can be used on clothing, shoes, bednets and camping gear. Permethrin is an insecticide, but also repels ticks and mosquitoes, and maintains repellency after repeated laundering of treated items. Oil of citronella is used for space repelling of mosquitoes outdoors. It is available in candles, torches, or coils for burning, produce a mosquito-repellent smoke. These products are of some use, but only under windless conditions. Citronella products are not as effective for personal protection those applied to the body or clothing.

Common sense rules for using repellents:

1. Apply sparingly to exposed skin or clothing.

2. Avoid contact with eyes, nostrils and lips, and dodo not inhale or ingest repellents.

3. Apply low-concentration (15-30% DEET) products to the skin (less than 15% for children).

4. Avoid applying repellents to children's hands that are likely to have contact with eyes or mouth.

5. Pregnant and nursing women should minimize use.

6. Never use repellents on wounds or irritated skin.

7. Use repellent sparingly. Saturation does not increase performance. An application of DEET lasts for 3 to 8 hours, depending on concentration.

8. Wash repellent-treated skin after coming indoors.

Health concerns about repellents. Although rare, skin irritation or slight to severe neurological side effects can occur in infants and young children as a result of DEET application. Adults with elevated sensitivity to the repellent could also have problems. Most cases of severe side effects have resulted from overapplication of high-concentration products and/or repeated applications for several consecutive days to bedding, clothing, and skin of young (< 5 yrs old) children. If a suspected reaction to an insect repellent occurs, promptly wash treated skin and seek medical attention. Take the repellent container to the medical facility.

Cultural Control:

Eliminate potential mosquito breeding sites:

1. Old tires, buckets, and other unused containers that collect rainwater.

2. Plugged rain gutters.

3. Stagnating water in wading pools on flat roofs, or on tarps used to cover boats, hot tubs, pools, etc.

4. Puddles near leaky outdoor faucets and air conditioner units.

5. Birdbaths and kiddie pools (change water weekly).

6. Seepage/accumulation from cisterns, cesspools, and septic tanks.

7. Standing water around animal watering troughs. (flush stock water troughs weekly).

Other cultural management steps include leveling areas of the yard where puddles form and taking care to avoid puddle formation while watering the garden.

Indoor Control. Keep windows, doors, and porches tightly screened. The fly swatter is still the best option for eliminating small numbers of mosquitoes that enter the home. The garage is another issue, especially if pets are kept in the garage at night. Constant vigilance in keeping garage lights off when not needed or keeping garage doors and windows closed or screened when lights are on can help minimize evening infestations. Household aerosol space sprays containing synergized pyrethrum or synthetic pyrethroids (allethrin, resmethrin, etc.) can help rid the garage of mosquitoes, but will not manage insects for long periods of time.

Outdoor Control. Adult mosquitoes commonly rest on weeds, tall grass, and other vegetation. Maintaining a well-groomed lawn and removing weeds adjacent to buildings minimizes these sites. Hand_held ULV foggers or attachments for tractors/lawn mowers can be used to apply insecticides for temporary relief from mosquitoes in larger areas. Pyrethrins or 5% malathion can be fog-applied outdoors.

Spraying insecticides to lower limbs of shade trees, shrubs, or other tall vegetation, may help. Apply as coarse sprays to vegetation using a compressed air sprayer.

Ornamental pools can be stocked with top-feeding predacious minnows (such as the flathead minnow, available as a bait fish), or may be treated with biorational larvicides containing Bacillus thuringiensis israelensis (Bti) or S_methoprene (an insect growth regulator). Most products can be found at home/garden, hardware, and discount stores.

Consult NDSU Extension circular no. E-472, "Mosquito Management", for more information on specific products for mosquito control. It is located online at:




Weather impacts on flies. Recent rainy and slightly cooler weather during the past couple of weeks is likely to delay emergence of root maggot flies. The extended forecast suggests several more days of low to mid-70s are ahead. Cool, breezy, and rainy conditions, especially in late afternoon hours, can create unfavorable flying weather for sugarbeet root maggot flies. Movement of flies into sugarbeet fields will continue at a slow pace until better flying weather returns. IMPORTANT: fly emergence is expected to continue "creeping" along. A couple of days at 80-degrees or warmer could result in a major influx of flies into beet fields. A rapid response with a liquid insecticide application would be the best tool to manage that type of situation.

Fly activity. Although fly emergence from soil got started several days ago, numbers of adults resting on utility poles and entering sugarbeet fields have been low. Currently, flies are being frequently observed in low numbers in sheltered areas (farmsteads, shelterbelts, road ditches, smallgrain fields and down-wind sides of utility poles). Soil samples collected by NDSU personnel recently indicate that high numbers of maggots are still in the larval and pupal stages, and will take several more days to reach the adult fly stage. Despite a few flies being out for almost 2 weeks, large numbers of flies are expected to gradually invade beet fields during the next 2 weeks. Pembina and, to a lesser extent, Walsh County are again most likely to have major infestations. However, fields in northern Grand Forks county should be monitored closely.

Control strategies. Growers in high-risk areas for maggot problems should prepare to apply a postemergence insecticide in the next several days. Granular materials will work well this year because soil moisture is adequate to high. Granules can be applied anytime from June 13 to18.

Growers preferring to apply a liquid insecticide should wait until the next report to time the application close to peak fly activity (within 3 days) in current-year beets. Last year’s late fly emergence could delay or result in a prolonged emergence period this year. It may be another good year for using 2 split applications of a liquid insecticide for maggot control. The first could be applied late next week, and the second at peak activity. Monitor farm radio, DTN, and Crop & Pest Report for further updates.

Always read, understand, and follow all pesticide labeling instructions and precautions - it’s the law.

Mark Boetel
Research & Extension Entomologist



It is time to prepare for collecting and redistributing Aphthona flea beetles for leafy spurge control. Several county Weed Control Officers host field days during June for collecting and redistributing the flea beetles. Contact your county weed control officer for the date, time, and location of a field day in your area. Also, the North Dakota Department of Agriculture has created an e-mail distribution list at ndda-weeds@state.nd.us where county Weed Control Officers can announce their field days for the collection and redistribution of the Aphthona flea beetles. If you are interest in receiving the distribution list contact the Department of Agriculture noxious weeds staff at 701-328-2980 or 701-328-2983.

Beetle Collecting and Redistribution

The overwintering larvae are currently finishing with their spring feeding on the spurge roots are moving near the soil surface where they will pupate. Expect to see adults feeding on the spurge foliage during the next few weeks.

Mid-June to early July is the best time period to collect adult flea beetles for redistribution. To collect the adult flea beetles you will need a sweep net, paper bag or paper container, and a cooler with blue ice. It is best to collect beetles after 10:00 a.m. when the air temperature has warmed to at least 70 oF and the spurge is dry. Beetles are easiest to collect when there is little or no wind.

Beetles can be collected from an established population only when the population has increased enough for redistribution. Using a sweep net, make five sweeps in a 10 square foot area and count the number of beetles in the net. If there are numerous beetles to count individually, remove the vegetative trash and other insects and pour the flea beetles into a graduated container. Every 10 ml equals approximately 1,000 flea beetles. You need to redistribute flea beetles when an established population yields 500 to 1,000 adults per five minute sweeping period.

For redistribution, the beetles need be placed in the paper bag or container with some leafy spurge. Transport the beetles in a cooler with blue ice. Remember the beetles are living organisms and the containers of beetles should not be left in the sun or a hot vehicle. The beetles need to be released preferably the same day of collection into the new release site. If the beetles cannot be released as soon as possible, they can be stored for a maximum of one week at 40 oF.

The flea beetles usually establish and control spurge sooner when large numbers are released into habitats that are similar to the habitat they were collected from. A minimum of 1,000 adults should be released at a single point, marked with a stake, along the margins of the spurge when the infestation is dense. Make multiple releases in a large spurge infestation. The new flea beetle release should yield at least 50 beetles per five sweeps the following summer. When the population is less than 50 beetles, make additional releases.

The flea beetles do have limitations and do not have an equal impact across all habitats. Flea beetles will establish sooner when released in moderate spurge densities of 60-90 stems per square yard with little grass cover and thatch. The Aphthona flea beetles establish faster on the south facing slops followed by the western and eastern slopes and usually noticeably slower on north facing slops.

The black flea beetle, Aphthona lacertosa, establishes at sites ranging from high and dry to cooler and moister habitats with shade and denser stands of spurge, and where spurge is growing in soils of silt loam, silt clay loam, clay loam, loam, or loam/fine sand loam. The brown flea beetle, Aphthona nigriscutis, is more successful in areas that are higher and drier with well-drained loam soil. When releasing beetles into a spurge infestation for the first time, release a mixture of both species to determine the species that is best suited for that spurge habitat.

Integrating Beetles With Other Management Methods

The Aphthona flea beetles can successfully be integrated with other management methods. Herbicides p

lus flea beetles have shown to give better results than either tactic used alone. Tordon (picloram) plus 2,4-D at 1 quart plus 1 quart per acre (0.5 + 1 pound per acre) can be applied during early September to mid-October on leafy spurge with an established flea beetle population. The herbicide treatment will help to open up the canopy, and allow the flea beetles to deposit their eggs at the base of the spurge plants.

Grazing by sheep or goats, or fire, can also be used to open up the spurge canopy and remove excess trash from the soil surface. When integrating these management tactics with an established flea beetle population, they should only be used after mid-August, when egg laying by the beetles is completed.

An important point to remember is that the Aphthona flea beetles do have limitations and are not a "quick fix" for controlling leafy spurge. The beetles may take several years to reduce a leafy spurge infestation. Every spurge infestation is different and the flea beetle population development will vary across habitats. The beetles may need to be integrated with other management tactics to achieve desirable results.

For more information on using the Aphthona flea beetles for leafy spurge control, refer to Leafy Spurge Control Using Flea Beetles (W-1183) at:




Assail 70WP, a neonicotinoid insecticide, is now labeled for potato insects. This insecticide has foliar activity against Colorado potato beetle (CPB), aphids, leafhoppers and flea beetles. Assail is a systemic insecticide that protects the new foliage and has translaminar movement across the leaf to protect the entire leaf. Acetamiprid is the active ingredient in Assail and provides fast knock down and long residual control of the target insect pests. Assail is classified as a "Reduced Risk" pesticide by the EPA because of its favorable environmental profile; only a 5_day soil residual and no concern with ground water contamination. This product can be applied by air or ground, and CANNOT be applied as chemigation under the current label. The recommended rates are 0.6 – 1 oz of product per acre for CPB, 1 – 1.7 oz/A for aphids and 1 oz/A for leafhoppers and flea beetles. Use the higher rate for CPB and aphids under conditions of heavy pest pressure and/or dense foliage. To reduce the risk of insect pests developing resistance to the neonicotinoid insecticides, rotate to an insecticide of a different mode of action for each treatment application. For CPB, only one application of a neonicotinoid should be restricted to a single generation. Assail 70WP is currently available through your local supplier of potato pesticides. REMEMBER to always read and follow the label directions.

Denise Olson
Research Entomologist



A black weevil, about 1/5 inch long, called the strawberry root weevil (Otiorhynchus ovatus), is a very common insect throughout North Dakota. In June, the adults emerge from the soil and feed on plant foliage but cause no significant damage to the plants. However, larvae can injure roots of hemlock, spruce, Taxus and arborvitae in nurseries and plantations. Other hosts include strawberry, raspberry, grape, apple, peach, etc. They would go unnoticed except that large numbers regularly wander into houses by mistake as "accidental invaders." They are not damaging to the house or furnishings and do not harm people or pets, but are a nuisance to homeowners. They crawl rapidly (they can not fly) throughout the house, and hide in clothing, bedding, and carpet or appear in sinks, bathtubs, drains and other places where moisture is present.

Combating strawberry root weevils in the house can be difficult and frustrating. Adults already inside need only be vacuumed or swept up and discarded. Household aerosol insecticides are not very effective for controlling these weevils, because weevils may become widely scattered throughout the house. To prevent invasion into houses, look for and seal off any points of entry, such as cracks and gaps in the foundation and around windows and doors. Spraying an outdoor insecticide on and along the foundation may reduce the number of weevils outside and thereby reduce the number wandering in. Be sure to read and follow the label directions and safety precautions.



A few fields were sprayed for diamondback moth larvae defoliating seedling canola near Mohall, Renville County (source: C. Michels). In May, diamondback moth adults migrated into the north central region of North Dakota earlier than normal. This has resulted in high trap counts (>100 moths per trap week) over the past several weeks. Injury to seedling canola is not typical, but has been observed previously in North Dakota during 2001. Larvae are about ˝ inch long and light green in color with a forked posterior. They have the habit of spinning down of a strand of silk when disturbed. It is difficult to predict if canola producers will have problems with the next generation (second) during flowering. Recent heavy rainfalls can drown many larvae of the first generation and favor development of fatal fungal diseases, such as Entomophthorales. Pheromone traps are a good indicator on whether scouting for the larvae of the second generation will be necessary during bolting to early flowering. Larvae prefer to feed on the buds, flowers, and pods. Economic thresholds are 10-15 larvae per square foot during flower or 20 larvae per square foot during podding.



The statewide cool, wet weather continues to suppress feeding activity of flea beetles and subsequent injury to canola. There have been no reports of foliar spraying for flea beetles in canola.

Janet Knodel
Area Extension Specialist
North Central Research Extension Center

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