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ISSUE 5    June 2, 2005

SUGARBEET ROOT MAGGOT: PEAK FLY ACTIVITY EXPECTED WITHIN TWO WEEKS

Significant numbers of sugarbeet root maggot flies emerged during the past week, and many are entering beet fields to mate and lay eggs. A steady increase of fly movement into beet fields is expected during the next several days.

Peak fly activity in current-year beet fields should occur in the next couple of weeks, depending on location and weather patterns. Fly emergence and movement into beet fields can be accelerated by a major increase in air temperatures, especially if accompanied by calm conditions that are conducive to fly movement. Alternately, activity will be slowed by cool, windy, or rainy weather.

Predicted degree-day (DD) accumulations for June 3 and expected peak fly dates by site in the Valley.

Site

Air DD

(sine)

Expected peak

fly activity*

Cavalier

415.58

June 13-16 + 80E day

Fargo

512.86

June 7-10 + 80E day

Grand Forks

442.34

June 11-14 + 80E day

Hillsboro

517.67

June 7-10 + 80E day

St. Thomas

424.19

June 12-15 + 80E day

*Peak activity usually occurs in current-year beets on the first calm day to reach about 80EF after accumulation of 600 air DD (sine).

Growers in high-risk areas for maggot attack (central and southern Pembina County, ND and central Walsh County, ND) should consider applying a postemergence insecticide. Granules should work well for postemergence this year because most soils are moist. Granular products should be applied within the next 5-7 days in high-risk sites. It is best to err on the early side of peak activity with granules. Liquid insecticides should be effective if applied at least 3 days before peak fly activity. Liquid materials containing chlorpyrifos as the active ingredient (Chlorpyrifos 4E, Lorsban 4E, Govern 4E, Nufos 4E, Warhawk 4E, and Whirlwind 4E) can be effective tools for managing adult flies, but will also provide control of root maggot larvae, especially if a rainfall event follows the application within a few days to incorporate the insecticide into soil.

For more information regarding postemergence root maggot control and for more specific product recommendations, refer to the "Insect Control" section of the 2005 Sugarbeet Production Guide or the "Sugarbeet Insects" section of the 2005 Field Crop Insect Management Recommendations. These publications are online at:

http://www.sbreb.org/Production/production.htm

and

http://www.ext.nodak.edu/extpubs/plantsci/pests/e1143w1.htm

Mark Boetel
Research & Extension Entomologist
mboetel@ndsuext.nodak.edu

 

FLEA BEETLE ACTIVITY LOW IN CANOLA

Most of the canola crop has escaped major flea beetle injury – so far! The cool, wet weather in May is part of the reason. This delays flea beetle emergence, reduces feeding activity and movements from overwintering sites to newly emerged fields, and slows crop emergence. As warmer weather occurs, it is advisable to scout fields on warm, calm days for flea beetle feeding injury and to ensure that seed treatment are still controlling flea beetles. A foliar insecticide spray may be necessary if the residue of the seed treatment is no longer killing flea beetles. Remember, flea beetles must feed on the seedling to ingest the insecticide from seed treatment before it will kill them. So, some feeding injury or pitting may be observed even when seed treatments efficacious. New research data from Canada indicates that mean ground temperatures must reach 15 C (or 59 F) for peak emergence of flea beetles (Ulmer and Dosdall). Currently, the average bare and turf soil temperatures from NDAWN stations range from 52-58 F and 49-60 F, respectively. So, we are getting close to the peak emergence period.

 

GRASSHOPPER HATCH DELAYED AND SLOW DUE TO COOL WEATHER

Again, the cool, wet weather of May prevented premature grasshopper hatch and insures adequate food supply for grasshoppers. As warmer weather returns this week, hatching will resume. Earlier hatching and faster development will occur on southern facing slopes and lighter sandier soils. Hatching can extend over three to six weeks depending on the habitat. If young grasshoppers (nymphs) reach threatening levels (50-75 nymphs per square yard), a treatment is recommended in hatching sites. Grasshoppers are more easily and economically controlled while they are in the nymphal stage and still within hatching sites (roadsides, fence row, etc.). There are a number of advantages in treating grasshoppers early:

1)  fewer acres will have to be treated and less insecticide is necessary to obtain control, thus reducing costs;

2) grasshoppers are killed before they cause significant crop loss;

3) smaller grasshoppers are more susceptible to pesticides than larger grasshoppers (or lower rates will kill smaller grasshoppers); and

4) early treatment before grasshoppers reach maturity prevents egg deposition, which may help reduce the potential grasshopper threat for the following crop year.

Jan Knodel
Area Extension Specialist
North Central Regional Extension Center
jknodel@ndsuext.nodak.edu

 

MOSQUITO REPELLENTS

As we are nearing mosquito season it is time to review ways to protect ourselves from mosquito bites. Of course the best way to prevent or limit mosquito bites is to avoid being in areas with lots of mosquitoes and to avoid being outdoors during the peak biting time of early evening. However, for many of us this is not a practical option.

If you can not avoid mosquitoes, wearing long-sleeved shirts and using a repellent are recommended.

Mosquito repellent products containing DEET (N,N-diethyl-m-toluamide) have long been the standard for mosquito repellents. DEET is very effective and any new products are compared against it. Recently, several new active ingredients have been registered with the EPA as mosquito repellents and have demonstrated good efficacy. These include picaridin that has been used in Europe and other locations for some time now. Another new ingredient is oil of lemon eucalyptus.

There have been some health concerns regarding DEE

T products but DEET has a very good 40 year safety record. The small numbers of irritant or other adverse effects from DEET use are usually associated with overuse. However, DEET is irritating to eyes and mucous membranes and because of that it is difficult to apply to the face.

But compared to the risk of acquiring a vector-borne infection, the risk from DEET is minute. Besides being a very good mosquito repellent DEET is advantageous in that it can be applied together with sunscreen products. It is not known how compatible the new repellents are with sunscreen.

Products with picaridin have been shown to give long lasting protection and to be less irritating than DEET. Picaridin products will be labeled as including KBR3023 and have been marketed under the trade names of Bayrepel, Hepidanin, and Autan Repel. A World Health Organization study showed that picaridin has a good safety record, cosmetic properties, and does not dissolve or attack certain plastics such as watch crystals and glasses frames and synthetic fabrics like DEET can.

Oil of lemon eucalyptus is a plant based repellent. Products containing oil of lemon eucalyptus state that they should not to be used on children under the age of three years.

A few years ago interest peaked in certain Avon Skin So-Soft products. Today Avon is marketing several product lines containing the repellent IR3535. In a 2002 test, products with a low DEET concentration of 4.75% protected against mosquitoes for an average of 88 minutes. IR3535 at a 7.5% concentration protected for about 23 minutes. I couldn’t find concentration data for the current Avon products but they may contain a higher concentration of IR3535 and give longer protection.

A USDA-ARS study compared 25% picaridin, 25% IR3535, and 40% oil of lemon eucalyptus against 25% DEET. For a 3 to 4 hour period, the alternative repellents were as effective as DEET and they did not have an objectionable odor or consistency and were not irritating to the skin.

Some Sources of Information:

Center for Disease Control http://www.cdc.gov/ncidod/dvbid/westnile/RepellentUpdates.htm.

See http://www.epa.gov/pesticides/factsheets/insectrp.htm  for information on using Environmental Protection Agency registered mosquito repellents.

Gary Brewer
Research Entomologist
North Dakota State University


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