ISSUE 6 June 10, 2004
SUGARBEET ROOT MAGGOT: PEAK FLY ACTIVITY LIKELY IN NEXT 12 DAYS
NDSU sugarbeet entomology personnel collected over 1,000 overwintered sugarbeet root maggots during the past week and most were in the late pupal stage. Degree-day (DD) information corresponds with our observations on maggot development.
Based on DD accumulations and the extended weather forecast, a significant amount of initial fly emergence should occur this weekend. Peak fly activity is likely to take place on the first calm or low-wind day to reach 80 degrees Fahrenheit between June 17 and 23. Temperatures, rainfall, and wind conditions during the next week will dictate when the exact peak occurs. Cool temps, stormy weather, and windy conditions can delay the actual occurrence of the peak.
Growers in high-risk areas desiring additional chemical protection from maggot injury should apply their preferred postemergence insecticide soon. Granular insecticides should be applied between now and June 16. Liquid materials should perform well if applied between June 16 and 23.
Damage assessments and population monitoring of commercial sugarbeet fields during 2003 indicate that these additive applications will be most useful in central and south central portions of Pembina County, ND and in extreme north central Walsh County, ND (mainly rural Glasston, Hensel, Hoople, and St. Thomas).
Research & Extension Entomologist
MOSQUITO TRAPS . . . ARE THEY THE SILVER BULLET?
With the recent rains thoughts are turning to mosquitoes and West Nile Virus. A popular topic of interest the past two years has been the effectiveness of the widely publicized mosquito traps now being marketed. There have been numerous studies established around the country designed to test just that. The American Mosquito Control Association (AMCA) has prepared a review article regarding these traps and how they might fit into a mosquito control program.
The entire article can be found on the AMCA web site, located at:
The general idea behind these trapping devices is to reduce the number of mosquitoes that pester the homeowner and their family.
The traps use attractants that lure the host-seeking female mosquitoes to the trap. Some devices use an impeller fan that draws the mosquitoes into a net, where they are trapped and eventually dye from desiccation. Some trapping systems use a sticky surface to capture the mosquitoes when they land. Others may rely on the popular electric grid approach which electrocutes mosquitoes upon contact. In general, all these devices require some level of regular maintenance to clean them of their "prey".
The vast majority of these traps use carbon dioxide, produced either through the combustion of propane or with a CO2 cylinder and release rate between 350m and 500 ml/min. The plume of CO2 mimics exhaling humans and makes these traps specific for capturing blood-feeding insects. This is an improvement over older trap designs, such as black-light traps, which captured mostly non-target insects such as moths and beetles. The CO2 is often combined with 1-Octen-3-ol, a derivative of gasses produced in the rumen of cows, to increase attractiveness by several orders of magnitude. The 1_Octen_3_ol is slow_released at a rate of ca. 0.5 mg/h.
The process of a mosquito searching for a blood meal is a complex pattern of behaviors, relying on multiple sensory cues that may be visual, thermal, or olfactory. These complex behaviors can explain some of the variations in trapping efficiency for these units noted for certain species of mosquitoes at different times. There certainly is variation among trap designs in their ability to attract and capture mosquitoes.
Nonetheless, these devices will, indeed, trap and kill measurable numbers of mosquitoes. The big question is whether these devices will produce a noticeable reduction in the mosquito population. Perception of effectiveness at achieving this goal may depend upon a number of factors, for example, an individuals tolerance level for mosquitoes, the absolute size of the mosquito population, the proximity, size and type of breeding habitat that produces the source of re-infestation, wind velocity and direction, and species of mosquito present, among many other things. Depending upon the traps placement, wind direction, and trapping efficiency, there is a risk that these traps may actually draw more mosquitoes into an area than they can possibly catch. Therefore, it is still strongly recommended that repellents be used when outdoors during periods of mosquito activity and practice other source reduction methods to produce a more comprehensive level of relief.
In conclusion, the AMCA article states, "Please be cautioned against putting too much faith in traps as your sole means of control. These traps represent an evolving technology that is a most welcome addition to our mosquito control armamentarium. Their potential is great, but shouldn’t be overestimated. It’s highly unlikely that these devices, whatever their improvements, will ever fully supplant organized community-wide mosquito control programs, for there is no single silver bullet that will prove to be the ultimate answer to mosquito problems. Effective mosquito management requires integrating a variety of available control strategies i.e. surveillance, source reduction, biological control methods, traps, environmentally friendly larvicides, and, when necessary, application of public health adulticides, into a comprehensive program that exploits known mosquito vulnerabilities."
Some comments on cost differences:
Power supplies for different trap types will vary. Some are totally self-contained, using propane to provide both power and the source of carbon dioxide for the attractant. These units have the advantage of portability, allowing them to be placed at a considerable distance away from home-sites. This may be an important consideration on larger properties such as those over an acre in area, by allowing mosquitoes to be intercepted long before they come into the vicinity of human activity. This portability comes at a price, though, for the thermoelectric generator that uses excess heat from the combustion process to generate electricity to run the intake fans is quite expensive. Most units rely upon power cords and AC current from outlets. This limits them to smaller areas served by extension cords, but their price is less than their self-contained counterparts.
For more information on mosquito control and health issues such as West Nile Virus, visit the following web sites:
Mosquito Management in North Dakota. NDSU Extension Publication E-472. 2000.
Centers for Disease Control - Q & A on West Nile Virus
Comparative Efficacy of Insect Repellents against Mosquito Bites. 2002. Mark S. Fradin, M.D., and John F. Day, Ph.D.New England Journal of Medicine, Volume 347:13_18 July 4, 2002 Number 1.
FIRST REPORTS OF MILLER MOTHS FLYING!
Starting to get some questions about the presence of "Miller Moths" flying around the outside and inside of homes and businesses. These are the adult moths of cutworms, Family Noctuidae. Cutworm moths are active at night and are attracted to lights. The main species typically flying at this time is the Army cutworm, a moth which actually migrates to the Rocky Mountains for the summer. It then returns to the plains in the late summer to lay eggs in fields. Unfortunately, these moths often get side-tracked when they are blown off course by storm fronts moving from the southwest, northward to the plains states.
Fortunately, this is probably the largest of the cutworm flights. However, several migratory moths can also start arriving, including the true armyworm, black cutworm and the variegated cutworm.
What to do about these Miller Moths? The best options are: 1) Turn the outside lights off when not in use. 2) Change the outside lights to a yellow bulb, which is less attractive to night flying insects. 3) Keep curtains closed at night, so night flying insects are not attracted to your windows. 4) Fix any holes in the screens to prevent moths (insects) from entering the house. Spraying insecticides outside or inside is NOT recommended and will not provide relief from the temporary invasion.
If you are interested in more information on moth identification for North Dakota, see Dr. Jerry Fauske’s website of "Moths of North Dakota."