Wing Beats Wing Beats

Transcription

1 Volume 9, Number 4 Winter 1998

2 Wing Beats Wing Beats PO Box Fort Myers, FL Editor-in-Chief Dennis Moore, Fort Myers, FL voice: fax: Managing Editor Tom Floore, Panama City, FL voice: ext 30 fax: Associate Editors Dave Dame, Gainesville, FL Tom Wilmot, Sanford, MI Stan Cope, Great Lakes, IL Regional Editors Massachusetts - Timothy D. Deschamps, Norwood Michigan - Thomas R. Wilmot, Sanford New Jersey - William C. Reinert, Northfield Texas - Dan Sprenger, Corpus Christi Utah - Glenn Collett, Salt Lake City Editorial Review Board Richard Berry, Columbus, OH Mark Latham, Palmetto, FL Gerry Hutney, Tampa, FL L. Philip Lounibos, Vero Beach, FL Robert Lowrie, Covington, LA John J. Smith, Norwood, MA James Webb, Santa Ana, CA Homestead Rd Lehigh, FL Florida Mosquito Control Association FMCA President: Mark Latham, Manatee MCD, Palmetto FL; manateemcd@aol.com Shelly Redovan, FMCA Executive Director PO Box Fort Myers, FL voice: ; fax: redovan@lcmcd.org American Mosquito Control Association AMCA President: David Brown, Elk Grove, CA dabrown@sac-yolomvcd.com Martin S. Chomsky, AMCA Business Manager P.O. Box 234 Eatontown, NJ voice: ; fax: amca@mosquito.org Volume 13, Number 4 of the Florida Mosquito Control Association Inside Out - Mosquito Identification Made Simple...5 by Marc Slaff Commentary - Public Health Agency Support for Vector Control...6 by Dave Dame From Where I Sit - Notes from the AMCA Technical Advisor...8 by Joe Conlon Under Surveillance - Mosquito Activity Related to Time of Day for Several Michigan Species...10 by Steve Crisp and Randy Knepper Fly Wheels - To Clean or Not to Clean...13 by Marin Brouillard Field Forum -- The Pest of the Pest: Ants (Hymenoptera: Formicidae)...14 by Lawrence J. Hribar Lines of Flight - Swath Characterization and Block Variability...22 by R. E. Mickle Vector Bearings - West Nile s Widening Toll...26 by Rick Weiss On the Books - A Titillans Lexicography for Everyday Mosquito Control:...33 Viewpoint - Better Safe Than Sorry...34 by Joe Conlon Teachers -- Bug Bus Hits the Road Teaching Children About Vector Control...38 by Stephanie Miladin About the Cover: Cover artwork courtesy of Bayer Biological Science. Wing Beats: An official publication of the American Mosquito Control Association, published quarterly by the Florida Mosquito Control Association. This magazine is intended to keep all interested parties informed on matters as they relate to mosquito control. All rights reserved. Reproduction, in whole or part, for educational purposes is permitted, without permission, with proper citation. The FMCA and the AMCA have not tested any of the products advertised or referred to in this publication, nor have they verified any of the statements made in any of the advertisements or articles. The FMCA and the AMCA do not warrant, expressly or implied, the fitness of any product advertised or the suitability of any advice or statements contained herein. Opinions expressed in this publication are not necessarily the opinions or policies of the FMCA or the AMCA. Subscriptions: Wing Beats is sent free of charge to anyone within the continental United States. Subscriptions are available for the cost of first class postage to any foreign address at the following rates: Europe, UK and Australia US$20; Canada, US$6; South America US$10. Make checks and purchase orders payable to the Florida Mosquito Control Association and send to FMCA, PO Box 60837, Fort Myers, FL Correspondence: Address all correspondence regarding Wing Beats to the Editor-in-Chief, Dennis Moore, PO Box 60005, Fort Myers, FL, Readers are invited to submit articles related to mosquito and biting fly biology and control, or letters to the Editors. There is no charge if your article or letter is printed. Photographers and artists are invited to submit color transparencies, high quality original artwork or artwork in electronic format for possible use in the magazine or on the cover; $100 will be paid for each cover photo. Businesses are invited to place advertisements through the Editor-in-Chief.

3 Mosquito Activity Related to Time of Day for Several Michigan Species by Steven Crisp & Randy Knepper Adult mosquito control in Michigan depends on several basic assumptions to determine when control measures are performed. These include the idea that peak flight time occurs around sunset, most species stop flying around midnight and cooler temperatures or rain will significantly reduce activity. However, the evidence to support these ideas was sparse and led to the justification for this study. A similar study was conducted in Ohio (Mitchell 1981) that laid some of the groundwork for this project. Our observations may be relevant to control observations in other areas with similar habitats. Figure 1. Bottle rotator trap During the spring and summer of 2002, a collection bottle rotator trap (Figure 1) was placed at a variety of habitats throughout Saginaw County to test these concepts. The rotator unit was purchased from the John W. Hock Company and consists of a motorized platen with eight bottles attached. A timer determines when and how long each bottle is in place under the trap. The trap itself was baited with CO 2 delivered from a 5 lb. tank connected to a regulator and orifice inline with a tube placed under the lid of the CDC trap. This setup allowed a constant release of 500 ml/minute of CO 2 to provide consistent attractant for every collection site. The unit is powered by a rechargeable sealed battery and mounted on a tripod approximately 5 ft above the ground. Initial deployments of the trap showed greater mosquito catches when the CO 2 tube was moved farther from the fan under the lid. Spring Ochlerotatus species were captured using just CO 2 ; the addition of a light bulb increased the number of captured summer species, but also increased the number of trash insects collected. A small, self-powered HOBO temperature and humidity data logger (about half the size of a deck of cards; figure 2) was also set out with the trap to record hourly weather conditions. The device was enclosed in a PVC container to protect the circuitry during a rain event. A ½ inch hole was drilled in the bottom of the container to permit circulation of air. This device allowed daily computer download of data after each placement. The collection sites were in logical habitats for the dominant species over the course of the season. Flooded woodlots were monitored until mid -June for Ochlerotatus species. Marshes were monitored from then until mid-july to sample for Anopheles and Coquillettidia perturbans. Culex and Ae. vexans habitat was monitored until late August. The following is a summary of the information collected from these habitats. Spring Mosquitoes: Oc. canadensis and Oc. stimulans/ fitchii group Initial placements of the trap during the month of May yielded low catches of one to four mosquitoes per bottle over a 24 hr period with each bottle representing a 3 hr Figure 2. HOBO data logger catch. This was in spite of reasonably high landing counts of species in the dark-legged Ochlerotatus group. In early to mid-june, the local population shifted to a greater composition of Oc. canadensis and stimulans/fitchii. Captures exploded to as many as 500 mosquitoes in some bottles with high activity observed over the 24 hr period, so the rotation interval was reset to 3 hr per bottle for 24 hr to capture the whole day s activity. The chart displayed in figure 1 represents data collected from flooded woodlot habitat in six collection sites from June 3-18, Bottle counts for the same collec- continued on page Wing Beats

4 Mosquito Activity continued from page 10 Figure 1. Mean number of Ochlerotatus tion times were averaged among sites. The greatest flight activity for both groups occurred before the traditional adulticiding start time of sunset. Oc. canadensis was active throughout the entire 24 hr period, peaking from 5 pm to 8 pm. Although Oc. stimulans/fitchii activity declined rapidly after the peak (2 pm to 11 pm), Oc. canadensis remained active at surprisingly high levels throughout the day. Temperatures ranged from a low of 52 at night to highs approaching 90 in the afternoon. Lower temperatures did not affect the overall collections. Permanent Water Mosquitoes: An. walkeri and Cq. perturbans From July 2 to July 17, 2002 the trap was moved to locations likely to capture Cq. perturbans. These included placements in Zilwaukee near the Crow Island State Game Area and Thomas Township along the Tittabawasse River. In addition to Coquilletidia, large numbers of An. walkeri were collected in Zilwaukee. The combined species totals ranged from 0 to 700 in a given collection bottle. Once again, the results were averaged among placements, seven in all. It was quickly observed that activity tapered off to practically nothing from 8 am until 4 pm, so a 2 hr rotation interval for a period of 16 hr was used in an effort to better quantify 18 Wing Beats the flight time. The results are displayed in figure 2. Flight activity of these species activities built to a plateau between 10 pm and 2 am, which seems to coincide well with traditional adulticiding times beginning after sunset. Cq. perturbans numbers fluctuated little among placements when temperatures were lower. Lows ranged from 71 to 54. An. walkeri disappeared almost entirely from collections when lows dipped below 60, but later recovered when nightly temperatures became warmer. Brief rain events during these periods slightly reduced the number of Figure 2. Mean number of An. walkeri and Cq. perturbans captured mosquitoes. Some bottles had approximately 200 mosquitoes floating in an inch of water. Taking into consideration the 2 hr rotation interval and the brevity of the rain, it is uncertain if the mosquitoes were captured before or after the rain. Flood Water and Culex Mosquitoes: Ae. vexans and Cx. pipiens From July 18 until the beginning of August, the trap was placed at various locations in Birch Run, Saginaw, Swan Creek, Thomas, and Zilwaukee townships. These two species happened to be caught in many of the same trap placements. This was probably due more to the time of year than to habitat or other factors. They were grouped together for examination as a matter of convenience. Numbers of mosquitoes caught per bottle tapered off dramatically during the period from 8 am to 4 pm, so once again a 2 hr rotation interval was used over 16 hrs. The catches remained fairly consistent among placements with the averages shown in figure 3. The most interesting trend in this group was the bimodal nature of flight activity observed in Ae. vexans. Peaks occurred at approximately sunset and again between 2 am and 4 am. Culex pipiens activity on the other hand rose quickly to a peak around 10 pm with numbers falling gradually toward sunrise. Both species were captured in lower numbers when nightly lows dipped below the mid-50 mark. Periods of rain produced much the same results as with Anopheles and Coquilletidia. Conclusions: One of the obvious questions this data raises is how well our traditional adulticiding times coincide with the peak flight activity of different species. In the case of spring species, it would appear that this operation could Figure 3. Mean number of Ae. vexans and Cx. pipiens commence at least 1-2 hr before sunset to affect the greatest number of mosquitoes. Spraying for spring mosquitoes takes place in rural areas of our county which are continued on page 30

5 Mosquito Activity Continued from p. 18 Figure 4. CDC traps at ground and higher elevations percent covered by woodland habitat. Theses areas are accessible by a mix of gravel/paged roads. Areas that are not woodland habitat are mostly agricultural with scattered homesteads. Our experience is that we often have meteorlogical conditions a few hours before sunset that allow for applications where the ULV fog stays close to ground level and drift appropriately. While Coquillettidia and An. walkeri activity coincided well with conventional times, the nature of Ae. vexans activity seems to indicate an early morning treatment would be effective for supplemental adulticiding during peak density periods. An additional aspect of this study that warrants deeper investigation is the flight habits of Culex. This species was caught in unexpectedly low numbers at many sites, including traditional habitats such as sewage lagoons. Preliminary experiments with CDC traps placed in tandem at ft and 5 ft (figure 4), yielded catches as much as 4 times greater at the higher elevations than those at ground level. Physical weight and bulkiness of the collection bottle rotator prevented these types of placements from being easily accomplished during this investigation. Given the initial data and vector potential of the species, this will become a focus in future studies. REFERENCES CITED: Mitchell, L Time Segregated Mosquito Collections With A CDC Miniature Light Trap. Mosquito News 42: Steven Crisp is a GIS Specialist at the Department of Entomology, Michigan State University and Randy Knepper is the Deputy Director/Biologist with the Saginaw Co. Mosquito Abatement Commission 30 Wing Beats continued on page 33