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Report of 2002 Mosquito Study
Conclusions and Recommendations
Reprinted in Town Report 2003

AUTHORITY:     In Town Meeting on March 11th, 2002, the voters of the Town of Cranberry Isles approved an item directing the selectmen to appoint a committee to “assess the severity of mosquito infestation within the Town, and to investigate methods for mosquito population control, with a report back to the Town.”  Hugh L. Dwelley was appointed Chairman of the Mosquito Committee, assisted by Mary Baldwin, Selig Harrison, Louise Millar, Rob Mocarsky and Barbara Stainton.

HISTORY:     The Cranberry islands were extensively ditched and drained in 1928 in an effort to control mosquitoes.  That effort was financed largely with contributions by summer residents under the leadership of Moorfield Storey on Great Cranberry Island.  In the 1930s and early 1940s the Town appointed a Mosquito Commissioner and contributed $500 annually towards maintaining the ditches.  In 1956, maintenance of the ditches and drains was discontinued in favor of aerial spraying of DDT [dichlorodiphenyltrichloroethane, a powerful insecticide now forbidden for use by public law].  The Town appropriated $2,000 to $2,500 annually to pay for this spraying.

While the DDT spraying was quite effective in controlling mosquitoes, it is also thought to have killed frogs, bats and other birds and insects.  Spraying was discontinued in 1962 and nothing was done from then on.  Many of the ditches are now clogged and themselves serve as breeding pools for mosquitoes.

Mosquitoes were particularly numerous and vicious during the summers of 2000 and 2001.  Thus the proposal for the present study contained in last year's warrant article.  Mosquitoes were less numerous and bothersome during the summer of 2002 due, perhaps, to a relatively dry spring and summer.  Mosquito borne West Nile Virus became a concern in Maine in 2001 and 2002.  Currently mosquitoes are being found in Virginia and Maryland that are carrying malaria as well.  Last summer the State of Maine reported that dead birds in Surry, Maine were found to be carrying the West Nile virus, a distance of approximately 30 miles as the crow flies.

DISCUSSION:     In May 2002 members of the committee began to contact persons and officials knowledgeable of mosquito control in Maine and elsewhere.  This included Florida where extensive spraying is being undertaken with Permethrin and Fairfax County, Virginia which uses a contractor to monitor for West Nile Virus and to place a slow release larvicide in the form of DUNKS on likely mosquito breeding places.  DUNKS can be purchased at local garden stores including Home Depot in Ellsworth.

We contacted the manufacturer of DUNKS who donated a supply of 100 for testing purposes.  We also purchased a small quantity of BITS which are a lavicide in granular form.  (Neither the donated DUNKS nor the BITS have yet been use

Members of the committee also contacted persons at the University of Maine (Mr. Jim Dill) and in the Maine State government who are concerned with mosquito control.  Our goal was to find someone to conduct a survey on the Cranberry Isles and to advise us as to how to proceed.  We learned that Mr. Richard Dearborn, Survey Entomologist with the Insect and Disease Laboratory of the Maine Forest Service is Maine’s expert on this subject.  However, Mr. Dearborn was fully engaged in a West Nile Virus study in Southern Maine.  He did agree, however, to test and identify our mosquitoes if we could send him samples.  Helen Merrill collected a sample of several hundred which we sent to Mr. Dearborn on July 18th.  At his request, we sent him a sizeable follow-up sample on August 29th.  The laboratory reports identifying the mosquitoes in our area can be obtained from the committee’s chairman, however, an excerpt follows of the key information:

“98% of the mosquitoes in the sample processed were: Ochlerotatus (aedes) cantator.  Mosquito species vary greatly with the season and with the nature of the landscape which governs breading sites.  For this reason each sample is a snapshot in time and will vary in composition from all others.  The one thing for certain from your sample, and my experience along the coast of eastern Maine, is that of our two salt marsh species, Ochlerotatus cantator and Ochlerotatus sollicitans, Ochlerotatus cantator is the more common in your area which can somewhat influence your approach to control as it will breed in water that is less saline than Ochlerotatus sollicitans.”

Mr. Dearborn did not have the time to conduct a survey for us but he recommended that we try to obtain the services of Mr. Michael Morrison, president of the Municipal Pest Corporation in York, Maine.  Mr. Morrison visited Great Cranberry on August 18th and Hugh Dwelley took him around Islesford on August 19th.  He spoke to us at a public meeting at the Islesford Neighborhood House on August 19th and recommended that a trial involving the use of DUNKS and BITS should be undertaken.  DUNKS in ponds and BITS spread over marshy areas.  He assured us that the larvicide released will not affect any life forms except mosquitoes and similar insects such as black flies.

From the start we were also in touch with the Chamber of Commerce at Wells, Maine which runs a program involving DUNKS and dragon flies.  The program has been running since the 1970s with a fair degree of success.  Wendy Griffiths runs this program in Wells and she attended our meeting on August 19th.  She explained that it is entirely a private program where the Chamber sells DUNKS and dragon fly nymphs to individuals who wish to use them on their own property.  There are already a few dragon flies on the Cranberry Isles so that we know there are areas compatible for them to live and breed.

The Wells Chamber of Commerce takes orders for dragon fly nymphs during April and early May.  Fifty of them cost $30.00 or 100 for $52.00.  They are released in shallow fresh water ponds.  On Islesford that might include the gravel pit, the old ice pond and the cranberry patch.  In mid-May Ms. Griffiths drives to Massachusetts to pick up the nymphs that have been ordered.  She would be willing to bring some as far as Wells for anyone on the Cranberry Isles who wishes to order them.

We also considered bats and were told that there were many more bats on the islands in the days when there were several barns and other places for them to roost.  Bats, as well as dragon flies, are heavy consumers of mosquitoes.  We found, however, that it is probably not possible to increase the bat population on the islands by introducing new ones since they have a strong homing instinct and are likely to go back where they came from.  However, we believe that if bat houses are placed on the islands, especially in areas where bats have been sighted, this will lead to growth in the existing population.

We talked with Jack Merrill and others who are using propane powered traps.  They are fairly effective in small areas such as a back yard or terrace but they are quite expensive.

The manufacturer of DUNKS and BITS (Summit Chemical Company, 7657 Canton Center Drive, Baltimore, Maryland 21224 Phone: 800-227-8664) advised that BITS are available in 40 pound bags under the name ACQUABAC GRANULES for $60 to $70 per bag.


  1. That the Town should conduct a major field trial in an effort to reduce The populations on Great and Little Cranberry Islands.  If successful, Sutton and Bear Islands could be included in another year if their residents so wish.  Not only does the present mosquito population cause discomfort but there is a growing danger of mosquitoes carrying West Nile virus.

  2. That wide spread spraying of pesticides as is being done in Florida and some other places is not desirable and would not be acceptable.  The Maine Lobstermen’s Association has recommended caution to the state in the use of pesticides to ward against mosquito borne West Nile virus.

  3. That thorough and timely application of larvicide in the form of BITS and ACQUABAC GRANULES will affect only mosquitoes and similar undesirable insects.

  4. Introduction of dragon flies and bats, etc. would be helpful and individuals should be encouraged to do so.


  1. That the Town conduct a thorough field test in 2003 involving the use of DUNKS on open stagnant water and GRANULES spread on marshy areas.  This will involve applications approximately monthly from late April through August.

  2. That the Town engage an experienced and licensed individual or company to carry out the applications employing and training several islanders in the process.  (This will fulfill a requirement of the Maine Pesticides Control Board that the work be done by a licensed applicator.)

  3. That the Town purchase a quantity of Granules in bulk for the purpose.  (We still have 100 DUNKS and may need only a few more.)

  4. That the Town mail to all residents and property owners a fact sheet explaining how and when to order dragon fly nymphs, urging residents with fresh water on or near their property to put in nymphs, and offering to pay for nymphs ordered.

  5. That the Town mail to all residents a fact sheet explaining how to order bat houses and where to place them and offer to pay for bat houses that residents order and put up.

  6. That the Town appropriate $6,000 for field trials.
    (Thirty 40 pound bags of granules @ $65/bag will cost $1,950 plus shipping.  More will probably be needed and there will also be supervision and labor costs.  This will also cover reimbursement costs for dragon fly nymphs and bat houses.)

NOTE:     Warrant 2004, Article 38, addresses the recommendations of the Mosquito Committee, as well as the petition signed by 66 voters on 21 July 2003 concerning the opening of drainage ditches on Little Cranberry Island in an effort to lessen the mosquito population.  This subject is more fully discussed in the Selectmen’s letter in the front of the 2003 Town Report.

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