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Date: Wed, 13 Nov 2002
Posted by: Randy Knepper (randy@scmac.org)

Dear Mr. Robbins

I share your concern that more research needs to be done to analyize the effects of larviciding and adulticiding in the prevention of mosquito-borne disease. These studies are complex and even though we are learning more every day I'm sure these same kinds of questions will be discussed 50 years from now.

However, I do think that some of your questions already have answers if you look for them. Many control district do research along with disease surveillance, larviciding and adulticiding.

In response to some of your questions

1. larviciding (at WHAT intensity and frequency) reduces mosquito populations (by species)? If you research the Journal of the American Mosquito Control Association you will find hundreds of articles on efficacy of larviciding. In a more practical application our district larvicides 45,000 acres ever year for spring mosquitoes. We routinely do pre and post checks in about 125 different woodlots. Over the past 10 years we have averaged 85% reduction of mosquito larvae.

2. URBAN adulticiding (at what intensity, frequency, area and method) reduces mosquito populations, by species and for how long? Again there is a lot of data on the efficacy of ULV spraying if you check the literature. Our agency did an extensive aerial ULV program in 2001 to prepare for WNV. In our study we got 100% control of mosquitoes in cages located in open areas. CDC traps placed in heavy wooded areas had up to 70% control with good weather conditions. For details of this study visit the Michigan Mosquito Control Association website at www.mimosq.org and go to the publications tab and then select 2002 proceedings.

3. there are (or are not) acute or chronic human health effects of urban adulticiding in typical ULV amounts and frequency? No scientific study on this issue but our district has been routinely spraying urban areas of our county for 26 years and have no knowledge of acute or chronic human health effects due to this activity.

5. one or another type of surveillance (dead crows, gravid or C0-2/light traps, virus-positive mosquitoes, etc.) predicts human disease with what kind of probability range. I don't think you can try to just do surveillance and then predict when to implement control measures and be real successful. If you are truly concerned about public health your best action is to have an integrated mosquito management program in action. As far as sequence of WNV activity our district tested 129 crows/blue jays this year for WNV and had 90 positives. All of these positives came in the months of July and August. We had a total of 16 sentinel birds positive for WNV this year with these being detected in late July and early August. We had a total of 25 positive mosquito pools with 23 of these in August and 2 in September. We had one positive human case in late September. As this data illustrates you can first detect the virus in birds, then mosquitoes, and final humans. I would want to be implemented control measure for Culex before any of this activity even started. To wait for all this activity and then make the decision to implement control, in my opinion is a mistake.

Randall G. Knepper
Saginaw County Mosquito Abatement Commission
211 Congress Street
Saginaw, MI 48602
Phone 989-755-5751
Fax 989-758-2309
E-mail randy@scmac.org

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