5% Sevin (Carbaryl) Data

Because the use of 5% Sevin dust for mite control in purple martin nests  is a very controversial subject, I decided to do some testing in my own colony for myself .  I've used it, as well as many other martin landlords, and our shying away from it simply because it's considered a poison is foolish and nonsense.  I feel that we need to educate ourselves about it and find out once and for all whether this stuff really is a threat or are some of us simply crying wolf without really knowing for sure whether or not it is a threat. Until someone with all the proper tools really does some in-depth research on the subject, we really won't know, so I decided to do some simple tests in mine and one other site for mite control and the results of that testing follows. 

I tested 5% Sevin dust for mite control on purple martin nests for the last 2 seasons using the birds of both sites as subjects.  I want it known that this is NOT a scientific study because I do not have the equipment nor the time to perform all the proper tests.  Instead, it is more empirical in nature, in other words, I would see an infestation of mites while doing nest checks, decide on what level it was and then apply a dosage of the Sevin and then watch and record the results.

For the season of 2001, I tried a couple of different things.  I purchased some pure talcum powder and tried cutting the Sevin from 5% down to 2½% and 1¼%.  I applied the same quantity of material to each nest regardless of infestation level, for example; 1 level teaspoon of Sevin in the infected nest in each case, but 3 different strengths.

I considered infestations to fall within 3 different categories:

Light: scattered mites, not enough to really bother the young birds as of yet.

Medium: a generic half way mix between light and heavy, a fair cloud on the outside of the gourd, but not dangerous yet. (Same as picture above).

Heavy:  a good bloom of mites, enough that if left alone, the health of the young martins would be a concern, enough to even cause premature jumping.

For the season, I tested a total of 16 gourds that became infected, ranging from light infestations to heavy infestations.

One level teaspoon of the Sevin mixture was sprinkled just inside the entrance hole and then tapped down into the nesting material.  I tried to mix my treatment strengths to get a good cross of data.  I would then recheck the nest the next day and record the results and if not satisfactory, retreat with full strength to eliminate the mites.

The results of this testing are as follows:

Season 2001

Observations:

1.  The 1 1/4% strength didn't seem to have enough potency to do the job on any of the two heavier infestation levels and re-treatment was almost always needed.

2.  The 2 1/4% strength worked for light infestations and sometimes on medium, but not on heavy.

3.  Mixtures of Sevin as I used them would probably not be available to the general public and most would probably not mix any up to do their treatments but instead use it full strength anyway.

4.  A more constant treatment would have to be developed if the general public was expected to use it.

5.  Weather conditions such as moisture content could cause changes in the results.

6.  None of this says anything about long term effects of Carbaryl on the birds themselves.  This would require banding and following those test birds from year to year.  My visualizations showed that the birds seemed very healthy and showed nothing out of the norm.

Comment:

Obviously, this is not a very scientific study.  The tests were simply done without actually counting the mites that were killed and of course, the conditions could have changed from day to day and my determination of light, medium or heavy could have been totally wrong because of the unseen mites that might have been inside the gourds.    But it did tell me a little about the different strengths of the Sevin.  I now know that a determination of how much to use has to be figured out, but how, I didn't know at that time.

Season 2002

For the season of 2002, I decided to change my method of treatment and rather than cut the Sevin itself, instead I decided to use the Sevin at full strength, but cut the application dosage and see what happens.  Since this product is bought off the shelf at the 5% strength, then giving a specific amount to use would be much easier for the average person using it.

Throughout this season, 24 gourds became infected and were treated for mite infestations.

The teaspoon I used was one of those long handled plastic Dairy Queen spoons, the kind that comes with the deep cup treats.  It's a little bit smaller than a real teaspoon and the long handle allowed me to get into the container that I kept the Sevin in.  I call it my DQ teaspoon.

The applications used were; 1 level DQ teaspoon and 1/2 level DQ teaspoon.  (I achieved 'level' by tapping the spoon on the side of the container until it was at or slightly more than perfectly level).

Again, when I would find an infected nest during nest checks, I would qualify it as either light, medium or heavy and then randomly apply one of the two applications and then note my 24 hour data results

The following are those results.

Observations:   

 1.  Surprisingly and although there was more mite activity this year, there was only one heavy infestation.  This was probably because I did nest checks every 4 days and none of the blooms got out of hand.

2.   In only 3 cases were mites still visible 24 hours later.  This happened only with the 1/2 teaspoon treatments and there could have been a couple of reasons why.

      A.  The infestation might have been a little on the heavy side for what I considered 'medium'.

      B.  Moisture content or temperatures may have had an effect on the effectiveness of the Sevin and the mite travel.

3.  In all cases the application was 'spread' just inside the entrance hole on the nesting material and left for the parent birds to disperse throughout the nest through normal activity.

Comment:

Obviously, this testing is not very scientific, but it is a start.  I am not an expert on the use of this material, but I did research Carbaryl and educated myself on it 'before' I decided to use it.  What I found out was that it's the least dangerous of all the pesticides in use today and in fact, is the most widely used by the average, everyday gardener.  If we humans can eat the stuff shortly after using it, then it really can't be all that dangerous.  (No, we are not baby birds, but that's what we need to do the testing on and figure out).  I simply feel that if we are ever going to find out about the use of this stuff, someone has to start some testing of some kind, somewhere.  Although this is obviously not done under controlled situations, it's the best I could do, with what I had to work with.  I do not know what any long term effects would be, because this is just the beginning.  Back when there was a major controversy on the PMCA forum, everyone against the use of this stuff was up in arms because it was a poison and that it was illegal to use it in a wild birds nest.  (To be technical, doing nest changes is just as illegal).  Because of the controversy, the PMCA said they were going to start looking into it last year, but as of now, nothing has been said about any research being done at their sites.  I understand their policy on the subject of mite control is 'nest changes', but 9 out of every 10 landlords 'cannot', 'do not', or 'will not' do nest changes and in fact a very low percentage of landlords even do 'nest checks', let alone, nest changes.  So until something starts there at the PMCA and their results are posted, the above will work for me.  If anyone else wants to use my data to determine whether or not they want to try it, then it's there for the using.  Whether or not the PMCA wants to use this data is totally up to them.

Chuck Abare