BEE-L Archives

Informed Discussion of Beekeeping Issues and Bee Biology

BEE-L@COMMUNITY.LSOFT.COM

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
Richard Cryberg <[log in to unmask]>
Reply To:
Informed Discussion of Beekeeping Issues and Bee Biology <[log in to unmask]>
Date:
Mon, 31 Oct 2016 00:12:20 +0000
Content-Type:
text/plain
Parts/Attachments:
text/plain (23 lines)
"  its from the same reason as inoculation or antibiotics fail usually,  incomplete application,  when you spray and don’t get good kill, those weeds are now  able to tolerate coverage."

Inoculation never fails due to incomplete application.  Inoculation fails when the inoculated individuals immune system fails to respond by making proper antibodies.  Giving a larger dose of inoculant would seldom, if ever, correct this problem providing the vaccine was properly administered in the proper doseage to start with.  Quite often a dosage of as little as 10% of the recommended dose is just as effective as the recommended dose.  In the case of flu vaccines quite often failure is due to our government guessing wrong about what strain of flu would be a problem next year.  You should get the vaccine anyhow, even if you happen to know it will not work this year.  That stain of flu will come along sooner or later and if you get the "ineffective this year" vaccine you will be protected at least partly when the strain does come along.  I have gotten the recommended flu vaccine every year since the late 1970s.  At this point I am immunized against so many flu strains I no longer even get a sore arm the day after vaccination.  The last time I had the flu was probably 1984.  At least I had the right symptoms in 1984 for it to have been due to the flu virus.

I have often heard people say an insect became resistant because the pesticide was under dosed allowing some to survive and evolve resistance or the same situation with a bacteria becoming resistant to an antibiotic.  This is a horribly complicated subject.  However, we have known for at least 40 years now that this statement is incorrect most of the time.  If you are really interested in this topic there was a very nice paper published in Science this spring in April that covers some of what is known on the topic.  I would also like to point out that lots of antibiotics do not kill any of the disease bacteria they are administered to control.  What they do instead is prevent those bacteria from reproducing and give the individual enough time for their immune system to kick into gear and clean up the disease.

There are no one size fits all rules for the amount of kill you want to minimize resistance development.  In some cases the optimum kill is zero as in the case of some antibiotics.  For some insect-insecticide combinations the optimum kill can be as low as 60%, where a higher kill would result in faster resistance development and a lower kill result in too much damage by the surviving insects.  There also exist situations where you want to get as close to 100% kill as possible to minimize resistance development.

I think it is only fair to also point out situations where pesticides have been used every year, with no rotation, for up to 50 or more years without resistance ever developing.  An example is the use of Chlorothalonil as the sole fungicide on peanuts and bananas as well as other crops for control of various fungal crop diseases with no resistance to date.  Yet, with some other fungicides resistance has rapidly developed.  The reasons for this contrast are fairly well understood on a molecular level.  Another would be DDT.  Flies rapidly developed resistance to DDT in only a few years to the point that doses thousands of times the original effective dose no longer worked.  Yet, after some 70 years of continuous use mosquitoes have not developed resistance to DDT.  In this case flies had a natural metabolic pathway that degraded carbon chlorine bonds and enhancement of this natural pathway led to dramatic resistance fast.  Mosquitoes lacked this metabolic pathway and had no starting point to optimize.

I have not dug into why glyphosate resistance weeds developed.  It could be the same as the fly situation with DDT.  Or, it might have been horizontal gene transfer from resistant crops into the weeds.  Such horizontal genetic transfer has happened many times in nature.  Every living human probably has some cells in his body that resulted from horizontal gene transfer, via viruses, that are brand new GMO  experiments never tried before by nature.  This in fact is the cause of some cancers.  Did you know that about 30% of the DNA in cattle came directly from snakes?  This was accomplished by horizontal gene transfer of a copy and paste transposon named BOVB that originated in snakes.  The transfer only happened in the last few million years.  I think it highly unlikely, but not impossible, that glyphostate resistance developed as a result of under spraying and allowing a few weeds to survive.  An under spraying pathway would probably take a lot more generations than weeds have had to evolve to the present resistance level.

In the case of oxalic acid we do not even know the mechanism by which it controls varroa mites.  Without such knowledge it is a pure guess what the optimum varroa kill rate would be to minimize resistance.  The best bet based on other known science on other pesticides is the optimum would be something less than 100% kill to minimize resistance development.

Dick

" Any discovery made by the human mind can be explained in its essentials to the curious learner."  Professor Benjamin Schumacher talking about teaching quantum mechanics to non scientists.   "For every complex problem there is a solution which is simple, neat and wrong."  H. L. Mencken

             ***********************************************
The BEE-L mailing list is powered by L-Soft's renowned
LISTSERV(R) list management software.  For more information, go to:
http://www.lsoft.com/LISTSERV-powered.html

ATOM RSS1 RSS2