"ALDEN MARSHALL" asked:

>Do sub-lethal doses of pesticide amplify the effects of parasites, 
>bacteria, viruses, fungi and poor nutrition

I do not personally know of specific research into this, but
Bayer's claim that "Premise plus nature" kills termites by
making them more susceptible to disease would tend to
indicate that.

I found in my hives that disappearance of adults was often
followed by appearance of chalkbrood and sometimes
EFB, both of which are endemic here (in my equipment anyway).
If I get a queen that becomes a drone layer, or laying worker
colony, it is usually the same.

Sub-lethal effects are still not well studied.  There is a
wonderful web-site for the journal "Apidologie" where
you can look at the papers that have been written about
this (very good search engine, and full papers with few of
them that are blocked by needing a fee and goes back
to 1958.)

Here is one on "Modes of honeybee exposure to
Systemic insecticides" that looks at the amounts of
nectar and pollen consumed by different types of bee
(nurse, forager, wax secretors and builders, winter...)
and does some calculations based on the amount of
material, it uses imidacloprid since it is so well
studied,  known to be in treated fields of sunflower
and corn and then relates that to sub lethal effects.

The full paper is at:

http://www.apidologie.org/index.php?option=article&access=standard&Itemid=129&url=/articles/apido/pdf/2005/01/M4053.pdf

 Abstract - The hazard posed to honeybees by systemic insecticides is 
determined by toxicity tests that are designed to study the effects of 
insecticides applied on the aerial parts of plants, but are not adapted to 
systemic substances used as soil or seed treatments. Based on the available 
data found in the literature, this paper proposes modes of honeybees 
exposure to systemic insecticides by estimating their pollen and nectar 
consumption. Estimates are given for larvae and for the categories of adults 
which consume the highest amounts of - pollen, the nurse bees, and - nectar, 
the wax-producing bees, the brood attending bees, the winter bees, and the 
foraging bees. As a case study, we illustrate these estimates with the 
example of imidacloprid because its concentrations in sunflower nectar and 
in sunflower and maize pollens of seed-dressed plants have been precisely 
determined, and because its levels of lethal, sublethal, acute, and chronic 
toxicities have been extensively investigated.

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