Subject: Varroa as bio control for feral bees

From: [email-masked] (Andy Nachbaur)
Date: Sat, 15 Jun 1996 00:38:00 GMT

----------------------------------------
* Personal e-mail from: [email-masked] (Adrian Wenner)
Date: Fri, 14 Jun 96 09:06:51 PDT
Subject: Re: Aggressive island bees

Hi, Andy.  You wrote:

>No I have never heard or experienced [strong aggression in a weak hive];
>if >anything the weaker the
>hives with varroa or without the less aggressive the bees to the point
>that the last dozen or so bees fly off into oblivion when opened.
>
>How did the bees on this isolated island get varroa mite in the first
>place?  How far from shore is it?

   We covered this topic in an abstract in last December's issue of the
AMERICAN BEE JOURNAL (p. 831).  That abstract was as follows:

******

Wenner, A. M., R. W. Thorp, and J. F. Barthell - VARROA MITES IN AN ISLAND
ECOSYSTEM - In October 1987, we initiated a program to remove all European
honey bees from Santa Cruz Island, California, in an attempt to help
restore native bee populations and pollination systems in the Channel
Islands National Park (Thorp, et al., 1994, Fourth California Islands
Symposium, pp. 351-365; Wenner and Thorp, 1994, Fourth California Islands
Symposium, pp. 513-522).  That island is the largest (25,000 hectares), the
most diverse of the five islands, and the only one with honey bees within
the park (for more than 120 years, with apparently no interchange of bees
between island and mainland during that time).

   Ironically, the first U.S. varroa decimated colonies were found in
Wisconsin as we conceived our program and on the nearby California mainland
in 1989.  Unaware of the universal threat posed by varroa, we proceeded
with our studies of competition between native and European honey bees and
continued to exterminate honey bee colonies on the island.  Besides
gathering data on flower visitation and seed set, we have so far located
and monitored the fate of a total of 280 colonies, those in original
cavities and those in many of the nearly 150 swarm hives we have installed
around the island.  We eliminated most colonies found until we recognized -
in the face of accumulating evidence of near total devastation of feral
colonies in the U.S. - that our island honey bee colonies

   To retain control of the system rather than wait for colony decimation,
in mid-winter of 1993-1994 we distributed 90 varroa mites on the eastern
half of the island (that portion of the island closest to the mainland).
We ceased efforts to eliminate colonies, permitted swarms to recolonize
cavities and swarm hives, and prepared to monitor mite spread.  To assist
in monitoring, we installed a few  colonies in Langstroth hives (with mite
trays) on each half of the island.  At the end of the 1995 season, 112
colonies now inhabit known sites.

   In the 20 months after mite dispersal, only two of the 78 pre-1995 feral
colonies had perished (of unknown causes but in inaccessible locations).
Monthly checks of the two Langstroth colonies indicate that varroa mites
are reproducing.  After a seven-hour Apistan treatment of each of the
Langstroth colonies 15 months after infestation, we found 137 mites in one
tray and 70 in the other.  Four months later, an examination of 56 drone
pupae in the former colony yielded 65 mites.  Worker brood remains largely
unaffected.

   An examination of a swarm hive colony from another drainage yielded
similar results; normal worker brood pattern occurred as found in the two
Langstroth colonies (very low infestation rates - 314 worker pupae had only
6 mites), but 463 drone pupae harbored 450 mites (all stages).

   We intend to continue monitoring the system, a unique opportunity in
that no uncontrolled beekeeping activity exists in that closed
(uninhabited) island situation.  We have not transported any mites from the
eastern half of the island to the western half, so we will eventually be
able to determine how much time passes before mites infest the entire
island.

**********

   We had hoped that a colony or two would survive and could serve as
breeding stock, but results from the last two trips indicate such a
possibility is remote.

   On the other hand, we seem to have the first documentation about the
time it takes for a whole population of feral colones to go under to the
mite onslaught.

   Best wishes.

                                                        Adrian

***************************************************************
* Adrian Wenner        E-Mail   [email-masked]  *
* Dept.Ecol.,Evol.,& Mar.Biol. Office Phone    (805) 893-2838 *
* University of California     Lab Phone       (805) 893-2675 *
* Santa Barbara, CA  93106     FAX             (805) 893-8062 *
*                                                             *
***************************************************************
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