Last July, I heard though the grapevine that Stratiolaelaps scimitus, a predatory mite formally known as Hypoaspis, were available locally. These little darlings eat mites, potentially varroa mites.
(A side note: links to photograph sources are in text under the image. WordPress is having issues with my 7 year old computer, and not all link options are available.)
STRATIOLAELAPS SCIMITUS – predatory mites
Stratiolaelaps scimitus eat lots of other insects. Technically they are termed a” non-specific predator”, gobbling down 1-5 other bugs every day. In the US nursery trade, they are used to kill thrips. Interestingly they have also been used to control mites on tarantulas, snakes, and hermit crabs. In the US, Canada, and the UK (and possibly other areas) some beekeepers are using repeated applications of these mites to control varroa. Here’s some UK links.
The Bee Vet (U.K.) : home page
The Bee Vet (U.K) : Predatory Mite PDF : Predatory Mite PDF from The Bee Vet, UKClare Densley (Beekeeper Buckfast Abby who uses these mites): homepage
Clare Densley : blog post about predatory mites:
There is a downside for their use in beekeeping: Stratiolaelaps scimitus, once placed in a hive, do not stay in the hive. They are ground dwellers. Conceptually, they eat and kill their way though the varroa, while heading for the ground where they will burrow in and reproduce.
MY MITES (the “good guys”) and HOW I TESTED FOR VARROA
My mites were raised in British Columbia, Canada, by Applied Bio-Nomics Ltd. and distributed by a Bellingham Horticulture company, Sound Horticulture . The 25,000 that I got arrived mingled with vermiculite in a one-liter canister. These predatory mites are tiny, smaller than 1 mm in length, which is about 1/25th of an inch.
Tube of Mites that Might eat Mites
There are mites in there
When I received the predatory mites, I was participating in the beeinformed.org bee health survey, which I mentioned in the last post. So every month I had the luxury of having bees from selected hives tested for both varroa and nosema loads. Seemed like a perfect time to test Stratiolaelaps scimitus mites against varroa in my hives.
Marker Designating A Bee Health Survey Hive
TEST OVERVIEW
I was not impressed by the mites work. The results were all over the place.
Treated hives: varroa number went:
- Down in one hive
- Up in two hives
- Down then up in the fourth hive
Control hives (no Stratiolaelaps scimitus applied): varroa numbers went:
- Up in three hives
- Down, then up in the fourth hive
I’ll get to the test results in a moment.
First I would stress that all the hives already had varroa present.
Other beekeepers in the UK and Canada have seemed to have some success
Those having success have noted that they do not work well if the hives have a varroa infestation.
- I used them in July. Varroa numbers were already high.
- I wanted to see what they would do if one had varroa.
HOW MANY MITES TO USE:
High Tech Calculations
I found a range of suggestions on how many mites to use.
The U.K. sources suggested:
- 800 mites / hive every month in the dormant season (hives with no varroa)
- 1000 mites/hive every 2 months, from March to September
Remember these folks are starting with non-infected hives.
My mite supplier suggested 2,500 mites for an infested hive
Another test I found (and then lost the link, sorry) used
- 3,750 mites on a non-infected hive
- 6,250 mites on an affected hive – that is one-quarter of the tube of mites
As you can see, there were a lot of options from which to choose.
I opted for 4 different doses. One dose per each hive. These were approximately:
1,000 mites
2,000 mites
2,500 mites
6,250 mites
MY TEST: (finally eh?)
- First, I gently rotated the container, as instructed, to mix the predatory mites in the vermiculite
- Then I measured the mite/vermiculite mix with tablespoons and teaspoons.
Applying Stratiolaelaps scimitus Mites
- The mixture was placed on top of newspaper, as suggested by my supplier.
Mites on top of brood top bars
- The newspaper was placed on top of the highest brood box.
The test results:
The numbers that precede each result is the number assigned to the hive in the bee health survey.
The varroa mite count number is the number of mites/100 bees
| Hive | Dosage(number of predatory mites) | Mite countPretreatmentJuly | Mite countPost-TreatmentAugust | Mite countPost-TreatmentSeptember |
| 2 | 2,500 mites(6 TB, 1.75 teaspoons) | 14.02 | 12.5 | 5.34 |
| 3 | 1,100 mites(3 TB) | 6.29 | 10.19 | 21.45 |
| 6 | 2,200 mites(6 TB) | 12.9 | 6.18 | 12.25 |
| 8 | 6,290 mites(17 TB) | 6.92 | 7.11 | 31.09 |
Non-treated hives of the same period:
| Hive | No Treatments | Mite countPretreatmentJuly | Mite countPost-TreatmentAugust | Mite countPost-TreatmentSeptember |
| 1 | No treatments | 9.53 | 11.93 | 11.26 |
| 4 | No treatments | 2.77 | 9.39 | 15.66 |
| 5 | No treatments | 5.3 | 4.2 | 24.57 |
| 7 | No treatments | 4.36 | 5.25 | 23.76 |
DISAPPOINTMENTS ARE PART OF LIFE
Did the predatory mites work in hive Number 2? I have my doubts, as hive 8 had similar varroa numbers; it got a higher dose of mites yet the varroa count went up, dramatically.
If the predatory mites worked in hive Number 6, then they were effective for only one month.
OK, I was bummed. I really wanted these little mites, who already live in the US, to be the magic bullet that was going to get rid of the Varroa mites. The only other varroa predator I have heard of would have to be imported to the US, and that is a really, really bad idea : the importation of a non-native animal to kill a pest. That leads to environmental destruction and chaos (as we humans have proved time and time again).
THE DOWN SIDE OF THE MITES (in my humble opinion)
- They do not take up residence in the hive.
- They, apparently, must be applied repeatedly, beginning before varroa season
- They do not attack varroa inside of capped brood (the real problem area).
- They are not inexpensive I figured that the suggested rate for application in an affected hive cost (one quarter of the tube) is around $6.50/hive. Hop Guard is cheaper, and it, like the predatory mites, affects varroa out and about in the hive but not in capped cells
- They don’t seem to work in my hives.
ANYONE OUT THERE FIND THEY WORK?
If you or a beekeeper you know has used these mites and they worked. Do write and share. As I have often said, every hive is different; every hive location is different. My results show results on only for four hives, with varroa, here a remote corner of northwest Washington state.
WHAT HAPPENED TO THE VARROA IN FURTHER TREATMENTS
The hives are fine. I used other natural treatments in the fall. The results of those treatments are in the previous post.
