Diagnosis of deadouts

PARASITIC MITE SYNDROME (PMS) Parasitic Mite Syndrome is a condition, not a specific disease whereby a honey bee colony dies rapidly in the fall months. The initial PMS field symptoms include reduced adult population and spotty brood pattern with dying larvae. These symptoms intensify over a short time as the colony gets close to dying.  Confusingly the symptoms may be independent of how heavy the Varroa mite infestation is in the colony.

A similar syndrome is CCD, Colony Collapse Disorder. Difference between the two is spottiness of brood pattern (evident in PMS, less so in CCD), how common varroa mites are (present in PMS until near end, not as evident in CCD) and how quickly colony collapses (in 2-4 weeks with CCD, over the fall into winter clustering in PMS). Outcome of both is death of the colony.

Two common characteristics of PMS are heavy numbers of Varroa mites and spotty brood pattern. Sampling bee adults yield mite counts generally exceeding 3% (and may be much higher), although when colony adult population are noticeably diminished mite counts may be lowered.  Female mites can be seen in the brood if there is a spotty brood pattern with open uncapped brood cells or if you open cells.  Mite poop can be readily seen. In earliest stages, spotty brood and presence of dying brood will likely be more observable.

Dying brood symptoms might appear similar to other diseases. However looking closely dying larvae resemble a glob of whitish-grayish larval mass, not yellowish or brown, more gray in color. Larvae dying will resemble a piece of crud or snot, sunken to the side of the cell. EFB might be present.  Death will be evident in both open and capped brood.  Colonies with PMS will show cappings removed from white pupae, some lacking the head that has been chewed down. Most of the symptoms are the result of hygienic bees trying to remove varroa mite infested brood. The death is caused by viral epidemics transmitted by Varroa mites.

How to look for (field symptoms) of Parasitic Mite Syndrome

  1. A.  Spotty brood pattern, varroa mites present on adult bees, in open cells (cells that have been uncapped by bees) or viewed in cells you uncap.
    1. B. Imbalance of adult population – lack of sufficient numbers of adult bees for amount of brood present
    1. C. Uncapped brood (cells uncapped exposing pupae) but pupae appear OK (unless bees have partially removed the body, starting at head)
    1. D. Cruddy brood – older larvae dying in numbers so adults not keeping cells cleaned – often a lack of eggs or young larval brood.
    1. E. Empty cells among spotty capped pattern show signs of mite poop; some may have mites at bottom; eventually no distinct brood cluster formation.
    1. F. Large colonies may show increased aggressiveness.
    1. G. Supercedure cells might be present.
    1. H. Bees reluctant to take sugar syrup from feeder, despite evident lack of stores.
    1. I. Crawling bees near hive entrance or bees dead or dying around entrance with DWV (deformed wing virus), dead and dying adults at entrance having difficulty moving normally.
    1. J. Smallish bee cluster may move from brood to area remote from the former brood combs
      K. No odor present  until the chewed down larvae start to change color and decay (then becomes a sour odor of death). .

How to confirm the PMS

  1. Have the colony examined by an individual trained in disease identification
  2. Sample for varroa mite population level using alcohol wash or powder sugar shake of 300 adult bee sample

How to avoid PMS

  1. Control varroa mites beginning in May. Seeking to control mites when mite populations are high  may not enable recovery of the colony.
  2. Feed colony sugar syrup – but they may not take the syrup
  3. Bolster colony with healthy brood from other colonies – this may not make difference if done too late in season (and you could risk weakening stronger colonies in the process).


  • Euthanize colony if too weakened and likely not to survive winter. NOT RECOMMENDED




CAPA: Bulletin Honey Bee Diseases & Pests 3rd Edition 2013

BIP: Diagnosis and Treatment of Common Bee Diseases Rev 2019.                                          

 Penn State: A Field Guide to Honey Bees and their Maladies (https://extension.psu.edu/a-field-guide-to-honey-bees-and-their-maladies)

The Bee MD  www.thebeemd.com

Bee app Alberta: https://play.google.com/store/apps/details?id=ca.ab.gov.beehealth&hl=en                    

How to Submit (adult bee) samples to Beltsville/OSU Lab
https://www.ars.usda.gov/northeast-area/beltsville-md-barc/beltsville-agricultural-research-center/bee-research-laboratory/docs/how-to-submit-samples/                                                                                   Varroa Mite sampling  kit (w/ powdered sugar) https://www.beelab.umn.edu/sites/beelab.umn.edu/files/varroa_brochure_final_print_2.23.17.pdf