8. Pests & Diseases

Ensure Bee Health

8.6 Fall - Mason Bee Cocoon Harvest

8.6 Fall - Mason Bee Cocoon Harvest

The following pests and diseases are found during the fall harvest of your mason bee cocoons.

Pollen Mites

  • What It Is: Pollen mites are the common name for Krombein's hairy-footed mites and are almost microscopic in size - you need a magnifier to see them. Pollen mites eat pollen, are picked up on flowers, and are found throughout North America and are more common in moist environments.
  • What You See: Clear in color, what you actually see is a yellow or orange mass of mite feces. The mass of pollen mites and their feces can completely fill a nesting chamber and they are loose to the touch.
  • Effect on Bees: Within a mason bee nesting hole the mites eat the pollen loaf and the mason bee larva can starve. The mites overwinter in the nesting holes and healthy adult bees spread the mites when they walk through unopened and infected nesting chambers in the following spring.
  • What You Can Do: Do not reuse nesting holes because the pollen mites can easily spread. As you harvest mason bee cocoons in the fall, keep an eye out for signs of pollen mites. Use a dry brush to clean reusable wood trays to remove debris and pollen mites. Harvesting mason bee cocoons is the easiest and best way to reduce pollen mite infections.

Chalkbrood

  • What It Is: A deadly fungal infection that is picked up on flowers. 
  • What You See: Chalkbrood cadavers are chalky, resemble the letter C, and the outer layer of chalkbrood breaks apart easily. Chalkbrood can range in color from salmon, brown, gray, or charcoal in color. Chalkbrood leaves behind a streak of fine black chalky powder.
  • Effect on Bees: When ingested by a bee larva, the chalkbrood spore kills the larva and the larva becomes a chalkbrood cadaver that is a mass of chalkbrood spores. Healthy mason bees emerging from unopened nesting holes brush past infected chambers and spread the spores to your mason bee house and flowers. Without harvesting or providing fresh nesting holes, two or three years of this cycle can devastate your entire mason bee population.
  • What You Can Do: Harvest your mason bee cocoons in the fall by opening nesting holes and dispose of all chalkbrood cadavers, being careful that other cocoons don't touch the chalkbrood. We recommend that you wash mason bee cocoons with cold water and a mild bleach solution, rinse with water, and pat them dry. 
  • Product Recommendation: Spray Clean Bee (a safe bleach alternative) on harvested mason bee cocoons that have been washed and dried. Apply Clean Bee to both sides of reusable wood trays.

Carpet Beetles

  • What You See: Carpet beetle larvae are small, hairy and look like short fat caterpillars.
  • Effect on Bees: The carpet beetle larvae eat mason bee cocoons. Mud capped ends or mud walls do not keep carpet beetles out of nesting chambers. 
  • What You Can Do: After female mason bees are finished nesting, remove nesting materials and store upright in a BeeGuard Bag. Store over the summer in a shed or garage with outdoor temperatures. During harvest eliminate these hairy pests.
  • Product Recommendation: Remove and protect filled nesting materials over the summer in a BeeGuard Bag.

Meal Moths

  • What It Is: Meal moths are small silver or tan moths and they are also known by many names such as Indian meal moth, corn meal moth, flour moth, or grain moth. 
  • What You See: They are most damaging as pink or white hairless caterpillars (skinny, under an inch long, and actively wiggling during mason bee harvest) found within nesting holes. The larvae can also be found within thin, nearly clear cocoons.
  • Effect on Bees: Meal moth larvae eat mason bee cocoons and they are not deterred by mud capped ends or mud walls. 
  • What You Can Do: After female mason bees are finished nesting, remove nesting materials and store upright in a BeeGuard Bag. Store over the summer in a shed or garage with outdoor temperatures. During harvest eliminate these pests.
  • Product Recommendation: Remove filled nesting holes and store in a BeeGuard Bag.

Ptinus Beetle

  • What It Is: A small beetle known around the world to attack food and even museum items. 
  • What You See: The beetle larvae are short, fat and surrounded by thin, curly orange frass.
  • Effect on Bees: The ptinus beetle eats the pollen loaf, mason bee eggs and larvae, and mason bee cocoons. 
  • What You Can Do: During mason bee cocoon harvest, remove all larvae of this pest.

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