Honey Bee Exotic Diseases and Pests

Special thanks to Murray Reid and AgriQuality NZ for allowing this pamphlet to be included.

Keeping Our Beekeeping Industry Safe - Border Protection

If you bring anything into the country which is related to the beekeeping industry, declare it to a Ministry of Agriculture and Forestry (MAF) Quarantine Officer. The officer will be able to tell you if importing the item is permitted, and under what conditions. Remember - even one undeclared pot of honey, purchased in an overseas supermarket, could threaten the health of New Zealand beekeeping.

What to Do if You Suspect an Exotic Pest or Disease

• Contact your nearest Apicultural Advisory Officer or call the MAF free phone for reporting suspect exotic disease, 0800 809 966. The receptionist will record your call and put you in contact with an apiculture specialist who will either visit to inspect the hives or ask you to send a sample to a laboratory

• If asked to send a sample carefully follow the instructions you are given

• If you become aware of any importations of live bees, either smuggled deliberately or as swarms on ships or in ship's cargo, contact your nearest MAF or AgriQuality NZ office immediately.

Overseas Threats to New Zealand Beekeeping

European Foulbrood

The organism which causes EFB (Melissococcus pluton) can survive in honey and other bee products. Illegal importation of honey or pollen would be the most likely mode of entry into New Zealand.

If EFB became established in New Zealand, present honey production levels and pollination services could only be maintained by the systematic use of antibiotics. This would increase production costs to beekeepers. Marketing problems could also develop because of consumer resistance to the feeding of antibiotics to bees.

Fig 1 : EFB-infected larvae showing yellow discolouration and prominent tracheae.

Symptoms: Infected larvae lose their distinct form and change from their normal pearly-white colour to yellow and finally dark brown. Tracheae (air tubes) may appear prominent as light lines in the larvae (fig. 1). Prior to dying, infected larvae travel up the cell wall instead of remaining in the normal curled position. The larvae thus appear to be twisted in the cells, in a corkscrew or half-moon shape (Fig. 2).

Fig 2 : EFB-infected larva showing typical twisted (corkscrew) shape.

In medium to heavy infections some larvae may die after capping. In this case the brood pattern may appear patchy and some cappings may be sunken or perforated. These symptoms are also characteristic of American foulbrood. However, unlike American foulbrood, EFB infected larvae rarely "rope out" when an inserted matchstick is slowly withdrawn from the larval remains. Once the larvae have dried down and form a thin scale, they can easily be removed from the cells. And unlike sacbrood, the dried scales appear rubbery rather than brittle.

Because EFB can easily be mistaken for sacbrood, American foulbrood, or halfmoon syndrome, all of which already occur in New Zealand, a summary of the distinguishing features of brood diseases and abnormalities is presented in Table 1.

Identification: Positive identification of EFB can only be made in the laboratory.

Varroa Mite

The varroa mite causes serious colony mortality. If it became established in New Zealand it would:

• Stop all exports of queens and package bees

• Kill a significant number of honey bee colonies within 2-3 years, possibly causing a temporary shortage of honey, jeopardising pollination of horticultural and agricultural crops, and creating serious financial hardship for many commercial beekeepers.

Identification: Varroa is an external parasitic mite large enough to be seen with the naked eye (fig. 3). It is reddish-brown in colour, oval in shape, and 1 mm long by 1.6 mm wide.

Fig 3 : Tropilaelaps mite (right) and Varroa mite (left) on honey bee pupa.

Another mite (Mellitiphis alvearius), found commonly in association with honey bees in New Zealand, is sometimes mistaken for Varroa. However, Mellitiphis is noticeably smaller than Varroa, and is not a parasite of honey bees.

Symptoms: Unless the beekeeper carefully examines brood cells as well as adult bees, early stages of Varroa infestation can be difficult to detect. Pupae, and especially drone pupae, should be examined for small pale to reddish-brown dots.

In heavier infestations, feeding by mites may result in emerging adult bees which appear disfigured or display crippled movements. In common with a number of other bee diseases, Varroa infestation is often associated with both crawling bees at the entrance of the hive and patchy brood patterns caused by nurse bees attempting to remove infected brood.

Spread: Female varroa mites have been shown to move from colony to colony on both drifting and robbing bees.

Beekeepers have played a major part in the rapid spread of Varroa throughout the world. Means of spread include the shifting of hives, interchange of equipment, and the uncontrolled or illegal shipment of queen bees.

Asian Mite

The Asian mite causes serious levels of colony mortality in all countries where it is found. The life cycle is not well known but appears to be similar to that of Varroa. If it became established in New Zealand it would cause the same problems as Varroa.

Identification: The Asian mite is visible to the naked eye, but is lighter in colour and somewhat harder to see than Varroa. The Asian mite moves very rapidly on the combs, going from one brood cell to another, and often entering uncapped cells. Adult mites appear less oval in shape than Varroa and are about 1.0 mm long by 0.6 mm wide (fig. 3).

Tracheal Mite

The tracheal mite has caused significant economic loss since its illegal introduction in the USA and Canada in the 1980's.

New Zealand honey bees would most likely suffer similar serious effects. Bee exports would be made so restrictive that the export trade would become uneconomic.

Identification: Identification can only be made in the laboratory with the aid of a microscope.

Spread: Tracheal mites move between apiaries mostly as a result of beekeeper actions. The mites move within apiaries generally on drifting and swarming bees.

Like the external parasitic mites, Acarapis woodi would enter New Zealand only on live bees.

Africanized Honey Bee

• Increase the number of serious bee sting incidents

• Make it more difficult for commercial beekeepers to find apiary sites where aggressive bees wouldn't affect humans or livestock

• Cause problems placing hives for orchard pollination

• Put pressure on local government officials to limit beekeeping activities, especially in towns and cities

Identification: The Africanized honey bee can be smaller than the other races of honey bee found in New Zealand, but it is similar in colour and shape. Watch out for bees that are exceptionally active on the comb, aggressive, prone to absconding and excessive stinging. An accurate diagnosis requires detailed laboratory analysis.

Spread: The Africanized honey bee would come to New Zealand through illegal importation of queen honey bees (which would carry Africanized genes), as a swarm on a ship, or as a colony living in a shipping container.

Fig 4: AFB-infected larva undergoing "ropiness" test. Note distinctive coffee-brown colouration of the larva and loss of body segmentation	Fig 5: Sacbrood-infected larvae. Note darkened head (larva on right) and bodies with pronounced segmentation.	Fig 6: Chalkbrood "mummies". Left-hand row shows grey-black colouration caused by spore formation. (Scale in millimetres).

Table 1: Distinguishing Features of Honey Bee Brood Diseases and Abnormaliti

Some other photographs of bee pests and diseases

American foulbrood

• Brood
  
• Cappings
  
• Dead larvae (initial phase)
  
• Dried Dead Larvae

European foulbrood

• Early Infection
  
• Advanced infection
  
• Brood Nest
  
• Dead Larvae
  
• Dead Scale

Chalkbrood

• Infected cell
  
• Spores on a larva Mummy
  
• Dead larvae litter the bottom board

Chilled brood, multiple eggs in cell

• Chilled Brood
  
• Multiple eggs in one cell
  

Sacbrood

• Brood nest
  
• Larvae in sac
  
• Larva dead in cell

Tracheal mites

• The tracheal mite

Varroa mites

• On bees
  
• The mite itself

And some more graphics and text about bee pests and diseases...