DISEASES OF HONEY BEES IN NEW ZEALAND T. PALMER-JONES Wallaceville Animal Research Centre, Department of Agriculture, Wellington. SUMMARY Diseases of honey bees a r e reviewed in relation t o their im- portance t o t h e New Zealand beekeeping industry. Honey bees (Apis mellifica L.) were first brought t o New Zea- land f r o m England in 1839. Beekeeping developed rapidly and importation of varieties of the various races of bees f r o m European countries, t h e United Kingdom, and the U.S.A. was f r e q u e n t until controls were introduced recently. We would expect t o find the main diseases of bees in this country and, with t h e noticeable ex- ception of acarine disease and European foulbrood, such is indeed the case. In what follows, organisms, and the disease they cause a r e discussed i n relation to their potential o r actual occurrence and importance a s entities in this country. ORGANISMS AFFECTING ADULT B E E S Acarapis woodi Rennie (Internal acarine mites) These cause acarine disease. They infest t h e prothoracic spiracles of honey bees, producing weakness and inability to fly, which often results i n rapid dwindling of colony strength. The mites have not been found in New Zealand in spite of widespread examination of bees over the last 20 years. The most effective control of acarine disease depends upon treating t h e hive with the miticide chlorobenzilate. Acarapis externus Morgenthaler and Acarapis dorsalis Morgenthaler. (External acarine mites) These mites were found during 1960 on local honey bees (Palmer-Jones, 1961). Although generally considered harmless, they feed directly on t h e bee and the author regards heavy infest- ation a s possibly causing weakness. A study of t h e possible harm- f u l effect of t h e external acarine mites on honey bees is planned. Chlorobenzilate treatment should also control external mites. Nosema apis Zander. Nosema, a protozoan intestinal parasite of a d u l t bees, is of world wide distribution. Bees become weakened by t h e enormous number of parasites in the cells lining their stomachs a n d often fail t o r e t u r n from foraging flights. The disease is spread by spores voided by infected bees. A New Zealand-wide outbreak of dwindling of hive strength during 1946-47 was caused by Nosema (Palmer- Jones, 1947). During the epidemic several commercial beekeepers suffered economic loss because little surplus honey could be col- lected. Nosema soon reverted t o the more usual endemic state and no large scale epidemic has occurred since (Palmer-Jones a n d Robinson, 1951). The disease can be controlled by treatment of combs from infected hives with glacial acetic acid which kills t h e spores, by feeding hives the antibiotic fumagillin in sugar syrup or by a combination of both methods. However, under our conditions of beekeeping i t is generally uneconomic to t r e a t the endemic form of Nosema. Malpighamoeba mellifica Prell. Malpighamoeba is caused by a n amoeba which infects and damages t h e malpighian tubules. Spread by cysts the disease is often associated with Nosema. I t was first identified in New Zealand by Cumber (1948) who found i t in Nelson infecting a single hive which was also suffering from Nosema. Although the present author has searched extensively f o r Malpighamoeba i t has not been found elsewhere. BROOD DISEASES Brood diseases a r e those affecting the larval or pupal stages. European Foulbrood This disease, caused primarily by Streptococcus pluton White, followed by the growth of secondary bacterial invaders, is regarded overseas a s serious. On several occasions t h e author has found hives apparently infected with European foulbrood b u t attempts to isolate Streptococcus pluton have been unsuccessful. American Foulbrood This disease is caused by Bacillus larvae White, which attacks worker brood, usually in the pre-pupal stage. The dried-up brood contains enormous numbers of spores formed when conditions be- come suitable f o r bacterial growth. The disease is spread by the robbing of diseased hives by bees from healthy ones, by the transfer of infected equipment, and by exposure of honey containing spores t o bees. American foulbrood has been recognised in New Zealand since the earliest days of beekeeping. It is persistent and wide- spread in occurrence, being regarded a s t h e most serious bee disease in New Zealand. I t may be treated by feeding sulphathiazole or terramycin in sugar syrup t o infected hives but this method of control suffers from serious drawbacks. Firstly, the drugs d o not aflect spores of t h e disease but only the vegetative stage, necessitat- ing time-consuming and meticulous manipulations of equipment to prevent t h e disease spreading during treatment. Secondly, there is a risk t h a t drug-resistant strains of the organism may arise. Finally, extracted honey may become contaminated with the drug so contravening the Food and Drug Regulations. For these reasons the Department of Agriculture strongly opposes treatment of t h e disease. Apiary Instructors control i t by gassing t h e bees of in- fected hives with a cyanide compound and burning them and t h e infected honey and equipment. Infected hives a r e located by a system of hive registration a n d inspection. Sac Brood A disease caused by a virus, sac brood affects only larvae, causing them t o die and assume a sac-like appearance. In New Zealand i t was first recognised (in Canterbury, under outbreak conditions) i n 1941 (Palmer-Jones, 1949). Though much reduction in hive strength occurred in some apiaries t h e outbreak did n o t cause serious economic loss. Sac brood, like Nosema, has now re- turned t o t h e more usual endemic s t a t e and is of little importance. Chalk Brood This disease, caused by t h e fungus Ascosphaera apis Maassen e x Clausen, attacks only larvae causing them t o d r y up and be- come chalky in appearance. Diseased larvae with a n appearance typical of chalk brood were examined by the a u t h o r i n 1957 in New Zealand. The larvae were permeated with t h e mycelium of a fungus tentatively identified a s Ascosphaera apis. Although chalk brood is promoted by damp conditions i t is seldom found in New Zealand even in high rainfall districts such a s the West coast of t h e South Island. DISCUSSION Apiaries Regulations were passed in 1948 mainly a s a precau- tion against t h e introduction of acarine disease. Under their authority t h e e n t r y of bees was prohibited, first from countries known t o have acarine and l a t e r from virtually all countries. Present control measures would appear adequate t o exclude acarine disease but a r e not proof against deliberate evasion. An a i r traveller could easily bring out a queen bee and attendants in a small cage and smuggle i t out of the airport in his pocket. One such instance is known, the queen having been established in a hive f o r some months before discovery and destruction. The recent de- velopment of methods of transporting immature stages of bees which do not harbour acarine mites (Smith, 1962) niay enable u s t o import fresh stock in safety. Bailey (1958, 1959) re-assessed the affect of acarine disease on bee colonies a n d concluded t h a t i t is not a s severe a s formerly believed. However, the U.S.A. which like New Zealand is f r e e f r o m acarine disease takes every precaution t o prevent its entry. The effect which acarine disease could have on t h e New Zealand bee- keeping industry is unpredictable and might be disastrous. Should the disease be discovered every effort will be made t o contain and eradicate i t by measures already planned. REFERENCES BAILEY, L., 1958: The epidemiology of the infestation of the honey bee, Apis mellifera L, by the mite Acarapis woodi Rennie and the mortality of infested bees. Parasitol. 48: 493- 506. 1959: Infectious diseases of the honey bee. Rep. Rothamst. exp. Sta. 204-215. CUMBER, R. A., 1948: Malpighamoeba mellifica Prell, a disease of the adult honey bee previously unrecorded in New Zealand. N.Z. Sci. Rev. 6: 85. PALMER-JONES, T., 1947: Nosema apis recognised a s the cause of spring dwindling in bee colonies. N.Z. J. Agric. 74: 48. 1949: Diseases of bees in New Zealand. N.Z. J. Agric. 79: 483- 86. 1861 : Tarsonemid (Scutacarid) mites and honey bees. N.Z. Entomol. 2: 50. PALMER-JONES, T. and ROBINSON, D.S., 1951: Observations on the treatment of Nosema apis with drugs. N.Z. J. Sci. Tech. A32: 28-38. SMITH, M. V., 1962: Establishment of honey bee stocks by trans- porting immature stages and semen. J. Apicultural Res. 1: 19-23. 1962: Importing acarine-free bees by transporting brood. Bee World 43: 42-44.