Smugglers bringing in disease killing bees?

Press, 17 December 1985, Page 13

Smugglers bringing in disease killing bees?

By

DERRICK ROONEY

Chalkbrood, the fungal disease recently found near Hanmer Springs, which attacks and kills bees at the larval stage, is a cosmopolitan disease found in all the important honey-producing areas of the world, but although it can severely weaken individual hives it is seldom regarded as more than a nuisance and has little or no economic effect, according to material supplied by the Ministry of Agriculture and Fisheries. Chalkbrood was first tentatively diagnosed in New Zealand in a Southland bee colony in 1957, but subsequent checks revealed no evidence that the disease had become established there.

Two years ago an outbreak was diagnosed in a sample from Kerikeri, and an emergency survey by the Ministry of Agriculture and Fisheries in January, 1984, showed that the disease was widespread north of Whangarei.

Subsequently it was found also in the Bay of Plenty, the Coromandel Peninsula,, and the Rotorua district. A survey a few weeks ago by the Ministry showed that as many as 10 per cent of the hives in these areas are affected. A year ago only 1 per cent of hives were affected. Chalkbrood spores infect bee larvae aged three or four days, and germinate in the larval gut. The fungal growth bursts through the gut wall and invades the body of the larva. Spores form on the outside of the body. Infected larvae turn vivid white,

and later dry out to become a hard, chalky lump, or “mummy.” A honeycomb with a lot of mummies in it will rattle when shaken, says the Ministry. In light infections the bees often discard the mummies, which may be found on the entrance board or on the ground outside the entrance. They can be confused with mouldy pollen, but the latter is cylindrical and is easily pulverised between fingers, whereas mummies are elongated, flatter, and not easily crushed.

The Ministry says that chalkbrood has a fairly low ability to spread naturally, and the most common means of spread are by the exchange of bees and equipment between colonies, feeding with contaminated honey or pollen, and the use of contaminated tools and gloves. “Drifting” of adult bees between hives may also spread the disease, and it is thought, too, that the spores can be windborne, and may remain viable as long as 15 years.

Most outbreaks occur in spring or early summer, because at this time the weather is usually favourable to the germination of fungal spores and bee colonies have high ratios of brood to adult bees.

Chalkbrood is usually most severe in colonies which are under stress, commonly from such causes as dampness in the hive, lack of re-

queening, and shortage of stores. No chemical means of controlling chalkbrood is known, and the Ministry says that infections are not serious enough to justify the cost of research needed to find a cure. Good management is the most reliable means of preventing infection, the Ministry says. “Good management” includes: Siting hives in a sheltered, sunny aspect with good air drainage. Providing good top ventilation to ensure that the interiors of hives do not become excessively damp in winter and spring. Breeding queens from colonies which show a low degree of infection. Italian bees, with their better housekeeping ability, are more resistant to chalkbrood than darker races of bees.

Keeping colonies strong at all times, to reduce the risk of brood chilling, which can result in increased fungal development in the larvae.

According to Mr Trevor Bryant, an apiculture adviser with the Ministry in Wellington, the risk of spread is greatest in districts such as the kiwifruit-growing areas, where there are large numbers of hives in small areas.

He estimates that in the Bay of Plenty, one of the main kiwifruit areas, as many as 4000 hives have been affected this spring.

The main source of infection is the transporting of queens and packages of bees from Northland, and beekeepers there should be taking more care to reduce their infection rate, he says. “Some Northland bee producers do not check their bees for chalkbrood before they are sold. That practice concerns the industry and there has been a move away from Northland-sourced bees. Some beekeepers are even raising their own queens,” Mr Bryant says. The means by which the disease entered New Zealand is not known, and will probably never be known. According to a Ministry spokesman chalkbrood spores could have come in with smuggled queen bees or with honey brought in illegally, or may have been windborne. “Queen smuggling has been known to occur, and could be either deliberate or innocent,” the spokesman said.

“We try to stop it, and we seize about 200 lots of honey a month. People who go overseas often see nice pots filled with honey, and bring them back as presents. The Agriculture Quarantine Service staff are doing an excellent job but are under tremendous pressure, and it is just not possible to check every passenger’s baggage when a jumbo jet has to be cleared in about 20 minutes.

“The Ministry is trying very hard to persuade people not to bring in honey,” he says.