Protecting Bee-combs from Wax-moth.

New Zealand Journal of Agriculture, Volume 57, Issue 6, 20 December 1938, Page 527

Protecting Bee-combs from Wax-moth.

Precautionary Measures Described.

T. S. Winter,

Apiary Instructor, Hamilton.

TVWRKERS .in wax are not a WORKERS in are not as numerous company so far as h ' species are concerned ; the true -workers are the honey-storing bees {apis). The discovery that if the socials (apis') ■ retained ’ honey in /their stomachs their vital chemistry would convert it into wax brought this species into world-wide prominence. / :; • -The. discovery of - the •’ secret waxproduction and the acquisition of the knowledge of its ductibility and application -to use of the' community -have made all the difference ■to the honey-bee and have brought one species (apis mellifica) completely -under the subjection of man. ■ In - New Zealand to-day : millions of bee-combs, each measuring 8 in. by 17 in., are in use in our commercial apiaries, and’;■ these combs must be stored away for months at a time when not in use in the hives. Not until recent years have bee-keepers in New Zealand been greatly troubled by the ravages of wax -moth. Infection. , This article is intended to show how bee-combs become infected’, and how to deal with their preservation. . '-■■■' In the early days of New Zealand pollinating insects which fed upon nectar were plentiful, but the chopping-down of bush areas and the clean cultivation of our fields have added greatly to the -‘difficulty of survival of many useful insects, with the result that more dependence has' to be placed upon the honey-bee, the only pollinating insect that can be controlled. This widespread cultivation of single plants over large areas has, to a certain extent, upset the' balance of Nature by - encouraging an abnormal condition of insect population. . .Injurious ■ species,, -which are afforded an enormous food-supplyprosper and multiply until they become a positive pest. - , ; .... So it.-is with the honey industry.. . Tens .of thousands,of hives scattered- throughout the country, each producing its quota of beeswax annually and making it into, combs for the storage, of pollen and honey, provide special feedingr-grounds for wax-moths. • .There are two kinds ■of wax-moth — ■ the larger one (Galleria mellonella) and the lesser wax-moth. {Achroia grisella).

They are of Oriental origin, and are now found in almost every country of the world; ‘ Large and Small Moth. The large moth was first .introduced into America from Europe / about 1805, although honey-bees were introduced long before that time. In New Zealand this moth was . .first ’ reported : in ■ 1904 in • the Taranaki district, and it has gradually spread over the - whole of the North Island, thriving -particularly well in the northern areas. ■■■ ■ ■ •- * Figure 1 (a) shows the larvae of. the greater . wax-moth, Fig. 1. (b) the greater wax-moth resting in the natural position, and Fig. 1 (c) the adult female with wings extended. The normal female adults are approximately g in. in length, with a wing, expanse of | in., while the.lesser wax-moth is about half that size. Life History and Habits. ... V.- G. Milum and H. W. . Geuther, Entomological Laboratories,. University of Illinois, who recently made exhaustive

investigations into the life history and habits of these moths, 'stated that the number of eggs laid by individual females of the greater -moth varied from 400 to 839 in a group of twelve females, the average being 754 per individual. Eggs were deposited singly to as many as .127 in one group. The proportion of sexes in a group to 323 adults was 172 males to 157 females. It was also observed that the female greater wax-moth preferred to lay her eggs in the tiniest cracks and crevices, which barely admitted her ovipositor. This is done, no doubt, for the protection of the eggs. In warm weather - the eggs may be hatched over a prolonged period, which means that the tiny larvae may be constantly entering the hives through the cracks and unsealed crevices. ‘ Wax-moth larvae are able to digest beeswax, yet. they require a mixed diet. They definitely do not thrive and. grow to normal size on combs free from pollen and on the remains of brood rearing, while comb foundation remains almost untouched by

them. When the greater -moth larvae are allowed to feed upon a limited supply of brood combs each succeeding generation of adults become smaller and smaller, and errors of identification are often accounted for by this fact. Lesser Wax-moth. G. Kunike, who thoroughly investigated the life history and habits of the lesser wax-moth, is frequently quoted by Milum and Geuther. Among, other things, Kunike reports that the male moths have an average life of twentythree days and the females seven days, and also that within . a few hours after -mating the female starts laying her eggs. The average number of eggs per female is from 250 to 300, although as many as 460 have been deposited. He found that at 86° F. eggs hatched in five days,, at 68° F. after ten days, and at 6o° F. after twenty-two days, while above and below these temperatures the eggs do not hatch, but are killed. The total time required for a generation is approximately two months, with variation due to temperatures and availability of food. Soon after hatching the larvae start, building individual tunnels of silk thread smeared with excretor and particles of comb in which they live, eating their way forward. When feeding ceases the tunnels are extended beyond the foodmass, and at the point of pupation a tight case is constructed. :■ The lesser moth larvae tends to have its own individual tunnel, while the greater wax-moth larvae congregate. The nature of the food eaten and the . general surroundings enable the larvae, when not disturbed, to withstand very - cold temperatures. Kunike clearly established that the larvae are the overwintering stage of,the moth —a period, when so much damage is done to unprotected bee-combs. Method of Control. Now that the large bee-moth is thoroughly established in . this country • beekeepers are warned to take the necessary measures to protect their beecombs from this pest, especially when the summer and autumn months are longer ‘ and warmer than usual, which provide . ideal breeding conditions. Colonies of bees in normal condition and housed in a proper manner can deal quite effectively with the - intruders. Even black bees, when kept strong, will keep their premises free of the pest. They should be helped, however, by keeping the floor boards clean and free from refuse. . If a colony becomes hopelessly queenless and is left unattended for any length of . time it will fall a prey to wax-moth.' •' ' The careful beekeeper has nothing to fear in the apiary if all colonies are kept in normal condition, but unprotected

stored combs provide natural feedinggrounds for these moths. The surest method of control is to keep the flying moths away from the supers and combs, and to do this it is necessary to provide a large moth-proof room which can be conveniently fumigated. Such rooms are

not available‘to the majority of large . commercial beekeepers in New Zealand, and therefore the supers and combs are usually stacked in . open sheds or some building with plenty of ventilation. ~i , ' Stacking the Supers. The supers may be stacked six or seven : high in rows on floor boards with the entrance closed, or in a : similar way to allow a dessertspoonful of calcium cyanide to be . placed in a shallow tin or just scattered inside . and . . underneath the bottom bars of the frames in the bottom super. If floor boards are not available, or they take up too much room, anything that will fit tightly and allow access to the bottom super will do. ■ Calcium cyanide is effective against the larvae pupa and the adults of the waxmoth, but it cannot be relied upon, to kill the eggs. ' It is therefore necessary to fumigate at intervals of not more than three weeks. Calcium cyanide is sold by wholesale manufacturers in powder form. It is non-inflammable and nonexplosive, but care must be taken not to ■. breathe the gas formed when the powder is exposed to the moisture-laden air. A hive lid or something similar should be firmly placed on top of each stack of supers. Carbon bisulphide may be used, but it is highly inflammable and poisonous. A sponge or cloth is saturated with the liquid and placed on top of each stack of combs underneath the lids. When exposed, the liquid changes to an evilsmelling gas, which is heavier than air and gradually filters down through, the

stack of combs. Fumigation should be repeated at intervals the same as with . calcium cyanide. Three Classes. Because of the feeding habits of the ..wax-moths domestic beekeepers and small commercial beekeepers should sort the bee-combs into three classes : (1) Clean, new combs, no brood-rearing and no pollen. (2) Empty combs, no pollen and little brood-rearing. (3) All dark combs containing pollen and the remains of broodrearing.. All combs classed under heading (3) should be safely stored to allow frequent treatment by fumigation. All combs should be spaced as wide apart as possible in the supers and not more than eight or nine to the super. If super accommodation is available it is best to place only eight in each. / One large beekeeper in. this district stores his combs in an open shed and places a double ■ sheet ■of newspaper between each two or three supers, with a quarter of a cake of camphor in each. He reports that the bees do not object to the combs stored over winter in this manner. . t Still another preparation, Para-dichlor-. benzol, which is packed in crystal form, is an excellent fumigant. A little more work is necessary, however, as the cracks between the supers must be gummed tight with paper. The gas generated is pleasant to smell, and is non-injurious. The white crystals should be placed in the top super on top of the frames, and, when dissolved, more crystals should be added. .'..’ A './ -'.A It should be remembered at all times by beekeepers that the moths fly at night, that the females lay their eggs at . night, and that the eggs are laid in crevices about the hive and supers where the newly hatched larvae will find easy access to the combs. These moths are not attracted at night by artificial light, and they shun the. daylight and rest during the daytime. :. - Four years ago a Hamilton orchardist put approximately six buds of Purple King plums per tree into several Burbank trees. These buds grew well, and there are now six vigorous Purple King arms overshadowing the Burbank. These arms are bearing this season. The effect of the vigorous growth of the Purple King has been to influence the Burbank in the same direction, and the past two years the Burbank limbs have commenced renewed growth and vigour, and the fruit has been favourably influenced and is much larger in size than normally. ■fr "fr .■