Control of Wasps in New Zealand

New Zealand Journal of Agriculture, Volume 89, Issue 6, 15 December 1954, Page 561

Control of Wasps in New Zealand

EUROPEAN wasps (Vespula germanica) made their first appearance in New Zealand *” in 1945. Experience has shown that total eradication is impossible, owing to their habit of nesting in inaccessible places and because their spread cannot be prevented, as hibernating queen wasps may be carried about the country in many kinds of merchandise. The public should, however, take measures to reduce the wasp population and retard their spread as far as possible, as they may cause much annoyance while searching for and robbing sweets such as ripe fruit, jams, and honey in summer and until late in autumn.

WASPS of this species are easily identified by their yellow bodies and black markings on their abdomens. The worker wasp is slightly longer than a honey bee and the queen wasp is about twice the size (Fig. 2). A maximum of control can be achieved only if the public endeavour to locate and destroy all wasp nests on their properties as soon as they are discovered and also kill every queen wasp found in hibernation or on the wing. This work must be accepted as the responsibility of the individual or local authority affected as is the case with other pests. When the occupiers of property are themselves unable to undertake the work or arrange for outside assistance the Department of Agriculture will assist when requested by nominating persons or firms who operate wasp extermination services within the area. Destruction of Queen Wasps Many young queen wasps are reared in each nest during autumn, and after mating they leave the parent nest to hibernate in some dark, sheltered place. As each queen is capable of starting a new nest the following spring, all queens should be destroyed

whenever they are discovered. Some of the places favoured are: Under loose bark on trees, under sacks hanging on fences or stacked in piles in sheds, under stack covers and roofs of buildings, in clothing hanging in open sheds, and in piles of stacked timber. Hibernating queen wasps, which may be found singly or in groups, are easily caught and destroyed by crushing. In spring, when queen wasps are more active, they can be killed with suitable swats. Destruction of Nests These European wasps usually build their nests in the ground. Occasionally, however, wasp nests are built on the limbs of trees and other exposed surfaces and within the roofs or walls or under floors of dwellings. Various methods for the destruction of wasp nests may be used successfully according to their location. Nests in the Ground The only indication of a wasp nest in the ground (Fig. 1) is a small opening at the surface from which wasps can be observed on the wing coming and going. The following methods may be used to destroy a nest in the ground: — 1. Petrol method: The use of motor spirit as a killing medium is usually

effective where the passage from the entrance into the nest slopes downward. Where conditions favour the application of petrol pour a quart down through the entrance to the nest and then cover the opening with a sack to confine the fumes. The petrol should not he ignited. Best results can be obtained when petrol is used in the evening when most of the flying wasps have returned to the nest. Diesel fuel is also effective, but a greater volume is usually needed to achieve the same killing effect as with petrol. 2. D.D.T. method: 2oz. of 10 per cent. D.D.T. powder well distributed inside the opening leading to a nest, so that all wasps entering and leaving the nest must come in contact with the powder, is usually effective in killing most of the active wasps within. a few hours. A complete kill should not be expected until a week or so later, however, as young wasps may continue to hatch from the combs for some days. A second application of the powder in 7 ' days is therefore advisable to ensure a complete kill. Ten per cent. D.D.T. powder is available from chemists, grocers, seedsmen, and all other firms selling agricultural chemicals. The powder can be applied to underground nests at any time of the day, or treatment may be delayed until evening, when the wasp activity has quietened down. An easy method of applying D.D.T. to underground nests with entrances either at ground level or through gaps in stone or concrete retaining walls is to use a short length of garden hose or similar piping about 3ft. long. Not less than 2oz. of D.D.T. powder is placed into the tube and the loaded end is gently inserted an inch or two into the opening leading to the nest. A strong blow by mouth at the free end of the tube will force the powder, well distributed, down the passageway to the nest (Fig. 3). Care should

be taken not to allow the D.D.T. to come in contact with the mouth. The tube should be prepared before the nest is approached; then a few seconds only is required to administer the powder, after which the entrance to the nest should be left open so that wasps can continue to fly in and out. 3. “Fumite” size 4 smoke generators: These smoke generators, which cost approximately 7s. 6d. each, contain a smoke-generating mixture in which is incorporated the gamma isomer of benzene hexachloride, a substance highly poisonous to wasps. When ignited (with a match) the generators burn quickly and the benzene hexachloride is evolved as a fine smoke. Though the smoke is irritating to the nose and throat, it is comparatively safe to use. Smoke generators of the type suitable for wasp nest destruction are available from firms selling agricultural chemicals. To light the generator remove the sealed disc at the flanged end, tear away the inner paper cover, and ignite the exposed powder with a match. As soon as the generator ignites (shown by the production of smoke) it is immediately placed down into the entrance to the wasp nest, which should then be blocked with earth or sacking to prevent the loss of smoke. Where smoke generators are used destruction work is best undertaken at dusk, when most of the wasps are in the nest. The nest can be dug out and burnt when all wasp activity has ceased.

Nests in Roofs or Basements ~,, , , ~ • , Where nests are established above a ceiling or under the floor of a buildmg and are easily accessible treatment with smoke generators is effective and is best carried out on the basement m the ng or at dusk. D.D.T. - B.H.C. smoke generator method: To ensure the introduction of sufficient smoke to kill wasps in

exposed nests in buildings and as a precaution against fire, a special type of applicator is necessary. A suitable gun can be improvised, however, with the use of a baking powder tin and a 12in. length of water hose tube. The tin should have a tight lid. Make a hole in the bottom of the tin near the outer edge just large enough to fit the rubber tube into and make a tight seal. When this unit has been securely tied with twine to a long stake as illustrated (Figs. 4 and 5) the

nest can be quickly and effectively dealt with. - When within reach of the nest prepare the generator for lighting, place it in the tin, ignite it, and close the tin quickly and securely. Smoke will then billow from the tube (Fig. 7) and should be directed over and around the nest. The tin holder gets very hot during the few minutes when the smoke generator is working. When a kill has been completed (12 to 24 hours after treatment) the nest should be removed and burnt.

Nests in Walls of Buildings Nests in walls of buildings can be treated with either D.D.T. or D.D.T.B.H.C. D.D.T. method: Where it is possible to locate the exact position of the nest a hole can be drilled through the weatherboarding above the nest and a liberal quantity of D.D.T. powder introduced through it by the same method as described for the D.D.T. method (2) with nests in the ground.

Smoke generator method: This is generally the most effective for destroying nests in the walls of buildings. An improvised applicator gun similar to that already described is a simple expedient for the introduction of smoke to a nest, and with this method it is not necessary to remove

weatherboards. The procedure is to drill a hole through a weatherboard as close as possible to the situation of the nest. To prevent wasps escaping, this hole should be plugged immediately the drill has been withdrawn. When the smoke generator has been ignited and placed within the applicator gun the plug should be removed from the weatherboard and the free end of the tube quickly inserted into the opening. The volume of smoke which is then applied within the confined space is usually sufficient to kill all the wasps. This . method is best employed in the evening. Nests in the Open Nests in suitable situations in the open can be sprayed and thoroughly saturated with. either petrol, diesel fuel, or kerosene where this can be done safely. It is not necessary to ignite the nests, as the fumes from these agents will make a satisfactory kill. Burning should be done only when conditions make it safe.