Male European Wasp (Vespula germanica). Scale bar = 5 mm.
Two species of the exotic wasp genus
occur in Tasmania. The European or German Wasp
(F.), was first found in a Hobart suburb in 1959 and has since spread to all parts of the State. By contrast the English or Common Wasp,
, is a relative newcomer to the state, where it is believed to have arrived around 1995 and is restricted to south-eastern Tasmania. Both species are also present on the mainland.
European Wasp and English Wasp appear extremely similar and are difficult to tell apart, but currently the former species is more common and widespread in the state. Both species have similar life cycles and behaviour. Vespid wasps are the most troublesome outdoor insect pest found around homes, in gardens, fruit orchards and especially where sweet foods, fruits or liquids are present. With their yellow and black stripes they are familiar to most Tasmanians.
Male Flower Wasp (Thynnus zonatus). Scale bar = 5 mm.
However, European or English Wasps are sometimes confused with a native species
, or Flower Wasp. This species is found in coastal areas in Tasmania. It is longer and more slender than the vespid wasps and only the males are winged. These wasps do sting but are not attracted to meat like the introduced vespids and are a solitary species that do not form nests. Flower Wasps are not regarded as pests as they do not interfere with outdoor eating or attack fruit like the introduced wasps.
Vespid wasps are swift, strong fliers and are likely, particularly in autumn, to become aggressive when interfered with. When wasps are close by, you should avoid sharp movements because these will attract their attention and may excite them so that they sting. They are capable of inflicting a severe sting. Unlike a bee, each wasp can sting repeatedly.
Wasps are social insects and live in nests where adults rear the young. New nests are begun by young queens, which leave the old nest in autumn, seek a warm protected place to spend the winter and begin making the new nest in spring. After finding a suitable space, the young queen constructs a few cells of a grey papery material made from saliva mixed with chewed wood fibres. The cells are attached to the roof of the cavity or space selected for the nest and one egg is laid in each. The queen tends the first brood of grubs through to maturity, but thereafter the workers take over the gathering of food and the rearing of grubs, leaving the queen to lay eggs.
The grubs are fed on insect and animal matter obtained by the workers. In this regard the wasps may be beneficial since they prey on many harmful insects, including flies and caterpillars. However their predatory activity, when intense, has been shown to severely diminish native insect fauna in some areas and has a detrimental effect on biodiversity.
Towards the end of summer the colony reaches its full size, and the workers forage for sweet materials much more than previously. Similarly their search for protein-based foods intensifies and often switches from insects to meat scraps,such as pet food or picnic food, to feed the rapidly increasing number of grubs. The wasps become more aggressive as their numbers increase and they are most troublesome during autumn.
Mating flights occur on fine, warm days in the autumn, after which the new queens seek over-wintering sites. The colony then declines and usually perishes, although in Tasmania some nests are maintained throughout the winter and are further enlarged in the following season.
Wasps attack a wide range of damaged, ripe fruit. In general they are unable to damage sound fruit and thus are rarely a problem in clean, commercial apple orchards. Sometimes the wasps will damage ripe grapes directly by entering the fruit where it joins the stalk. Thin-skinned fruits such as raspberries, peaches and apricots may also be subject to direct attack when they are ripe and particularly when they are overripe.
Occasionally wasps may be seen in large numbers about pine or gum trees. They are attracted to the sweet secretions of scale insects, aphids or plant exudates. Alternatively control the scale insects or aphids.
Wasps will sometimes enter beehives in search of food, and persistent attacks may weaken the hives. Restricting the hive entrance to a width of 4-6 cm during the winter has been found to assist the bees in keeping wasps out. The hive can be protected further by placing a sheet of glass about 35 cm x 10 cm against the front of the hive with its top edge leaning against a 6 mm piece of wood or a short twig. Bees pass through the gap at the top, but wasps are more likely to enter through the open ends, and are more easily repelled by the bees. In hives of reasonable strength, the glass may rest on two 6 mm pieces of wood but if the hive is weak the glass may rest on the board.
Locating and destroying nests with a registered insecticide is the most effective method of controlling European wasps. To locate nests, follow the flights of adults as they return to the nest with food. Nests are often underground, in earth banks, rock walls, house foundations and bases of old tree stumps. The possibility of a nest being in open ground should not be overlooked. Nests also occur in the wall cavities and eaves of houses. The entrance to the nest (there is normally only one, except in large nests where there may be several) is often inconspicuous; sometimes it is hidden by vegetation.
For information on registered chemicals and current off-label permits for European wasp, visit the APVMA website:www.apvma.gov.au
Agricultural chemicals, including insecticides, are not to be used for any purpose or in any manner contrary to the label or APVMA permit unless authorised under appropriate legislation. Before using a chemical, read and adhere to the instructions for use on the label or APVMA permit.
IF YOU ARE UNSURE ABOUT DOING THE TREATMENT YOURSELF, IT IS BEST TO
OBTAIN THE SERVICES OF A LICENSED PEST CONTROLLER.